Journal of nuclear medicine technology最新文献

The lack of pediatrics-specific equipment for nuclear medicine imaging has resulted in insufficient diagnostic information for newborns, especially low-birth-weight infants. Although PET offers high spatial resolution and low radiation exposure, its use in newborns is limited. This study investigated the feasibility of cardiac PET imaging using the latest silicon photomultiplier (SiPM) PET technology in infants of extremely low birth weight (ELBW) using a phantom model. Methods: The study used a phantom model representing a 500-g ELBW infant with brain, cardiac, liver, and lung tissues. The cardiac tissue included a 3-mm-thick defect mimicking myocardial infarction. Organ tracer concentrations were calculated assuming ¹⁸F-FDG myocardial viability scans and ¹⁸F-flurpiridaz myocardial perfusion scans and were added to the phantom organs. Imaging was performed using an SiPM PET/CT scanner with a 5-min acquisition. The data acquired in list mode were reconstructed using 3-dimensional ordered-subsets expectation maximization with varying iterations. Image evaluation was based on the depiction of the myocardial defect compared with normal myocardial accumulation. Results: Increasing the number of iterations improved the contrast of the myocardial defect for both tracers, with ¹⁸F-flurpiridaz showing higher contrast than ¹⁸F-FDG. However, even at 50 iterations, both tracers overestimated the defect accumulation. A bull's-eye image can display the flow metabolism mismatch using images from both tracers. Conclusion: SiPM PET enabled cardiac PET imaging in a 500-g ELBW phantom with a 1-g heart. However, there were limitations in adequately depicting these defects. Considering the image quality and defect contrast,¹⁸F-flurpiridaz appears more desirable than ¹⁸F-FDG if only one of the two can be used.

This study aimed to evaluate the measurement and prognostic ability of the SUV_max of whole-body tumors (SUV_maxwb) in non-small cell lung cancer (NSCLC) patients, comparing high-definition (HD) PET imaging with standard-definition (SD) PET imaging. Methods: The study included 242 consecutive NSCLC patients who underwent baseline ¹⁸F-FDG PET/CT from April 2018 to January 2021. Two imaging techniques were used: HD PET (using ordered-subsets expectation maximization with point-spread function modeling and time-of-flight techniques and smaller voxels) and SD PET (with ordered-subsets expectation maximization and time-of-flight techniques). SUV_maxwb was determined by measuring all the tumor lesions in the whole body, and tumor-to-background ratio (TBR) was calculated using the background SUV_mean of various body parts. Results: The patient cohort had an average age of 68.3 y, with 59.1% being female. During a median follow-up of 29.6 mo, 83 deaths occurred. SUV_maxwb was significantly higher in HD PET than SD PET, with respective medians of 17.4 and 11.8. The TBR of 1,125 tumoral lesions was also higher in HD PET. Univariate Cox regression analysis showed that SUV_maxwb from both HD and SD PET were significantly associated with overall survival. However, after adjusting for TNM (tumor, node, metastasis) stage, only SUV_maxwb from SD PET remained significantly associated with survival. Conclusion: HD PET imaging in NSCLC patients yields higher SUV_maxwb and TBR, enhancing tumor visibility. Despite this, its prognostic value is less significant than SD PET after adjusting clinical TNM stage. Thus, consideration should be given to using HD PET reconstruction to increase tumor visibility, and SD PET is recommended for NSCLC patient prognostication and therapeutic evaluation, as well as for the classification of lung nodules.

A new ⁹⁰Y SIR-Spheres delivery kit (SIROS D-vial and shield) has been introduced with a different physical form from the legacy V-Vial kit. Here, we establish the dose calibrator settings and exposure-rate-to-activity conversion factor to assay ⁹⁰Y SIR-Spheres activity in the new SIROS kit. Methods: Eight D-vials with initial ⁹⁰Y activities from 1.2 to 6.6 GBq within acrylic shields were assayed with dose calibrators and exposure-rate meters until activities decayed to approximately 0.1 GBq. The dose calibrator settings resulting in the lowest median activity errors and the best-fit slope of exposure rate versus activity were identified. Results: SIROS D-vial ⁹⁰Y activity can be accurately and reliably estimated directly using setting 51 × 10 on both the CRC-15R and the CRC-55tR dose calibrators (errors within ±0.5%) and indirectly with an exposure-rate reading at 30 cm using conversion factor 0.664 ± 0.003 GBq/(mR/h) (R ² = 0.985). Conclusion: Dose calibrator settings and exposure-rate-to-activity conversion factor for ⁹⁰Y activity assays with new SIROS kit should be updated from legacy V-Vial parameters to avoid an approximately 10% underestimation.

