Helical/spiral computed body tomography

PET/CT (and CT) instrumentation, image reconstruction and data transfer for radiotherapy planning

The positron emission tomography in combination with CT in hybrid, cross-modality imaging systems (PET/CT) gains more and more importance as a part of the treatment-planning procedure in radiotherapy. Positron emission tomography (PET), as a integral part of nuclear medicine imaging and non-invasive imaging technique, offers the visualization and quantification of pre-selected tracer metabolism. In combination with the structural information from CT, this molecular imaging technique has great potential to support and improve the outcome of the treatment-planning procedure prior to radiotherapy. By the choice of the PET-Tracer, a variety of different metabolic processes can be visualized. First and foremost, this is the glucose metabolism of a tissue as well as for instance hypoxia or cell proliferation. This paper comprises the system characteristics of hybrid PET/CT systems. Acquisition and processing protocols are described in general and modifications to cope with the special needs in radiooncology. This starts with the different position of the patient on a special table top, continues with the use of the same fixation material as used for positioning of the patient in radiooncology while simulation and irradiation and leads to special processing protocols that include the delineation of the volumes that are subject to treatment planning and irradiation (PTV, GTV, CTV, etc.). General CT acquisition and processing parameters as well as the use of contrast enhancement of the CT are described. The possible risks and pitfalls the investigator could face during the hybrid-imaging procedure are explained and listed. The interdisciplinary use of different imaging modalities implies a increase of the volume of data created. These data need to be stored and communicated fast, safe and correct. Therefore, the DICOM-Standard provides objects and classes for this purpose (DICOM RT). Furthermore, the standard DICOM objects and classes for nuclear medicine (NM, PT) and computed tomography (CT) are used to communicate the actual image data created by the modalities. Care must be taken for data security, especially when transferring data across the (network-) borders of different hospitals. Overall, the most important precondition for successful integration of functional imaging in RT treatment planning is the goal orientated as well as close and thorough communication between nuclear medicine and radiotherapy departments on all levels of interaction (personnel, imaging protocols, GTV delineation, and selection of the data transfer method).

Renovascular disease

The gold standard for the diagnosis of renal artery stenosis is angiography, with response to treatment the proof of its significance. Non-invasive methods of investigation are required and are now available including functional imaging, ultrasound, CT and MR angiography and the merits and limitations of these tests are discussed.

Utility of CT angiography for evaluation of living kidney donors

We reviewed our initial experience with helical computed tomography (CT) angiography in the evaluation of living kidney donors which, until now, has necessitated arteriography. Nineteen donors (12 women, 7 men) have had their renal anatomy evaluated solely by CT angiography preoperatively. All scans demonstrated normal collecting systems and single ureters. Five donors (26%) had supernumerary renal arteries. Fourteen donors had single, 4 donors had two, and 1 donor had three renal arteries. Helical CT demonstrated small polar vessels in several donors. Two donors (10%) had supernumerary renal veins. Accuracy of vascular anatomy defined on CT was 90% when confirmed at operation. Anatomically all CT findings were consistent with operative findings except in 1 donor who was found to have a 0.8 cm lesion near the renal hilum. At our institution, the total charges for selective renal arteriography are $3845 and for helical CT with three-dimensional (3-D) reconstruction are $1546. The amount of contrast dye (approximately 100 mL) is equivalent. Patients uniformly reported that the CT scan was a convenient and painless procedure. The accuracy of helical CT angiography is equivalent to arteriography in assessing renal vascular anatomy (with the additional benefit of imaging venous and parenchymal anatomy). Charges for helical CT are 59% less. There is greater patient acceptance and potentially less morbidity associated with the non-invasive nature of helical CT. We believe that CT angiography is the radiologic procedure of choice for the assessment of renal anatomy in potential living kidney donors.