Third-order nonlinear optical properties of highly electron deficient, nonplanar push-pull porphyrins: ß-nitro-hexa-substituted porphyrins bearing bromo, phenyl, and phenylethynyl groups.

ß-Heptasubstituted porphyrins [MTPP(NO2)X6; M = 2H, NiII, CuII, and ZnII; X = Br, Ph, and PE] were synthesized and their third-order nonlinear optical (NLO) properties explored using the single-beam Z-scan technique with femtosecond, MHz pulses in the visible range. The three-photon absorption (γ), third-order nonlinear optical susceptibility (χ3), three-photon absorption cross-section (σ3), and nonlinear refractive index (n2) have been determined from theoretical fits with experimental results. The sign and magnitude of the nonlinear refractive index (n2) have been obtained from the closed-aperture experiment while the three-photon absorption coefficient and three-photon absorption cross-section were determined from the open-aperture experiment. The magnitudes of the 3PA and σ3 extended in the range of (2.7-3.4) × 10-23 cm3 W-2 and (5.5-7.0) × 10-78 cm6 s2, respectively. The higher magnitude of the NLO coefficients ensures their utility in optical and photonic applications.

68Ga-DOTA.SA.FAPi as a Versatile Diagnostic Probe for Various Epithelial Malignancies: A Head-to-Head Comparison with 18F-FDG.

RATIONALE AND OBJECTIVES: Fibroblast Activation Protein (FAP) expressing cancer-associated fibroblasts has been a major breakthrough causing a paradigm shift in targeted theranostics focusing on the tumor microenvironment. In this study, a squaric acid derivative DOTA.SA.FAPi (SA.FAPi) has been evaluated as a potential diagnostic probe in diverse epithelial cancers and compared to the standard-of-care 18F-FDG. METHODS: 25 patients enrolled in this prospective study underwent 18F-FDG and 68Ga-SA.FAPi PET scans on two different days. For biodistribution, standardized uptake values (SUV) were computed by delineating region-of-interest on various body organs. For comparative analysis in disease identification, lesion tracer uptake was quantified using SUVs corrected for lean body mass (SUL), SUVmax, tumor-to-background ratio (TBR) with liver and blood pool as the reference, total lesion glycolysis (TLG for 18F-FDG) and total lesion FAP expression (TLF for 68Ga-SA.FAPi). RESULTS: 25 patients (mean age: 58 ± 8 years) with four types of cancers including hepatocellular carcinoma (HCC, 56% of cohort), gall bladder carcinoma (GB Ca, 12%), adrenocortical carcinoma (ACC, 16%), and breast carcinoma (breast Ca, 16%) were prospectively evaluated. Physiological tracer uptake of 68Ga-SA.FAPi was noted in the salivary glands, thyroid, liver, pancreas, muscles and kidneys with variable uptake in the lacrimal glands, extra-ocular muscles, oral mucosa and uterus. Lesion-based comparative analysis between both the radiotracers demonstrated complete concordant findings in detection of all primary lesions and distant metastases in liver, bones, adrenals and peritoneum whereas discordant findings were noted in lung nodules (20%) and lymph nodes (13%). In overall analysis, 68Ga-SA.FAPi exhibited significantly higher SUVmax (10.3 vs 8.8, p-0.019), SULpeak (6.8 vs 4.9, p-0.000) and SULavg (5.4 vs 4.1, p-0.019) in comparison to 18F-FDG whereas TBR was comparable for both the tracers [TBRLiver: median 1.9 (IQR: 2.6-1.4) vs 1.8 (2.6-1.1), p-0.275; TBRBloodpool: 2.1 (3.7-1.4) vs 2.0 (2.7-1.4), p-0.207]. In subcategorical analysis, 68Ga-SA.FAPi demonstrated higher SUVmax, SULpeak and SULavg values for primary disease (SUVmax: 14.8 (18.7-9.7) vs (12.9-6.6), p-0.087; SULpeak: 8.2 (11.2-6.8) vs 6.3 (8.5-4.4), p-0.037; SULavg: 6.9 ± 2.5 vs 5.1 ± 2.2, p-0.023] and distant metastases (8.8 vs 7.2, p-0.038); 6.3 (8.8-4.4) vs 3.6 (4.4-2.0), p-0.000; 5.4 vs 3.5, p-0.000] whereas comparable values were noted for both the tracers in nodal metastases [9 (13.5-4.1) vs 8 (12.7-4.7), p-0.726; 4.5 (6.2-1.8) vs 4.3 (5.7-2.2), p-0.727; 4.1 ± 2.3 vs 3.7 ± 1.8, p-0.129]. In primary disease, highest 68Ga-SA.FAPi avidity was noted in ACC followed by GB Ca and HCC. In distant metastases, gall bladder, lung and skeletal lesions demonstrated higher 68Ga-SA.FAPi avidity. Moreover, 68Ga-SA.FAPi identified five additional lung lesions which were missed by 18F-FDG in one case of ACC. CONCLUSION: 68Ga-SA.FAPi emerged as an effective, versatile diagnostic probe for imaging various epithelial malignancies similar to 18F-FDG.

