جستجوی مقالات مرتبط با کلیدواژه « intensity modulated radiation therapy » در نشریات گروه « پزشکی »

To assess accurately the URT treatment planning system from the United Imaging Healthcare, the American Academy of Pain Medicine (AAPM) TG 119 test plans for Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT) were used.

Based on the URT-Linac 506C, the plans were sent to the phantom. The overall accuracy was tested and examined using five geometry tests supplied in TG 119 for various treatment modes of IMRT and VMAT, with three types of beams using the Flattening Filter modality, estimated using the URT-TPS Monte Carlo algorithm. Moreover, a Farmer-type ion chamber was used to measure the point values, and a film was used to measure the fluence.

The disparities between the measured point doses and the anticipated doses for the FF photon beams for static MLC, dynamic MLC, and VMAT were within 2.16%, 1.89%, and 1.89%, respectively. The TG 119 report confidence limits were all met, and SMLC, DMLC, and VMAT had gamma passing rates greater than 99.80%, 99.60%, and 99.70%, respectively.

The URT treatment planning system and the URT-Linac 506C have correctly commissioned IMRT and VMAT processes, according to this analysis, which was completed following the recommendations given by TG 119.

This study aimed to investigate the effect of the patients’ setup errors on dosimetric and radiobiologic parameters for left-sided Whole-Breast Irradiation (WBI) in three different radiotherapy techniques, including Intensity-Modulated Radiation Therapy (IMRT), Field-In-Field (FIF), and Conventional Wedge (CW).

Computed Tomography (CT) images of 10 female patients with early-stage left-sided breast cancer were used to simulate different radiotherapy techniques (IMRT, FIF, and CW). The dosimetric parameters; Conformity Index (CI), Homogeneity Index (HI), the dose received by at least 95% (D95%) of Planning Tumor Volume (PTV), the volume of lung and heart that respectively received at least 20% (V20%) and 40% (V40%) of the prescribed dose, as well as, the radiobiologic parameters, including Tumor Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) were assessed for setup errors in patients. The setup errors were assessed by shifting the isocenters and gantry angles of the treatment plans.

The D95% of the PTV for an isocenter misplacement plan in the posterior direction decreased by 66.99 (IMRT), 71.86 (CW), and 68.25% (FIF). The TCP of the PTV was reduced by 26.66, 39.16, and 36.97% for IMRT, CW, and FIF techniques, respectively. Increasing gantry angle by a ±10 degree caused a 43%, 41%, and 41% decrease in the D95% of IMRT, FIF, and CW techniques, respectively. The TCP values decreased about 18% in all three techniques with a ±10 degree gantry angle shift; however, the NTCP values of the heart and lungs increased for all three methods. The CI and HI values had significantly more changes with increasing setup errors in the IMRT than in the two techniques.

The radiobiologic parameters in IMRT were less sensitive to setup errors compared to FIF and CW techniques. The radiobiological parameters can help estimate the setup errors along with physical parameters during breast radiotherapy.

Various developed intensity modulated radiation therapy (IMRT) and a three dimensional conformal radiation therapy (3D-CRT) protocols were assessed for treating nasopharyngeal cancer (NPC) based on radiobiological parameters.

Treatment plans were made for 30 NPC patients using 15 developed IMRT and 3D-CRT protocols. The IMRT protocols comprised of three 7-fields with various collimator (0°, 5°, and 10°) and couch (0°, 4°, 8°, 12°) angles. The 3D-CRT technique included two phases. In the 1st phase a dose of 60 Gy was prescribed to the total PTV, but in the 2nd phase a dose of 10 Gy was prescribed to the PTV-70. The tumour control probability (TCP), normal tissues complication probability (NTCP), and complication-free tumor control probability (P+) parameters were estimated for assessing the IMRT protocols. Then, the ideal protocol (s) were proposed through comparing the IMRT protocols with each other and 3D-CRT protocol based on TCP, NTCP, and P+ values.

The IMRT protocol with 10° collimator and 8° couch angles had the lowest NTCP mean values. Significant differences were observed among the mean NTCP values for the brainstem and parotid glands, and P+ of the developed IMRT and 3D-CRT protocols. However, no significant differences were observed among the mean NTCP values for the spinal cord, optic chiasm and optic nerves among the protocols.

The 3D-CRT protocol had a good outcome for the NPC patients having a lower common volume between their total planning target volume and OARs, while the results of the IMRT showed the opposite.

There is no clear guideline regarding the optimum intensity modulated radiation therapy (IMRT) technique for patients with breast cancer (BC) requiring radiotherapy (RT) treatment of the regional node area but not of the internal mammary node (IMN). We evaluated the IMRT technique with a focus on secondary cancers of stomach and thyroid.

