Currently, if a research or clinical study requires both PET and MRI data, the patient must endure two exams in confining scanners, which is problematic for patients who suffer

from even mild claustrophobia. This duplication not only increases the discomfort (both physical and psychological) the patient must endure, but also effectively doubles the chances of motion during one or both scans with the subsequent need to rescan particular sequences or even the entire study. In light of the discussion in the previous section if, as some studies suggest, there is an added diagnostic benefit to combing PET and MRI, then it is of great import to minimize the difficulties associated with acquiring both data sets. The problem of patient anxiety and discomfort is a well-known phenomenon extending back (at least) mTOR inhibitor to the first few years after the widespread introduction of clinical MRI [86], [87], [88] and [89]. A review of the topic shows that as many as 37%

(range: 4%–-37%) of patients undergoing MRI had an anxiety-related reaction to the procedure [90] and [91]. In one study, which found that approximately 14% of MRI patients required some form of sedation to tolerate a standard-of-care MRI, the use of sedation was actually more common in patients who had already had previous MRI exams, indicating that familiarity with the procedure may not reduce stress related to the procedure [92]. The problem of anxiety and discomfort Dichloromethane dehalogenase during imaging is not unique to MRI, as similar issues arise for PET examinations. learn more It has been noted that a patient that is stressed and fidgeting can have elevated FDG uptake in skeletal muscle, which may adversely affect tumor-to-muscle ratio measurements [93]. Additionally, there is a well-known anxiety-induced increase in FDG uptake in brown fat that has been linked to false-positive

interpretations in 2%–4% of all studies, as well as false-negative interpretations due to brown fat uptake masking lesion detectability [94], [95] and [96]. The problem is often exacerbated in pediatric patients where stress-induced muscle tension, crying and the associated coughing can yield increased muscle FDG uptake [97]; these issues are well known amongst technologists, and efforts have been made to address the particular issues surrounding pediatric PET studies [98]. A final, extremely practical, point to note is that a combined PET–MRI exam would preclude the patient from having to endure the (sometimes lengthy) periods in multiple waiting rooms waiting for their scans. As many of these patients are missing work and/or traveling from far distances to undergo their testing, a combined exam would undoubtedly enhance their experience and make it more tolerable. For the cancer patient who already may not have a great deal of strength to attend these imaging tests, eliminating one set of waiting rooms and preps would be greatly appreciated.