68 Ga-DOTA.SA.FAPI as a Potential, Noninvasive Diagnostic Probe for Recurrent and Metastatic Adrenocortical Carcinoma : A Head-to-Head Comparison With 18F-FDG.

ABSTRACT: Metastatic or recurrent adrenocortical carcinoma (ACC) is a potentially fatal malignancy, which poses major challenges in disease management owing to lack of effective systemic therapies. The drastically reduced survival rates require prompt identification of selective molecules for development of targeted therapeutics. We evaluated the squaric acid containing FAPI derivative, DOTA.SA.FAPI (FAPI), as a potential diagnostic probe in 2 cases of histopathologically proven metastatic and recurrent ACC. Both patients underwent 18 F-FDG and 68 Ga-FAPI PET/CT scans for comparative analysis. 68 Ga-DOTA.SA.FAPI emerged as an excellent diagnostic agent for ACC and performed similar to 18 F-FDG.

68Ga-DOTAGA-IAC PET/CT for Imaging Metastatic and Recurrent Adrenocortical Carcinoma: A Case Series.

ABSTRACT: Adrenocortical carcinoma (ACC) is a rare malignancy with a prevalence of 1 to 2 cases/million/year. The diagnosis depends upon endocrine workup followed by imaging with CT, MRI, and 18F-FDG PET/CT. The treatment includes surgical resection, debulking surgery, chemotherapy, and radiotherapy. However, patients do not respond well to any of the available therapies. We present noninvasive imaging of histopathology-proven ACC patients using 68Ga-DOTAGA-IAC PET/CT, specific for integrin αvß3. 68Ga-DOTAGA-IAC PET/CT 45 minutes after IV injection showed a decent tumor-to-background ratio and could be used as a promising radiotracer for metastatic and recurrent ACC.

Potential Role of 68Ga-NOTA-Duramycin PET/CT Imaging for Early Response Evaluation in a Lymphoma Patient: A Case Report.

ABSTRACT: Duramycin, a 19 amino acids peptide, is known for its potential to target phosphatidylethanolamine. During cell death (apoptosis), rearrangement of membrane phospholipids results in the externalization of phosphatidylethanolamine to the outer leaflet of the cell membrane, which can be imaged using 68Ga-NOTA-duramycin. We report 68Ga-NOTA-duramycin imaging in a 50-year-old man with biopsy-proven diffuse large B-cell lymphoma planned for anthracycline-based chemotherapy. 68Ga-NOTA-duramycin PET/CT imaging along with 18F-FDG PET/CT was performed before and after 2 cycles of chemotherapy. The tracer avidity in interim 68Ga-NOTA-duramycin PET/CT showed its diagnostic potential to assess early response to chemotherapy.

