Iranian Journal of Medical Physics
Volume:19 Issue: 6, Nov-Dec 2022

In this study, Radiomic features analysis of CT scan images of the irradiated breast compared to the contralateral breast after a 12 Gy boost radiation dose in IOERT was conducted to obtain radiation-sensitive indicators (parameters) biological markers or biological dosimeters. 35 contrast chest CT scans (with unilateral ductal carcinoma in situ (DCIS) who had undergone boost IOERT) were used in this study. The total number of 259 CT radiomic features (first-order, textural, gradient, and autoregressive model-based features) were extracted using Mazda software. The features that were significantly different in the two breasts were selected. A score was assigned to each of the features and the highest scores were characterized (according to the level of significant differences). The feature selection process was performed using the hybrid feature selection method. CT Texture analysis indicated that radiation dose causes significant changes in some radiomic features of the breast tissue.  With more research in the future, we can fit the Delta-Radiomics values with the received radiation dose and achieve a biological dosimeter to detect low-dose radiation.

Long term cardiac morbidity is a concern with left sided breast/chest wall irradiation. In this present study, we have evaluated the Impact of Voluntary deep inspiratory breath hold (V-DIBH) Vs Free Breathing (FB) technique on heart and lung doses for left-sided breast cancer with audio visual guidance.
A total of 31 patients diagnosed with left breast cancer were found to be suitable for V-DIBH. Patients were trained for breath hold technique for 3 to      4 days on CT simulator. Seven  patients being non-compliant to  V-DIBH  therefore 24 patients were simulated for breath hold. We made tangential IMRT plans for all the patients on both V-DIBH and free breathing scans for dosimetric comparison. D95% target and organ at risk (OARs) like Dmean of heart, LAD, lung and opposite breast were compared for both plans. 
A significant reduction of mean cardiac dose from 5.7 ± 1.58 Gy to 3.45 ± 0.68 Gy (p<.05) and cardiac V25Gy from 7.28 ±3.97 % to 1.64 ± 1.35% (p<.05) in V-DIBH cases as compared to FB. Mean dose to the LAD was reduced by 3.9 Gy in DIBH cases (p<.05). Differences between FB and V-DIBH mean lung dose was 2.47 Gy (p=.106, ns) and ipsilateral lung V20Gy was 2.57% (p=.078, ns).
This study demonstrates dosimetric benefits of V-DIBH over FB in reducing dose to heart, LAD and ipsilateral lung without compromising the target volume coverage. We should opt for V-DIBH over FB for left sided breast cancer cases

Radiotherapy and nuclear medicine extensively use Monte Carlo simulation to study particle transport and interactions. The aim of this task is the investigation and simulation of leakage and transmission (L&T) particles using the Multi-Leaf Collimator version i2 applied to the Elekta Synergy linac. In this study, all linac segments are included in the simulation model. In order to reduce MC calculation time, the new HPC-Slurm cluster platform and the Python phase space approach are used. To study the transmission between MLCi2 leaves, a detailed analysis of the dose distribution was conducted. The simulation results obtained with Gate 9.0 MC are excellently correlated with the measured data with error estimates for the 6 MV photon beam parameters less than 1% and a validation level of 99% in terms of the gamma index's (2%/2mm) threshold formalism for the cross profiles and PDD's dose distributions. The results indicate that contamination particles (e-, e+) have an effect on the distribution of dose in the patient. These particles are present in the beam produced previously and which is assumed to contain only X-rays. In addition, a three-dimensional distribution of dose inside the tumor (CT-scan) confirms the L&T effect of the studied version of the multi leaf collimator (MLCi2), with a dose range of around 70% of the delivered dose to the tumor, resulting in secondary outcomes at the DNA. Consequently, the production of a new generation of MLC that can limit this L&T effect should be encouraged.

The study aims to compare target coverage and critical structure dose difference between various dose computing algorithms with small segment dose calculation in Intensity Modulated Radiation Therapy (IMRT) and large segment dose calculation in 3-Dimensional Conformal Radiation Therapy (3DCRT) treatment plan for Head and Neck (H&N) tumor. For the present study, thirty-eight H&N cancer patients were selected retrospectively. Twenty-seven patients were planned with IMRT plan using Monte Carlo (MC) algorithm and eleven patients with 3DCRT plan using Collapsed Cone/Superposition (CCS) algorithm. IMRT plan was recalculated with Pencil Beam (PB) and the 3DCRT plan was recalculated with MC and PB algorithms. An Independent student t-test was performed as a part of statistical analysis for dosimetric comparison of the p-value. In the IMRT plan, mean dose, Conformity Index (CI), D2%, D98%, and D50% showed a significant difference in p-values (p<0.05), but the critical structure did not have a significant difference in p-value between the MC and PB algorithms, except Planning Risk Volume (PRV) spine. In the 3DCRT plan, mean dose, CI, Homogeneity Index (HI), D98%, D50%,and all the critical structures showed no statistically significant p-values (p<0.05) between the CCS with MC and CCS with PB algorithms. The study concludes that in the IMRT treatment technique, PB algorithms overestimate the dose compared to the MC algorithm, even in the head and neck treatment area. For 3DCRT treatment plans, CCS, MC, and PB algorithms showed no statistically significant differences between them. Moreover, this study ensured the accuracy of various dose calculation algorithms in H&N radiotherapy.

