Comparison of Ga-68 PSMA PET/CT and Multiparametric MRI for Initial Detection and Staging of Prostate Cancer.

Background Multiparametric magnetic resonance imaging (mpMRI) is widely used for the evaluation of prostate cancer and is known to have better accuracy. Gallium-68 prostate-specific membrane antigen (Ga-68 PSMA) is a radiotracer that shows high localization in prostate cancer cells. Purpose The purpose of this study was to assess the sensitivity and utility of Ga-68 PSMA positron emission tomography/computed tomography (PET/CT) in comparison with mpMRI as a noninvasive imaging technique for the initial diagnosis and locoregional staging of prostate cancer using transrectal ultrasound (TRUS)-guided biopsy as gold standard. Materials and Methods This prospective observational study conducted from August 2017 to April 2020 evaluated 60 men ( n = 60) with biopsy-proven prostate carcinoma. They underwent mpMRI and Ga-68 PSMA PET/CT scans within 14 days with TRUS biopsy being gold standard. T staging of disease, N staging of lymph nodes within the pelvis, and M staging of lesions in pelvic bones (within the imaging field of mpMRI) were compared using PSPP version 1.0.1 statistical software. Results All 60 men with a mean age of 69.9 ± 9.35 years showed Ga-68 PSMA avid disease, whereas 55 were detected by mpMRI. The sensitivity in detection of prostate lesions (with 95% confidence interval) was 99.08% for Ga-68 PSMA PET/CT and 84.40% for mpMRI. Ga-68 PSMA PET/CT detected greater number of patients with regional lymph nodal involvement (19/60) as compared with mpMRI (12/60). Ga-68 PSMA PET/CT showed PSMA avid pelvic skeletal lesions in nine patients, whereas mpMRI detected pelvic lesions in six patients. In addition, four other patients showed extrapelvic skeletal lesions on Ga-68 PSMA PET/CT. Conclusion Ga-68 PSMA PET/CT has superior sensitivity in detection of primary prostate tumor, as compared with mpMRI. Both modalities correlate well in detection of seminal vesicle involvement. Ga-68 PSMA PET/CT outperformed mpMRI in detection of lymph nodal and skeletal metastases. Hence, Ga-68 PSMA PET/CT should be considered as first-line diagnostic modality for carcinoma prostate. Summary Statement : Ga-68 PSMA PET/CT shows superior diagnostic performance than mpMRI in the evaluation of prostate cancer.

Ga68-FAPI Imaging and Lu177-FAPI Therapy in a Case of Metastatic Solitary Fibrous Tumor.

Solitary fibrous tumor (SFT) of the central nervous system (previously called hemangiopericytoma) is a rare mesenchymal tumor. Malignant SFT has a tendency to recur after surgery and can metastasize to distant organs. Treatment options for metastatic disease are limited. This case demonstrated high expression of FAP (fibroblast activating protein) in all metastatic sites with Ga-FAPI positron emission tomography-computed tomography imaging. Subsequently, the patient was treated with Lu177-FAPI-targeted radionuclide therapy. There was significant clinical response. There was mild partial morphological response seen on follow-up imaging.

Current and upcoming radionuclide therapies in the direction of precision oncology: A narrative review.

As new molecular tracers are identified to target specific receptors, tissue, and tumor types, opportunities arise for the development of both diagnostic tracers and their therapeutic counterparts, termed "theranostics." While diagnostic tracers utilize positron emitters or gamma-emitting radionuclides, their theranostic counterparts are typically bound to beta and alpha emitters, which can deliver specific and localized radiation to targets with minimal collateral damage to uninvolved surrounding structures. This is an exciting time in molecular imaging and therapy and a step towards personalized and precise medicine in which patients who were either without treatment options or not candidates for other therapies now have expanded options, with tangible data showing improved outcomes. This manuscript explores the current state of theranostics, providing background, treatment specifics, and toxicities, and discusses future potential trends.

