Deutsche Gesellschaft für Medizinische Physik e.V. DGMP-Report

Deutsche Gesellschaft für Medizinische Physik e.V.

DGMP-Report

DGMP-Report No. 16 2001

Guideline for Medical Physical Aspects of Intravascular Brachytherapy

ISBN 3-925218-71-8

Published DGMP-Reports

DGMP-Bericht Nr. 1, 1981: "Grundsätze zur Bestrahlungsplanung mit Computern", Göttingen DGMP-Bericht Nr. 2, 1982: "Tabellen der radialen Fluenzverteilung in aufgestreuten Elektro-

nenstrahlbündeln mit kreisfömigem Querschnitt", Göttingen, ohne ISBN

DGMP-Bericht Nr. 3 und PTB-Bericht -MM-3, 1985: Th. Bronder, J. Jakschik und DGMP- Arbeitskreis, "Vorschlag für die Zustandsprüfung an Röntgenaufnahmeeinrichtungen im Rahmen der Qualitätssicherung in der Röntgendiagnostik", ISSN 0721-0906

DGMP-Bericht Nr. 4 und PTB-Bericht -MM-4, 1987: Th. Bronder, J. Jakschik und DGMP-Ar- beitskreis, "Vorschlag für die Zustandsprüfung an Röntgendurchleuchtungseinrichtun- gen im Rahmen der Qualitätssicherung in der Röntgendiagnostik", ISSN 0721-0906, ISBN 3-88314-633-1

DGMP-Bericht Nr. 5, 1986, "Praxis der Weichstrahldosimetrie", ISBN 3-925218-30-0

DGMP-Bericht Nr. 6, 1989, "Praktische Dosimetrie von Elektronenstrahlung und ultraharter Röntgenstrahlung", ISBN 3-925218-40-8

DGMP-Bericht Nr. 7, gemeinsam mit DRG und DGN, 1990, "Pränatale Strahlenexposition aus medizinischer Indikation. Dosisermittlung, Folgerungen für Arzt und Schwangere", ISBN 3-925218-41-6

DGMP-Bericht Nr. 8, gemeinsam mit DRG und DGN, 1994, "Empfehlungen zum Personalbe- darf in der Medizinischen Strahlenphysik", ISBN 3-925218-54-8

DGMP-Bericht Nr. 9, 1997, "Anleitung zur Dosimetrie hochenergetischer Photonenstrahlung mit Ionisationskammern", ISBN 3-925218-42-4

DGMP-Bericht Nr. 10, gemeinsam mit DRG, DEGRO und DGN, 1998, "Empfehlungen zum Personalbedarf in der Medizinischen Strahlenphysik Teil II: Ergänzungen für Spezial- techniken und Spezialaufgaben", ISBN: 3-925218-64-5

DGMP-Bericht Nr. 11, gemeinsam mit DEGRO und ARO, 1998, "Dosisspezifikation für die Teletherapie mit Photonenstrahlung", ISBN: 3-925218-65-3

DGMP-Bericht Nr. 12, gemeinsam mit DEGRO und ARO, 1998, "Konstanzprüfungen an Thera- piesimulatoren", ISBN: 3-925218-66-1

DGMP-Bericht Nr. 13: "Praktische Dosimetrie in der HDR-Brachytherapie", H. Krieger, D.

Baltas, ISBN 3-925218-67-X

DGMP-Bericht Nr. 14, gemeinsam mit DEGRO, 1999, "Dosisspezifikation in der HDR- Brachytherapie", ISBN 3-925218-13-0

DGMP-Bericht Nr. 15, 2000, "Meßverfahren und Qualitätssicherung bei Röntgentherapie- anlagen mit Röhrenspannungen zwischen 100 kV und 400 kV", ISBN 3-925218-69-X DGMP-Bericht Nr. 16, 2001, "Leitlinie zu Medizinphysikalischen Aspekten der intravaskulären

Brachytherapie", ISBN 3-925218-70-X

Acknowledgement

This translation of the German "Leitlinie zu Medizinphysikalische Aspekte der intravaskulären Brachytherapie" kindly was performed by the Guidant corporation under the coordination of Jürgen Skoczowski, clinical specialist, RTS Germany, Guidant VI Germany with the financial support of the companies: Cordis, Guidant, and Novoste (in alphabetic order).

Deutsche Gesellschaft für Medizinische Physik e.V.

Medical Physical Aspects of intravaskular Brachytherapy

This DGMP Guideline was created by:

Ulrich Quast, Prof., Dr.rer.nat., Klin. Strahlenphysik, Strahlenklinik, Universitätsklinikum, Essen, Theodor W. Kaulich, Dr.rer.nat., Abt. Medizinische Physik, Radiookol. Universitätsklinik, Tübin- gen,

Dirk Flühs, Dr.rer.nat., Klinische Strahlenphysik, Strahlenklinik, Universitätsklinikum, Essen;

With contributions by:

Michael Andreeff, Dipl.-Phys., Klin. f. Nuklearmedizin, Uniklinikum, TU-Dresden, Kurt Baier, Dipl.-Phys., Klinik für Strahlentherapie, Universität Würzburg,

Markus Bambynek, Dr.rer.nat., Physikalisch Technische Bundesanstalt, PTB, Braunschweig, Ilona Barth, Dipl.-Biol., Bundesamt für Strahlenschutz, Berlin,

B. Bauer, Dr.med., Bundesamt für Strahlenschutz, Oberschleißheim,

Dietrich Baumgart, PD, Dr.med, Abt. f. Kardiologie, Universitätsklinikum Essen,

Jürgen Böhm, Prof., Dr.rer.nat., Physikalisch Technische Bundesanstalt, PTB, Braunschweig, Klaus Bratengeier, Dr.rer.nat., Klinik für Strahlentherapie, Universität Würzburg,

Gunnar Brix, PD, Dr.rer.nat., Med. Strahlenhygiene, Bundesamt f. Strahlensch., Oberschleißheim, Wolfgang Fasten, Dipl.-Phys., AEA Technology QSA GmbH, Braunschweig,

Martin Heintz, Dipl.-Phys., Klinische Strahlenphysik, Strahlenklinik, Universitätsklinikum, Essen, Klaus Helmstädter, Dipl.-Phys., Physikalisch Technische Bundesanstalt, PTB, Braunschweig, Thomas Herrmann, Prof., Dr.med., Univ.-Klinikum, Strahlentherapie und Onkologie, Dresden, S. Hornik, Abt. Med. Strahlenhygiene, Bundesamt f. Strahlensch., Oberschleißheim,

Christian Kirisits, Dipl.-Ing., Abt. Strahlentherapie und Strahlenbiologie, Universitätsklinik, Wien, Irene Langner, Dipl.-Phys. Ing., Klinische Strahlenphysik, Strahlenklinik, Uniklinikum, Essen, Joachim Lorenz, Dr.-Ing., Sächsisches Landesamt für Umwelt und Geologie, Dresden,

