Iranian Journal of Medical Physics
Volume:18 Issue: 6, Nov-Dec 2021

The aim is to observe that the measurement of tissue maximum ratio (TMR) by water phantom directly differs from the calculation of TMR from percentage depth dose (PDD) or not.
The linear accelerator Siemens (6 MV & 10MV) with 82 leaves (MLC)-based stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). The water phantom (PTW) was used for measuring the dosimetric parameter of TMR &%DD. This data was calculated using 0.125 cc simeflex ionization chamber. The small fields have different sizes ranging from 12.50 to 40.00 mm in diameter.
There were small observations of mean error ≤ 1.50 % for all collecting data related to depths and field sizes.  The Statistical Package of Social Science (SPSS) (version 26) to generate results. Wilcoxon Signed Ranks Test was used to compare two groups; (p ≤ 0.05) was considered significant. There were no significant differences between TMR data. The measured TMR data calculated from %DD had a strong positive correlation for cone sizes from 1.0 cm x1.0 cm to 10.0 cm x10.0cm.
It has been shown that the calculation of TMR data from PDD agrees with the measuring values directly, and it is accepted for use in treatment.

The evaluation of occupational exposure and related trends due to external ionizing radiation in diagnostic and therapeutic purposes has become crucial to understanding the implementation of regulatory acts and technological advancement. This study describes the status of occupational radiation exposure in the radiotherapy (RT) and diagnostic X-ray (DR) sector and the comparison with related research.
Overall, 12141 radiation workers were monitored using thermoluminescent dosimeters (TLDs) read-out by Harshaw TLD Reader (Model 4500) on a quarterly basis. Several parameters such as annual collective effective dose, average annual effective dose, collective and individual dose distribution, and the probability of cancer risk were analyzed.
The number of monitored workers increased by around 35%, whereas the number of radiation workers who received a measurable amount of doses decreased by around 37% during 2014-2018. The annual average effective doses in RT and DR were in the range of 0.017-0.1112 and 0.076-0.1702 mSv, respectively. The results indicate that more than 94% of the total collective dose was for the non-physician group. Among exposed radiation workers, almost 78% received doses below 1mSv and <1% received doses over 15mSv. The annual average effective dose is five times lower than the worldwide average value. Depending on the average occupational dose, the expected number of radiation-induced cancer cases among the monitored workers is below 1.
Dose distribution tends to move towards lower levels and reveals that the majority of the organizations maintain adequate radiation protection.

Radiomic features robustness analysis is a critical issue before clinical decision making. In this study, the reproducibility and robustness of radiomic features in computed tomography (CT) and magnetic resonance (MR) images of glioblastoma cancer patients were analyzed regarding inter-scanner and inter-modality variations.
CT and MR Images of eighteen glioblastoma cancer patients were used to extract the radiomic features following image segmentation. Coefficient of variation (COV), intraclass correlation coefficient (ICC), and concordance correlation coefficient (CCC) analysis were done to select the most robust features in all paired combinations of CT and MR images include T1-T2, T1-FLAIR, T1-ADC, T1-CT, T2-FLAIR, T2-ADC, T2-CT, FLAIR-ADC, FLAIR-CT, and ADC-CT.
The features with COV ≤ 5% or ICC ≥ 90% or CCC ≥ 90%, considered as the most robust features, include the shape features, Minimum (belong to first-order Features), IMC1, IDN, IDMN (belong to GLCM), and Run Length Non-Uniformity (belongs to Gray Level Run Length Matrix).
In this study we presented a large image feature variation among different imaging modalities including CT and MRI. Our results identified several robust features that could be used for further clinical analysis.

