Nuclear Medicine Technology: Procedures And Quick Reference.epub
Everardo Laboy
CT replaced a number of more invasive procedures. It completely replaced pneumoencephalograms, a very difficult procedure for patient and physician and reduced the use of catheter angiography and nuclear medicine.2 Images are from Ref. 3.
The growing market and enthusiasm also brought competition to EMI from companies adopting the first- or second-generation designs to quickly get to market. In 1974, Siemens and Hitachi introduced first-generation translate-rotate head scanners, with Siemens installing a Siretom at the University of Frankfurt, June 19, 1974. Ohio Nuclear, part of BCC (which became Technicare in 1973) and already successful in providing systems for the nuclear medicine imaging market, quickly developed the DeltaScan 50 whole body scanner (see below) and a less costly Delta 25 model, a head-only two-slice scanner, like the EMI system. A number of players new to diagnostic imaging, including pharmaceutical companies, entered the imaging field during the early years of CT. Syntex, a California drug company, introduced a head scanner. Neuroscan introduced a head-only scanner that GE licensed as a way to enter CT quickly. CGR, a major French medical imaging company, introduced an early head-only system. None of these were very successful in the marketplace.
The development and adoption of CT arguably marked the beginning of a major transformation of diagnostic imaging and of radiology as a field, from analog imaging largely involving film, to digital imaging in which pixel values are calculated by algorithms, and the beginning of imaging in which computers play a major role. Certainly, computers had started to be used in radiology and nuclear medicine prior to CT (e.g., Ref. 73) and ultrasonography was generating images algorithmically, but those were exceptions. Radiologists were not familiar nor comfortable with computers. Even CT (and MRI) images were, for many years, printed on photographic film and read using film-changers. The field has changed dramatically. In hindsight, given the total conversion of radiological imaging from film to digital, it is remarkable that the first digital x-ray imaging technology that came into widespread use was an entirely new modality, CT. That said, the significant film budgets for film use by CT and MRI undoubtedly contributed to the adoption of Picture Archiving and Communication Systems (PACS).
Covers all relevant imaging modalities, including hybrid imaging systems such as SPECT/CT, PET/CT, and PET/MRI, as well as targeted radionuclide therapy, theranostics, and translational molecular imaging as it relates to nuclear medicine in adults and children.
During the course of the Fellowship, neuroradiology fellows will be exposed to all imaging modalities used to evaluate neurologic disease, including CT, MR, myelography, angiography, ultrasound, nuclear medicine and radiographic studies. Interventional neuroradiologic procedures are also performed at state-of-the-art levels at OHSU, and neuroradiology fellows will actively participate in these procedures with the neurointerventional service.
However, when reducing activity care must be taken to ensure that the scan quality is not compromised, where higher noise images can obscure small lesions [23, 66]. Dose optimisation is not synonymous with dose reduction, and activities should be defined according to their diagnostic yield rather than arbitrary or subjective image quality [67, 68]. The magnitude of any theoretical benefit to an individual patient through only modest reductions in radiation dose, for example a 50% reduction in activity [40] is questionable. Moreover, as nuclear medicine physicians, we must be careful that we do not inadvertently contribute to radiation induced phobia through overstating the risks of radiation doses routinely used in diagnostic procedures, which in many cases are smaller in magnitude than the risks inherent to the car journey to the hospital [69,70,71,72]. Furthermore, care must be taken that the potential advantages of a high-quality, low-noise examination are not unnecessarily forfeited in the pursuit of radiation doses lower than those already accepted as safe in routine clinical imaging. For example, the present generation of SiPM-based PET-scanners are known to demonstrate higher detection rates [15, 18,19,20], diagnostic certainty and inter-rater reliability [22] and these benefits could extend to LAFOV systems.
Cognisant of a preponderance of data that fully quantitative kinetic analysis will yield superior results to traditional single-time point imaging, if successfully translated into clinical routine, it promises to fundamentally alter the way in which PET data are interpreted and reported. In recent decades, training programmes in nuclear medicine have been reconfigured with heavy emphasis on training in anatomic imaging modalities or the training of dual-certified radionuclide radiologists. Consequently, in many countries there has been a decline in the number of nuclear medicine physicians being trained [85,86,87]. We predict that LAFOV PET could act as a catalyst for truly quantitative functional and kinetic imaging. With exciting possibilities on the horizon, such as personalised cocktails of multiple tracers or the ability to probe whole-body metabolic connectome data, interesting questions will arise about how we might best train and educate nuclear medicine residents to best exploit these technologies. Whereas physician training has previously emphasised mastery of anatomical imaging modalities, nuclear-medicine specific skills and knowledge, such as the ability to code and manage data, perform and interpret kinetic modelling and knowledge of advanced radiomics techniques might need to be given greater weight to educate the molecular imager and therapist of the future.
However, ensuring maximum benefit to risk ratio for the patient is not a trivial task. Referring medical practitioners, in a large part of the world, lack training in radiation protection and in risk estimation. 97% of practitioners who participated in a study underestimated the dose the patient would receive from diagnostic procedures. The average mean dose was about 6 times higher than the physicians had estimated. The fundamental principles of radiation protection in medicine are justification and optimization of radiological protection. Referring medical practitioners have a major role in justification. They are responsible in terms of weighing the benefit versus the risk of a given radiological procedure.
Interventional diagnostic and therapeutic procedures that utilize fluoroscopy may also be a source of high radiation doses. Such procedures carry the risk of causing erythema to patients that receive high dose in single or repeated procedures. Some nuclear medicine procedures are also responsible for high radiation doses to patients.
As a rule of thumb one can assume that properly carried out diagnostic radiological procedures to any part of the body other than the pelvic region or when the primary X-ray beam is not passing through the foetus can be performed throughout pregnancy without significant foetal risk, if clinically necessary and justified. For radiological procedures where the primary beam intercepts the foetus, advice from the medical physicist should be obtained, who will calculate radiation dose to the foetus and, based on that, the practitioner and patient should make a decision. However, doses associated with radiotherapy procedures and interventional procedures are high and they require the attention of experts (including medical or health physicists, practitioners, and sometimes engineers and epidemiologists). In the case when a practitioner is responsible for a patient who has undergone a radiological procedure inadvertently and has subsequently been found to be pregnant, advice from the individuals listed above is needed. For more information, please click here where comprehensive information is provided not only for diagnostic radiology but also for nuclear medicine and radiotherapy.
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