Periodic and brief electrical stimulations (ES) are used as therapeutic protocols to improve nerve regeneration and functional recovery in various nervous system disorders. Periodic ES is applied transcutaneously for several sessions post-surgery, but brief ES is applied directly to the nerve during the surgery. Brief ES has no negative effects on functional recovery but applying periodic ES may delay the recovery. In most research studies, brief ES has been applied for 1-hour, although in some studies shorter durations were used. In this research, to reduce the risk of infection and cost, brief ESs with different durations (1-hour and shorter durations) were studied in a comparative study.

The right sciatic nerve of 24 adult male Wistar rats was transected and sutured to a silicone tube. Experimental groups were stimulated by 10, 30, and 60 minutes ES (20Hz, 3V, 100µs). The hot plate test was done biweekly. At the end of the experimental period (12 weeks), the histomorphometric assessments were performed on the intra silicon tube segment of the regenerated nerve and its tibial branch.

Hot plate test results showed an increase in the regeneration speed in experimental groups; furthermore, the 60-min ES group had better outcomes in histomorphometric assessment than other groups that may be due to the ES effect on the neuronal cell bodies.

As the results indicate, the 60-min ES had a better outcome compared to other groups. Other specifics of a brief ES such as frequency, pulse width, and waveform (monophasic or biphasic) may be studied in future research.

Chest X-ray imaging has become the most commonly used, as it is the primary method for lung cancer screening during medical check-ups.  The radiation dose should be minimized to ensure that the patients are not overexposed to radiation. However, radiation dose reduction results in increased noise in the chest X-ray image. Thus, the purpose of this study was to evaluate the utility of fast non-local means (FNLM) filters to reduce radiation dose while maintaining sufficient image quality. This study evaluates three filters (median, Wiener, and total variation) and a newly proposed filter (fast non-local means (FNLM)), which reduce image noise. A realistic anthropomorphic phantom is used to compare images acquired depending on positions such as anterior-posterior, lateral, and posterior-anterior, using a self-produced 3D printed lung nodule phantom. To evaluate image quality, we used the normalized noise power spectrum (NNPS), contrast to noise ratio (CNR), and coefficient of variation (COV) evaluation parameters. The NNPS and COV were lowest and the CNR was highest with FNLM images. FNLM filter outperforms other compared filters in terms of noise reduction. Therefore, the use of an FNLM filter is recommended, because it reduces the radiation dose to a patient and thus minimizes the risk of cancer, while maintaining diagnostic quality.

To compare the three-dimensional conformal radiotherapy (3DCRT), dynamic conformal arc therapy (DCA), and volumetric modulated arc therapy (VMAT) in stereotactic body radiation therapy (SBRT) of liver cases using 6MV and 10 MV flattened beam (FB) and flattening filter-free beam (FFFB).Twenty liver SBRT patients were selected. The dose prescription was 40 Gy delivered in 5 fractions. 3DCRT, DCA and VMAT planning was performed using 6 MV FB, 6 MV FFFB, 10 MV FB and 10 MV FFFB. Planning target volume (PTV) coverage, organs at risk (OARs) doses, monitor units (MU), and beam on time (BOT) were noted.VMAT plan produces better PTV coverage in the D98% and D95% region. 6 MV and 10 MV VMAT FB and FFFB reduced the D700cc, V10Gy, and Dmean of the liver minus gross tumor volume region compared to 3DCRT and DCA plans. FFFB in combination with VMAT producing highly conformal plan (Conformit index=1.19), better conformity number (CN=0.85), and lowering Paddick gradient index (GIpad=3.29) in comparison to 3DCRT and DCA. The FFFB needs higher monitor units to achieve the plan in all the techniques. FFFB reduces the BOT, body-PTV mean dose in the non-tumour volume. VMAT combined with FFFB will produce a highly conformal plan, spare the OAR’s, deliver fast and dose fall off in the body-PTV region is more as compared to 3DCRT and DCA. The VMAT will more advantage to treat the multiple lesions simultaneously and reducing the intra-fraction motion error in liver SBRT.

The objective of this study is to assess the role of diffusion weighted (DW) magnetic resonance imaging (MRI) along with its corresponding apparent diffusion coefficient (ADC) values in differentiating malignant from benign breast lesions. Patients with breast lesions and those who met inclusion and exclusion criteria were included in this study. MR Mammography (MRM) was performed on 1.5 Tesla MR Scanner (Siemens® Magnetom Avanto®). DWI was performed at b-values of 50, 400 and 800 s/mm2 followed by ADC sequence. 50 patients with a total of 81 breast lesions and whose diagnosis was histopathologically confirmed following MRM were included in the study. We observed that benign lesions showed no restricted diffusion with an ADC value of >1.3 x 10-3 mm2/s. Most of the malignant lesions showed restricted diffusion with ADC value of < 1.3 10-3 mm2/s. A non-malignant condition, Benign Phyllodes tumor (n=1) showed no restricted diffusion but had a low ADC of 1.1 x 10-3 giving false positive result. Mucinous carcinomas (n=5) showed no restricted diffusion and had a mean ADC value of >1.3 x 10-3. We observed sensitivity of DWI along with ADC value to be 86.8% and specificity as 97.6%. DW-MRI can be employed as a fast unenhanced screening modality for breast cancer with high sensitivity. Considering ADC values along with DW-MRI increased its detection rates and hence both can be incorporated as supplementary techniques in multiparametric MRM.