Radiation Exposure to the Personnel Performing Myocardial Blood Flow Quantification Study Using 13N-ammonia Positron Emission Tomography/Computed Tomography.

Purpose: The present study aimed to evaluate radiation exposure to staff performing coronary flow reserve (CFR) measurement using 13N-ammonia. Materials and Methods: The radiation exposure rate during the administration of 13N-ammonia for the rest and stress part of the study was noted using an ionization chamber-based calibrated survey monitor. The radiation exposure to persons involved in dispensing radioactivity (D1), administering radioactivity (D2) and monitoring the patient during pharmacological stress (D3) were measured using an energy compensated Si-diode personal pocket dosimeter. Results: The average dose received by individuals with dosimeters D1, D2, and D3 was 1.28 ± 0.79 µSv, 1.56 ± 0.51 µSv, and 0.88 ± 0.97 µSv per injection, respectively, during the rest of study and 1.56 ± 0.96 µSv, 2.64 ± 1.22 µSv, and 2.2 ± 1.7 µSv per injection, respectively, during stress study. The average exposure rate during the administration of 13N-ammonia at 0.5 m and 1.5 m from the injection site was found to be 259 µSv/h and 53.4 µSv/h, respectively, during the rest study and 301 µSv/h and 67.25 µSv/h, respectively, during stress study. Conclusion: The exposure to the staff performing CFR study with 13N-ammonia was well within prescribed limits by the International Commission on Radiological Protection 103. The CFR measurement with 13N-ammonia positron emission tomography/computed tomography can be included in routine workups of cardiac patients without the fear of radiation exposure.

Ex vivo Measurement of the Radioactivity of PET/CT-Guided Biopsy Specimen: Is it Helpful to Confirm the Sampling from a Viable Region of the Tumor and the Nature of the Lesion?

Objective: Ex vivo radioactivity measurement of positron emission tomography/computed tomography (PET/CT)-guided biopsy tissue specimen to check the viable tumor sampling and predict the nature of the biopsied lesion. Materials and Methods: We prospectively evaluated the retrieved tissue specimens during PET/CT-guided biopsies for the presence of radioactivity. The qualitative radioactivity was measured by acquiring PET/CT images of the specimen. For quantitative analysis, a multichannel-analyzer (MCA) was used, and a counting-factor (CF) in counts/mCi.mm3 was calculated based on background-corrected net-counts, tissue-volume (mm3), and exponential tracer-activity during biopsy (mCi). The CF-values were compared with the 2-(fluorine-18) fluoro-2-deoxy-D-glucose-avidity in the target lesion and correlated with the histopathology. Results: A total of 49 patients (30 males) aged 51.8 ± 17.8 years were recruited for the biopsy, and radioactivity was measured. All the specimens revealed the presence of radioactivity on PET/CT images of the specimens and MCA counting. The mean CF-values were 17.2 ± 15.6 counts/mCi.mm3. One sample had meager counts with a CF-value of 0.162 and was subjected to re-biopsy after repositioning the coaxial needle to the hypermetabolic site. Pathological diagnosis was established in all the patients (malignancy-29, benign-20). The CF-values were significantly higher in malignant lesions than benign (21.45 ± 18.05 vs. 10.76 ± 8.96 counts/mCi.mm3, P = 0.025). CF-values and maximum standardized uptake value had a significant correlation (Pearson's r = 0.457, P = 0.001). Conclusion: The ex vivo measurement of the radioactivity of retrieved tissue specimens during PET/CT-guided biopsy helps to confirm the sampling from viable region and a highly practical approach to avoid erroneous sampling of a lesion with a large necrotic area. It is also helpful in predicting the nature of the biopsied lesion before the histopathological analysis.

Evaluation of Radiation Exposure to the Patients Undergoing Positron Emission Tomography/Computed Tomography-Guided Biopsies.

