Indian Journal of Nuclear Medicine最新文献

Aims: This study aimed to evaluate the principal technical characteristics of a well-type gas-filled ionization chamber dose calibrator used in measuring radiopharmaceutical activity, namely accuracy, repeatability, and linearity. Furthermore, this work also explored the correlation between the device's response and the position and volume of the radiopharmaceutical I-131.

Materials and methods: Experimental measurements were conducted on the ATOMLAB 500 dose calibrator using NIST traceable Cs-137 source to determine the accuracy and repeatability. For the linearity test, the Tc-99m solution produced at the Dalat Nuclear Research Institute, Vietnam was utilized to examine the performance of the device over a wide measurement range. Effects resulting from different volumes and measuring positions were also determined by experiments and Monte Carlo simulations.

Results: Based on acceptance test results, it is revealed that the dose calibrator's characteristics comply with international standards, where the deviations of accuracy, repeatability, and linearity are all lower than 1.0%. The response of the dose calibrator to different measuring positions and volumes was well controlled. To rectify the discrepancy in the response to the changes in solution volume, correction functions were proposed.

Conclusions: It is concluded that the dose calibrator is suitable for radioactivity quantification and adheres to standards recommended by international organizations for nuclear medicine activities. The outcome of this work will serve as the foundation for establishing a standard for I-131 radiopharmaceuticals' radioactivity in Vietnam.

Over the last 15 years, there has been substantial growth in the installation of medical cyclotrons. This is mainly due to the increased demand for the production of positron emission tomography radiopharmaceuticals. In every country, there is a regulatory body that regulates the uses of medical cyclotron intending to protect occupational workers, the public, and the environment. It regulates the entire stages of such facilities, which mainly controls regulatory activities such as construction, commissioning, operation, and decommissioning. This article primarily highlights the key practices for planning and installation of a medical cyclotron facility (MCF). It also covers the particular aspects that should be considered in the early stages of project planning and provides information for best practices and challenges. If these aspects are properly addressed, then it ensures the safe operation of the MCF. The texts also elaborate on the necessary requirements for effective planning of the MCF, such as layout and space considerations, workload plan and maximum research capacity of the institute and equipment, shielding requirements, water cooling circuit, storage of radioactive components, management of radioactive waste from medical cyclotron and radiochemistry laboratory, construction and commissioning project management, exhaust system and filtration options, plans for staffing and training, and combination of equipment safety systems and building safety systems.

Objectives: The objective is to evaluate the efficacy of ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) computed tomography (CT) in the evaluation of tumor response to preoperative/palliative chemoradiotherapy (CRT) for advanced colorectal cancer; including metastatic cancer at primary presentation and recurrent cancers with local and/or distant metastasis.

Materials and methods: Fifty patients with advanced rectal cancer underwent two point imaging with 18 FDG PET-CT before and after 3 weeks of completion of preoperative/palliative CRT in between 2016 and 2022. Patients with locally recurrent cancer also underwent radical surgery. The assessment consisted of the evaluation of the following metabolic PET parameters: Maximum standardized uptake value (SUV_max), SUV_ratio, metabolic tumor volume (MTV), and total lesion glycolysis (TLG). Response was assessed among the followed patients using RECIST 1.1 criteria.

Observations and results: There was a significant decline in the mean post therapy SUV_max and SUV_ratio as compared to baseline (P = 0.0001). Twenty-six out of 50 (52%) patients were classified as responders. A significant decrease in all parameters (SUV_max, SUV_ratio, TLG, and MTV) from baseline was observed in responders of the study when comparing with nonresponders (P < 0.05). Besides SUV_max and SUV_ratio, the mean posttherapy TLG was significantly reduced in responders than nonresponders (P = 0.0065).

Conclusion: PET-CT is a useful combined anatomic and functional imaging modality in monitoring tumor response to preoperative/palliative CRT in advanced rectal cancer, whether primary or recurrent, including metastatic cancers at presentation. Posttherapy SUV and TLG in particular are significantly associated with treatment response.