A Pictorial Essay of Somatostatin Receptor Imaging in Tumor-Induced Osteomalacia: A Single Institutional Experience.

Tumor-induced osteomalacia (TIO) is a rare cause of severe debilitating osteomalacia, due to hypophosphatemia. A strong clinical suspicion based on biochemical parameters can lead to the search for a culprit tumor in the body. The disease entity is more commonly caused by benign mesenchymal tumors. While many imaging modalities have been tried, it is now known that these tumors show high somatostatin receptor (SSTR) expression. Hence SSTR receptor imaging has emerged as a useful diagnostic tool. Here we present a series of TIO cases with clinical presentation and imaging characteristics.

68 Ga-DOTATATE PET/CT imaging in endogenous hyperinsulinemic hypoglycemia: A tertiary endocrine centre experience.

OBJECTIVE: Literature regarding utility of 68 Ga-DOTATATE PET/CT in insulinoma localization across various subgroups [benign/malignant/multiple endocrine neoplasia-1 (MEN-1) syndrome associated] remains scarce. In this study, the performance of 68 Ga-DOTATATE PET/CT was compared with contrast-enhanced computed tomography (CECT) and 68 Ga-NODAGA-Exendin-4 PET/CT (whenever available) in an endogenous hyperinsulinemic hypoglycemia (EHH) cohort. DESIGN: Retrospective audit. PATIENTS: EHH patients [N = 36, lesions (n) = 49, final diagnosis: benign sporadic insulinoma (BSI) (N = 20), malignant insulinoma (N = 4, n = 14), MEN-1 syndrome associated insulinoma (N = 9, n = 15), Munchausen syndrome (N = 2) and drug-induced hypoglycemia (N = 1)] having both preoperative imaging modalities (CECT and 68 Ga-DOTATATE PET/CT). MEASUREMENTS: Per-lesion sensitivity (Sn) and positive predictive value (PPV) for histopathological diagnosis of insulinoma. RESULTS: Sn and PPV of 68 Ga-DOTATATE PET/CT were 67.3% and 89.2%; 55% and 100%; 85.7% and 100%; and 66.7% and 77% for overall EHH, BSI, malignant, and MEN-1 syndrome associated insulinoma cohorts respectively. Despite having comparatively lower sensitivity in BSI cohort, 68 Ga-DOTATATE PET/CT localized a pancreatic tail lesion missed by other modalities. 68 Ga-DOTATATE PET/CT had comparatively higher sensitivity in malignant insulinoma than BSI cohort. 68 Ga-DOTATATE PET/CT also paved the way for successful response to 177 Lu-based peptide receptor radionuclide therapy (PRRT). In MEN-1 cases, lower PPV as compared with BSI was due to uptake in non-insulinoma pancreatic neuroendocrine tumours (Pan-NET). CONCLUSIONS: 68 Ga-DOTATATE PET/CT has supplemental role in selected cases of BSI with negative and/or discordant results with CECT and 68 Ga-NODAGA-Exendin-4 PET/CT. In malignant insulinoma, 68 Ga-DOTATATE-PET/CT has an additional theranostic potential. Interference due to uptake in non-insulinoma Pan-NET in MEN-1 syndrome may hinder insulinoma localization with 68 Ga-DOTATATE-PET/CT.

Worldwide Variation in the Use of Nuclear Cardiology Camera Technology, Reconstruction Software, and Imaging Protocols.

