mikaeil molazadeh

This study aimed to evaluate the impact of Contrast-Enhanced Computed Tomography (CECT) on treatment planning for rectal cancer using Helical Tomotherapy (HT).

A total of patients with known rectal tumors were included, and both CECT and non-CECT images were obtained. Patients adhered to a low-fat diet and received oral and intravenous iodine-based contrast agents. Target volumes, including Gross Tumor Volume (GTV), Clinical Target Volume (CTV), and Planning Target Volume (PTV), were delineated by a radiation oncologist using DICOM images. Intensity-Modulated Radiation Therapy (IMRT) techniques with Simultaneous Integrated Boost (SIB) methods were employed to optimize dose delivery while minimizing exposure to Organs at Risks (OARs).

The analysis revealed that the use of CECT significantly increased. Hounsfield Unit (HU) values across all structures, enhancing visibility and accuracy in target volume delineation. Dosimetric evaluations indicated minimal differences in dose distributions between CECT and non-CECT plans. However, certain indices such as Dmax, Dmin, Dmean, Homogeneity Index (HI), and Conformity Index (CI) showed significant changes that could influence clinical outcomes.

The incorporation of CECT in radiation therapy planning for rectal cancer improves the delineation of critical structures, potentially leading to better treatment outcomes. The findings underscore the importance of using contrast media in enhancing imaging quality, which is crucial for effective target volume definition and OAR contouring. Future research should explore the long-term clinical implications of these findings on patient outcomes and quality of life post-treatment.

In radiotherapy, the accuracy of dose calculation systems plays a key role in the treatment of cancer patients. The current research aimed to evaluate the dose calculation accuracy of Monaco Treatment Planning System (TPS) in estimating the Effective Wedge Angle (EWA) using two different mathematical Elekta formula and ICRU-24 formula. In this experimental study, EWAs for different field sizes (5×5, 10×10, 15×15, 20×20, 25×25, and 30×30 cm2) at standard angles (15°, 30°, 45°, and 60°) were computed by the Monaco TPS using two different analytical methods. The practical EWAs were measured according to the conditions outlined in the Elekta formula and the ICRU-24 formula, and these measurements were compared with the results derived from the TPS. The planned and measured EWAs are consistent with the Elekta formula, and the error value was less than ±0.5 in all radiation fields and EWAs. In the ICRU-24 formula, the maximum deviation was ±2.6° between the computational and practical EWAs.  The Elekta-based analytical method demonstrates a good agreement between planned and measured EWAs, while the ICRU-24 formula exhibited the greatest discrepancies.

Cancer is estimated to overtake cardiovascular diseases and take the top spot as the leading and most important cause of mortality globally in the near future. Given the importance of early diagnosis to reduce mortality, many efforts have been made to discover a theranostic system for simultaneous cancer diagnosis and treatment. So far, the use of nanotechnology has greatly contributed to the improvement and development of these systems. Meanwhile, dendrimer nanoparticles have attracted considerable attention in medical research due to their unique properties. Poly(amidoamine) (PAMAM) dendrimers have become the primary category of dendrimers and have been widely studied for their possible application in cancer treatments. These nanoparticles have features including interior cavities and peripheral functional groups that allow the encapsulation of diverse medications or diagnostic agents. As a result, these particles can function as efficient nanocarriers and vectors for medical applications. This capability allows for the resolution of the obstacles presented by the tumor microenvironment. The prospective use of multifunctional PAMAM holds promise in enabling thorough monitoring of different stages of treated cancer tissue, hence providing substantial support in the early detection and prediction of tumor response. The primary focus of this study will be to investigate the most recent developments of PAMAM dendrimers in the field of cancer theranostics. The employment of NPs in anticancer medicine administration for radiation treatment, chemotherapy, and diagnostic imaging is underscored due to its significant potential.

