Normative Data of Liquid Gastric Emptying and Small-bowel Transit: A Prospective Cross-sectional Study.

Purpose of the Study: The primary objective was to establish the reference values for liquid gastric emptying and small bowel. The secondary objectives encompassed comparing the anterior view and geometric mean methods, assessing gender differences, and exploring potential correlations with age. Materials and Methods: Thirty-five consecutive healthy participants (28 females and 7 males) with a mean age of 42 ± 11 years (median, 42; range, 23-65) underwent liquid gastric emptying scintigraphy at five intervals (0, 0.5, 1, 2, and 4 h), with optional additional imaging at 24 h. Liquid gastric emptying was evaluated using percent retention and half-time (T1/2). Small-bowel transit was assessed using the index of small-bowel transit (ISBT), calculated as the ratio of terminal ileal reservoir counts to total abdominal counts at 4 h. Reference values were established based on percentiles or mean and standard deviation (SD). Rapid small-bowel transit was determined through visual inspection. Statistical analysis involved paired Samples t-test or Wilcoxon signed-rank test for comparing imaging methods, independent Samples t-test or Mann-Whitney U-test for gender comparison, and Spearman's rank correlation for assessing age-related associations. A 2-tailed P < 0.05 indicated significance. Results: Rapid liquid gastric emptying based on the geometric mean method was defined as percent retention <8% at 30 min, while delayed emptying as percent retention >33%, >20%, and >4% at 1, 2, and 4 h, respectively. The reference range of T1/2 of gastric emptying was 10-60 min. The reference value for small-bowel transit using the geometric mean method was established as ISBT >30% at 4 h, while rapid small-bowel transit was defined as the first visualization of activity in the cecum-ascending colon within 1 h. Parameters for liquid gastric emptying and small-bowel transit were notably higher in the anterior view method compared to the geometric mean method (P ≤ 0.019), except for percent retention at 2 h (P = 0.510). Nevertheless, the obtained reference values, whether based on percentiles or mean and SD, showed no notable variance between the two methods to warrant clinical significance. Gender did not display an impact on liquid gastric emptying or small-bowel transit in either method (P ≥ 0.173), and age demonstrated no significant moderate or strong correlations (Spearman's ρ ≤ 0.397). Conclusion: The study determined reference values for liquid gastric emptying and small-bowel transit through a standard gastric emptying scintigraphy protocol, avoiding additional complex procedures or extended imaging sessions. The established normative data can apply to individuals of both genders aged ≥18 years. While advocating the geometric mean method as the primary choice, the study acknowledges that in busy centers handling multiple studies with limited resources and a single-head gamma camera catering to multiple studies, the anterior view method remains a feasible alternative.

Assessment of Small-bowel and Colonic Transit on Routine Gastric Emptying Scintigraphy: Establishment of Reference Values.

Purpose of the Study: The primary objective was to establish the reference values for small-bowel and colonic transit within the context of the routine standard solid meal gastric emptying scintigraphy (GES). The secondary objective was to compare the small-bowel and colonic transit between the anterior view and geometric mean methods. Materials and Methods: Twenty-nine healthy controls underwent routine GES, with additional imaging at 24 h if feasible. Small-bowel transit was assessed using the index of small-bowel transit (ISBT), calculated as the ratio of terminal ileal reservoir counts to total abdominal counts at 4 h. Colonic transit was evaluated using the colonic geometric center (CGC) by dividing the large bowel into four segments, with an additional fifth segment accounting for the eliminated counts. Reference values were established based on the fifth percentile or mean ± 1.96 standard deviations. Rapid small-bowel transit was visually determined. Paired Samples t-test or Wilcoxon signed-rank test, as applicable, was used to compare the small-bowel and colonic transit between the anterior view and geometric mean methods. For comparing small-bowel and colonic transit between females and males, the Independent samples t-test or Mann-Whitney U-test was applied, as appropriate. The correlation between age and small-bowel and colonic transit was assessed using Spearman's rank correlation analysis. Results: The reference value for small-bowel transit using the geometric mean method was established as ISBT >37% at 4 h, whereas rapid small-bowel transit was defined as the first visualization of activity in the cecum-ascending colon within 2 h. For colonic transit, the reference range was established as CGC 2.8-4.4 at 24 h. Comparing the anterior view and geometric mean methods, there were no significant differences in ISBT and CGC values (P ≥ 0.125). Gender did not affect small-bowel and colonic transit in both methods (P ≥ 0.378), and age showed no significant correlations (P ≥ 0.053). Conclusion: This study determined the reference values for small-bowel and colonic transit in the Indian population using routine GES, avoiding the need for additional complex procedures. The results may be generalized to the Indian population, emphasizing the importance of assessing small-bowel and colonic transit in patients with normal gastric emptying parameters to enhance gastrointestinal transit evaluation.

