Background Corticotrophin releasing hormone (CRH) is the major regulator of ACTH secretion from the anterior pituitary and acts via CRH-1 receptors (CRH-1R). Corticotropinoma though autonomous still retain their responsiveness to CRH and hence, we hypothesize that in vivo detection of CRH-1 receptors on pituitary adenoma using Gallium-68 ( 68Ga) tagged CRH can indicate the functionality of adenoma and combining it with Positron emission tomography-computed tomography (PET-CT) can provide requisite anatomical information. Methods Subjects with ACTH dependent Cushing's syndrome (CS) [n = 27, 24: Cushing's disease (CD), 3: ectopic Cushing's syndrome (ECS)] underwent 68Ga CRH PET-CT. Two nuclear medicine physicians read these images for adenoma delineation and superimposed them on MRI sella. The information so provided was used for intra-operative navigation and compared with operative and histopathological findings. Findings 68Ga CRH PET-CT correctly delineated corticotropinoma in all the 24 cases of CD, including the ten cases with size < 6mm (four cases negative on MRI). Corticotropinoma location on 68Ga CRH PET fusion images with MRI were concordant with operative findings and further confirmed on histopathology. There was no tracer uptake in pituitary in two patients with ECS while in another, the diffuse uptake in pituitary suggested ectopic CRH production. Conclusion 68Ga CRH PET-CT represents a novel non-invasive molecular imaging targeting CRH receptors that not only delineates corticotropinoma and provides surgeon with valuable information for intra-operative tumour navigation but also helps in differentiating pituitary from extra-pituitary source of ACTH dependent Cushing’s syndrome.

The present study aimed to optimize the injected dose of 18 F-FDG in whole-body PET/CT scans and assess its effect on noise-equivalent count rate (NECR) and visual image quality (IQ). Methods: Patients scheduled to undergo 18 F-FDG PET/ CT were prospectively recruited in the study from January to December 2019, regardless of the indication or underlying disease. Patients were divided into 4 groups and injected with different amounts of 18 F-FDG radioactivity per kilogram of body weight (1.85, 3.7, 5.5, and 7.4 MBq/kg). All patients underwent 18 F-FDG PET/CT studies, and NECR local was calculated by noting the trues rate, total prompts, and randoms rate for each bed position. Whole-body NECR global was calculated as the average NECR for all bed positions. IQ was qualitatively assessed for each bed position (IQ local ) and for whole-body PET (IQ global ) by 2 readers using 5-point scores based on prevalence of noise, contrast, and lesion detectability. NECR and IQ were compared among all 4 activity groups. Patients were also subdivided into 4 body-mass-index groups (group I, 15-20 kg/m 2 ; group II, 20.1-25 kg/m 2 ; group III, 25.1-30 kg/m 2 ; and group IV, 30.1-35 kg/m 2 ) for comparison. A P value of less than 0.05 was considered significant. Results: In total, 109 patients underwent 18 F-FDG PET/CT studies after injection of different amounts of 18 F-FDG radioactivity and a mean uptake time of 62.32 min. The mean NECR global and IQ global for each group were significantly different from other groups (P , 0.05), with NECR and IQ being higher in high-activity groups than in low-activity groups. The overall IQ was acceptable in all patients, even in the lowest-activity group (1.84 MBq/kg). The mean NECR global and IQ global were significantly different in all 4 body-mass-index groups (P , 0.05), except between groups II and III (P . 0.05). NECR local and IQ local correlated moderately (r 5 0.64). Conclusion: Optimization of injected 18 F-FDG radioactivity from 7.4 MBq/kg (200 μCi/kg) to 1.85 MBq/kg (50 μCi/kg) resulted in acceptable IQ, despite a reduction in NECR.

Purpose of the Report Tuberculosis (TB) is a major health problem. Activated macrophages in TB lesions show high metabolic activity and can be assessed using 18F-FDG PET/CT. This retroprospective study was done to evaluate the utility of 18F-FDG PET/CT in initial assessment and therapeutic response in patients with TB. Materials and Methods Eighty-seven patients (male-to-female ratio, 46:41) diagnosed with pulmonary TB and extrapulmonary TB underwent whole-body 18F-FDG PET/CT for initial assessment and a follow-up scan 3 to 4 months after initiation of antitubercular therapy (ATT). Visual and semiquantitative (SUVmax) analyses were used for scan assessment. Treatment responses on interim scans were categorized as complete metabolic response (CMR), favorable response to therapy (FRT), stable disease (SD), and disease progression (DP). CMR, FRT, and SD cases were considered as responders and DP cases as nonresponders. Treatment response was correlated with clinical outcome (mortality) and ATT duration. Results Baseline 18F-FDG PET/CT scans were positive in all the patients and detected additional disease sites than suspected clinically in 72% patients. On interim PET/CT, 13 patients showed CMR, 43 showed FRT, 8 showed SD, and 23 showed DP. A longer duration of ATT was seen in nonresponders (P ≤ 0.001) than responders. During follow-up, 9/87 patients died, out of which 8 patients were of DP group and 1 patient belonged to SD. Nonresponders showed 35% mortality compared with 1.6% in the responder group (P ≤ 0.001). Conclusions 18F-FDG PET/CT is a valuable imaging modality for disease mapping and assessing therapeutic response. Treatment response in the interim PET/CT done at 3 to 4 months predicted the duration of ATT and clinical outcome of the patients.

18F-FDG PET/CT imaging is an important diagnostic tool for accurate staging and assessment of response to neoadjuvant chemotherapy (NACT) in patients with locally advanced breast carcinoma (LABC). However, 18F-FDG being non-specific marker, it also accumulates in inflammatory conditions, leading to false positive results. Angiogenesis, an essential characteristic for tumor development, intrusion and metastasis can be imaged using 68Ga-labeled RGD tripeptide. We here depict a series of clinically staged LABC patients who underwent both 68Ga-DOTA-RGD2 and 18F-FDG PET/CT imaging for staging and illustrate the similarities and significant differences between the two tracers.