Purpose: We aimed to evaluate the radiation exposure to patients undergoing positron emission tomography/computed tomography (PET/CT)-guided biopsies. Materials and Methods: Patients undergoing PET/CT-guided biopsy were recruited prospectively from October 2019 to April 2020. PET/CT-guided biopsy from a tracer avid site was done using an automated-robotic-arm 1 h after intravenous injection of F-18-fluorodeoxyglucose (FDG) (2-5 mCi) or Ga-68-PSMA (1-4 mCi). Regional CT-images were acquired for biopsy planning and confirmation of needle placement. The internal radiation exposure due to the PET component was estimated using the value of activity injected and dose-coefficient for FDG and PSMA. The external radiation exposure due to the CT component was estimated using the value of dose length product and organ coefficients conversion factor. The total effective dose during the procedure was calculated by adding exposure due to both CT and PET components. Percentage contribution from CT and PET component to total effective dose was compared using a paired t-test. Results: A total of 101 patients (76 males) were recruited for PET/CT-guided biopsy using FDG (n = 79) and PSMA (n = 22). The mean effective-dose due to PET and CT components and total effective-dose was 2.49 ± 1.02 mSv, 2.35 ± 1.03 mSv and 4.83 ± 1.90 mSv, respectively, for FDG-guided procedures and 1.60 ± 0.57 mSv, 3.06 ± 1.36 mSv, and 4.66 ± 1.37 mSv for Ga-68-PSMA-guided procedures. The percentage contribution of PET and CT in total effective-dose was comparable in F-18-FDG and Ga-68-PSMA PET/CT-guided biopsy procedures; however, for Ga-68-PSMA PET/CT-biopsies, CT contributed a higher radiation dose than PET component. Conclusion: PET/CT-guided biopsy is a safe interventional procedure, and radiation exposure to the patients was less than routine whole-body PET/CT-imaging.

18F-NaF PET uptake characteristics of coronary artery culprit lesions in a cohort of patients of acute coronary syndrome with ST-elevation myocardial infarction and chronic stable angina: A hybrid fluoride PET/CTCA study.

BACKGROUND: 18F-NaF PET/CT identifies high-risk plaques due to active calcification in coronary arteries with potential to characterize plaques in ST-elevation myocardial infarction (MI) and chronic stable angina (CSA) patients. METHODS: Twenty-four MI and 17 CSA patients were evaluated with 18F-NaF PET/CTCA for SUVmax and TBR values of culprit and non-culprit plaques in both groups (inter-group and intra-group comparison), and pre- and post-interventional MI plaques sub-analysis. RESULTS: Culprit plaques in MI patients had significantly higher SUVmax (1.6; IQR 0.6 vs 1.3; IQR 0.3, P = 0.03) and TBR (1.4; IQR 0.6 vs 1.1; IQR 0.4, P = 0.006) than culprit plaques of CSA. Pre-interventional culprit plaques of MI group (n = 11) revealed higher SUVmax (P = 0.007) and TBR (P = 0.008) values than culprit CSA plaques. Culprit plaques showed significantly higher SUVmax (P = 0.006) and TBR (P = 0.0003) than non-culprit plaques in MI group, but without significant difference between culprit and non-culprit plaques in CSA group. With median TBR cutoff value of 1.4 in MI culprit plaques, 6/7 plaques (85.7%) among the event prone non-culprit lesions had TBR values > 1.4 in CSA group. CONCLUSION: The study shows higher SUVmax and TBR values in MI culprit plaques and comparable TBR values for event prone plaques of CSA group in identifying high-risk plaques.

Humanoid Training Phantom for Positron Emission Tomography-Computed Tomography-Guided Percutaneous Biopsy.

Positron emission tomography-computed tomography (PET-CT)-guided biopsy is being increasing practiced worldwide with indications in sampling of lung, abdominal, bone lesions, and among others. Training for PET-guided Interventions at select centers is carried out under supervision of an expert on real patients, similar to training for interventional radiology procedures. Simulation center training has been shown to be useful in improving efficiency of resident trainees. We report the development of concept, design, and practical application of a simplified humanoid training phantom for PET-guided interventions.