Jürgen Mielcarek, Dipl.-Phys., Bundesamt für Strahlenschutz, Berlin, Ernst Moser, Prof., Dr.Dr.Dr.hc, Radiologische Univesitätsklinik, Freiburg, Gerhard Mühl, Dipl.-Ing., Philips Medizin Systeme, Philips GmbH, Frankfurt/M, Sigfried Mühle, Dr.rer.nat., Inst. f. Mediz. Physik, Klinikum Nürnberg,

Wolfgang Müller-Schauenburg, Prof. Dr.Dr., Abt. Nuklearmedizin, Universitätsklinikum Tübingen, Hans-Christoph Murmann, Dr.rer.nat., Strahlenth./Nuklearmedizin, Klinikum Ludwigsburg, D. Noßke, Abt. Med. Strahlenhygiene, Bundesamt f. Strahlenschutz, Oberschleißheim,

Fridtjof Nüsslin, Prof., Dr.rer.nat., Abt. Medizinische Physik, Radiol. Universitätsklinik, Tübingen, Wolfgang Pricken, Dipl.-Ing., Novoste GmbH, Krefeld,

Christian Pychlau, Dr.Ing., Geschäftsführer, Physikalisch Technische Werkstätten, Freiburg, Jürgen Richter, Prof., Dr.rer.nat., Klinik für Strahlentherapie, Universität Würzburg,

Rainer Schmidt, Prof., Dr.rer.nat., Strahlentherapie, Univers.-Krankenhaus, HH-Eppendorf, Michael Sennwitz, Dipl.-Ing., Sennwitz & Partner Ing.-Büro, Ges. für Geräteprüfung, Brühl, Klaus Thieme, Dr., AEA Technology QSA GmbH, Braunschweig,

Wolfgang Weber, Dr.rer.nat., Dipl.-Phys., Novoste GmbH, Krefeld, Jens Zurheide, Dipl.-Phys., Project Engineer, BrainLAB AG, Heimstetten,

Joachim Zwinscher, Dipl.-Phys., Klinik f. Radioonkologie, Klinikum Chemnitz GmbH.

Deutsche Gesellschaft für Medizinische Physik e.V.

DGMP Guideline

Medical Physical Aspects of Intravascular Brachytherapy

Contents

1. Introduction 1.1 Scope

1.2 Importance of intravascular brachytherapy (IVB) 1.3 Concepts in intravascular brachytherapy

2. Procedures for vascular radiotherapy

2.1 Procedures of intravascular brachytherapy 2.1.1 Temporary short-term IVB of peripherals 2.1.2 Temporary short-term IVB of coronaries 2.1.3 Long-term IVB of coronaries

2.2 Vascular radiotherapy with external beams 3. Responsibilities and tasks of the medical physicists 4. Prerequisites for use

4.1 IVB of peripheral vessels 4.1.1 Need of premises 4.1.2 Need of equipment 4.1.3 Need of personnel 4.2 Intracoronary brachytherapy

4.2.1 Need of premises 4.2.2 Need of equipment 4.2.3 Need of personnel 4.3 Organizational requirements 5. Radiation protection

5.1 Radiation protection areas

5.2 Structural, device-related radiation protection 5.2.1 General requirements

5.2.2 Special requirements 5.3 Area monitoring

5.4 Area dosimetry 5.5 Personnel dosimetry

5.6 Organizational radiation protection

6. 6. Quality management

6.1 Traceability to national standards 6.2 Manufacturer’s specifications 6.3 Internal controls

6.3.1 Close range dosimetry

6.3.2 Dosimetric tests of β- and γ-afterloaders 6.3.3 Dosimetric tests of sources

6.4 Constancy checks

6.4.1 Equipment for angiography

6.4.2 Maintenance, supervision and sealing tests 7. Treatment planning and performing IVB

8. Documentation

8.1 Radiotherapeutic prescription

8.1.1 Relevant parameters for reporting 8.1.2 Irradiation treatment plan 8.2 Treatment record

8.3 Patient list, operating logbook, device logbook 9. Transitional regulations

10. Summary of recommendations 11. Literature

12. Appendix: Samples and examples 12.1 Room concept

12.2 Radiation protection instructions 12.3 Recording: IVB of peripheral vessels 12.4 Recording: Intracoronary brachytherapy 12.5 Radiation sources

12.7 Depth dose distributions

12.7 Recommendations of AAPM TG 60 12.8 Terminology

1. Introduction 1.1 Scope

The purpose of this guideline is to summarize the principles and procedures of intravascular brachytherapy (IVB) and information to demand a minimum standard with the goal of ensuring optimum treatment of the patients with high reliability and safety while minimizing the radiation exposure of the personnel by optimizing preventive radiation protection measures. The guideline is especially intended for medical physicists, but also for radiotherapists and nuclear medicine physicians, for cardiologists, angiologists and radiologists, for manufacturers and users, for ra- diation protection officers for the medical and medical physical sector as well as for those work- ing for the relevant authorities in charge of approvals and supervision.

Intravascular brachytherapy is an interdisciplinary treatment. Thus, it could be suggested that an interdisciplinary guideline should be established, too. The very rapid development does demand, however, that this DGMP guideline on medical physical aspects of intravascular brachytherapy is available as soon as possible. In approximately two years time the guideline is supposed to be amended. Until then, the results of clinical studies will provide more clarity regarding biological

questions so that guidelines regarding the radiotherapeutical, cardiological and clinical aspects can complement the DGMP Guideline. Currently, this is not possible yet.

This guideline orients itself by the methodical recommendations for the establishment of guide- lines for diagnostics and therapy of the AWMF (Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften). The current draft for the amendment of the Radiation Pro- tection Regulations (Strahlenschutzverordnung, StrlSchV) and the Guidelines for Radiation Pro- tection in Medicine (Richtlinie Strahlenschutz in der Medizin, Richtl StrlSch i d Med), the tech- nical standards (IEC/DIN standards) and the recommendations of the task group 60 of the Ameri- can Association of Physicists in Medicine (AAPM TG 60) have been taken into consideration.

1.2 The importance of intravascular brachytherapy

Intravascular brachytherapy can significantly reduce the risk of restenosis (30-60%) associated with the interventional treatment of arterial stenosis. This has been demonstrated in clinical studies (e.g. Waksmasn: Clinical trials …, 1999; cf. section 11).

Indications for intravascular brachytherapy are restenoses (especially intra-stent restenoses) and de-novo stenoses of atherosclerotic coronary arteries, but also stenoses in peripheral vessels, renal arteries and arterio-venous shunts (in dialysis patients). Just for intracoronary brachytherapy itself in Germany more than 100,000 patients are expected per year.