The objective of this study was to evaluate the usefulness of Computed Tomography (CT) images acquired through repeated subtraction reconstruction algorithms to reduce metal artifacts in CT Treatment Planning System (TPS).
Origin images of Gammex phantom and Rando phantom and non-orthopedic metal artifact reduction (O-MAR) images were obtained after high density implantation. O-MAR applied images were also obtained. For evaluation of images, regions of interest (ROI) were set at five tissue rods and three points directly affected by artifacts in Gammex phantom. CT number and noise were compared and analyzed. Based on the investigated results using the Gammex phantom, three virtual cylinder target volumes were set on the Rando phantom to dose change of the radiation treatment planning according to the O-MAR. The average dose was then compared and analyzed.
CT number difference according to the application of O-MAR showed significant difference among lung and bone rod and 3 ROI directly affected. Noise difference according to O-MAR application was significantly different in rod except for bone rod. In the treatment plan using Rando phantom, non-O-MAR and O-MAR images showed -4.3 ~ 1.9% and -0.4 ~ 2.3% dose differences, respectively.
Applying an O-MAR can reduce image distortion due to high-density implantation, improve image quality, and correct CT numbers.

The present study aimed to compare plans with Bone Marrow sparing (BM-IMRT) and without Bone Marrow Sparing (N-IMRT).
Fifteen cases of cervical cancer cases were selected for retrospective study. All the cases were previously treated with normal IMRT. For this study, plans with BM-IMRT were created again for all patients following RTOG guidelines. The prescribed dose of 50Gy in 25 fractions was given. The plan having coverage of 95% of PTV receiving 95% of the prescribed dose was accepted. The plans were compared based on PTV coverage (dose to 2%, 98% of target); constraints of OARs (Organs at Risk) were the volume of 40% < 40Gy for normal bladder and rectum (volume receiving dose 5Gy) V5<95%, V10<80%, V20<60%, V30<50% and V40<35% respectively for Bone marrow and lowest possible doses to bowel were given for planning criteria. Apart from this, HI, CI and R50% were also calculated concerning PTV coverage to analyze plan quality.
There was a statistical difference in P-values of D2, D98, TV95, HI, R50% but the actual difference is less than 2%. In the case of OARs, there were also significant differences in statistical as well longitudinal in values of V10, V20, V30 and V40 of Bone Marrow (P<0.01) and there was only statistical differences (p<0.05) at V50 of bladder and rectum.
Without scarifying dose coverage for planning target volume, bone marrow can be spared while treating cervical cancer patients using IMRT technique with bone marrow as an extra constraint.

Bilateral breast cancer cases are classified as complex in radiotherapy treatment, especially those with the left side mastectomy and right-side lumpectomy with left side supraclavicular lymph nodes patients. The purpose of this study is to find the optimum treatment planning technique among the three available techniques: 3Dimentional conformal Radiotherapy (3D-CRT), Intensity modulated radiation therapy (IMRT), and Volumetric Modulated Arc Therapu (VMAT).
Ten Bilateral breast cancer included in this study with left-side mastectomy and right-side lumpectomy with left-side supraclavicular lymph nodes. The patients are delineated by oncologists and prepared for radiation planning by MONACO 5.1 treatment planning system (TPS) with an X-ray photon beam of 6 MV or 10 MV energy using ‎ELEKTA‏’‏s Agility linear accelerator. The prescribed dose is set at 4005 cCy per 15 fractions. Statistically with anova test among each other.
The treatment with 3D-CRT, IMRT, and VMAT show a significant difference in the results. VMAT gives high dose distribution for the left mastectomy breast and its regional supraclavicular lymph nodes, while the IMRT gives a higher value for the right side breast with lumpectomy. The good homogeneity index is acquired with IMRT, while VMAT gives a better conformity index. The 3D-CRT planning technique lowers the dose to the heart and lunges better than the other techniques.
depending on the patient health and stage, the optimum treatment planning is applied. VMAT and IMRT give effective results than the 3D-CRT.