F-18 fluorocholine positron emission tomography- computed tomography in initial staging and recurrence evaluation of prostate carcinoma: A prospective comparative study with diffusion-weighted magnetic resonance imaging and whole-body skeletal scintigraphy.

Prostate cancer (PCa) is one of the major causes of death due to cancer in men. Conventional imaging modalities such as magnetic resonance imaging (MRI) provide locoregional status, but fall short in identifying distant metastasis. C-11 choline F-18 fluorocholine (F-18 FCH) has been shown to be useful in imaging of PCa. The present prospective study evaluates and compares the role of F-18 FCH positron emission tomography-computed tomography (PET-CT) with locoregional MRI and whole-body bone scintigraphy in PCa patients for initial staging and recurrence evaluation. This study included a total of 50 patients. Tc-99m skeletal scintigraphy, F-18 FCH PET-CT, and diffusion-weighted MRI of the pelvic region were performed within a span of 2-3 weeks of each other, in random order. For the primary site, core biopsy findings of the lesion were considered as gold standard. The kappa test was used to measure agreement between bone scintigraphy, F-18 FCH, and MRI. For comparing Tc-99m bone scintigraphy, F-18 FCH, and MRI, McNemar's test was applied. F-18 FCH PET-CT and MRI were able to detect primary lesion in all initial staging patients. The sensitivity and specificity of F-18 FCH PET-CT versus MRI were found to be 92.8% versus 89.2% and 100 versus 80%, respectively, for the recurrence at the primary site. A total of 55 bony lesions at distant sites were detected on F-18 FCH PET-CT in comparison to 43 bone lesions on whole-body bone scintigraphy. F-18 FCH PET/CT also detected additional lung lesions in 2 patients and abdominal lymph nodes in 12 patients. F-18 FCH PET-CT could detect primary lesions, local metastasis, bone metastasis, and distant metastasis in a single study and is also a useful modality in recurrence evaluation in PCa patients.

Development of 68Ga DOTA-CRH for PET/CT Imaging of ACTH-Dependent Cushing's Disease: Initial Study.

Purpose: Adrenocorticotropic hormone (ACTH)-dependent Cushing's disease accounts for 75% cases of the endogenous Cushing's syndrome. The size of lesion is usually very small, which results in false-negative magnetic resonance imaging (MRI) even after biochemical confirmation of the disease. Corticotrophin-releasing hormone (CRH) the key controller of hypothalamus-pituitary--adrenal axis binds to CRH receptor R1 and R2. CRH R1 is overexpressed in pituitary adenomas. The present study aims to target these overexpressed receptors with 68Ga-DOTA-CRH for noninvasive imaging of ACTH-dependent pituitary adenomas. Materials and Methods: Custom-synthesized 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-CRH peptide was purified by high performance liquid chromatography (HPLC) and characterized by mass spectra. Postradiolabeling optimization with 68Ga, quality control tests were carried out to ensure the suitability of 68Ga DOTA-CRH for intravenous administration. A pilot study consisting of 15 patients including 6 known cases of macroadenoma underwent 68Ga-DOTA-CRH regional brain positron emission tomography/computed tomography (PET/CT). The optimal imaging time and biodistribution studies were performed in five patients' whole-body and serial brain PET/CT imaging. Lesion activity was determined as SUVmax and correlated with CE-MRI and histopathology of excised tissue. Results: A retention time of 11.3 min and mass of 5145 Da was observed on HPLC and mass spectra. Radiolabeling yield of >98% was achieved under optimized conditions using 25-100 µg of conjugated peptide for 10-22 mCi of 68Ga. The quality control results were in agreement with acceptable criteria. 68Ga-DOTA-CRH was able to delineate ACTH secreting corticotropinoma in all 15 patients. Physiological uptake of radiotracer was observed in liver and spleen with diffused marrow activity. Excretion was noted by renal route. Imaging results were in correlation with CE-MRI and histopathology of excised tissue. Conclusion: 68Ga-DOTA-CRH PET/CT is a promising molecular imaging modality for detection of ACTH-dependent microadenoma.