Myocardial perfusion imaging (MPI) provides physiologic and functional information about the heart muscle and its blood flow. Extracardiac radioactivity can interfere with visualization of the inferior wall of the myocardium, leading to poor-quality images, difficulties in interpretation, and delays in routine practice. This study aimed to identify the efficiency of having the patient consume a carbonated lemon drink to minimize the extracardiac radioactivity of ^99mTc-sestamibi in comparison to ^99mTc-tetrofosmin during MPI. Methods: This was a retrospective study that recruited 158 patients with known or suspected coronary artery disease referred to undergo ^99mTc-sestamibi or ^99mTc-tetrofosmin rest/stress single-day MPI. The patients were divided into 2 groups of mixed sexes and different ages. The first group comprised 78 patients injected with ^99mTc-sestamibi, and the second group comprised 80 patients injected with ^99mTc-tetrofosmin. For both groups, the patients drank 30 mL of fresh lemon juice diluted with 150 mL of soda water, and then we gave the patients about 100 mL of straight soda water, before imaging for both the rest and the stress phases. Results: Generally, in both groups, the ^99mTc-tetrofosmin produced a good-quality image in comparison with the ^99mTc-sestamibi. The mean rank of the total score for ^99mTc-tetrofosmin (62.75) was less than that for ^99mTc-sestamibi (96.68), and this difference was highly statistically significant (P = 0.000). There were statistically significant differences in the ratios and mean ranks for both groups in favor of ^99mTc-tetrofosmin in patients having coronary artery disease. Conclusion: The use of a carbonated lemon drink minimizes extracardiac activity from both ^99mTc-labeled MPI radiopharmaceuticals. This finding was more statistically significant for ^99mTc-tetrofosmin MPI, providing better image quality and earlier imaging in both the rest and the stress phases because of faster hepatobiliary clearance.

Diagnostic reference levels (DRLs) are an important tool for controlling radiation exposure and ensuring safety in medical applications. In Thailand, DRL data have been gathered and established for nuclear medicine diagnostics since 2021. However, there is a lack of information on PET imaging examinations. At the National Cyclotron and PET Scan Centre, Chulabhorn Hospital, radiopharmaceuticals are produced for medical imaging and research, and a wide range of PET/CT and PET/MRI examinations are performed. Our objective was to investigate the administered activity of radiopharmaceuticals in patients undergoing PET imaging, especially the existing data on DRLs in medical diagnostic imaging. Methods: This was a retrospective study on nuclear medicine patients at the National Cyclotron and PET Scan Centre in 2023. Statistical analysis, including the mean and the 75th percentile values, was conducted to determine DRLs according to the International Commission on Radiological Protection guidelines. Results: The center performed 8,711 PET/CT and PET/MRI studies with 13 protocols in 2023. The most commonly administered activity was ¹⁸F-FDG in oncology and neurology examinations, with DRLs of 186.11 and 136.16 MBq, respectively. These values were notably almost twice lower than several reports in other countries. Conclusion: There is a lack of comprehensive data on most DRLs for PET imaging at this center because of the nonwidespread use of several radiopharmaceuticals. However, the lower DRLs for ¹⁸F-FDG can highlight the need for ongoing investigation toward the establishment of local DRLs, as well as assurance on the safety and efficiency of radiation used in nuclear medicine.

Brain death denotes the loss of function in both the cerebrum and the brain stem, leading to coma, absence of spontaneous respiration in the setting of adequate stimulus, and the cessation of all brain stem reflexes. Although spinal reflexes such as deep tendon, plantar flexion, and withdrawal reflexes may persist, recovery is not possible. The cessation of brain function qualifies as death because of its central role in coordinating vital bodily functions. Although brain death is largely determined by a clinical and neurologic examination, confounding variables may necessitate ancillary testing such as cerebral brain perfusion imaging.

^99mTc-labeled dimercaptosuccinic acid (^99mTc-DMSA) imaging is a well-established and highly sensitive method for the diagnosis of several renal cortical disorders affecting children and adults. Beginning in 2014, ^99mTc-DMSA availability was severely impaired when it was added to the Drug Shortages List of the U.S. Food and Drug Administration and was commercially unavailable thereafter. The agent shortage negatively impacted practitioners' ability to evaluate renal cortical defects in children and adults and changed renal imaging practice. A survey among pediatric nuclear medicine clinicians confirmed the clinical need for ^99mTc-DMSA. Finally, in early 2023 the Food and Drug Administration again approved ^99mTc-DMSA in the United States. During the ^99mTc-DMSA shortage, established practitioners may not have had the opportunity of using ^99mTc-DMSA as they were accustomed in their experience. Also, newer imaging specialists and referring physicians and technologists may not have benefited from having ^99mTc-DMSA in their training. Therefore, it is time to bring back ^99mTc-DMSA into the armamentarium of imaging methods available to evaluate regional cortical renal function.

Our aim was to develop communication support material for information sharing related to an ¹⁸F-FDG PET/CT examination. Methods: The study had a qualitative design adapting a multiphase structure. A prototype of communication support material consisting of illustrations and text related to an ¹⁸F-FDG PET/CT examination was developed. Interviews were conducted with patients scheduled for an ¹⁸F-FDG PET/CT examination for the first time, and questionnaires were collected from health care professionals with experience in ¹⁸F-FDG PET/CT. The communication support material was revised until consensus was reached about it. Results: The results are based on interviews with patients (n = 10) and questionnaires collected from health care professionals (n = 9). The overall theme revealed that patient information about an ¹⁸F-FDG PET/CT examination is a balancing act between text and illustrations. The analysis showed 2 categories: "illustrations as a complement" and "easy-to-understand layout." Conclusion: The participants strengthened the development of the communication support material by bringing in valuable viewpoints from various perspectives. The results support a person-centered approach in which information about an ¹⁸F-FDG PET/CT examination can be adapted to each patient's needs as a balancing act between text and illustrations.