Background: Prostate-specific membrane antigen (PSMA) has shown to be a promising agent for prostate cancer imaging under PET-CT. With the automation in radiolabeling with 68Ga, using iTG 68Ge/68Ga generator, it has helped introduce various new diagnostic agents and achieve good manufacturing practices (GMP) simultaneously. However, before any radiopharmaceutical is put into clinical usage, it should always be checked for its radiochemical purity and other quality parameters before injecting in the patient. Chromatography techniques such as Gas Chromatography (GC), High-Performance Liquid Chromatography (HPLC), and Thin-Layer Chromatography (TLC) are the most frequently utilized separation technique for purity analysis. A rapid quality control HPLC based methodology was required for radiopharmaceuticals.

Aim & objective: In our current setting, we conducted quality control analysis and standardized and validated HPLC method for the routine quality check of 68Ga-PSMA-11.

Materials and methods: The QC of 68Ga PSMA-11 was performed under ITLC and HPLC.

Results: Linearity, accuracy, precision and specificity were assessed and quantified in accordance with International conference on harmonisation of technical requirements for registration of pharmaceuticals for human use (Q2 (R1) ICH) guidelines, which can be implemented in resource-limited settings to check the quality.

Conclusion: The current HPLC based methodology is rapid, with a retention time of 2.24 min, rendering it a favorable analytical standard operating procedure for QC analysis of 68Ga-PSMA-11.

Objective: ¹⁷⁷Lu-DOTATATE peptide receptor therapy (PRRT) is an established treatment for patients suffering from neuroendocrine tumors. In the last few years, intra-arterial PRRT is being considered for patients having liver metastatic disease predominantly. The aim of our study is to measure the radiation doses received by the treating intervention radiologists involved in intra-arterial PRRT treatment using ¹⁷⁷Lu-DOTATATE.

Materials and methods: Radiation safety-related data of 31 patients who underwent 177Lu-DOTATATE intra-arterial PRRT treatment were used for this study. The exposure rate was measured at the hand and eye and chest level of treating intervention radiologists continuously from the beginning to the end of the administration. Exposure from the patient at the body surface (at the level of liver, thigh, and extremities) and 1 m from the body surface was measured just after the administration. The mean radiation exposure from the patient at the body surface and 1 m from the body was also calculated.

Results: The mean administered activity was found to be 194 (±17) mCi. The mean radiation exposure at the surface at the level of the liver, thigh, and feet and at 1 m from the surface was found to be 100 (±25.11), 9 (±1.27), 5.6 (±0.52), and 5.3± (0.50) μSv/hr, respectively. The mean administration time was found to be 23 ± 5.6 min. The mean radiation dose to the hands, and eyes, of the treating intervention radiologist per procedure, was found to be 6.425 ± 2.75 μSv, 5.43 ± 1.76 μSv and 1-m exposure from the patient was found to be 5.3 ± 0.246 μSv, respectively.

Conclusion: Our result shows that the radiation exposure from the patient postadministration is below the permissible limit of discharge. The radiation exposure to the intervention radiologist is also suggestive of a safe procedure to be performed by maintaining the radiation dose well within the permissible limit for radiation professionals.

Background: The introduction of positron emission tomography/computed tomography (PET/CT) has significantly advanced medical imaging. In oncology, ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/CT is particularly crucial for staging, evaluating treatment response, monitoring follow-up, and planning radiotherapy. However, in resource limiting hospitals, the availability of fluorine-labeled ¹⁸F-FDG limits optimal scan acquisition. This study aims to determine the optimal dosage and acquisition time to maximize patient throughput during shortages.

Aim and objective: To optimize low-dose ¹⁸F-FDG scan protocols while maintaining high image quality despite radiotracer availability challenges.

Materials and methods: PET/CT scans were performed using GE's Discovery IQ 5-ring, 16-slice system within 40-60 minutes of intravenous ¹⁸F-FDG injection. The protocol was adjusted to a low-dose (0.05 mCi/kg of ¹⁸F-FDG), and the PET data acquisition time was increased to 3 min per bed position to ensure image quality.

Results: Notable differences were observed in image quality scores based on varying acquisition times, with the extended acquisition time helping maintain diagnostic standards despite reduced tracer doses.

Conclusion: The high sensitivity and long axial length of the PET/CT system (with five rings spanning 26 cm AFOV) can significantly alleviate the challenges faced by cyclotron-dependent centers. By leveraging the increased sensitivity, we successfully reduced the injected activity rather than the scan time to address the tracer shortage at our institute. This approach proved to be effective in maintaining image quality and patient care standards.