Early Quantification of Salivary Gland Function after Radioiodine Therapy.

PURPOSE OF THE STUDY: Radioiodine (I-131) is used as an effective noninvasive treatment for thyroid malignancies. Salivary gland is one of the most affected nontarget organs. The present study aims to perform early quantification of salivary gland function after I-131 therapy (RIT) for thyroid cancer considering I-131 down-scatter in the Tc-99m window. MATERIALS AND METHODS: A total of 20 patients (6 males and 14 females) with differentiated thyroid carcinoma were enrolled in the study. Baseline dynamic salivary scintigraphy was performed in all patients using 185-370 MBq (5-10 mCi) Tc-99m pertechnetate. Posttherapy, salivary scintigraphy was performed 10-25 days after RIT in the range of 1.85-7.4 GBq (50-200 mCi). Time-activity curves obtained from the pre- and posttherapy dynamic salivary scintigraphy were used for semi-quantitative analysis. Uptake ratio (UR), ejection fraction (EF%), and maximum accumulation (MA%) were calculated by drawing regions of interest of individual parotid and submandibular glands over a composite image, after correcting for down-scatter from I-131 in the Tc-99m window. A paired t-test was used for comparison of the parameters obtained. RESULTS: Significant changes were observed in UR and EF% of both parotid and submandibular glands (P < 0.05). No significant changes were found in the value of MA% of left parotid gland and both submandibular glands in the posttherapy scans in comparison to pretherapy scans (P > 0.05). However, significant difference was observed in the MA% of the right parotid gland (P = 0.025). CONCLUSION: Salivary gland function was found to deteriorate after RIT, with the parotid glands affected more than the submandibular glands.

Prospective Comparison of Angiogenesis-Specific 68Ga-RGD2 PET/CT Imaging Parameters and DAS28-ESR in Rheumatoid Arthritis.

OBJECTIVE: The aim of this study was to compare the performance of angiogenesis-specific 68Ga-RGD2 PET/CT with Disease Activity Score 28-erythrocyte sedimentation rate (DAS28-ESR) in assessing disease activity and treatment response in rheumatoid arthritis (RA). METHODS: This was a prospective study comparing the performance of 68Ga-RGD2 PET/CT and DAS28-ESR in 30 RA patients. All of them underwent 68Ga-RGD2 PET/CT scan from head to toe and clinical examination at the baseline. A repeat scan and clinical examination were done in 27 patients after 3 months of treatment with disease-modifying antirheumatic drugs ± steroids. Three PET parameters, that is, PJC (PET-positive joint count), aSUVmax (average SUVmax), and hSUVmax (highest SUVmax), of positive joints were compared with the DAS28-ESR for disease activity assessment and response evaluation. RESULTS: Among the 3 PET parameters, PJC showed a significant correlation with the DAS28-ESR (0.64, P < 0.01). A significant change was observed with treatment in the DAS28-ESR and PET parameters of 27 patients at follow-up. There was significant correlation between percentage changes in DAS28-ESR and scan parameters such as PJC (0.689, P < 0.001), aSUVmax (0.712, P < 0.001), and hSUVmax (0.555, P = 0.003) values. The absolute change in aSUVmax value could accurately discriminate (area under the curve, 0.98; P = 0.001) European League Against Rheumatism responders from nonresponders. CONCLUSIONS: 68Ga-RGD2 PET/CT is a promising tool for objective assessment of disease activity and treatment response in patients with RA.

Dose Optimization in 18F-FDG PET Based on Noise-Equivalent Count Rate Measurement and Image Quality Assessment.