Utility of 99mTc-Sulfur Colloid Lymphoscintigraphy and SPECT/CT in Chylothorax and Chylous Ascites.

Purpose: To assess the diagnostic efficacy of 99mTc-sulfur colloid lymphoscintigraphy in chylothorax and chylous ascites, and the utility of single-photon emission computed tomography-computed tomography (SPECT/CT) in localizing the sites of leaks. Methods: Data from patients who underwent lymphoscintigraphy for clinical suspicion of chylothorax or chylous ascites were retrospectively analyzed. Biochemical fluid analysis was taken as the reference standard. Pleural fluid triglyceride level > 110 mg/dL (with pleural fluid/serum ratio > 1) and a cholesterol level < 200 mg/dL (with pleural fluid/serum ratio < 1) were considered confirmatory for chylothorax. Ascitic fluid triglyceride level > 200 mg/dL with a low cholesterol level (ascites fluid/serum ratio < 1) was considered confirmatory for chylous ascites. Results: 26 patients (15 males, 57.7%) aged 9 months to 68 years were enrolled in the study. Based on the reference standard, 17 had chylothorax or chylous ascites (9 with surgical history). Lymphoscintigraphy was positive in 16 (with 1 false positive) and negative in 10 (with 2 false negatives). The sensitivity, specificity, negative predictive value, positive predictive value, and accuracy of lymphoscintigraphy were 88.2% (63.6-98.5%), 88.9% (51.8-99.7%), 80.0% (51.6-93.8%), 93.8% (70.1-99.0%), and 88.5% (69.9-97.6%), respectively. SPECT/CT could localize sites of leaks in 61.5% (8/13) with a localization rate of 77.8% (7/9) and 25.0% (1/4) in patients with surgical and nonsurgical causes, respectively. Conclusion: 99mTc-sulfur colloid lymphoscintigraphy is a highly efficacious noninvasive modality to diagnose chylothorax or chylous ascites with a high positive predictive value. SPECT/CT could localize the sites of leaks more frequently in patients with surgical causes.

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.

Utility of 68Ga-DOTANOC PET/CT in therapeutic monitoring of cardiac sarcoidosis.

Cardiac sarcoidosis usually occurs as a manifestation of systemic sarcoidosis, even though isolated cardiac involvement is not uncommon. The usefulness of 68Ga-DOTANOC PET/CT in the diagnosis of CS has been previously documented in the literature. We present a case of cardiac sarcoidosis, where 68Ga-DOTANOC PET/CT was used for monitoring response to therapy.

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.

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.

Novel Quantitative PET Imaging Techniques in Tuberculosis.

The role of fluorodeoxyglucose (FDG)-PET/computed tomography (CT) in tuberculosis (TB) continues to expand in disease detection, assessment of the extent of the disease, and treatment response monitoring. This article reviews available data regarding the use of FDG-PET/CT in patients with TB. A new method of quantification for patients with TB is introduced. This method produces robust parameters that represent the total disease burden.

Equilibrium Radionuclide Angiography in Evaluation of Left Ventricular Mechanical Dyssynchrony in Patients with Dilated Cardiomyopathy: Comparison with Electrocardiographic Parameters and Speckle-Tracking Echocardiography.