Breast cancer requires evaluating treatment plans using dosimetric and biological parameters. Considering radiation dose distribution and tissue response, healthcare professionals can optimize treatment plans for better outcomes.
This study aimed to evaluate the effects of the different Dose Calculation Algorithms (DCAs) and Biologically Model-Related Parameters (BMRPs) on the prediction of cardiopulmonary complications due to left breast radiotherapy.
In this practical study, the treatment plans of 21 female patients were simulated in the Monaco Treatment Planning System (TPS) with a prescribed dose of 50 Gy in 25 fractions. Dose distribution was extracted using the three DCAs [Pencil Beam (PB), Collapsed Cone (CC), and Monte Carlo (MC)]. Cardiopulmonary complications were predicted by Normal Tissue Complication Probability (NTCP) calculations using different dosimetric and biological parameters. The Lyman-Kutcher-Burman (LKB) and Relative-Seriality (RS) models were used to calculate NTCP. The endpoint for NTCP calculation was pneumonitis, pericarditis, and late cardiac mortality. The ANOVA test was used for statistical analysis.
In calculating Tumor Control Probability (TCP), a statistically significant difference was observed between the results of DCAs in the Poisson model. The PB algorithm estimated NTCP as less than others for all Pneumonia BMRPs. 
The impact of DCAs and BMRPs differs in the estimation of TCP and NTCP. DCAs have a stronger influence on TCP calculation, providing more effective results. On the other hand, BMRPs are more effective in estimating NTCP. Consequently, parameters for radiobiological indices should be cautiously used s to ensure the appropriate consideration of both DCAs and BMRPs.

Prostate cancer is one of the most common malignant diseases among males. External beam radiation therapy (EBRT) is one of the major curative treatment modality for the localized prostate cancer. High-dose radiotherapy for localized prostate cancer is a well-established method to improve tumor control but is also resulted in increased rectal toxicity. Major concern of dose escalation in prostate cancer is the toxicity of surrounding normal tissues, in particular rectum because the rectum is anatomically close to the prostate gland and limits prescribed dose. Radiotherapy associated rectal toxicities have a negative impact on patient’s quality of life (QOL). The primary efforts for reduction of rectal toxicities are the application of image guided radiation therapy (IGRT), intensity modulated radiation therapy (IMRT) or adaptive radiotherapy. However, the part of the rectum receives high doses even with modern radiotherapy techniques. Hence, physical displacement of the rectum from the prostate can be effective in reducing rectal radiation doses. To date, three different rectal displacement devices such as Endorectal balloons (ERBs), tissue hydrogel spacers, and rectal retractor (RR) have been developed to push the rectal wall away from the prostate. Previously, the effectiveness of ERBs and tissue hydrogel spacers has been widely investigated. A RR, as a novel device, inserted into the rectum can be utilized to push the rectal wall away from high-dose regions and potentially reduce radiotherapy-induced rectal toxicity. Regarding RR, conflicting reports in the literature debate its efficacy in prostate cancer EBRT. Therefore, the aim of this review is to evaluate the effect of RR during prostate cancer external beam brachytherapy with regard to dosimetric results, preliminary clinical outcomes, prostate motion, and procedure-related toxicity. To have a comprehensive study, we searched PubMed, Scopus, and Google Scholar studies from January 1th, 2010 to September 30th, 2022. The following keywords were used for the searches: rectal retractor, Rectafix, rectal displacement device, and synonyms combined with one or more of the following: prostate radiotherapy and prostate cancer radiotherapy. Reference lists of articles were also reviewed for relevant articles. Published articles and abstracts in English from preclinical and clinical studies were included. Fifteen articles were included in this review. No serious complications such as severe anal irritation or rectal bleeding occurred with daily insertion of the RR. The magnitude of rectal retraction is determined by patient's discomfort. Although the rectal retraction induces a mild rectal pain, it is well tolerated. Daily use of the RR can lead to anorectal irritation, thus the RR cannot be used during the entire treatment sessions with the conventional radiation therapy regimen (more than 35 sessions). All of these events were self-limited and resolved with no additional treatment during radiotherapy. The insertion of the RR required approximately 3-4 additional minutes of routine set-up time. The application of RR can increase the space between the prostate and the anterior rectal wall. Using RR achieved the average distance of 4 mm between the prostate and the anterior rectal wall. The RR usage resulted in significant radiation dose reductions to the rectal wall, posterior rectal wall, and anterior rectal wall. Preliminary clinical data showed that using RR does not reduce acute rectal toxicities, but the rate of late rectal toxicities is lower in patients treated with a RR in-place. The RR can reduce prostate intra-fractional motion. Several reports indicated that in vivo rectal dosimetry was feasible using RR equipped with different active or passive dosimeters during prostate radiotherapy. The use of RR for patients undergoing EBRT for prostate cancer was feasible and it did not lead to serious complications such as rectal bleeding. Using RR in definitive prostate EBRT resulted in reducing dose to the rectal wall. The RR can increase prostate and rectal inter- and intra-fractional stability. However, further randomized clinical trial with a large sample size will be required to clear the clinical benefits of the application of the RR during prostate radiotherapy.