The success of intravascular brachytherapy is based on the intensive interdisciplinary co-opera- tion between cardiologists/angiologists/radiologists, radiotherapists/nuclear medicine physi- cians and medical physicists in the "Intravascular Brachytherapy Team".

Because of the broad use of smaller beta and photon sources with high dose rates for intra- arterial application of high doses at one time, this new type of radiation therapy requires special knowledge and experience in this special area of brachytherapy.

1.3 Concepts in intravascular brachytherapy

A definition of terms can be found in the relevant standards as well as in the amendments of the Radiation Protection Regulations (StrlSchV) and of the Guidelines for Radiation Protection in Medicine (Richtl StrlSch i d Med.) (cf. 11. Literature or refer to table 12.8 for a list of defined and undefined concepts of IVB):

• DIN 6814-4: Begriffe: Radioaktivität.

• DIN 6814-8: Begriffe: Strahlentherapie.

• E DIN 6804-1: Strahlenschutzregeln: Umschlossene radioaktive Stoffe.

• DIN 6843: Strahlenschutzregeln: Offene radioaktive Stoffe.

• DIN 6844-2: Therapeutische Anwendung offener radioaktiver Stoffen.

• DIN 6853-1: Afterloading-Anlagen: Sicherheit der Geräte.

• DIN 6853-2: Afterloading-Anlagen: Errichtung.

• DIN 6853-3: Afterloading-Anlagen: Strahlenquellen.

• DIN 6853-5: Afterloading-Anlagen: Konstanzprüfung

• DIN 6855-11: Konstanzprüfung von Aktivimetern.

• DIN 6809-2: Klinische Dosimetrie: Brachytherapie

• DIN 6818-1: Strahlenschutzdosimeter.

• DIN 6827-2: Protokollierung: Therapie mit offenen radioaktiven Stoffen.

• DIN 6827-3: Protokollierung: Lokale Anwendung umschlossener radioaktiver Strahler.

• DIN 44801: Oberflächen-Kontaminationsmessgeräte

• E DIN 25422: Aufbewahrung radioaktiver Stoffe: Aktivitäts-, Brand- und Diebstahlschutz-Klassen.

• DIN 25426-1: Umschlossene radioaktive Stoffe: Anforderungen und Klassifikation.

• DIN 25426-2: Umschlossene radioaktive Stoffe: Anforderungen, besondere Form.

• DIN 25426-3: Umschlossene radioaktive Stoffe: Dichtheitsprüfungen.

Some special terms should be defined more extensively for IVB:

• Brachytherapy

The concept brachytherapy should also include intravascular irradiation procedures where unsealed, but encapsulated radioactive substances are applied locally in the vessel to use the emitted beta (β), gamma (γ) or X radiation for treatment. These can be for example bal- loon catheters filled with liquid or gasuous radioactivity (f, cf. section 2.1) or having a radio- active layer in its wall (e), or radioactive stents. Although some intravascular sources do not fulfil the definitions (DIN 6814-4 and 6814-8) and test conditions for "sealed radioactive material" according to DIN 25426-1 to –3, this is primarily a radiotherapeutical treatment with radiation from emitters. In regard to radiation protection, however, especially as far as malfunctions are concerned where unsealed radioactive substances may be released, the nu- clear medical principles apply.

The concept brachytherapy also should include the application of IVB X-ray sources.

• Afterloading

Definition according to DIN 6814-8, IEC 60788).

• Dose rate classes

The definitions of the dose rate classes (HDR and LDR) for therapeutical brachytherapy sources are derived from intra-cavitary brachytherapy (ICRU 38).

HDR: High Dose Rate, dose rate > 0.2 Gy/min at reference dose point;

LDR: Low Dose Rate, dose rate < 0.033 Gy/min at reference dose point.

These definitions for dose rate classes can be transferred if the fact is taken into account that for intravascular brachytherapy the reference dose point is not at a distance of 2 cm but at 2 mm (or 5 mm, respectively), cf. section 6.2.

IVB concepts are listed in Table 12.8.

2. Procedures for vascular radiotherapy

Intravascular radiotherapy uses almost exclusively brachytherapy procedures. Numerous radia- tion sources and source assemblies have been newly developed or especially adapted, cf. Appen- dix 12.5. Flexibility and vary small dimensions (1 to 2 F; 1F = 1/π mm) of the line sources or source trains should allow insertion into the body by catheters through the typical interventional access even into thin, tourtuous, and pulsating coronaries. Cylindrical or volume sources as well as centering devices have to adapt their size to the lumen size of the vessel treated.

During temporary intravascular brachytherapy (a - f) the sources remain in the vessel only temporarily (2 to 30 min). With permanently implanted sources (h) the activity decreases over a longer period of time. For some indications (e.g. arterio-venous shunts), external beam radio- therapy (i) may be used as well. The development of new procedures for intravascular radiother- apy is not yet finished. Therefore, the following list (a - i) can only show examples.

In case intravascular brachytherapy is utilizing fluid or gasuous radioactive substances (f), then - considering possible emergency cases - the procedure should be regarded as the application of pharmaceuticals. The radiopharmaceutical used has to fulfill the legal requirements (Arzneimit- telrichtlinien). Besides radionuclide purity also the chemical purity has to be proven.

2.1 Procedures of intravacular brachytherapy

2.1.1 Temporary short-term brachytherapy of peripheral vessels

(a) Remote controlled automatic afterloading using sealed HDR gamma emmitters (>100 keV) (e.g. stepping ¹⁹²Ir sources).

2.1.2 Temporary short-term brachytherapy of coronaries

(b) Manual afterloading using sealed HDR gamma emitters (>100 keV) (e.g. ¹⁹²Ir wires or ¹⁹²Ir source trains).

(c) Automatic or manual afterloading using sealed HDR low energy photon emitters Sealed radionuclides with γ energies ≤100 keV and stepping miniature X-ray sources with maximum energies <50 keV.

(d) Automatic or manual afterloading using sealed HDR beta emitters

With catheter-based β radiation afterloading devices, the sources can be advanced and retracted or positioned mechanically (using a source guide wire) or hydraulically using a thin catheter. Point sources are used, for example, for stepping source IVB as well as source wires or source trains for brachytherapy with a „linear" source.

(e) Manual application of HDR beta emitters (e.g. using balloon catheters, where a ra- dioactive layer was introduced into the cylindrical part of the balloon wall).

(f) Brachytherapy with unsealed beta or gamma emitters (e.g. with balloon catheters, which are filled with radioactive liquids or gases).

(g) Interventional local radionuclide radiotherapy with unsealed radionuclides (direct or indirect application of radioactive substances into the arterial wall).

