PATIENT-SPECIFIC DOSIMETRY FOR PEDIATRIC IMAGING OF 99mTc-DIMERCAPTOSUCCINIC ACID WITH GATE MONTE CARLO CODE

Patterns and trends of population radiation exposure and projected the risk of exposure-induced death from gamma camera examinations in Yazd Province

INTRODUCTION

The use of nuclear medicine examinations as imaging modalities has recently increased. This study aimed to assess the radiation dose delivered to patients from common diagnostic nuclear medicine examinations and estimate the risk of exposure-induced death (REID). In addition, the frequency of nuclear medicine procedures were evaluated from 2015-2018.

MATERIALS AND METHODS

The data were collected from adult patients who had undergone cardiac, skeletal, renal, lacrimal, and thyroid imaging. For each patient, the effective dose was calculated using dose conversion factors, and REID was estimated using PCXMC. The frequency of examinations between 2015 and 2018 was obtained from the hospital information system (HIS).

RESULTS

The highest estimated effective dose was attributed to the scans of myocardial stress (8.09 ± 1.28 mSv), myocardial rest (5.59 ± 1.27 mSv), and thyroid imaging (3.93 ± 0.55 mSv). In addition, cardiac stress examination had the highest REID values for solid cancers (212.5 ± 67.5) and bone scans had the highest REID values for leukemia (11.5 ± 2.5). A large increase in the number of myocardial perfusion scans was a significant contributor to an increase in collective effective dose from 23.37 man-Sv in 2015 to 49.47 man-Sv in 2018, a compound annual growth rate (CAGR) of 26%.

CONCLUSION

Although the annual frequency and per capita effective dose of nuclear medicine procedures in Yazd Province increased continuously, they were comparably lower than those reported for other countries. Despite this, the cancer risks of nuclear medicine scans at the individual level are negligible (around 0.01% excess fatal cancer risk), yet the increasing tendency for these examinations could be of concern.

Prediction of Absorbed Dose to Normal Organs with Endocrine Tumors for I-131 by use of 99mTC Single Photon Emission Computed Tomography/Computed Tomography and Geant4 Application for Tomographic Emission Simulation

Introduction:

This study aimed to predict the dose absorbed by normal organs with neuroendocrine tumors for ¹³¹I using single photon emission computed tomography/computed tomography (SPECT/CT) images and Geant4 application for tomographic emission (GATE) simulation.

Materials and Methods:

Four to 5 whole-body planar scan series, along with one SPECT/CT image, were taken from four patients following ^99mTc-hynic-Tyr³-octreotide radiotracer injection. After image quantification, the residence time of each organ was calculated using the image analysis and the activity time curves. The energy deposit and dose conversion (S-value) were extracted from the GATE simulation for the target organs of each patient. Using the residence times and S-values, the mean absorbed dose for the target organs of each patient was calculated and compared with the data obtained from the standard method.

Results:

Very close agreement was obtained between the S-value of the self–organ irradiation. The mean percentage difference between the two methods (i.e. GATE and Medical Internal Radiation Dose [MIRD]) was 1.8%, while a weak agreement was observed for cross-organ irradiation. The percentage difference between the total absorbed doses by the organs was 2%. The percentage difference between the absorbed doses obtained for tumors and three considered normal organs estimated by the GATE method was slightly higher than the MIRD method (about 11% on average for tumors).

Conclusion:

Regardless of the small difference between the obtained results for the organs and absorbed doses of the tumors in the present study, patient-specific dosimetry by the GATE methods is useful and essential for therapeutic radionuclides such as ¹³¹I due to high cross-dose effects, especially for young adult patients, to ensure the radiation safety and increase the effectiveness of the treatment.

Implementation of dose point kernel (DPK) for dose optimization of 177Lu/90Y cocktail radionuclides in internal dosimetry

BACKGROUND

Due to the importance of choosing the applicable dosimetry method in radionuclide therapy, the present study was conducted to investigate the efficiency of the implementation of Dose Point Kernel (DPK) for dose optimization of ¹⁷⁷Lu/⁹⁰Y Cocktail Radionuclides in internal Dosimetry.