OBJECTIVES: This study sought to describe worldwide variations in the use of myocardial perfusion imaging hardware, software, and imaging protocols and their impact on radiation effective dose (ED). BACKGROUND: Concerns about long-term effects of ionizing radiation have prompted efforts to identify strategies for dose optimization in myocardial perfusion scintigraphy. Studies have increasingly shown opportunities for dose reduction using newer technologies and optimized protocols. METHODS: Data were submitted voluntarily to the INCAPS (International Atomic Energy Agency Nuclear Cardiology Protocols Study) registry, a multinational, cross-sectional study comprising 7,911 imaging studies from 308 labs in 65 countries. The study compared regional use of camera technologies, advanced post-processing software, and protocol characteristics and analyzed the influence of each factor on ED. RESULTS: Cadmium-zinc-telluride and positron emission tomography (PET) cameras were used in 10% (regional range 0% to 26%) and 6% (regional range 0% to 17%) of studies worldwide. Attenuation correction was used in 26% of cases (range 10% to 57%), and advanced post-processing software was used in 38% of cases (range 26% to 64%). Stress-first single-photon emission computed tomography (SPECT) imaging comprised nearly 20% of cases from all world regions, except North America, where it was used in just 7% of cases. Factors associated with lower ED and odds ratio for achieving radiation dose ≤9 mSv included use of cadmium-zinc-telluride, PET, advanced post-processing software, and stress- or rest-only imaging. Overall, 39% of all studies (97% PET and 35% SPECT) were ≤9 mSv, while just 6% of all studies (32% PET and 4% SPECT) achieved a dose ≤3 mSv. CONCLUSIONS: Newer-technology cameras, advanced software, and stress-only protocols were associated with reduced ED, but worldwide adoption of these practices was generally low and varied significantly between regions. The implementation of dose-optimizing technologies and protocols offers an opportunity to reduce patient radiation exposure across all world regions.

Worldwide Diagnostic Reference Levels for Single-Photon Emission Computed Tomography Myocardial Perfusion Imaging: Findings From INCAPS.

OBJECTIVES: This study sought to establish worldwide and regional diagnostic reference levels (DRLs) and achievable administered activities (AAAs) for single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). BACKGROUND: Reference levels serve as radiation dose benchmarks to compare individual laboratories against aggregated data, helping to identify sites in greatest need of dose reduction interventions. DRLs for SPECT MPI have previously been derived from national or regional registries. To date there have been no multiregional reports of DRLs for SPECT MPI from a single standardized dataset. METHODS: Data were submitted voluntarily to the INCAPS (International Atomic Energy Agency Nuclear Cardiology Protocols Study), a cross-sectional, multinational registry of MPI protocols. A total of 7,103 studies were included. DRLs and AAAs were calculated by protocol for each world region and for aggregated worldwide data. RESULTS: The aggregated worldwide DRLs for rest-stress or stress-rest studies employing technetium Tc 99m-labeled radiopharmaceuticals were 11.2 mCi (first dose) and 32.0 mCi (second dose) for 1-day protocols, and 23.0 mCi (first dose) and 24.0 mCi (second dose) for multiday protocols. Corresponding AAAs were 10.1 mCi (first dose) and 28.0 mCi (second dose) for 1-day protocols, and 17.8 mCi (first dose) and 18.7 mCi (second dose) for multiday protocols. For stress-only technetium Tc 99m studies, the worldwide DRL and AAA were 18.0 mCi and 12.5 mCi, respectively. Stress-first imaging was used in 26% to 92% of regional studies except in North America where it was used in just 7% of cases. Significant differences in DRLs and AAAs were observed between regions. CONCLUSIONS: This study reports reference levels for SPECT MPI for each major world region from one of the largest international registries of clinical MPI studies. Regional DRLs may be useful in establishing or revising guidelines or simply comparing individual laboratory protocols to regional trends. Organizations should continue to focus on establishing standardized reporting methods to improve the validity and comparability of regional DRLs.

Comparison of 68Ga-DOTA-NaI3-Octreotide/tyr3-octreotate positron emission tomography/computed tomography and contrast-enhanced computed tomography in localization of tumors in multiple endocrine neoplasia 1 syndrome.

