A multi-institutional assessment of eye lens dose in nuclear medicine clinics.

AIM: The endeavor was to measure the lens dose of actively working staff in nuclear medicine departments. MATERIAL AND METHODS: This study was accomplished in three nuclear medicine sites. A total of 23 workers in nuclear medicine joined this work. Among them are 6 SPECT/ CT technologists, 6 PET/CT technologists, 3 PET/MRI technologists, 5 radiopharmacists, 2 physicists, and 1 physician. EXTDOSE Hp(3) OSL dosimeter with tissue equivalent beryllium-oxide crystal was used for lens dose measurement. All participants were asked to wear the lens dosimeter for 2 months as near to the eye level as possible. RESULTS: Pooling the dose measures together yielded an average lens dose of 1.48 ±â€…0.77 mSv for the radiopharmacy team, 1.44 ±â€…0.26 for PET/ CT technologists, 0.86 ±â€…0.45 mSv for SPECT/ CT technologists, 0.38 mSv for the sole physician administered 177Lu, and 0.45 ±â€…0.02 mSv for the physicists conducting 131I therapy. Moreover, normalizing the lens dose to the labeled activity led to a lens dose of 2.2 ±â€…1.4 µSv/GBq for the radiopharmacy team. Likewise, per administered activity: 23.8 ±â€…7.3 µSv/GBq for PET/CT and PET/MRI technologists, 12.2 ±â€…10.5 µSv/GBq 99mTc for SPECT/CT technologists, 6.0 ±â€…0.81 µSv/GBq 131I for physicists, and 3.0 µSv/GBq 177Lu for the physician. CONCLUSION: It was deduced that the annual occupational lens dose of the nuclear medicine workers varied from 2.3 to 11.5 mSv/year; however, one radiopharmacist projected annual lens dose as close to the lens equivalent dose limit (20 mSv/year) as 17.9 mSv.

SPECT/CT-based dosimetry of salivary glands and iodine-avid lesions following 131I therapy.

Objective: The purpose was to provide uptake and radiation dose estimates to salivary glands (SG) and pathologic lesions following radioiodine therapy (RIT) of differentiated thyroid cancer patients (DTC). Methods: A group of DTC patients (n = 25) undergoing 131I therapy joined this study with varying amounts of therapeutic activity. Sequential SPECT/CT scans were acquired at 4 ± 2, 24 ± 2, and 168 ± 3 h following administration of 3497-9250 MBq 131I. An earlier experiment with Acrylic glass body phantom (PET Phantom NEMA 2012 / IEC 2008) was conducted for system calibration including scatter, partial volume effect and count loss correction. Dose calculation was made via IDAC-Dose 2.1 code. Results: The absorbed dose to parotid glands was 0.04-0.97 Gy/GBq (median: 0.26 Gy/GBq). The median absorbed dose to submandibular glands was 0.14 Gy/GBq (0.05 to 0.56 Gy/GBq). The absorbed dose to thyroid residues was from 0.55 to 399.5 Gy/GBq (median: 21.8 Gy/GBq), and that to distal lesions ranged from 0.78 to 28.0 Gy/GBq (median: 3.12 Gy/GBq). 41% of the thyroid residues received dose > 80 Gy, 18% between 70-80 Gy, 18% between 40-70 Gy, and 23% has dose < 40 Gy. In contrast, 18% of the metastases exhibited a dose > 80 Gy, 9% between 40-60 Gy, and the dose to the vast majority of lesions (64%) was < 40 Gy. Conclusion: It was inferred that dose estimation after RIT with SPECT/CT is feasible to apply, together with good agreement with published 124I PET/CT dose estimates. A broad and sub-effective dose range was estimated for thyroid residues and distal lesions. Moreover, the current methodology might be useful for establishing a dose-effect relationship and radiation-induced salivary glands damage after RIT.

Embryo/Fetus Doses from 18F-Fludeoxyglucose Radiopharmaceutical in Positron Emission Tomography/ Computed Tomography.

Aim: The embryo/fetus may be accidentally exposed to ionizing radiation. The aim of this study is to calculate embryo/fetus doses in pregnant women who underwent F-18 fludeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) scan. Materials and Methods: Between June 2015 and June 2021, 15 pregnant women underwent F-18 FDG PET/CT applied to the Genetic Research Center (GETAM). The OLINDA/EXM package program was used for internal radiation dosimetry according to the Medical Internal Radiation Dose scheme. FetDose V4 computer software was used to compute the embryo/fetus absorbed dose from CT scan. Results: The amount of the injected F-18 FDG activity to patients varied between 333 and 555 MBq. The mean embryo/fetal dose from F-18 FDG was 7.2 ± 2.8 mGy. In addition, the CT component dose to the embryo/fetus dose ranged from 8.5 to 16 mGy with a mean of 12.14 ± 2.05. Conclusions: The embryo/fetus dose from F-18 FDG PET/CT was <15 mGy, however, questioning the women's childbearing prior to scintigraphy is the first-line strategy to avoid accidental radiation exposure and stochastic risks.

Quantitative improvement of lymph nodes visualization of breast cancer using 99mTc-nanocolloid SPECT/CT and updated reconstruction algorithm.