Over the last decades, there has been an increasing trend in using cell phones which are exposing us to Radio-Frequency (RF) and Extremely Low Frequency (ELF) magnetic fields with various known and unknown biological effects. This protective study aimed to investigate the impact of environmental 217 Hz (as an ELF) magnetic fields generated by mobile phones on angiogenesis as an essential factor in tumor growth, in vitro and in vivo.
Magnetic fields with amplitudes of 0.5, 6, 22, 44, 65 & 159 µT were exposed on Human umbilical vein endothelial cells (HUVECs) and proliferation and viability of cells were measured. 3D angiogenesis assay was done by culturing HUVEC-covered microbeads in collagen gel and counting the number of sprouting micro-vessels per microbead. The percent of CD31 positive areas in breast tumor tissues of mice was assessed in the in vivo study.
Results showed that some of the applied amplitudes could increase proliferation as well as the viability of HUVECs. Furthermore, 22 and 44 µT magnetic fields could significantly increase the angiogenesis of breast tumors in the mouse.
There is a promoting effect from ELF magnetic fields generated by cell phones on the angiogenesis of tumors. It will be helpful if we recommend that cancer patients not to be exposed to cell phones.

According to new developments in radiation therapy techniques, accurate dose verification in three dimensions has become more critical. Polymer gel dosimeters (PGDs) are valuable tools to be used for this purpose. Nowadays, various imaging modalities are employed to read out the gels. This study was aimed to investigate the measured dose distribution recorded in MAGIC-f PGD with optical computed tomography (OCT) by comparison with MRI.
We developed an in-house charge-coupled device (CCD) based cone-beam OCT scanner. A phantom of MAGIC-f PGD was used to measure a four-field box dose distribution. MRI and OCT scanners were performed for gel readouts. Both measurement results were compared by gamma index analysis with various acceptance criteria. The temporal stability of the gel was also evaluated with the OCT readout system.
The percentage of isodose lines from two measured datasets agreed well together. The pass rates were 99.02%, 96.8%, and 89.8% with 5%/5mm, 4%/4mm, and 3%/3mm criteria, respectively, at the phantom's central axial slice.
The results indicate that the performance of this OCT system is almost the same with acceptable discrepancies to the MRI as accepted standard readout modality, and it can be used for three-dimensional dose verifications.

Bolus-type materials are needed in case of superficial lesions radiotherapy. This work determined the dosimetric accuracy of two commercial treatment planning systems (TPS) for calculating photon dose distribution in the presence of eXaSkin bolus.
Dose calculations were performed on collapsed cone convolution/superposition (CCC) and anisotropic analytical algorithm (AAA) using computed tomography (CT) images of heterogeneous CIRS phantom. EBT3 film was used to obtain percentage depth dose (PDD) curves and gamma index was utilized to compare the accuracy of the two algorithms. The passing rate of the global gamma index with the passing criterion of 3mm/3% as the standard criterion was considered 95% in this study.
Surface dose in PDD curves increased in the presence of 0.5 cm thick eXaSkin bolus. The passing rates of gamma index with standard passing criterion between AAA algorithm and EBT3 film measurements without and with bolus were 95% and 95.5%, respectively, while they were equal to 96% and 97.5% for CCC algorithm.
There was a good agreement in dose calculation between AAA and CCC algorithms. Furthermore, eXaSkin bolus increased the surface dose by a factor of 25%.

State-of-art radiotherapy technique as Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) are being used to treat cancer with high accuracy. Verification of planned and delivered dose distribution is critical; in this study we evaluated quality assurance (QA) results and effectiveness of Electronic Portal Imaging Device (EPID) and IMatriXX.
Performance of EPID and IMatriXX was assessed with dose measurements using ionization chamber. Calibrated IMatriXX and EPID are used for pre-treatment patient-specific quality assurance (PSQA) for 204 patients plans with IMRT treatment technique on LINAC. Dose image were compared for gamma evaluation (3%/3mm) and combination of three scalar parameters were assessed against EPID to quantify gamma results within region of interest; namely average g(gavg), maximum g(gmax) and Area Gamma<1.
The g correlation comparisons yielded an average correlation of 0.991 for IMatriXX and 0.978 for EPID. The maximum gamma value is 0.99, while the minimum gamma is 0.872 for IMatriXX and 0.926 for EPID, which can be used as baseline. Our result suggests that EPID dosimetry, provides lower gamma correlation values than IMatriXX. Students Unpaired t-Test analysis was applied to two data sets. The calculated p-value 0.001 shows good correlation.
The EPID and IMatriXX have significantly improved dosimetric properties, providing more sensitive, accurate pre-treatment PSQA. The result shows EPID can replace other 2D dosimetry methods and ionization chamber measurements. It’s an efficient, sensitive and accurate dosimetry tool and is primary protocol of pre-treatment quality assurance.