2.1.3 Long-term brachytherapy of coronaries

(h) Brachytherapy using permanently implanted LDR beta or gamma emitters (e.g. ra- dioactive stents emitting LDR β radiation or LDR low-energy photon radiation).

2.2 Vascular radiotherapy with external beams

(i) External beam vascular radiotherapy is in test.

3. Responsibilities and tasks of the medical physicists

The devices used for intravascular brachytherapy are medical products and as such are subject to the Laws on Medical Products (Medizinprodukterecht), especially to RL 93/42 EWG and its national application in the Medizinproduktegesetz (MPG). It requires that medical products are classified in hazard categories (Gefährdungsklassen) which take into account their hazard po- tential for patients, users and third parties and it requires that proof is provided within the scope of a conformity evaluation procedure that the respective medical products fulfil the Basic Re- quirements. Radiation equipment for intravascular brachytherapy is in category III, so that a noti- fied body must be included in the conformity evaluation procedure and that the CE marking must bear an additional code number of this notified body. Only then such a medical product may be distributed in the area of the EEC. Besides the regulations for distribution, which are essentially directed at the manufacturers, the regulations for the operation and use must be ob- served, which are included in the MPG in Section 5 and detailed in the Medizinprodukte- Betreiberverordnung (MPBetreibV). For angiographic X ray localization units, the legal re- quirements are summarized in section 6.4.1.

This results in the following obligations for the user - and therefore especially for the medical physicist or a person delegated by him - including:

- Reporting of events (§3, MPBetreibV), - Maintenance (§4, MPBetreibV), - Introduction (§5, MPBetreibV),

- Performance of technical safety checks (§6, MPBetreibV), - Maintenance of a medical device log (§7, MPBetreibV),

- Maintenance of operating logbook and inventories (§8, MPBetreibV),

- Storage of instruction manuals and medical product logbooks (§9, MPBetreibV), - Performance of measurement controls (§11, MPBetreibV).

Since the devices for intravascular brachytherapy use radioactive sources, they are also subject to the requirements of the Radiation Protection Regulations (Strahlenschutzverordnung), accord- ing to which the handling of radioactive sources must be approved (§7 StrlSchV, in the follow- ing, only the §§ of the Amendment of the StrlSchV are indicated) and the relevant protection regulations of the Radiation Protection Regulations StrlSchV and/or the Guidelines for Radiation Protection in Medicine, Richtlinie Strahlenschutz in der Medizin (Richtl StrlSch i d Med), must be observed.

The medical physicist and his representatives are appointed by the operation authority for radia- tion protection in the physical technical area of intravascular brachytherapy. The responsibilities result in the following professional obligations and tasks of the medical physicist, especially:

• The medical physicist is strongly involved in the process of choosing the irradiation equip- ment and sources.

• Normally, the medical physicist is responsible for the preparation of the application for the license for handling. His tasks include determining the needs – in agreement with the rele- vant supervisory body – to fulfil the following requirements:

- the need of premises;

- the structural and device-related radiation protection, - the need of equipment and need of personnel.

• The medical physicist must ensure that the requirements of the license for handling and the legal regulations and/or standards (e.g. StrlSchV, RöV, Richtl. StrlSch. in der Med., MPG, MPBetreibV, DIN standards) are met. In emergency and assistance situations as well as where all kinds of physical technical aspects are concerned in his position the radiation pro- tection officer has the authority to issue directives to all other members of the IVB team.

• It is the task of the medical physicists - in agreement with the relevant cardiologist/angiolo- gist/radiologist and/or radiotherapist/nuclear medicine personnel – to ensure the safe estab- lishment and reliable performance of intravascular brachytherapy.

• The medical physicist is responsible for dosimetry measurements and the physical part of quality management. This includes:

- the internal tests for new or modified irradiation equipment, the reference data set, and new sources,

- periodic constancy checks of devices and accessories, - the initiation of repairs and routine maintenance.

• He is responsible for the physical part of treatment planning and recording. This implies:

- checking the proper use of the dosimetry reference data set,

- checking the correct calculation of irradiation time and irradiation parameters.

The medical physicist must be continuously present during IVB.

• The medical physicist is responsible for the radioactive sources. This includes:

- checking completeness,

- storage, delivery of radioactive sources, initiation of disposal,

- bookkeeping and reporting (§70), - archiving of documents (30 years).

• The physical technical part of radiation protection in intravascular brachytherapy in the interventional catheter laboratory is a part of his responsibilities, especially including:

- the creation of radiation protection instructions and assistance measures,

- radiation protection training and methodical introduction of the relevant personnel before the introduction of this type of therapy and/or if there are changes in personnel. Trainings and introductions must be repeated on a periodical basis,

- the performance of physical radiation protection checks (personnel dosimetry).

• The medical physicist should be included in the analysis of clinical results.

To minimize the risk of mistakes, a close cooperation including the medical physicist is rec- ommended in the preparatory and planning state of IVB.

4. Prerequisites for use

In the following, the need of premesis, the need of personnel and the need of equipment are summarized and explained.

The following recommendations are essential goals. In case of explained deviations during a transitional period (s. 9.), however, enforced careness for safety and radiation protection is demanded.

4.1 Prerequisites for intravascular brachytherapy of peripheral vessels

If ¹⁹²Ir HDR afterloading is used for intravascular brachytherapy of peripheral vessels (a) the need of premises is comparable to that of conventional afterloading brachytherapy. The quality assurance measures are usually performed in the treatment room. For storage of the required measuring devices and for archiving the documents an additional room should be reserved, cf.

12.1.

4.1.2 Need of equipment

The required equipment includes a remote controlled automatic afterloading systems, special (angiographic) X-ray examination equipment for the verification of the position of the irradia- tion catheter, as well as a treatment planning system and a recording system. The planning sys- tem should be based on the recommendations of AAPM TG 43, to be able to calculate the dose distribution in the vicinity of a source as precisely as possible.

For an exact measurement of the irradiation length as well as the verification of the catheter po- sition after transporting the patient from the angiographic laboratory to the brachytherapy de- partment appropriate dummy sources and radiopaque rulers should be used.

Appropriate dosemeters and phantoms should be provided for quality assurance. The measure- ment of the absorbed dose (rate) to water in the vicinity of the source and the determination of the nominal air kerma rate are performed using calibrateable therapy dosemeters, traceable to national/international standards. In addition, the established procedures and equipment for qual- ity control of ¹⁹²Ir gamma sources are required.

4.1.3 Need of personnel

Cardiovascular (intravascular) brachytherapy depends on the interdisciplinary co-operation be- tween cardiologists (intracoronary treatment) or angiologists/radiologists (treatment of peripheral vessels) and specialized radiotherapists (sealed radionuclides) and/or specialized nuclear medical physican (unsealed radionuclides) with special education in radiation protection (in accordance with the Guidelines for Radiation Protection in Medicine [Richtl StrlSch i d Med]).

