Journal of nuclear medicine technology最新文献

Various techniques have been used in attempts to reduce interfering gastrointestinal activity in myocardial perfusion imaging (MPI); however, these approaches have yielded inconsistent results. The goal of this study was to investigate the efficacy of monitored walking, a previously unexplored technique, in reducing subdiaphragmatic activity-related artifacts during pharmacologic stress ^99mTc-tetrofosmin MPI with SPECT to improve the overall image quality. Methods: The study included patients who underwent MPI with pharmacologic stress. They were given a step counter immediately after the radiotracer injection and were randomized into a group A, with a request to walk at least 1,000 steps before imaging, and a group B, with no specific instructions about walking. The reconstructed SPECT images were assessed visually. Moderate and severe levels of subdiaphragmatic tracer activity were considered relevant for the interpretation of the scans. Additionally, myocardial and abdominal activity was semiquantitatively assessed on raw planar images, and the mean myocardium-to-abdomen count ratios were calculated. Results: We enrolled 199 patients (95 patients in group A and 104 patients in group B). Clinical characteristics did not differ significantly between the 2 groups. Patients in group A walked more steps than patients in group B (P < 0.001), but there were no differences in the proportion of accepted scans between the 2 groups (P = 0.41). Additionally, there were no differences in the proportion of relevant subdiaphragmatic activity between the groups (P = 0.91). The number of steps did not impact the acceptance rate (P = 0.29). Conclusion: A higher number of steps walked during the waiting period between pharmacologic stress and acquisition does not affect subdiaphragmatic activity-related artifacts or the proportion of accepted scans after pharmacologic stress. However, pedometer use and clear instructions motivate patients to walk while awaiting imaging. Larger studies are required to compare a higher-step-count group with a sedentary control group to assess the influence of walking on gastrointestinal artifacts in MPI.

Many nuclear medicine technologists find themselves in the role of clinical instructor, often without much in the way of educational background. This article provides a few recommendations on how to get started in this role. After distinguishing between the roles of affiliate education supervisor and clinical instructor, the article discusses 2 basic tools: the clinical course learning outcomes and the student handbook. Expectations for students are reviewed. An important aspect of clinical instruction is the attitude of the instructor. Clinical instructors can motivate students or demotivate them, with this choice having a significant impact on the student's development. Overall, the desire and determination to be pleasant and helpful to students make the greatest difference in their development into nuclear medicine technologists.

We devised and clinically validated a schema of rapid personalized predictive dosimetry for ¹⁷⁷Lu-PSMA-I&T in metastatic castration-resistant prostate cancer. It supersedes traditional empiric prescription by providing clinically meaningful predicted absorbed doses for first-strike optimization. Methods: Prostate-specific membrane antigen PET was conceptualized as a simulation study that captures the complex dosimetric interplay between tumor, marrow, and kidneys at a single time point. Radiation principles of fractionation, heterogeneity, normal-organ constraints (marrow, kidney), absorbed dose, and dose rate were introduced. We created a predictive calculator in the form of a free, open-source, and user-friendly spreadsheet that can be completed within minutes. Our schema achieves speed and accuracy by sampling tissue radioconcentrations (kBq/cm³) to be analyzed in conjunction with clinical input from the user that reflect dosimetric preconditions. The marrow-absorbed dose constraint was 0.217 Gy (dose rate, ≤0.0147 Gy/h) per fraction with an interfraction interval of at least 6 wk. Results: Our first 10 patients were analyzed. The first-strike mean tumor-absorbed dose threshold for any prostate-specific antigen (PSA) response was more than 10 Gy (dose rate, >0.1 Gy/h). The metastasis with the lowest first-strike tumor-absorbed dose correlated the best with the percentage decrease of PSA; its threshold to achieve hypothetical zero PSA was 20 Gy or more. Each patient's PSA doubling time can be used to personalize their unique absorbed dose-response threshold. The predicted mean first-strike prescription constrained by marrow-absorbed dose rate per fraction was 11.0 ± 4.0 GBq. Highly favorable conditions (tumor sink effect) were dosimetrically expressed as the combination of tumor-to-normal-organ ratios of more than 150 for marrow and more than 4 for kidney. Our schema obviates the traditional role of the SUV as a predictive parameter. Conclusion: Our rapid schema is feasible to implement in any busy real-world theranostics unit and exceeds today's best practice standards. Our dosimetric thresholds and predictive parameters can radiobiologically rationalize each patient's first-strike prescription down to a single becquerel. Favorable tumor-to-normal-organ ratios can be prospectively exploited by predictive dosimetry to optimize the first-strike prescription. The scientific framework of our schema may be applied to other systemic radionuclide therapies.

The radiation exposure of the hands of nuclear medicine laboratory technicians is largely due to the dispensing of radiopharmaceuticals into syringes. To reduce this exposure, a multiradionuclide automatic dispensing system (ADS) for syringes of radiopharmaceuticals was introduced. The aim of this study was to determine the effect of this ADS on hand dose compared with manual dispensing. Methods: The total hand dose per month for all personnel (12 technicians) was measured with ring dosimeters at the base of the index finger for 13 mo: 7 mo with manual syringe dispensing (radiopharmaceuticals containing ^99mTc,¹⁸F, ¹⁷⁷Lu, ⁶⁸Ga, ⁹⁰Y, and ²²³Ra) and 6 mo with ADS (automatic: radiopharmaceuticals containing ¹⁸F and ¹⁷⁷Lu; manual: radiopharmaceuticals containing ^99mTc, ⁶⁸Ga, ⁹⁰Y, and ²²³Ra). Results: The mean total hand dose per month was reduced from 52.8 ± 10.2 mSv with manual dispensing to 21.9 ± 2.7 mSv with ADS (P < 0.001), which is an absolute decrease of 59%. Meanwhile, the total handled activity increased from 369 to 505 GBq (P < 0.001). ¹⁸F-containing radiopharmaceuticals were the most commonly dispensed, at 182 GBq per month. The increase in total handled activity was largely due to an increase in ¹⁷⁷Lu (from 25 to 123 GBq), partially because of the introduction of [¹⁷⁷Lu]Lu-PSMA-I&T. When correcting for this increase in handled activity, the hand dose was reduced by 69%. Conclusion: The introduction of a multiradionuclide syringe ADS decreased the hand dose to personnel by 69% when corrected for the increase in handled activity. Expanding the number of radiopharmaceuticals being dispensed by the system could potentially further decrease personnel hand dose.

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.