The optimum imaging modality for the screening of multiple endocrine neoplasia type 1 (MEN1)-associated tumors is not well established. Here, we compare the performance of contrast-enhanced CT (CECT) versus 68Ga DOTA-NOC/TATE PET/CT in MEN1 patients. The retrospective case record study is conducted at a tertiary health-care center. Thirty-four patients, who have undergone both CECT and 68Ga DOTA-NOC/ TATE PET, were included in the analysis. CECT had higher per-lesion sensitivity than 68Ga DOTA-NOC/TATE PET/CT for the detection of parathyroid lesions, (82.6% vs. 24.6%, P < 0.001). 68Ga DOTA-NOC/TATE PET/CT had higher per-lesion sensitivity than CECT for the detection of metastases (85% vs. 47.5%, P < 0.001) and gastrinomas (90% vs. 10%, P = 0.003). When combined use of the two imaging modalities is compared to CECT alone (63.7% vs. 93.1%, P = 0.00012) and 68Ga-DOTA-NOC/TATE PET/CT alone (74.1% vs. 93.1%, P = 0.0057), it provided significantly higher per-lesion sensitivity for the detection of gastroenteropancreatic neuroendocrine tumors (GEP-NETs). 68Ga-DOTA-NOC/ TATE PET was more sensitive for the detection of gastrinomas and metastases than CECT, whereas it was less sensitive for the detection of parathyroid lesions than CECT. The combined use of both the imaging modalities significantly increases the sensitivity for detection of GEP-NETs.

Exendin-4-based imaging in endogenous hyperinsulinemic hypoglycaemia cohort: A tertiary Endocrine centre experience.

CONTEXT: Insulinoma needs accurate preoperative localization for minimally invasive surgery. Exendin-4-based imaging has shown promising results. OBJECTIVE: To evaluate performance parameters of exendin-4-based imaging in insulinoma localization and compare with other imaging modalities. DESIGN: Retrospective cross-sectional study. PATIENTS: We report 14 patients with endogenous hyperinsulinemic hypoglycaemia (EHH) managed at our centre; in whom, the final diagnosis was insulinoma (n = 11), Munchausen syndrome (MS) (n = 2) and inconclusive (n = 1). Retrospective reporting of CECT, 68 Ga-DOTATATE PET/CT and 68 Ga-NODAGA-exendin-4-PET/CT was done. With per-lesion analysis, performance parameters were calculated for the histopathological diagnosis of insulinoma. MAIN OUTCOME MEASURES: True positive (TP), false positive (FP), false negative (FN), true negative (TN), sensitivity (Sn), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) for insulinoma localization. RESULTS: In our cohort, 12 histopathologically proven insulinoma lesions [(TP): 11 primary lesions, 1 metastasis] were detected in 11 patients, whereas two patients had MS (TN). Sn and PPV were 75% and 100%, 33.3% and 80% and 83.3% and 71.4% for CECT, 68 Ga-DOTATATE PET/CT and 68 Ga-NODAGA-exendin-4-PET/CT, respectively. With exendin-4-based imaging, FP uptake in normal pancreatic tissue and FN results in the pancreatic tail lesion was seen. In one patient, TN result suggested the correct diagnosis of MS. CONCLUSION: 68 Ga-NODAGA-exendin-4-PET/CT has higher sensitivity than 68 Ga-DOTATATE PET/CT and CECT for insulinoma localization. FP uptake in normal pancreas and FN result in tail lesions are limitations of currently utilized exendin-4-based imaging.

Nuclear Cardiology Practice in Asia: Analysis of Radiation Exposure and Best Practice for Myocardial Perfusion Imaging　- Results From the IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS).