Table 4.1 Medical physical personnel - Minimum requirements for intravascular brachytherapy of peripheral vessels

Brachytherapy of peripheral vessels

Requirements for med. phys. personnel

med. phys. personnel total

thereof

medical physicists*

A)Afterloading (AL) analogue to afterloading Part I: 3.2 (4)

+0.42 +0.18

B) Intravascular AL- planning system

analogue to AL planning Part I: 3.2 (7)

+0.08 +0.03

IVB of peripherals A) and B) total: +0.50 +0.21

C) Afterloading:

per 100 pt./year

analogue to afterloading Part I: 3.2 (9)

+0.22 +0.09

D) Intravascular AL:

per 100 pt./year

analogue to IORT AL Part II: 3.2.5 (6)

+0.05 +0.02

IVB of peripherals per 100 pt./year

C) and D) total: +0.27 +0.11

Example Total requirement

IVB of peripherals 200 pt./year:

+1.04 +0.43

*) Medical physicist with special education in radiation protection and special further training and ongoing training in the area of intravascular brachytherapy. Additional personnel is required for tasks in research, development, theory, teaching.

Concerning intravascular brachytherapy of peripheral vessels, the medical physical tasks listed in Section 3. should be executed and/or monitored by a specialized medical physicist with spe- cial education in radiation protection (in accordance with the Guidelines for Radiation Protection in Medicine) and with special further education and ongoing training in the area of IVB.

In accordance with the DGMP Guidelines in the Recommendations for Needs of Personnel in Medical Irradiation Physics Part I and Part II (Empfehlungen zum Personalbedarf in der Medizinischen Strahlenphysik Teil I and Teil II), the minimum requirements for medical physical personnel for routine IVB of peripheral vessels were derived, cf. Table 4.1.

4.2 Prerequisites for intracoronary brachytherapy

Premises should be available which meet the requirements for the physical technical prepara- tion of intravascular brachytherapy, cf. Appendix 12.1: Example of room concept. The require- ments include e.g. rooms for

• Internal tests and quality assurance of irradiation equipment and sources,

• laboratory rooms for handling of sealed radioactive sources,

• laboratory rooms for dosimetry measurements,

• laboratory rooms for preparation of unsealed radioactive sources,

• rooms - protection against fire must be garanteed - for the storage of radioactive sources or for the disposal of radioactive waste.

4.2.2 Need of equipment

All physical technical requirements for the application of intravascular brachytherapy should be met. This includes the measuring devices needed for dosimetry of intravascular sources. The specific requirements for dosemeters for intravascular brachytherapy are: a calibrateable therapy dosemeter with high precision and a large dynamic range, suitable detectors with high spatial resolution (e.g. radiochrome films, cf. AAPM TG 55, or very small volume detectors (<1 mm³), e.g. plastic scintillators or TLD), linearity of response over several orders of magnitude of dose (rate) and the independence of energy. The following systems are required in addition:

• Dosimetry systems

- Dosemeter to check the absorbed dose calibration of the source,

- dosemeter to measure relative depth and axial and/or radial dose distributions, - dosemeter with accessories for internal tests of new sources,

- water and water-equivalent solid phantoms, dosimetry and test phantoms, - calibrated radioactive check source, traceable to national/international standards.

• Devices for consistancy checks of steril packed sources.

- measuring devices (e.g. a wellchamber) to check e.g. the emitted bremsstrahlung.

•

- Equipement and devices for the production, quality assurance, and application of radio- pharmaceuticals,

- calibrated activity meter.

• Treatment planning and recording system

- Tomographic localization: intravascular ultrasound (IVUS),

- an IVUS-based treatment planning system for intravascular brachytherapy (not yet com- mercially available),

- an automatic recording system.

• Radiation protection equipment

- Radiation measuring device for area dosimetry and personnel dosimetry, - contamination measuring device to be able to preclude the loss of a source, - devices for sealing checks,

- transport devices for the safe transport of sources/irradiation equipment, - appliances for the safe storage of sources,

- devices for the preparation and application of unsealed radiopharmaceuticals, - protective shieldings to minimize the exposure of hands and fingers,

- suitable devices for assistance.

The minimum equipment of required devices should be available before the initiation of intra- vascular brachytherapy. The extent of the required equipment - or deviations during a transition period – should be discussed with the license authority.

4.2.3 Need of personnel

The very special requirements (cf. 3.) demand the continuous presence of a medical physicist during intracoronary brachytherapy (b-h).

The required personnel for intracoronary brachytherapy – apart from the physicians of the differ- ent fields listed in 4.1 – consists of at least one medical physicist. He should have special educa- tion in radiation protection (in accordance with the Guidelines for Radiation Protection in Medi- cine, Richtl StrSch i d Med), with special further training and ongoing training in the area of in- travascular brachytherapy.

Table 4.2 Medical physical personnel - Minimum requirements for intracoronary brachytherapy

Intracoronary brachytherapy (BT)

Requirements for med. phys. Personnel

med. phys. personnel total

thereof

medical physicists*

A) Intracoronary Afterloading (AL)

analogue to afterloading

Part I: 3.2 (4) +0.42 +0.21

B) Intracoronary AL planning

analogue to AL planning Part I: 3.2 (7)

+0.08 +0.06

Intracoronary BT A) and B) total: +0.50 +0.27

C) Afterloading:

per 100 pt./year

analogue to afterloading Part I: 3.2 (9)

+0.22 +0.15

D) Intracoronary AL:

per 100 pt./year

increased time needed +0.22 +0.15

Intracoronary BT per 100 pt./year

C) and D) total: +0.44 +0.30

Example:

Total requirement

Intracoronary BT:

200 pt./year

+1.38 +0.87

*) Medical physicist with special education in radiation protection and special further training and ongoing training in the area of intravascular brachytherapy. Additional personnel is required for tasks in research, development, theory, teaching.

In Table 4.2 the minimum requirements for medical physical personnel for intracoronary rou- tine brachytherapy are derived in accordance with the DGMP Guidelines Recommendations for Needs of Personnel in Medical Radiation Physics Part I and Part II (Empfehlungen zum Person- albedarf in der Medizinischen Strahlenphysik Teil I and Teil II).

For additional tasks, e.g. IVUS localization and treatment planning, there will be additional per- sonnel needed. Personnel for research studies, theory and teaching is not included in the table.

The personnel requirements for intracoronary brachytherapy differ considerably from brachy- therapy of peripheral vessels. It is performed in the cardiological catheter laboratory apart from the radiotherapy department. There are often indications where quick treatment is required. The presence of the medical physicist during IVB has to be ensured.

