The evolving hybrid systems of PET/CT and SPECT/CT: A threat to the sovereignty of nuclear medicine

摘要

The propagation of the hybrid PET-CT & SPECT-CT systems, as a routine test for all requests for the conventional SPECT & PET imaging could be regarded as a threat to the nuclear medicine integrity. Though informative in some selected cases, it may actually lead to misinterpretation of the imaging results and confusion in clinical decision making in most other cases. On the other hand, fusion of the anatomic and functional results in a hardware format in most of the time is a time-consuming, complex job for the interpreter, making conflict among the radiologists and nuclear medicine specialists.In most cases, PET and SPECT images contain enough information to answer relevant clinical questions. Additional information may be retrieved from the referring physician or from previous imaging, such as CT, Sonography, or MRI. According to the most recent literature, there is a need to look at CT images in only about 20% of cases and even in the majority of such cases, visual fusion gives sufficient information with no actual need for soft- or hardware image fusion. In cases in which more accurate localization is required, software fusion can be used to align the two sets of images. Since the main purpose of the CT scan in this combination is co-registration and attenuation correction and on the other hand in most cases the patient has already undergone a high-quality diagnostic CT scan before referral for PET or SPECT, even a single-slice CT scan is sufficient; but unfortunately In the evolving modern scanners a multislice scanner is attached to the PET/SPECT system, with implying a second considerable radiation dose. While a standard PET scan delivers a radiation dose to the body of 5–10 mSv, using a modern multislice CT, the received dose may be between 10 to 20 mSv. This would be a significant increase in total radiation to the patient and could be considered a real health problem. Even in the case of attenuation correction, It would be poor radiation safety to acquire a whole-body CT scan only for faster attenuation correction. The last but not the least is that the purchase of a combined PET/CT or SPECT/CT scanner is quite costly. The difference in price between a Hybrid unit and a dedicated PET or SPECT scanner is sufficiently large to warrant reconsidering the budget and the ongoing plans to establish such centers.