BACKGROUND: This paper examines the current status of radiation exposure to patients in myocardial perfusion imaging (MPI) in Asia.Methods and Results:Laboratories voluntarily provided information on MPI performed over a 1-week period. Eight best practice criteria regarding MPI were predefined by an expert panel. Implementation of ≥6 best practices (quality index [QI] ≥6) was pre-specified as a desirable goal for keeping radiation exposure at a low level. Radiation effective dose (ED) in 1,469 patients and QI of 69 laboratories in Asia were compared against data from 239 laboratories in the rest of the world (RoW). Mean ED was significantly higher in Asia (11.4 vs. 9.6 mSv; P<0.0001), with significantly lower doses in South-East vs. East Asia (9.7 vs. 12.7 mSv; P<0.0001). QI in Asia was lower than in RoW. In comparison with RoW, Asian laboratories used thallium more frequently, used weight-based technetium dosing less frequently, and trended towards a lower rate of stress-only imaging. CONCLUSIONS: MPI radiation dose in Asia is higher than that in the RoW and linked to less consistent use of laboratory best practices such as avoidance of thallium, weight-based dosing, and use of stress-only imaging. Given that MPI is performed in Asia within a diverse array of medical contexts, laboratory-specific adoption of best practices offers numerous opportunities to improve quality of care.

Diffuse Large B-Cell Lymphoma in the Era of Precision Oncology: How Imaging Is Helpful.

Diffuse large B cell lymphoma (DLBCL) is the most common histological subtype of Non-Hodgkin's lymphoma. As treatments continues to evolve, so do imaging strategies, and positron emission tomography (PET) has emerged as the most important imaging tool to guide oncologists in the diagnosis, staging, response assessment, relapse/recurrence detection,and therapeutic decision making of DLBCL. Other imaging modalities including magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, and conventional radiography are also used in the evaluation of lymphoma. MRI is useful for nervous system and musculoskeletal system involvement and is emerging as a radiation free alternative to PET/CT. This article provides a comprehensive review of both the functional and morphological imaging modalities, available in the management of DLBCL.

Nuclear Cardiology Practices and Radiation Exposure in the Oceania Region: Results From the IAEA Nuclear Cardiology Protocols Study (INCAPS).

BACKGROUND: There is concern about radiation exposure with radionuclide myocardial perfusion imaging (MPI). This sub-study of the International Atomic Energy Agency (IAEA) Nuclear Cardiology Protocols Study reports radiation doses from MPI, and use of dose-optimisation protocols in Australia and New Zealand (ANZ), and compares them with data from the rest of the world. METHODS: Data were collected from 7911 MPI studies performed in 308 laboratories worldwide in one week in 2013, including 439 MPI studies from 34 ANZ laboratories. For each laboratory, effective radiation dose (ED) and a quality index (QI) score (out of 8) based on pre-specified "best practices" was determined. RESULTS: In ANZ patients, ED ranged from 0.9-17.9 milliSievert (mSv). Median ED was similar in ANZ compared with the rest of the world (10.0 (IQR: 6.5-11.7) vs. 10.0 (IQR 6.4-12.6, P=0.15), as were mean QI scores (5.5±0.7 vs. 5.4±1.3, P=0.84). Use of stress-only imaging (17.6% vs. 31.8% of labs, P=0.09) and weight-based dosing of technetium-99m (14.7% vs. 30.3%, P=0.07) was lower in ANZ compared with the rest of the world but this difference was not statistically significant. Median ED was significantly lower in metropolitan versus non-metropolitan laboratories (10.1 mSv vs. 11.6 mSv, P<0.01), although mean QI scores were similar (5.4±0.8 vs. 5.5±0.7, P=0.75). CONCLUSION: Across ANZ, there is variability in ED from MPI, and use of radiation safety practices, particularly between metropolitan and non-metropolitan laboratories. Overall, ANZ laboratories have a similar median ED to laboratories in the rest of the world.

Clinical translation of (177)Lu-labeled PSMA-617: Initial experience in prostate cancer patients.