Intracoronary brachytherapy requires additional personnel for the transport of sources and equipment as well as due to increased requirements for performing the treatment. The longer presence of the medical physicist in the catheter laboratory (possibly changing into adequate clothes, waiting periods caused by unplanned longer cardiological interventions, etc.) requires additional logistic efforts and leads to higher personnel costs.

Since the medical physicist is on his own in the catheter laboratory, he must have an adequate education in radiation protection and the competence to make immediate decisions, e.g. in case of emergencies. All in all, the personnel requirements for medical physical personnel in regard to quantity and qualification are considerably higher for intracoronary brachytherapy.

In preparing the personnel key, stant ins for long treatment days, for holidays, and posible illness have to be taken into account.

4.3 Organizational prerequisites

To ensure optimum interdisciplinary intravascular brachytherapy, a quality management system according to ISO 9001 should be established (cf. transition period regulations 9.).

5. Radiation protection

It is the basic principle of radiation protection to keep the radiation exposure as low as reasona- bly achievable. The radiation exposure of the personnel must be minimized, so that the values will be as far below the body dose limits as possible (§6 StrlSchV). Exceeding the limits is not acceptable.

In brachytherapy, apart from the protection of the whole body there must be special radiation protection of the skin and hands from deterministic damage. The radiation exposure of patients must be minimized by appropriate means.

5.1 Radiation protection areas

Radiation protection areas (prohibited area, controlled area and supervised area) must be clearly determined and marked in accordance with StrlSchV (§ 36).

Brachytherapy may generally only be performed in controlled areas. The IVB afterloading de- vices should be shielded in a way that the area dose rates never exceed 3 mSv/h, and thus pro- hibited areas can be avoided - even during transfer of the source through the catheter.

For HDR ¹⁹²Ir afterloading (a) with activities above 5 x 10¹⁰ Bq (e.g. intravascular brachytherapy of peripheral vessels) the StrlSchV (§ 84) requires the instalment of an irradiation treatment room.

The irradiation treatment controll devices which control radiation on or off need to be installed in a separate room outside the controlled area. For dose rates above 3 mSv/h during irradiation treat- ment the treatment room is a prohibited area.

Even if a catheter laboratory is only temporarily used for intravascular brachytherapy, the room should be generally declared to be a controlled area. The authorities will have to agree, under which prerequisites other uses are possible as well. This procedure is clearer and safer and should therefore be preferred to a declaration of temporarily controlled areas.

5.2 Structural and device-related radiation protection

For structural and device-related radiation protection the dose rates of the sources (HDR or LDR), the type (β,β⁺, γ, X, or mixed β/γ radiation) and the quality of the radiation (energy), as well as the method (temporary or permanent) and the type of application (sealed or unsealed sources) must be considered. The relevant requirements for the different fire classifications and theft protection classifications must be regarded.

The user of the radiotherapy equipment should ensure that a safe storage room is available for the storage of the irradiation unit and/or the source while it is not used. Requirements for fire pro- tection must be regarded. Radioactive material must be protected against theft and any access of unauthorized persons. Suitable transport containers and procedures for the safe transport of sources and/or disposal of radioactive waste are a prerequisite.

5.2.1 General requirements for device-related radiation protection

The manufacturer should warrant that the following radiation protection requirements are met:

• For reasons of precision and safety automatic afterloading procedures with automatic re- moval of the sources are required after irradiation time has expired.

• The control of irradiation time, of the introduction and the removal of the source(s) should be performed redundantly by two independent timer integrated into the device.

• The documentation of the irradiation procedure should be performed automatically.

• For exact positioning of the source in the target volume and for safe brachytherapy during afterloading procedures:

the source length or the total travelling distance of the source in the source (guiding) catheter should be clearly indicated by radiopaque markers,

an initial test of the irradiation parameters, of the proper positioning capability of the source in the catheter, of the total travelling distance and the repositioning of the source should be possible using a dummy source of the same shape and without switching de- vices;

in case of faulty coupling of the catheter blocking of the transfer of the radioactive source(s)/the dummy source(s) should be ensured;

clear indication of the status of the position of the source(s)/of the dummy source and of the source position should be ensured using the following indicators: resting position, transfer, irradiation, and interruption;

appropriate measures, such as dose rate comparison, should ensure the completeness of the sources: before transfer, to avoid underdosage of the target volume, and after removal, to identify the position or the loss of the source. In addition, independent appropriate radiation protection monitors should be used.

• The shielding of the device, source transport containers and emergency containers should be such that at a distance of 0.05 m from the accessible surfaces a dose rate of 100 µSv/hr will not be exceeded even with maximum allowed activities. In Germany, for gamma sources in particular for ¹⁹²Ir sources the radiation protection shielding must be in accord to the DIN 6853 standard and must be such that the limits will not be reached by far.

• Appropriate shielding of the source transfer catheter should ensure that the dose rate is be- low 3 mSv/hr. For beta radiation, this can be achieved e.g. by covering the transfer catheter by a flexible layer which thickness must be larger than the range of the beta radiation used (cf. Fig. 12.6). Instalment of a prohibited area should be avoided.

• Technical systems (devices) should ensure that keeping the selected source position during irradiation is possible automatically (without tensing the muscles of the operator).

• The irradiation treatment unit should be freely transportable (movable) and the installation site should be in the non-sterile area (possibly e.g. by extending the catheter) so that the ma- nipulations required for operation are outside the sterile area.

Since intravascular brachytherapy is urgently required for the treatment of patients - but many sys- tems do not fulfil these necessary requirements entirely - a transitional regulation should be ap- plied for a limited transition period (cf. 9.) which should be identified in co-operation with the license authority before the first treatment. In regard to operation safety and radiation protection and taking into account the possible radiation exposure, special solutions for individual cases (radiation protection plan, emergency assistance plan) must be established and trained periodically.

5.2.2 Special requirements for device-related radiation protection

(a) Remote controlled, automatic afterloading using sealed HDR γ emitters (>100 keV) For the structural and device-related radiation protection the special regulations of the DIN 6853 series of standards should be applied accordingly. When performing IVB in the brachytherapy treatment rooms of the radiotherapy department, the device-related and me- thodical prerequisites for the performance of interventional treatments should be fulfilled.

(b) Manual afterloading using sealed HDR gamma emitters (>100 keV)

For the structural and device-related radiation protection the special regulations of the DIN 6853 series of standards must be applied accordingly. Especially the skin and hands must be protected.

(c) Automatic or manual afterloading using HDR low-energy photon emitters (≤100 keV) The radiation protection against diagnostic X-rays used in a catheter laboratory is generally sufficient for the protection of the body. The skin and hands require additional protection.

The recommendations (d) should be applied accordingly. To determine the exposition the dose from diagnostic X-rays has to be taken into account.