PURPOSE OF THE STUDY: The purpose of this study was to study the role of equilibrium radionuclide angiography (ERNA) in the assessment of left ventricular (LV) mechanical dyssynchrony in patients with dilated cardiomyopathy (DCM), by correlating the findings with electrocardiographic parameters and speckle-tracking echocardiography (STE). METHODS: This was a prospective observational study. A total of 55 patients with a mean age 42.5 ± 11 years (range: 19-61 years) diagnosed with DCM underwent ERNA and echocardiography sequentially. On ERNA, phase images of LV were obtained, and standard deviation of LV mean phase angle (SD LVmPA) was derived to quantify intra-LV mechanical dyssynchrony (ILVD). Similarly, on STE, "dyssynchrony index" was calculated as the standard deviation of time-to-peak systolic circumferential strain (SDCS) of the six mid-LV segments. The cutoff values used to define mechanical dyssynchrony were SD LVmPA >13.2° (or >27.1 ms) and SDCS >74 ms on ERNA and STE, respectively. The results obtained from the two modalities were then compared. RESULTS: Speckle-tracking analysis could be done on the echocardiographic data of only 42 patients. Paired data from ERNA and STE studies of these 42 patients (26 males and 16 females) were compared, which showed no significant difference in the detection of ILVD (P = 0.125). The two modalities showed good agreement with Cohen's kappa value of 0.78 (P < 0.0001). SD LVmPA and SDCS values showed moderately strong linear correlation (ρ = 0.69; P < 0.0001). No significant association of mechanical dyssynchrony on ERNA or STE was found with QRS duration and with the presence or absence of left bundle branch block. ILVD was also found to be negatively correlated with LV ejection fraction. CONCLUSION: ERNA is comparable to STE for the assessment of LV mechanical dyssynchrony.

Tc-99m Glucoheptonate Single Photon Emission Computed Tomography-Computed Tomography for Detection of Recurrent Glioma: A Prospective Comparison with N-13 Ammonia Positron Emission Tomography-Computed Tomography.

PURPOSE OF THE STUDY: To assess the efficacies of Tc-99m glucoheptonate single photon emission computed tomography-computed tomography (Tc-99m GHA SPECT-CT) and N-13 ammonia positron emission tomography-computed tomography (N-13 NH3 PET-CT) in detecting recurrent glioma. MATERIALS AND METHODS: Fifty-five consecutive, histologically proven, and previously treated glioma patients (age, 38.9 ± 12.2 years; 61.8% males) presenting with clinical suspicion of recurrence were evaluated with Tc-99m GHA SPECT-CT and N-13 NH3 PET-CT. Images were evaluated both qualitatively and semiquantitatively. A combination of clinicoradiological follow-up, repeat imaging, and/or biopsy (when available) was considered as the reference standard. RESULTS: Based on the reference standard, 28/55 (50.9%) patients had recurrence. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy of Tc-99m GHA SPECT-CT, and N-13 NH3 PET-CT were 85.7%, 85.2%, 85.7%, 85.2%, 85.5% and 78.6%, 88.9%, 88.0%, 80.0%, 83.6%, respectively (concordant findings in 46 patients). The performances of the two modalities were equivalent both in overall and subgroup McNemar analyses (P = 0.508, overall; P = 0.687, low grade; P = 1.000, high grade). CONCLUSION: Tc-99m GHA SPECT-CT is an alternative imaging modality equally efficacious as N-13 NH3 PET-CT in detecting recurrent glioma.

Surgical Scar Site Recurrence in Patients With Cervical Cancer on 18F-FDG PET-CT: A Case-Control Study.