Linear accelerator multileaf collimator (MLC) requires to be tested with best possible quality assurance tools and accordingly treatment planning system input with the data for appropriate modeling of MLC. Dose calculation is affected due to MLC modeling, especially when using the high standard treatment techniques like intensity-modulated radiation therapy (IMRT) or volumetric modulation arc therapy (VMAT).
An MLCI 2 (Elekta Inc.) multileaf collimator is verified by 2D detector matrix (IBA dosimetry, Germany) using the quality assurance kit Express QA test package & clinical cases verification. The standard plan in QA mode is made in TPS and delivered under a medical linear accelerator like pre-treatment verification. The measured and calculated fluence is compared and accordingly the Gamma analysis is done.
Express QA tests & clinical cases fields showed a great agreement with TPS calculations with 3% Dose Distribution ( DD ) and 3 mm Distance to Aggrement ( DTA) Gamma criteria. The open field 10 x 10 cm2 and 20 x 20 cm2 found to be passed with 100% results for 3% &3mm criteria. 3ABUT test helped in setting the leaf offset value from default 0.0mm to 0.15mm. FourL test provides adjustment in leaf transmission value and leaf groove width from 0.012 to 0.0073 and 1.0mm to 0.7mm respectively. H&N and Prostate clinical cases passed with more than 95% for set criteria (3%DD&3mm). The absolute point dose measurement agreement was found to be more than 97%.
This study confirmed that the appropriate MLC check before starting IMRT and VMAT in a clinic and even after any repair is required thorough quality assurance check using Express QA and TG 119 package. Small changes in the MLC parameters like leaf offset, groove width and transmission n the TPS model can cause large changes in the calculated dose. At least annually Express QA test is recommended to every user to confirm the status of changed MLC parameters in due course of time.

Current reported values of fetal doses from 18F Fluorodeoxyglucose (FDG) in pregnant women imaged with PET scan showed a significant variation. This study aimed to evaluate fetal radiation doses using the last generation of computational pregnant phantoms and also to shed light on one of the uncertainty components of the fetal dose.

In this respect, we used a boundary representation (BREP) series of computational pregnant phantoms to evaluate radiation doses to the fetus. We also reviewed available data on fetal time-integrated activities and evaluated the confidence and prediction (95%) intervals for the existing data. By doing this, the uncertainty of fetal Biokinetic data was taken into account in fetal dose calculations.

The fetal doses of 2.30E-02, 1.53E-02, and 1.02E-02 mGy/MBq at 3, 6 and 9 months of gestation were estimated. The results also showed the contributions of source organs to the fetal doses. The maternal “urinary bladder contents” and “other organs and tissues” are the main source regions contributing to fetal dose. We also indicated that the Biokinetic variation caused a large uncertainty on fetal dose (with a prediction interval from 1.73E-02 to 3.93E-02 mGy/MBq) at the first trimester of pregnancy, while it is much lower at second and third trimesters. Furthermore, it is indicated that variations on fetal dose outside the determined intervals may be related to the geometrical differences of used computational phantoms.

Since the fetal dose is much higher and the radiation exposure is more deterministic at the first trimester of pregnancy, attempting to evaluate the fetal dose is relevant at this stage accurately.