Besides radioactive sources, micro X-ray tubes (radiation on demand) are in use for IVB, which have to meet the IEC/DIN/ISO requirements for electrotechnical safety as potentials of 20 to 35 kV and high anode currents are applied inside the catheter to produce X-rays of suf- ficient high energy and dose rate.

(d) Automatic or manual afterloading using sealed beta emitters

According to § 6 StrlSchV it should be ensured that unnecessary radiation exposure is avoided. A dose reduction even below the limits stated in the StrlSchV must be aimed at.

Therefore, the manufacturers of β emitter afterloading devices should ensure by an appropri- ate design of the unit and the source guide that direct β radiation exposure of the personnel is precluded during the use of the devices. There should be no dose rate values during any phase of the therapy which might lead to exceeding the legal limits for the personal dose.

If, during the transition period (cf. 9.) these requirements cannot be fulfilled safely, special solutions for individual cases while taking the possible radiation exposure into account (ra- diation protection plan, emergency assistance plan) must be established and tried out during the periodical trainings.

(e) Manual application of beta emitters

Utmost care should be taken during manual handling of brachytherapy sources, during their ap- plication in the catheter laboratory, during their positioning in the target volume and for the cor- rect determination and adherence to the irradiation time.

In addition, the recommendations for β afterloaders (Section d) should be observed. The con- tamination-free disposal of radioactive waste should be ensured. For emergencies, such as the damage of a balloon source, an emergency plan must be established and drills must be performed during the periodic, generally biannual trainings.

(f) Brachytherapy with unsealed beta or gamma emitters

For the use of balloon catheters as volume sources which are filled with radioactive material, the requirements for radiation protection in nuclear medicine apply, cf. e.g. DIN 6844-2. Ac- tivity checks are required before and after the treatment to promptly detect leaks in the bal- loon catheter. Contamination checks are obligatory. In addition, the recommendations for β afterloaders (d and e) should be observed. The safe disposal of radioactive waste should be ensured. For emergencies, such as a balloon rupture in the patient, an emergency plan must be established and drills must be performed during the periodic, generally biannual trainings.

For brachytherapy with unsealed radioactive material the room must also meet the usual re- quirements for controlled areas for handling unsealed radioactive material.

(g) Interventional local radionuclide radiotherapy with unsealed radionuclides

The requirements for radiation protection in nuclear medicine apply. In addition, the re- quirements in (d-f) should be observed accordingly.

(h) Brachytherapy using permanently implanted LDR beta or gamma emitters

Radioactive stents with beta sources or low-energy gamma sources should be manufactured under certified conditions.

The implantation of radioactive stents requires the establishment of controlled areas. For emergencies including the loss of a radioactive stent in the catheter laboratory and/or in the

patient, an emergency and assistance plan should be established and drills should be per- formed during the periodic, generally biannual trainings. The storage and disposal of radio- active stents which have not been used should be ensured. For the safe handling of radioac- tive stents suitable procedures/aids for safe source manipulation should be available.

(i) External beam vascular radiotherapy

For external beam vascular radiotherapy, the legal requirements for the use of medical accel- erators apply.

5.3 Area monitoring

Dosimetric room monitoring is required for HDR γ brachytherapy. It also makes sense for brachytherapy with HDR beta or HDR low-energy photon emitters, but it is not practised yet. A suitable local shielding of the source guide is recommended (cf. 5.2.1).

5.4 Area dosimetry

The evaluation of the necessity and effectiveness of the radiation protection measures requires to perform area dosimetry measurements or to have them performed by an expert. For the quanti- ties ambient dose equivalent H*(10) and/or ambient dose equivalent rate H*(10)

in photon radiation fields and directional dose equivalent H’(0.07 ,Ω ) and/or directional dose equivalent rate H ’(0.07 ,Ω) in beta and photon radiation fields suitably calibrated dose and/or dose rate measurement devices should be used.

Preferably, area dose rate measuring devices with ionization chamber should be used, which after taking off the protective and/or build-up cap can also measure beta radiation. Beside the use of area dose rate measurement devices for beta and photon radiation, "passive" area dosimetry with thermoluminescence detectors (TLD) is recommended. It can be performed easily, specifi- cally and repeatedly (e.g. after changes of procedure) – and using the support of the accredited personnel dosimetry service.

Since emergency situations cannot be precluded – e.g. in order to react appropriately in case a source is lost or a contamination in the catheter laboratory occurs - in every intravascular brachytherapy area an operational, directly indicating, electronic dose/dose rate measuring de- vice and a contamination measuring device should be available.

5.5 Personnel dosimetry

For the physical radiation protection control of personnel in IVB which is exposed to radiation for professional reasons (e.g. cardiologists, angiologists, radiotherapists, nuclear medical per- sonnel, medical physicists, assistants, nurses), wearing an appropriate personal dosemeter is obligatory. These are primarily the personal dosemeters, which are provided by the measuring office appointed by the authority and which are exchanged monthly.

The relevant authority should determine in each case how the body dose is to be determined and whether surface dose measurements are required.

When handling beta emitters outside of the shielding, during direct manipulation of radioactive material for intravascular radiotherapy (e.g. during stent implant), or for personnel, which must possibly act during assistance in case of an emergency rescue of a brachytherapy source, wearing an additional β sensitive personal dosemeter and a partial body dosemeter calibrated for β ra- diation is required (e.g. thermoluminescence dosemeter with thin entry window for finger do- simetry).

During the handling of low-energy photon emitters for intravascular brachytherapy, too, appro- priate calibrated partial body dosemeters (for fingers/hand) should be worn.

For each work place and each use, for the handling of therapeutic beta sources and low-energy photon sources there should be an additional evaluation of the relationship between the indicated value of the partial body dosemeters and the dose at the most exposed part of the body. This re- lationship – or the correction factor, resp. – should be applied to the indicated value as soon as it is known. Measurements have shown that there are considerable differences between the dose at the most exposed site of the skin and the dose at the site where the finger dosemeter is usually worn (one order of magnitude or more).

Monitoring devices for the detection of a contamination of hands, feets or cloths have to be in- stalled if unsealed radioactive substances are applied.

5.6 Organizational radiation protection

Advices for radiation protection as well as the first and regularly (biannually) repeated trainings have to include details of purchase, storage, transport and disposal, handling and application of sealed/unsealed radioactivity; the behaviour in case of a fault, in case of emergency or assistance, and in cases of a contamination or incorporation. The alarm plan has to be included, too.

The type and number of the existing radiation sources must be safely established by inventory checks and bookkeeping (source logbook). New acquisitions and disposals must be indicated.

The inventory of sources with a halflife T1/2 >100 d must be reported to the authority annually.

For dose meters, the calibration schedule must be observed. The correct handling of the area dose rate measurement device with ionization chamber should be described and the knowledge about it should be refreshed in the periodic radiation protection trainings.