PURPOSE: The purpose of this study was to assess the role of fluorine 18 ((18)F)-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG PET-CT) in evaluating various parameters in patients with surgical scar site recurrence in cervical carcinoma. METHODS: Data of all patients with cervical cancer (n = 329) who underwent PET-CT at our institute between 2005 and 2013 was reviewed. Of these 329 patients, 132 patients who were surgically treated and underwent restaging/follow-up PET-CT were included in the present study for final analysis. Tumor recurrence at the abdominal surgical scar site was looked for. Abnormal uptakes suggestive of active disease at other sites were also noted. Maximum standardized uptake value was measured for all the lesions. Patients with scar site recurrence were taken as cases (n = 6), whereas the remaining patients served as controls (n = 126). Comparison with conventional imaging modalities was made wherever available. Histopathological examination was always sought for. RESULTS: The incidence of scar site recurrence after surgery was found to be 4.5% (6/117). A total of 56 of 132 patients had recurrent disease, including 6 patients with scar site recurrence. All of the patients with scar site recurrence also had recurrent disease at other sites (local, nodal, or distant). Conventional imaging modalities were available in 4 of these 6 patients and detected scar site recurrence in 3 of those 4 patients. In patients with scar site recurrence, the mean ± SD time to scar site recurrence was 14.0 ± 10.9 months (median, 10 months; range, 7-36 months). Significant difference was seen between cases and control for International Federation of Genecology and Oncology stage (P = 0.001) and nodal recurrence (P = 0.007). Additionally, age, nodal recurrence, distant recurrence, and scar site recurrence were significantly associated with death. CONCLUSIONS: Scar site recurrence carries a poor prognosis, and the incidence is much higher than previously known when PET-CT is used as a modality for its detection.

Perfusion-metabolism coupling in recurrent gliomas: a prospective validation study with 13N-ammonia and 18F-fluorodeoxyglucose PET/CT.

INTRODUCTION: We assessed the validity of "perfusion-metabolism coupling" hypothesis in recurrent glioma with 13N-ammonia (13N-NH3) PET/CT and 18F-fluorodeoxyglucose (18F-FDG) PET/CT. METHODS: Fifty-six consecutive patients (age, 38.8 ± 12.1 years; 62.5% males) with histologically proven and previously treated glioma presenting with clinical suspicion of recurrence were prospectively enrolled and evaluated with 13N-NH3 PET/CT and 18F-FDG PET/CT. PET/CT images were evaluated both qualitatively and semiquantitatively. Tumor to white matter uptake ratio (T/W) and tumor to gray matter uptake ratio (T/G) were calculated and analyzed for both the modalities. A combination of clinico-radiological follow-up, repeated imaging, and biopsy (when available) were considered as the reference standard. RESULTS: Based on the reference standard, 27/56 patients had recurrence. 13N-NH3 PET/CT and 18F-FDG PET/CT were concordant in 55/56 patients. Overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 13N-NH3PET/CT were 77.8, 86.2, 84.0, 80.7, and 82.1%, respectively, and for 18F-FDG PET/CT were 77.8, 89.7, 87.5, 81.2, and 83.9%, respectively. There was excellent agreement between results of 13N-NH3 PET/CT and 18F-FDG PET/CT (ĸ = 0.964; P < 0.001). The performances of 13N-NH3 PET/CT and 18F-FDG PET/CT were not significantly different between high-grade and low-grade glioma (P = 1.000). A strong positive correlation was noted between the uptake ratios derived on the two modalities (ρ = 0.866, P < 0.001 for T/W; ρ = 0.918, P < 0.001 for T/G). CONCLUSION: A combination of 13N-NH3 PET/CT and 18F-FDG PET/CT demonstrates that perfusion and metabolism are coupled in recurrent gliomas. These tracers target two different but interrelated aspects of the same pathologic process and can be used as surrogates for each other.

Can (18)F-FDOPA PET/CT predict survival in patients with suspected recurrent glioma? A prospective study.