OBJECTIVE: PSMA-617 is reported to exhibit very high binding affinity towards PSMA receptors, over-expressed on prostate cancer cells and therefore, (177)Lu-labeled PSMA-617 is expected to play a pivotal role in the clinical management of patients suffering from ca prostate. The objective of the present study is to formulate the patient dose of (177)Lu-labeled PSMA-617, pre-clinical studies in animal model and clinical investigation in limited number of prostate cancer patients as well evaluating its potential for theranostic application. EXPERIMENTAL: Patient dose of 7.4 GBq (200 mCi) of (177)Lu-labeled PSMA-617 was prepared by incubating 100 µg of PSMA-617 with (177)LuCl3 at 95 °C for 15 minutes. Radiochemical purity as well as in-vitro stability of the preparation was determined by PC and HPLC methods. The pharmacokinetic behavior and in-vivo distribution of the agent were studied by carrying out biodistribution studies in normal male Wistar rats. Preliminary clinical investigation was performed in 7 patients suffering from prostate cancer. RESULTS: The complex was prepared with >98% radiochemical purity under the optimized reaction protocols and the preparation exhibited adequate in-vitro stability. Biodistribution studies revealed no significant uptake in any of the major organ/tissue along with major clearance through renal pathway. Clinical studies showed similar distribution in lesions and physiologic areas of uptake as seen in diagnostic (68)Ga-PSMA-11 PET scans performed earlier. CONCLUSION: Preliminary clinical studies indicated the promising potential of the agent for theranostic applications. However, further investigations in large pool of patients are warranted to establish the theranostic potential of the agent.

Comparison of 68Ga-DOTANOC PET/CT and contrast-enhanced CT in localisation of tumours in ectopic ACTH syndrome.

BACKGROUND: Localising ectopic adrenocorticotrophic hormone (ACTH) syndrome (EAS) tumour source is challenging. Somatostatin receptor-based PET imaging has shown promising results, but the data is limited to case reports and small case series. We reviewed here the performance of (68)Ga-DOTANOC positron emission tomography (PET)/computed tomography (CT) and contrast-enhanced CT (CECT) in our cohort of 12 consecutive EAS patients. MATERIALS AND METHODS: Retrospective data analysis of 12 consecutive patients of EAS presenting to a single tertiary care centre in a period between January 2013 and December 2014 was done. CECT and (68)Ga-DOTANOC PET/CT were reported (blinded) by an experienced radiologist and a nuclear medicine physician, respectively. The performance of CECT and (68)Ga-DOTANOC PET/CT was compared. RESULTS: Tumours could be localised in 11 out of 12 patients at initial presentation (overt cases), whereas in one patient, tumour remained occult. Thirteen lesions were identified in 11 patients as EAS source (true positives). CECT localised 12 out of these 13 lesions (sensitivity 92.3%) and identified five false-positive lesions (positive predictive value (PPV) 70.5%). Compared with false-positive lesions, true-positive lesions had greater mean contrast enhancement at 60s (33.2 vs 5.6 Hounsfield units (HU)). (68)Ga-DOTANOC PET/CT was able to identify 9 out of 13 lesions (sensitivity 69.2%) and reported no false-positive lesions (PPV 100%). CONCLUSION: CECT remains the first-line investigation in localisation of EAS. The contrast enhancement pattern on CECT can further aid in characterisation of the lesions. (68)Ga-DOTANOC PET/CT can be added to CECT, to enhance positive prediction of the suggestive lesions.

Vitamin D as a marker of cognitive decline in elderly Indian population.

OBJECTIVES: Very few studies in India have addressed the role of vitamin D in cognitive function. The present study was conducted to assess the serum levels of 25-hydroxyvitamin D (25(OH)D) and its association with markers of cognitive impairment and homocysteine levels in the elderly Indian population. MATERIALS AND METHODS: The study population consisted of patients with dementia (Group A, n = 32), mild cognitive impairment (MCI; Group B, n = 24), and elderly age-matched controls (Group C, n = 30). Measurement of serum levels of 25(OH)D and total homocysteine were done. RESULTS: Significant decreased concentration of 25(OH)D and increased concentration of homocysteine was observed. Association of serum levels of vitamin D with markers of cognitive decline as well as serum homocysteine levels was observed in patients with dementia and MCI when compared to controls. CONCLUSION: Correlation of vitamin D with markers of cognitive decline and homocysteine opens a new door for early diagnosis of cognitive impairment.

Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS).

AIMS: To characterize patient radiation doses from nuclear myocardial perfusion imaging (MPI) and the use of radiation-optimizing 'best practices' worldwide, and to evaluate the relationship between laboratory use of best practices and patient radiation dose. METHODS AND RESULTS: We conducted an observational cross-sectional study of protocols used for all 7911 MPI studies performed in 308 nuclear cardiology laboratories in 65 countries for a single week in March-April 2013. Eight 'best practices' relating to radiation exposure were identified a priori by an expert committee, and a radiation-related quality index (QI) devised indicating the number of best practices used by a laboratory. Patient radiation effective dose (ED) ranged between 0.8 and 35.6 mSv (median 10.0 mSv). Average laboratory ED ranged from 2.2 to 24.4 mSv (median 10.4 mSv); only 91 (30%) laboratories achieved the median ED ≤ 9 mSv recommended by guidelines. Laboratory QIs ranged from 2 to 8 (median 5). Both ED and QI differed significantly between laboratories, countries, and world regions. The lowest median ED (8.0 mSv), in Europe, coincided with high best-practice adherence (mean laboratory QI 6.2). The highest doses (median 12.1 mSv) and low QI (4.9) occurred in Latin America. In hierarchical regression modelling, patients undergoing MPI at laboratories following more 'best practices' had lower EDs. CONCLUSION: Marked worldwide variation exists in radiation safety practices pertaining to MPI, with targeted EDs currently achieved in a minority of laboratories. The significant relationship between best-practice implementation and lower doses indicates numerous opportunities to reduce radiation exposure from MPI globally.

Direct myocardial ischemia imaging: a new cardiovascular nuclear imaging paradigm.

Myocardial perfusion imaging (MPI), using radiotracers, has been in routine clinical use for over 40 years. This modality is used for the detection of coronary artery disease (CAD), risk stratification, optimizing therapy, and follow-up of patients with CAD. Molecular cardiovascular imaging using targeted radiotracers provides a unique opportunity for imaging biochemical and metabolic processes, and cell membrane transporter and receptor functions at a cellular and molecular level in experimental animal models as well as in humans. Cardiac imaging using radiolabeled free fatty acid analogues and glucose analogues enable us to image myocardial ischemia directly as an alternative to stress-rest MPI. Direct ischemia imaging techniques can avoid and overcome some of the limitations of standard stress-rest MPI. This article describes recent studies using (18) F-fluorodeoxyglucose ((18) FDG) for myocardial ischemia imaging.

Poor fluorodeoxyglucose uptake in myocardial viability study in nondiabetic Friedreich's ataxia patient.

A 48-year-old man, a known case of Friedreich's ataxia (FRDA) underwent cardiac fluorodeoxyglucose (FDG) positron emission tomography -computed tomography (PET/CT) for evaluation of myocardial viability. Tetrofosmin images showed an enlarged left ventricular cavity with small mid and basal inferior and apical infarct global hypokinesia with ejection fraction of 39%. Fluorodeoxyglucose images showed poor quality myocardial images. Friedreich's ataxia is associated with a high incidence of diabetes mellitus. Non-diabetic patients with Friedreich's ataxia have insulin resistance. This is associated with a reduction in the affinity of insulin receptors and membrane abnormality that alters the binding function of the insulin receptor.

Fludeoxyglucose positron emission tomography-computed tomography in limbic encephalitis.

A 66-year-old male patient presented with low grade fever without chills associated with simple partial seizures. He was advised whole body positron emission tomography-computed tomography (PET/CT) (fluorodeoxyglucose PET/CT) scan which demonstrated an increase in metabolic activity in the limbic system. There was no evidence of active disease anywhere else in the body. Thus, in the setting of limbic encephalitis PET-CT helps in locating the cancerous origin as well as gives information about functional abnormality of the brain.