The present study aimed to optimize the injected dose of 18F-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 18F-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 18F-FDG radioactivity per kilogram of body weight (1.85, 3.7, 5.5, and 7.4 MBq/kg). All patients underwent 18F-FDG PET/CT studies, and NECRlocal was calculated by noting the trues rate, total prompts, and randoms rate for each bed position. Whole-body NECRglobal was calculated as the average NECR for all bed positions. IQ was qualitatively assessed for each bed position (IQlocal) and for whole-body PET (IQglobal) 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/m2; group II, 20.1-25 kg/m2; group III, 25.1-30 kg/m2; and group IV, 30.1-35 kg/m2) for comparison. A P value of less than 0.05 was considered significant. Results: In total, 109 patients underwent 18F-FDG PET/CT studies after injection of different amounts of 18F-FDG radioactivity and a mean uptake time of 62.32 min. The mean NECRglobal and IQglobal 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 NECRglobal and IQglobal were significantly different in all 4 body-mass-index groups (P < 0.05), except between groups II and III (P > 0.05). NECRlocal and IQlocal correlated moderately (r = 0.64). Conclusion: Optimization of injected 18F-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.

Molecular Imaging Targeting Corticotropin-releasing Hormone Receptor for Corticotropinoma: A Changing Paradigm.

BACKGROUND: Corticotrophin-releasing hormone (CRH) is the major regulator of adrenocorticotrophic hormone (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 with Cushing's disease [CD], 3 with ectopic CS [ECS]) underwent 68Ga CRH PET-CT. Two nuclear medicine physicians read these images for adenoma delineation and superimposed them on magnetic resonance imaging (MRI) sella. The information provided was used for intraoperative 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 10 cases with adenoma size < 6mm (4 cases were negative on MRI). Corticotropinoma location on 68Ga CRH PET fusion images with MRI were concordant with operative findings and were further confirmed on histopathology. There was no tracer uptake in the pituitary in 2 patients with ECS, while, in another, the diffuse uptake in pituitary suggested ectopic CRH production. CONCLUSION: 68Ga CRH PET-CT represents a novel, noninvasive molecular imaging, targeting CRH receptors that not only delineate corticotropinoma and provides the surgeon with valuable information for intraoperative tumor navigation, but also helps in differentiating a pituitary from an extra-pituitary source of ACTH-dependent CS. FUNDING: None.

Correction of Positron Emission Tomography Maximum Intensity Projection Image Artifact Using Retro Reconstruction Method.

Artifacts in positron emission tomography (PET)/computed tomography imaging can result from a number of factors. Presence of imaging artifacts affects interpretation and can sometimes render the image uninterpretable. Correction of artifacts can be attempted by reprocessing of data. In the present study, one PET maximum intensity projection image artifact was corrected by employing the method of retro-reconstruction.

18F-FDG PET/CT in Tuberculosis: Can Interim PET/CT Predict the Clinical Outcome of the Patients?

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 F-FDG PET/CT. This retroprospective study was done to evaluate the utility of F-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 F-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 F-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: F-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.

Dynamic 18F-Fluoro-Ethyl-Tyrosine Positron Emission Tomography/ Computed Tomography: A Better Predictor of Isocitrate Dehydrogenase Mutation in Presurgical Evaluations of Glioma.

The recent WHO classification of gliomas has incorporated molecular markers such as isocitrate dehydrogenase (IDH) mutation and 1p/19q co-deletion into the ambit of morphological diagnosis, and 18F-fluoro-ethyl-tyrosine (18F-FET) positron emission tomography (PET) has shown its utility in noninvasive glioma grading and prognosis. Both dynamic and static FET PET parameters may assist in predicting the IDH mutational status, but time to peak derived from dynamic data may be a better predictor for IDH status. We present a case of left frontal lobe lesion suggestive of high-grade glioma on magnetic resonance imaging and static 18F-FET PET images, however, dynamic FET image was suggestive of low-grade IDH1-mutated glioma which was later confirmed on histology and immunohistochemistry.