Hepatopulmonary syndrome (HPS) is a rare pulmonary vascular complication of chronic liver disease characterized by dilatation of pulmonary capillaries leading to vascular shunting and systemic hypoxemia. Diagnosis of HPS requires documentation of intrapulmonary vasodilation (IPVD), the two most common imaging studies performed for the detection of IPVD include transthoracic contrast echocardiography (TTCE) and 99m-Tc-macroaggregated albumin scintigraphy (99mTc-MAA scan). TTCE has high sensitivity and thus, is the preferred initial investigation, while 99mTc-MAA scan is highly specific and plays an adjuvant role in diagnosis. 99mTc-MAA scan can, however, identify some cases of HPS not apparent on TTCE and can also quantify the shunt fraction. The current study describes the utility of 99mTc-MAA scan in the detection of IPVD in two suspected cases of HPS.

Background: With the increasing number of oncology cases and a parallel surge in chemotherapeutic drugs for treatment, the treating physicians conducts nephrotoxicity evaluation to provide a personalized dosing strategy. Of the various tests available, glomerular filtration rate (GFR) under gamma camera with help of Gates method has gained importance, being a good index of overall kidney functions. In addition to this, there has been an alternate and old method for GFR estimation: plasma sampling. We at our Institution conducted both the methods for better evaluation of GFR in cancer patient management.

Aim: Comparison of Gates' camera based GFR based on kidney depth correction using Tonessen's method and CT based manual depth calculation with dual time point plasma sampling in cancer patients.

Method: A retrospective study wherein patients' database were evaluated over a period of four months after approval from our Institutional Review Board. Thirty patients were included in the study. GFR was evaluated by two methods: Gates camera based and dual time plasma sampling method. Statistical analysis was done to help evaluate a correlation coefficient between the methods (Gates' method with and without CT based manual depth correction and dual time point plasma sampling).

Results: Our study showed moderate correlation between Gates' camera based GFR and dual time plasma sampling method.

Conclusion: One need to understand the limitation of each method and see if the renal depth corrections can be done with the help of CT or lateral images of NM for near accurate GFR and in case of selecting dual plasma sampling, errors to be minimized in pipetting and sample counting. Hence, it will be better to use both the methods for coming to a conclusion.

Renal cell carcinoma accounts for 3% of all malignancies with many of them presenting with metastasis at the time of presentation. The abscopal effect, a phenomenon characterized by systemic bystander effects on nontargeted lesions due to local therapy, has been extensively studied in the context of radiotherapy and immunotherapy. However, documentation of the abscopal effect following surgery remains limited. We present a case of a 67-year-old Indian male diagnosed with clear cell renal cell carcinoma (RCC), who underwent left radical nephrectomy. Baseline staging and postnephrectomy follow-up scans with fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET-CT) revealed an FDG-avid primary lesion in the left kidney with metastasis to the left lung. Surprisingly, the follow-up FDG PET-CT scan demonstrated the resolution of the left lung metastasis, indicating the occurrence of the abscopal effect resulting from the local nephrectomy. This rare clinical observation highlights the potential of surgery to induce immunogenic tumor neoantigens release and inflammatory factors, leading to systemic antitumor effects. While the abscopal effect has been extensively studied in the context of radiotherapy and immunotherapy, there is a scarcity of studies reporting nephrectomy promoting such systemic effects. The combination of radiotherapy and immunotherapy has shown promising results in enhancing tumor immunosuppression and facilitating the abscopal effect. We report a case of RCC with lung metastasis showing abscopal effect with resolution of lung nodule postnephrectomy on 18-F-FDG PET-CT.

Primary pericardial mesothelioma is a highly aggressive and rare neoplasm that arises from the pericardial mesothelial cell and has a poor prognosis. The diagnosis is usually established by histological and immunohistochemical studies. Malignant mesothelioma most frequently occurs from the pleura (90%), less frequently from the peritoneum and pericardium (6%-10%), and very rarely from the tunica vaginalis in the testis. Most of the patients were retrospectively diagnosed after surgery or an autopsy due to the absence of specific clinical manifestations. We present a case study of a 65-year-old female with primary pericardial mesotheliomas who was investigated with 18F-fluorodeoxyglucose positron emission tomography with computed tomography (FDG PET/CT) scan for biopsy and staging, which shows significant resolution of disease on postchemotherapy response evaluation and underwent pericardiectomy with a progression-free survival of over 12 months.