1.1 History and clinical application of the radiological imaging
Radiological imaging remains one of the most commonly used diagnostic tools in medicine. Since Wilhelm Konrad Roentgen discovered the x-ray in 1895[1, 2], plain radiograph has been the initial step of clinical application and has been utilized extensively in many fields of medicine especially in orthopaedics and trauma care.
In orthopaedics and traumatology, most of the skeletal injuries can be diagnosed primarily by using the plain radiographs alone. Standard anterior-posterior and lateral projections of the x-ray are required for most conditions. However, in some circumstances, several different projections of the radiograph may be necessary to provide more information prior to make an appropriate diagnosis. This is especially true in the region with a complex anatomy such as spine, pelvis and skeletal articulation. Although many attempts have been made to improve the quality of images, there are still limitations because of the 2-dimensions (2D) nature of plain radiograph. Many authors found that it was difficult to define some fractures and gave appropriate classification (AO classification) according to 2D X-ray images[3-6]. The inter-observer reproducibility of the classification of bone fracture by conventional X-ray films was only 38%[7, 8]. Some authors found that in 64% of the cases the pre-operation classification defined by X-ray images are inconsistent with the post-operation classification.[9, 10]. In order to overcome this limitation, the idea of using computer software to reconstruct 3-dimensional (3D) images based on the information obtained from multiple radiographic scans came up and eventually became a reality in 1973 when Hounsfield and McCormack introduced the computerized tomography (CT) to clinical practice[11]. 3-dimensional (3D) images can provide much more useful information than conversional plain radiograph [12, 13]. As
whole body scan within a couple of minutes and the computer software is able to reconstruct high quality 3D images to meet more clinical requirement[15].
In addition to making primary diagnosis and following up on treatment of orthopaedic and trauma conditions, radiological imaging has also been used intra-operatively to improve the quality and accuracy of surgical procedures. However, intra-operative 2D imaging is not able to provide as much information to the surgeons as CT would[16-18]. Since high quality image is needed while there is limited space in the operating room and the operative field is restricted, CT scan is not suitable for this situation. To achieve this purpose, 2-dimensional (2D) C-arm image intensifier followed by 3D C-arm were invented.
1.2 3D fluoroscopic imaging
1.2.1 History of 3D fluoroscopic imaging
Intraoperative imaging using fluoroscopy is well integrated into many orthopedic and general trauma procedures. In 2001, Siemens Medical Solutions introduced the first intraoperative 3D imaging system (Siremobil Iso-C 3D; Siemens, Medical Solutions, Erlangen, Germany), a C-arm imaging system that is able to reconstruct a 3D image immediately based on single fluoroscopic exposures obtained during surgery, therefore broadened the spectrum of available intraoperative imaging modalities. The new device is used widely in diagnosis, intraoperative imaging, navigation system and many other fields. Later another company (Ziehm Imaging, Nuernberg, Germany) introduced its product Vario 3D, which is able to provide intraoperative three-dimensional image like the Iso-C 3D does.
1.2.2 Principles and clinical applications in Orthopaedics and Traumatology Principles of 3D fluoroscopic imaging are similar to those of CT scan. The data from multiple scans were automatically taken by the C-arm within 190 degrees of arch of motion at certain degree intervals and were transferred to the computer. This
series of basis images are referred to as the projection data. Software incorporating sophisticated algorithms including back-filtered projection are applied to these image data to generate a 3D volumetric data set, which can be used to provide primary reconstruction images in three orthogonal planes (axial, sagittal and coronal)[19].
3D fluoroscopic imaging can provide multiplanar images for the object of interest while the device is small and movable compared to any other 3D imaging device such as CT. Therefore, it is applicable for intraoperative use.
Based on Multi-Planar Reformation (MPR), minimally invasive navigation techniques by 3D surgical tool control became possible. This is not possible with fluoroscopic or CT based navigation. Other applications with Iso-C 3D navigation in osteoid osteoma resection, neurosurgery etc. have been mentioned in the literatures[20-22].
Intraoperative 3D imaging can be used to make more accuracy diagnose in articular fracture, in treatment of foot or radius fracture. Many clinical trials showed the outcome are comparable to using the CT in terms of intraoperative control of the reduction and the position of implants, even in pelvic operations,[23-27]. The intraoperative application of 3D is considered to offer clear advantages over current 2D C-arm visualization tools [28-30].
The intraoperative 3D imaging demonstrates a major advantage, but it still has its limitations. The image quality is inferior to that of CT images[20, 25, 31, 32]
. Imaging bone in the surrounding area of metal implants is challenging. Lastly, the scan field is also limited
1.3 Objective of this study
Now the intraoperative 3D imaging has become one of the most useful instruments
shoulder joint. Ziehm Company introduced a new intraoperative 3D imaging device, Vario 3D, which is a smaller, better handling, interrupted scan. The isocenter is variable which can reduce the radiological exposure of the patient and provide theoretically better image quality.
Because there is limited information regarding the application of the new 3D fluoroscopic imaging device, Vario 3D (Ziehm Imaging, Nuernberg, Germany), our study was carried out in order to evaluate the image quality and diagnostic accuracy of this device. We will compare those features to the previous model, Siremobil Iso-C 3D (Siemens, Medical Solutions, Erlangen, Germany), which is now wildly used and proved to be a useful intra-operative imaging system. The question we are trying to answer is that whether the new 3D C- arm can provide intra-operative 3D imaging as good as the Iso-C 3D would in terms of image quality and diagnostic accuracy in different anatomy regions with or without implant.