UNLABELLED: Purpose of the present study was to evaluate the role of (18)F-FDOPA PET/CT for predicting survival in patients with suspected recurrent glioma. METHODS: A total of 33 previously treated, histopathologically proven glioma patients with clinical and contrast enhanced MRI findings suspicious for recurrence were enrolled in this prospective study. All patients underwent (18)F-FDOPA PET/CT. Ratios of tumor uptake to normal tissue uptake were generated by dividing the tumor SUVmax with SUVmax of the contralateral normal brain tissue (T/N), normal striatum (T/S), normal white matter (T/W) and normal cerebellum (T/C). Patients were followed up clinically and by repeated imaging. Data was censored, if the patient died of disease or at the end of the study. Survival analysis was performed for the distributions of each variable and by multivariate analysis. RESULTS: (18)F-FDOPA PET/CT was positive for recurrence in 25 patients and negative in 8. Death occurred in nineteen patients. Median follow up period was 20.2 months. Median survival in this study was 39.2 months. In univariate analysis significant association of survival was noted with results of (18)F-FDOPA PET/CT (P=0.007) and (18)F-FDOPA PET/CT quantitative parameters namely SUVmax (P=0.001), T/S (P=0.005), T/W (P=0.0004), T/N (P=0.001) and T/C (P=0.003) were found to be significant. On multivariate analysis, only MRI size of the recurrent tumor (P=0.002) and T/N ratio of (18)F-FDOPA PET/CT (P=0.005) were found to be independent predictors of survival. CONCLUSION: T/N ratio on (18)F-FDOPA PET/CT is an independent predictor of survival in patients with suspected recurrent glioma, along with size of recurrent tumor on MRI.

Solitary breast metastasis from recurrent gallbladder carcinoma simulating a second primary on 18F-FDG PET/CT.

Gallbladder carcinoma is characterized by poor prognosis. It spreads by direct, lymphatic, vascular, neural, intraperitoneal, and intraductal routes. The most commonly involved organ is the liver followed by regional lymph nodes. Extra-abdominal metastases are comparatively rare. We present a case of solitary breast metastasis from recurrent gallbladder carcinoma mimicking a primary breast cancer in (18)F-FDG PET/CT.

13N-Ammonia PET/CT for detection of recurrent glioma: a prospective comparison with contrast-enhanced MRI.

PURPOSE: We assessed the value of N-ammonia PET-computed tomography (PET/CT) in recurrent glioma and compared the results with those of contrast-enhanced MRI (CE MRI). MATERIALS AND METHODS: Fifty-two (mean age, 39.8±11.6 years; male, 33; female, 19) histopathologically proven and previously treated glioma patients with clinical suspicion of recurrence were evaluated with 13N-ammonia PET/CT and CE MRI. PET/CT images were evaluated qualitatively and quantitatively (maximum standardized uptake value). Tumour to white matter (T/W), tumour to grey matter (T/G) and tumour to pituitary (T/P) ratios were calculated and cutoff levels were derived with receiver operating characteristic curve analysis. Sensitivity, specificity and predictive values were compared. A combination of clinical follow-up, repeat imaging and biopsy (when available) was taken as the reference standard. RESULTS: On the basis of the reference standard, 23 out of 52 patients were seen to have recurrence. Overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 13N-ammonia PET/CT were 82.6, 86.2, 82.6, 86.2 and 84.6%, respectively, whereas those of CE MRI were 96.7, 48.3, 59.5, 93.3 and 69.2%, respectively. Overall, 13N-ammonia PET/CT was statistically superior to CE MRI (P=0.001). In low-grade tumours, 13N-ammonia PET/CT performed better than MRI with an accuracy of 86.8 versus 68.4% (P=0.003). In high-grade tumours, both the modalities had comparable performances with accuracies of 78.6% for N-ammonia PET/CT and 71.4% for CE MRI (P=0.250). Among the ratios, T/P was the most useful, with the largest area under the curve (0.825; P=0.0001). CONCLUSION: N-Ammonia PET/CT shows higher accuracy compared with contrast-enhanced MRI for detecting recurrent gliomas, particularly in low-grade tumours.

Diagnostic accuracy of 18F-FDG PET/CT for detecting recurrence in patients with primary skeletal Ewing sarcoma.