METHODS

In this study, simulations and calculations of DPK were performed using the GATE/GEANT4 Monte Carlo code. For specific liver dosimetry, the NCAT phantom and convolution algorithm-based Fast Fourier Transform method was used by MATLAB software.

RESULTS

The self-dose of ¹⁷⁷Lu and ⁹⁰Y radionuclides in the liver of NCAT phantom were 1.1708E-13, and 4.8420E-11 (Gy/Bq), respectively, and the cross-dose of ¹⁷⁷Lu and ⁹⁰Y radionuclides out of the liver of NCAT phantom were 2.03615E-16, and 0.8422E-13 (Gy/Bq) respectively. Overall results showed that with an increase the value of ⁹⁰Y with quarter steps in a cocktail, the amount of the self-dose increase 1.5, 6, and 29 times respectively, and with an increase the value of ¹⁷⁷Lu in quarter step in a cocktail, the amount of the cross dose decrease 3, 15 and 68 percent respectively.

CONCLUSION

Generally, the present results indicate that the calculated DPK functions of ¹⁷⁷Lu and ⁹⁰Y cocktails can play an important role in choosing the best combination of radionuclide to optimize treatment planning in cocktail radionuclide therapy.

Data on biodistribution and dose calculation of 99mTechnetium -Dimercaptosuccinic acid in pediatric patients using a hybrid planar/single emission computed tomography method

The Biodistribution and absorbed dose data from the administration of radiopharmaceuticals are necessary to analyze the risk-benefit of the procedure. It has particular significance in children, as their metabolism is very different from adults. ^99mTc-DMSA scintigraphy is the golden standard imaging technique for the assessment of renal involvement in febrile urinary tract infection and renal sequels. However, ^99mTc-DMSA biodistribution data for children are scarce and usually outdated which have been obtained by older methods. In this data article, we analysed the biodistribution of ^99mTc-DMSA in 12 pediatric patients using planar/SPECT method. In addition, the radiation absorbed doses were calculated by MIRDOSE software.

Estimating the Absorbed Dose of Organs in Pediatric Imaging of 99mTc-DTPATc-DTPA Radiopharmaceutical using MIRDOSE Software

Introduction:

In this study, organ radiation doses were calculated for the renal agent ^99mTc-DTPATc-DTPA in children. Bio-kinetic energy of ^99mTc-DTPATc-DTPA was evaluated by scintigraphy and estimates for absorbed radiation dose were provided using standard medical internal radiation dosimetry (MIRD) techniques.

Material and Methods:

In this applied research, fourteen children patients (6 males and 8 females) were imaged using a series of planar and SPECT images after injecting with technetium-^99mTc-DTPA diethylenetriaminepentaacetic acid (^99mTc-DTPATc-DTPA). A hybrid planar/SPECT method was used to plot time-activity curves to obtain the residence time of the source organs and also MIRDOSE software was used to calculate the absorbed dose of every organ. P-values were calculated using t-tests in order to make a comparison between the adsorbed doses of male and female groups.

Results:

Mean absorbed doses (µGy/MBq) for urinary bladder wall, kidneys, gonads, liver and adrenals were 213.5±47.8, 12.97±6.23, 12.0±2.5, 4.29±1.47, and 3.31±0.96, respectively. Furthermore, the mean effective dose was 17.5±3.7 µSv/MBq. There was not any significant difference in the mean absorbed dose of the two groups.

Conclusion:

Bladder cumulated activity was the most contribution in the effective dose of patients scanned with ^99mTc-DTPATc-DTPA. Using a hybrid planar/SPECT method can cause an increase in accumulated activity accuracy for the region of interest. Moreover, patient-specified internal dosimetry is recommended.