Semiquantitative evaluation of 68Ga-DOTANOC uptake in the normal myocardium: establishment of reference values

BACKGROUND

To ascertain presence of physiological uptake and derive standardized uptake values (SUV) of 68Ga-DOTANOC in normal myocardium and establish reference values.

METHODS AND RESULTS

Dedicated cardiac 68Ga-DOTANOC PET/CT studies of patients referred for evaluation of cardiac sarcoidosis (CS) or myocarditis and found to be normal on visual assessment and on cardiac MRI were analyzed semiquantitatively. The studies were acquired 45-60 minutes after intravenous injection of 111-185 MBq of 68Ga-DOTANOC. Myocardial SUVmax normalized to lean body mass (SUVmax_lbm) values for septum, anterior wall, proximal lateral wall, distal lateral wall, inferior wall, and apical region were 1.12 ± .39, 1.09 ± .42, 1.26 ± .49, 1.16 ± .40, 1.23 ± .39, and 1.05 ± .40, respectively. Myocardial SUVmax_lbm-to-blood pool SUVmean_lbm ratios were calculated for each region and 95th percentile values of these ratios were considered the upper limit of normal. 95th percentile values of myocardial SUVmax_lbm-to-blood pool SUVmean_lbm ratio for the corresponding regions were 1.70, 1.70, 2.00 1.95, 2.05, and 1.70, respectively.

CONCLUSION

There can be physiological uptake of 68Ga-DOTANOC in normal myocardium and the reference values of semiquantitative parameters established in this study may be employed as a corroborative tool for visual assessment in patients undergoing 68Ga-DOTANOC PET/CT for suspected CS or myocarditis.

Utility of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Cardiac Infections

Diagnosis of cardiac infections, which includes infective endocarditis (IE) and cardiac device infections, despite having a high death rate, is still challenging. Frequently used modalities such as echocardiography, computed tomography (CT), and magnetic resonance imaging cannot confirm the presence of an active infection or extracardiac findings. Taking these things to consideration, newer guidelines have suggested the inclusion of 18F fluorodeoxyglucose positron emission tomography/CT (18F FDG PET/CT) in the workup of patients with suspected prosthetic valve IE. In this pictorial essay, we are demonstrating the utility of 18F-FDG PET/CT in varied cases of IE, cardiac implantable electronic devices, and coronary stent infection and how they helped in solving diagnostic dilemmas.

Imaging Acute Myocarditis with 68Ga-DOTANOC PET/CT

Somatostatin receptor (SSTR) imaging is a useful method in the diagnosis of acute myocarditis. We present a case of a 54-year-old male with a clinical diagnosis of acute myocarditis in whom, 68Ga-DOTANOC positron emission tomography/computed tomography PET/CT showed diffuse left ventricular myocardial uptake. SSTR imaging can act as a surrogate marker of active inflammation. SSTR imaging is useful in deciding site of biopsy, assessing response to therapy and for prognostication.

Global and Regional Gastric Emptying Parameters: Establishment of Reference Values and Comparison of Different Camera View Methods

PURPOSE OF THE STUDY

The purpose of the study is to establish the reference values of global and regional gastric emptying parameters (GEPs) using a standard vegetarian meal acceptable to the Indian population and compare the values derived on different camera view methods.

MATERIALS AND METHODS

Thirty-six consecutive healthy subjects with age ≥18 years underwent gastric emptying scintigraphy using anterior, posterior, and left anterior oblique (LAO) views. GEP was derived based on decay corrected counts in regions of interest defined on the whole and proximal stomach. Counts in the anterior and posterior view images were used to derive GEP based on geometric mean (GM) method. Comparison of GEP among different camera view methods was done with Friedman test and post hoc Wilcoxon signed-rank test after Bonferroni correction. Reference values were derived based on percentiles.

RESULTS

Rapid gastric emptying based on GM method was defined as percent retention <20% at 1 h while delayed emptying as percent retention >40% and >5% at 2 h and 4 h, respectively. The reference range of half-time of gastric emptying was 23-109 min. The reference value of intragastric meal distribution at time t = 0 was >64%, while the reference range of retention index was 0.7-1.3. Although the overall distribution of GEP derived on different camera view methods could be statistically significant (P < 1.00), the small differences in the derived reference values are likely to be of no clinical significance.

CONCLUSION

The reference values of GEPs established in this study can be generalized for the Indian population and may be applied to aid in clinical decision making. We recommend the GM method as the preferred method, although single view method (LAO preferred over anterior) can also be an acceptable alternative.

Predictors of Macrovascular Invasion and Extrahepatic Metastasis in Treatment Naive Hepatocellular Carcinoma: When Is [18F] FDG PET/CT Relevant?

Purpose

Hypermetabolic macrovascular invasion (MVI) and extrahepatic metastasis (EHM) occur in aggressive hepatocellular carcinoma (HCC) and carry unfavorable prognosis. [¹⁸F] FDG PET/CT, despite having low sensitivity in primary HCC, is valuable in patients with aggressive HCC for detection of hypermetabolic MVI and EHM. The study aimed at identifying the parameters that could predict hypermetabolic MVI and/or EHM in treatment naive HCC patients for tailored approach to utilize [¹⁸F] FDG PET/CT.

Methods

Data of 131 treatment naive HCC patients (median age, 60 years; range, 21-80 years; 90.8% males) who underwent [¹⁸F] FDG PET/CT were retrospectively analyzed to determine the proportion of patients with hypermetabolic MVI and/or EHM. Logistic regression analysis was performed to define independent predictors of hypermetabolic MVI and/or EHM.

Results

78/131 (59.5%) patients had hypermetabolic MVI and/or EHM. 52/131 (39.7%) patients had EHM. 56/131 (42.7%) patients had hypermetabolic MVI of which, 30 had concomitant EHM with majority (90%; 27/30) having distant metastasis. 26/131 (19.8%) patients had hypermetabolic MVI without EHM while 22/131 (16.8%) patients had EHM without hypermetabolic MVI of which, majority (95.5%; 21/22) had distant metastasis. Hypermetabolic MVI was associated with EHM (χ² = 7.868; p value = 0.007). AFP > 93.7 ng/ml, SUVmax > 3.5, and maximum tumor size > 5.0 cm were the independent predictors of hypermetabolic MVI and/or EHM.

Conclusion

In treatment naive HCC patients with AFP > 93.7 ng/ml or maximum tumor size > 5.0 cm, [¹⁸F] FDG PET/CT can be valuable.