Adequate patient preparation to suppress the physiologic uptake of FDG by the normal myocardium is essential when performing PET imaging for inflammation. There are multiple protocols (Table 6.2) that have been used by different centers and no clear data to support the superiority of any one particular method. Cheng et al. studied 63 patients referred for oncologic imaging, and found that a low carbohydrate diet followed by a fast resulted in greater reduction in SUV (versus a controlled group of patients following an unrestricted diet) than a high fat low carbohydrate diet in which patients also drank a 250 cc beverage of mostly non-saturated fat 1 h prior to FDG injection [7]. Recently, Demeure et al. showed that a high fat low carbohydrate diet followed by a 12 h fast effectively suppressed FDG uptake in most (8 out 9) subjects. In their study, and consistent with the results of Cheng et al. administering an extra fat load 1 h before the scan did not offer any benefit [8]. Based on these two studies, administering a high fat beverage prior to imaging is not recommended. It is possible that such an approach of overloading the myocardium with free fatty acids could increase myocardial oxygen consumption leading to a paradoxical increase in glucose metabolism. In general, even under optimal conditions, approximately 10 % of patients may have diffuse non-specific uptake of FDG by the myocardium.

At our center we recommend a high fat/low carbohydrate diet for two meals prior to the scan followed by a fast of at least 4 h. Prior to imaging, all patients are asked about their diet, and if there are any issues (i.e. patient inadvertently ate carbohydrates), the study is postponed. In addition, patients are asked to avoid any strenuous exercise for 1 day prior to the scan. In patients who are unable to follow this diet (e.g. NPO for other medical reasons) we suggest a prolonged fast of at least 18 h.

FDG image acquisition is typically performed 90 min after the administration of 10–12 mCi of F18-FDG although a shorter uptake period of 60 min has also been used by some centers. Our suggested protocol includes:

Whole body FDG is an important component of the cardiac PET exam as this information can identify the presence and severity of extra cardiac disease. When present, such disease may help inform the role of anti-inflammatory therapies. In addition, when the diagnosis of sarcoidosis is uncertain, the presence of extra cardiac FDG avid disease may identify potential biopsy targets that are more accessible than the heart. These images should be interpreted by a physician who is trained at body PET/CT as it is important to recognize normal distribution of FDG by various organs from pathologic uptake.

Image interpretation requires simultaneous visualization of both rest MPI and FDG PET images. Normal scans will have complete suppression of FDG from the myocardium with normal resting perfusion (Fig. 6.1). At times, patients without cardiac disease may also have diffuse homogenous uptake of FDG by the myocardium. This pattern should be distinguished from diffuse patchy myocardial involvement which can be seen in patients with extensive myocardial inflammation.