Within the radiation protection instructions (cf. example in Attachment 12.2) area dosimetry should be demanded:

• before first starting up of a brachytherapy system,

• after the introduction of basic changes in the course of the therapy,

• after providing assistance in emergencies.

Important events concerning the technical safety must be reported to the supervisory body for nuclear technology (atomrechtliche Aufsichtsbehörde) and the Bundesamt für Arzneimittel und Medizinprodukte (BfArM).

6. Quality management

The physical part of quality management for intravascular brachytherapy concerns especially the procedures for the manufacturing and use of radiation sources, the reliability and precision as well as the representation and documentation of the events. It is performed by quality assurance of the processes and periodic internal checks before use. The calibration of all measuring de- vices should be traceable to national standards.

For all steps in the procedures detailed written work instructions should be available. In regards to its contents, the quality management system (QM system) should fulfil the requirements of ISO 9001.

6.1 Traceabilty to national standards

In Germany, the Radiological Standards Committee (Normenausschuss Radiologie) has decided

to use the quantity absorbed dose to water in water in radiotherapy in general. The basic impor- tance of the absorbed dose in comparison to the quantity air kerma is that the uncertainties in the measurements performed in the clinical environment are much smaller when using the quantity absorbed dose to water, and if the manufacturer has already calibrated the dosemeter in terms of absorbed dose to water in a water phantom.

Therefore, all intravascular brachytherapy sources – emitting beta or photon radiation, sealed or unsealed – should be calibrated at the calibration reference point at the clinically relevant distance PRef from the center of the source in terms of absorbed dose (rate) to water (Gy or Gy/min).

The calibration of the dose measuring and evaluation devices for the respective measuring pro- cedures should be traceable to national/international standards. For recalibration periods the usual intervals determined for the respective devices or those used in common practise apply.

Most of the sources used in intravascular brachytherapy are line sources. Reference conditions for their calibration are the position of the source in the middle of the water phantom with a di- mension of 15 cm x 15 cm x 15 cm and a specific position of measurement at the calibration reference point in a radial distance PRef from the middle of the source axis:

• P_Ref = 2 mm for all sources for intracoronary brachytherapy and

• PRef = 5 mm for all sources for brachytherapy in peripheral vessels.

Primary standards used to represent as well as secondary standards and transfer standards to transfer the basic data for the determination of the dose at the calibration reference point PRef are currently being developed by the Physikalisch Technische Bundesanstalt, Braunschweig (PTB).

For some photon sources (¹⁹²Ir, ¹⁰³Pd, ¹²⁵I), the PTB offers calibrations in terms of the nominal air kerma (rate) to perform a dose determination according to DIN 6809-2 (1993) for interstitial brachytherapy. A corresponding standard for intravascular brachytherapy does not exist. Proce- dures and data for the determination of the dose at the calibration reference point can be found in the literature, cf. e.g. AAPM TG 60 Report (1999).

In Germany, the calibration of for β sources by the National Institute of Standards and Technol- ogy, Gaithersburg, MD, USA, NIST, will be accepted until an appropriate standard is available at the PTB, cf. also (9.).

6.2 Manufacturer’s specifications

The manufacturer of sources for intravascular brachytherapy – in case of a source which has been manufactured by the user the user himself – should provide a completely documented reference data set. It should at least contain the following specifications (cf. also Attachment 12.7):

• Radionuclide and purity of radionuclide, nominal activity,

• the method for determining the absorbed dose (rate) to water in Gy or Gy/min at the cali- bration reference point P_Ref , traceable to the standards of PTB or NIST (National Institute of Standards and Technology, Gaithersburg, MD, USA),

• measured spatial distributions of dose (AAPM TG 60) or measured depth dose distributions (radial to the source axis, and in at least three representative areas of the source) and the measured dose profiles (along and around the source axis) for all types of sources,

• for β radiation sources: the relative depth dose values in specified depths in water, e.g. at 50%, 75%, and 125% of the range of the β radiation (or at corresponding measuring positions of a supplied test phantom) related to the value at a radial distance of 2 mm from the center of the source axis (the determination of the range of β radiation is explained in Fig. 12.6),

• the radial dose (rate) uniformity, measured in at least one plane perpendicular to the source axis at a distance PRef from the source axis (the values for the dose (rate) uniformity should be within ± 10%, AAPM TG 60),

• the axial dose (rate) uniformity, measured at a distance PRef from the source axis (the values for the dose (rate) uniformity should be within ± 10%, AAPM TG 60).

For a transition period, the following information should also be given:

• for gamma sources also the nominal air kerma rate (AAPM TG 60, TG 43, TG 32),

• the radial dose function, geometry function and anisotropy function (AAPM TG 43).

The source certificate contains all the required data to be able to retrieve the required informa- tion for treatment planning using the reference data set. The manufacturer is liable for his prod- ucts according to legal requirements (Medizin-Produkte-Gesetz, MPG).

6.3 Internal controls

The internal control measurements, demanded by the MPG and the Guidelines for Radiation Protection in Medicine (Richtl StrlSch i d Med), form an essential part of the quality assurance performed by the user.

6.3.1 Near field dosimetry

In close proximity to intravascular brachytherapy sources, dosimetric measurements are very difficult to performe due to the high attenuation of the beta or photon radiation, respectively.

Dose measurements within these extremely inhomogeneous dose distributions have to performed within very small volumes. Thus, the dosimetry detector probe must be as tiny and as water sub- stituting as possible.

As the energy dependence and the anisotropy of response can be high, their inflence has to be determined and considered. In IVB dosimetry the spatial variation of the dose distribution inside the detector volume is not negligible. The effective reference point of absorbed dose measure- ment is not the center of the detector. The position depends apon the distance and detector ori- entation as well. Thus, the effective reference point of dose measurement in the vicinity of a source has to be determined and considered for each detector, each type of IVB radiation field, for each position inside the field and for the orientation of the detector probe.

Relative values of absorbed dose, e.g. isodoses, should be normalized to the water absorbed dose (rate) at the calibration reference point PRef .

6.3.2 Internal dosimetric acceptance test of β and γ afterloaders

When afterloaders are used for intravascular brachytherapy, an acceptance test fulfilling the re- quirements of the DIN 6853 standard series – adapted to the requirements of intravascular brachytherapy – should be performed.

6.3.3 Internal dosimetric acceptance test of radiation sources

The test of the calibration in terms of absorbed dose (rate) to water (in Gy or Gy/min) should be performed for all radiation sources for intravascular brachytherapy in the clinically relevant radial calibration reference point PRef:

• at PRef = 2 mm for all radiation sources for intracoronary brachytherapy and

• at PRef = 5 mm for all radiation sources for brachytherapy in peripheral vessels.