PURPOSE: To evaluate the diagnostic accuracy of (18)F-FDG PET/CT for detecting recurrence in patients with primary skeletal Ewing sarcoma. METHODS: We retrospectively analysed data from 53 patients (age 20.1 ± 10.5 years, 39 male) who had undergone 71 (18)F-FDG PET/CT studies for suspected recurrence (52 studies) or for routine follow-up (19 studies) after primary therapy of skeletal Ewing sarcoma. (18)F-FDG PET/CT studies were evaluated qualitatively and quantitatively (maximum standardized uptake value, SUVmax) by two nuclear medicine physicians in consensus. Sensitivity, specificity, predictive values and accuracy were calculated on per study basis. Clinical/imaging follow-up (minimum 6 months) and/or histopathology (when available) were taken as the reference standard. RESULTS: Of the total of 71 (18)F-FDG PET/CT studies, 42 (59.1%) were positive for recurrence and 29 (40.9%) were negative for recurrence. Local recurrence was most common (38 studies) followed by bone metastasis (9 studies), and node and lung metastasis (2 studies each). Of the 71 studies, 38 were true-positive, 27 were true-negative, 4 were false-positive and 2 were false-negative. Overall per study based sensitivity was 95%, specificity was 87%, PPV was 90%, NPV was 93% and accuracy was 91.5%. No significant difference was found in the accuracy of PET/CT between the suspected recurrence group and the routine follow-up group (94% vs. 84%; P = 0.390). Overall mean lesion SUVmax was 7.8 ± 4.1 (range 1.9-17.2). No site-based difference was found in SUVmax. CONCLUSION: (18)F-FDG PET/CT demonstrates high diagnostic accuracy for detecting recurrence in patients with primary skeletal Ewing sarcoma, when it is suspected (clinically or on imaging) or during routine follow-up.

Comparative diagnostic accuracy of contrast-enhanced MRI and (18)F-FDOPA PET-CT in recurrent glioma.

OBJECTIVES: To compare the diagnostic accuracy of contrast enhanced magnetic resonance imaging (Ce-MRI) and (18)F-fluorodopa ((18)F-FDOPA) positron emission tomography (PET)-computed tomography (CT) for detecting recurrent glioma. METHODS: In this prospective study, 35 patients (age, 36.62 ± 0.86 years; 80 % male) with histopathologically proven glioma with clinical suspicion of recurrence were evaluated using Ce-MRI and (18)F-FDOPA PET-CT. (18)F-FDOPA PET-CT images were evaluated qualitatively and semi-quantitatively. Combination of clinical follow-up (minimum 1 year), repeat imaging and/or biopsy (when available) was taken as the reference standard. RESULTS: Based on the reference standard, 26 patients were positive and nine were negative for recurrence. The sensitivity, specificity and accuracy of Ce-MRI were 92.3 %, 44.4 % and 80 % respectively, whereas those of (18)F-FDOPA PET-CT were 100 %, 88.89 % and 97.1 % respectively. Results of Ce-MRI and (18)F-FDOPA PET-CT were concordant in 74.3 % (29/35) and discordant in 17.1 % of patients (6/35). On McNemar analysis the difference was not statistically significant overall (P = 0.687), for high-grade tumour (P = 0.5) or low-grade tumours (P = 1.0). However, (18)F-FDOPA PET-CT was more specific than Ce-MRI overall (P = 0.0002), for high-grade tumour (P = 0.006) and low-grade tumours (P = 0.004). CONCLUSION: F-FDOPA PET-CT shows a high but comparable diagnostic accuracy to Ce-MRI for the detection of recurrent glioma. However, it is more specific than Ce-MRI. KEY POINTS: • Recurrent glioma in the postoperative site remains a diagnostic dilemma. • (18) F-FDOPA PET-CT shows high diagnostic accuracy for detecting recurrent glioma. • Diagnostic accuracies for (18) F-FDOPA PET-CT and contrast enhanced MRI are comparable. • However, (18) F-FDOPA PET-CT is more specific than Ce-MRI for recurrent glioma.