This study aimed to evaluate the impact of attenuation and scatter correction on the contrast to noise ratio values of SPECT and SPECT/CT images in sentinel lymph nodes scintigraphy. In addition, the effect of using an iterative reconstruction algorithm with variable iterations number and fixed subsets was also investigated. 35 patients with a total of 44 lymph nodes were recruited in the current study. SPECT/CT scans were performed 3-4 h following peri-tumoral 99mTc-nanocolloid injection (≈1 mCi) at four points. Two image types were generated including SPECT with attenuation and scatter correction (AC-SC) and SPECT without any correction (NoAC-NoSC). The acquired projections were repeatedly reconstructed with eight subsets and 10, 20, 30 and 40 iterations. Afterwards, the calculated contrast to noise ratio values were used to investigate the effect of number of iteration and to compare the image quality of SPECT/CT and SPECT only. The mean contrast to noise (CNR) values of SPECT/CT scans were found to be 19,737, 26,418, 34,282 and 31,187 at 10, 20, 30 and 40 iterations, respectively. Whereas, the mean CNR values in SPECT (NoAC-NoSC) were as low as 8506, 10,582, 13,791 and 12,143 at 10, 20, 30 and 40 iterations, respectively. The CNR values of both SPECT and SPECT/CT improved with increasing number of iterations up to 30 iterations and then slightly decreased after 30-40 iterations. Likewise, no significant difference was found between 10 and 20 iterations (Pvalue = 0.06) in SPECT/CT, while a statistically significant difference was observed between 10 iterations and both 30 and 40 iterations (Pvalue < 0.05). It is concluded that the attenuation and scatter correction in SPECT/CT optimized the CNR values up to threefold compared to SPECT alone. Thus, a considerable improvement in the CNR values and the image quality can be obtained by increasing the iterations number to peak of 30 iterations.

Comparison between planar, SPECT and SPECT/computed tomography systems in 99mTc- nanocolloid sentinel lymph node imaging: phantom design and clinical investigations.

PURPOSE: It was aimed to examine the performance of planar, SPECT and SPECT/CT in lymph nodes detection of breast cancer. MATERIALS AND METHODS: In-house made phantom was immersed in water-filled container. Disparate activities were injected into spheres emulating breast tumour (1.5 cm), and adjacent lymph nodes (1, 0.5 and 0.25 cm). Planar, SPECT and SPECT/CT scans were made at depths of 1, 3, 5, 7 and 9 cm. Rose Criteria was employed to investigate the detectability in planar imaging, and contrast to noise ratios (CNRs) were used in SPECT and SPECT/CT images. SPECT and SPECT/CT of 20 patients were randomly incorporated in the current study. RESULTS: CNR values from planar images at 1 cm depth for the simulated nodes of 1, 0.5and 0.25 cm were 36, 18 and 17, respectively. Whereas, those from SPECT/CT were 94.5, 63.3 and 20.9, repectively. CNRs from SPECT were lower than SPECT/CT in order of 60.1, 41.8 and 17.1 at the same depth. At 9 cm, CNR values of 1, 0.5 and 0.25 cm from the planar images were 14, 6 and 5, respectively. While CNR values from SPECT were higher as 53.6, 38.0, and 14.9, respectively, and the greatest CNRs were in SPECT/CT as 85.7, 55.8, and 19.1, repectively. CONCLUSION: The CNR values in SPECT/CT were 1.5- and 3.5-folds higher than SPECT and planar imaging at depth range 1-9 cm. The patients study exhibited larger SPECT/CT CNRs over SPECT as great as 1.6-fold.

Red bone marrow dose estimation using several internal dosimetry models for prospective dosimetry-oriented radioiodine therapy.

The aim of the present study was to review the available models developed for calculating red bone marrow dose in radioiodine therapy using clinical data. The study includes 18 patients (12 females and six males) with metastatic differentiated thyroid cancer. Radioiodine tracer of 73 ± 16 MBq 131I was orally administered, followed by blood sampling (2 ml) and whole-body scans (WBSs) done at several time points (2, 6, 24, 48, 72, and ≥ 96 h). Red bone marrow dose was estimated using the OLINDA/EXM 1.0, IDAC-Dose 2.1, and EANM models, the models developed by Shen and co-workers, Keizer and co-workers and Siegel and co-workers, and Traino and co-workers, as well as the single measurement model (SMM). The results were then compared to the standard reference model Revised Sgouros Model (RSM) reported by Wessels and co-workers. The mean dose deviations of the Traino, Siegel, Shen, Keizer, OLINDA/EXM, EANM, SMM, and IDAC-Dose 2.1 models from the RSM were - 17%, - 24%, 6%, - 29%, - 15%, 40%, 48%, and - 8%, respectively. The statistical analysis demonstrated no significant difference between the results obtained with the RSM and with those obtained with the Shen, Traino, OLINDA/EXM, and IDAC-Dose 2.1 models (t test; pvalue > 0.05). However, a significant difference was found between RSM doses and those obtained with the EANM, SMM, and Keizer models (t test; pvalue < 0.05). The correlation between red marrow dose from the SMM and EANM models was modest (R2 = 0.65), while the crossfire dose calculated with the OLINDA/EXM and IDAC-Dose 2.1 models were in good agreement with each other and with the reference model. The findings obtained indicate that most of the dosimetry models can be used for a reliable dosimetry, and the calculated total body doses can be considered as a reliable non-invasive option for a conservative activity planning. In addition, the excellent performance of the IDAC-Dose 2.1 model will be of particular importance for a practical and accurate dosimetry, with the advantages of allowing for the use of realistic advanced phantoms and updated dose fractions, and of providing information about the blood dose contribution to the red bone marrow.