Virtual wedge (VW) is used in radiotherapy to compensate for missing tissues and create a uniform dose distribution in tissues. According to TECDOC‑1583 and technical reports series no. 430, evaluating the dose calculation accuracy is essential for the quality assurance of treatment planning systems (TPSs). In this study, the dose calculation accuracy of the collapsed cone superposition (CCS) algorithm in the postmastectomy radiotherapy of the chest wall for breast cancer was evaluated by comparing the calculated and measured dose in VW fields.

Two tangential fields with the typical VW angles were planned using ISOgray TPS in a thorax phantom. The CCS algorithm was used for dose calculation at 6 and 15 MV photon beams. The obtained dose distributions from EBT3 film spaces and TPS were evaluated using the gamma index.

The measured and calculated dose values using VW in a heterogeneous medium with different beam energies were in a good agreement with each other (acceptance rate: 88.0%–93.4%). The calculated and measured data did not differ significantly with an increase/decrease in wedge angle. In addition, the results demonstrated that ISOgray overestimated and underestimated the dose of the soft tissue and lung in the planned volume, respectively.

According to the results of gamma index analysis, the calculated dose distribution using VW model with the CCS algorithm in a heterogeneous environment was within acceptable limits.

One of the key factors in the assessment of the quality assurance in advanced radiotherapy treatments such as IMRT and VMAT is obtaining different types of dose leakages related to the MLCs used in these techniques. In this study, different dose leakage parameters from TiGRT Dynamic MLC, which was externally added to the lower part of the collimator system of Siemens linear accelerator, were measured using different dosimeters (diode dosimeter and radiochromic film) and compared with Monte Carlo simulation results. Measurement indices include radiation beam leakage from the air gap between the leaves (inter-leaf leakage), the amount of X-ray passage through individual leaves (intra-leaf transmission), average leakage and leakage related to the air gap of the leaves in the completely closed radiation field (abutting air gap leakage) were at  6-MV energy. In measuring the various leakage dose indices from TiGRT Dynamic MLC, a good agreement was observed between the measured data and the simulation results. According to the TG-50 protocol, the average interleaf leakage and interleaf leakage should be less than 2%; and the results of our study showed that the leakage parameters obtained from this type of MLC agree with the universal protocols.

In radiation cancer treatments، the most of the side effects could be minimized using a proper dosimeter. Gel dosimeter is the only three‑dimensional dosimeter and magnetic resonance imaging (MRI) is the gold standard method for gel dosimeter readout. Because of hard accessibility and high cost of sample reading by MRI systems، some other alternative methods were developed. The optical computed tomography (OCT) method could be considered as the most promising alternative method that has been studied widely. In the current study، gel dosimeter scanning using a prototype optical scanner and validation of this optical scanner was performed. Optical absorbance of the irradiated gel samples was determined by both of conventional spectrophotometer and the fabricated OCT system at 632 nm. Furthermore، these irradiated vials were scanned by a 1. 5 T MRI. The slope of the curves was extracted as the dose‑response sensitivity. The R2‑dose sensitivity measured by MRI method was 0. 1904 and 0. 113 for NIPAM and PAGAT gels، respectively. The optical dose sensitivity obtained by conventional spectrophotometer and the fabricated optical scanner was 0. 0453 and 0. 0442 for NIPAM gels and 0. 0244 and 0. 0242 for PAGAT gels، respectively. The scanning results of the absorbed dose values showed that the new OCT and conventional spectrophotometer were in fair agreement. From the results، it could be concluded that the fabricated system is able to quantize the absorbed dose values in polymer gel samples with acceptable accuracy.