Eight patients with left BC treated with RT after breast conserving surgery at a single institution in 2017 were enrolled. Three-dimensional conformal radiation therapy (3D-CRT) consisting of two opposed half tangential breast fields and IMRT plans was performed. Normal organ dosimetric parameters were compared. Excess absolute risks, excess relative risks, and lifetime attributable risks (LAR) were calculated.

Stomach V30 values were 10.27 and 1.31 for tangential 3D-CRT and IMRT, respectively, and corresponding V40 values were 7.46 and 0.2, whereas V5 values were 21.15 and 49.62, respectively. Thyroid values were similar; V30 26.53 and 7.93, V40 22.37 and 2.63, and V5 40.93 and 88.86, respectively. LAR values of stomach were 1.76 (per 100 persons) and 2.31 and for thyroid were 5.3 and 9.5, respectively. LAR values of contralateral breasts were 0.35 and 0.99, of ipsilateral lungs were 1.68 and 2.39, and of contralateral lungs were 0.58 and 1.73. All values were​significantly different (p<0.05).

LAR values of stomach and thyroid were higher for IMRT than 3D-CRT in left BC patients requiring regional node treatment without including IMN. Consensus on the priority ​​among disease control rate, secondary cancer risk, and toxicity is required.

Aim of this study was to evaluate the extent of the error that the gating system incorporates into an intensity-modulated radiation therapy (IMRT) delivery for the different duty cycles of beam gated treatments (beam-interruption) by comparing the gamma between the dose planes.

Respiratory motion patterns was recorded in the real-time position management (RPM) software, which controls the triggering of the linear accelerator for the beam ON/OFF based on the predefined gating window. 10 IMRT plans consisting of 60 IMRT fields were delivered for three different duty cycles (20%DC, 30%DC and 40%DC) of gated and non-gated delivery. Planar dose measurements of IMRT delivery were performed with the commercially available two-dimensional ion chamber array and portal dosimetry. Gamma evaluation was carried out for the three different duty cycles of gated delivery with that of the reference of non-gated delivery, and the measured dose planes of gated and non-gated delivery were gamma analyzed with the treatment planning system (TPS) dose planes. Multileaf collimator (MLC) dynalog files were acquired and analyzed for the different duty cycles of gated and non-gated IMRT deliveries.

Gamma between the gated and non-gated dose planes were found within the 3% deviation.  Area gamma for the gated and non-gated delivery to the reference of TPS dose planes were found within the deviation of 6%.

Gamma comparison of the gated delivery with the reference of non-gated delivery results demonstrated that increasing the duty cycle reduced the deviation between the gated and non-gated delivery.

In head and neck radiotherapy, immobilization devices can affect dose delivery. In this study, a comprehensive end-to-end test was developed to evaluate the accuracy of radiotherapy treatment.

An Alderson Radiation Therapy (ART) anthropomorphic phantom with EBT3 film was used to mimic the actual patient treatment process. Ten patients treated for nasopharyngeal carcinomas with IMRT were retrospectively selected. For each patient, the treatment plan, as well as the targets and OARs was transplanted onto the phantom, and the IMRT plan was subsequently recalculated to the phantom with EBT3 film. Two quality assurance (QA) plans were generated, namely “Plan-with” wherein the immobilization device was contoured and “Plan-without” wherein it was omitted. EBT3 measurements were compared with the results of the TPS calculation.

With different gamma calculation criteria applied, the results obtained for Plan-with were closer to the dose measured with the EBT3 film. Moreover, 1.8% deviation was observed in the posterior neck skin dose for Plan-with when compared to the film measurements while the value was 33.1% lower for Plan-without. When compared to Plan-without, each target volume in Plan-with exhibited a 1–4% reduction in the maximum dose (D2%), minimum dose (D98%) and mean dose (Dmean).

Immobilization devices decrease the radiation dose to target volumes while increasing the skin dose and should be included within the body contour to ensure an accurate planning dose. The end-to-end IMRT test using an ART anthropomorphic phantom is a valuable tool to identify discrepancies between calculated and delivered radiation doses.

We investigated the usefulness of patient-customized cast type M3 wax bolus (MWB) in radiation therapy in scalp malignant tumor patients by 3D conformal radiation therapy (3D CRT) and intensity-modulated radiation therapy (IMRT).
A helmet-type polylactic acid (PLA) hollow model was fabricated using a 3D Printing, and the molten MWB was poured into the mold and allowed to harden. Subsequently, a solid MWB head cast was obtained by removing the PLA. The radiation volume was verified using a metal oxide semiconductor field-effect transistor (MOSFET) dosimeter and EBT3 film.
Radiation dose verification was performed at the anterior, right, and left angles of planning tumor volume. The error rate demonstrated a maximum value of 5.5% and an average of 3.3% using the MOSFET dosimeter, and a maximum value of 7.0% and an average of 5.4% applying the EBT3 film. The homogeneity indices of the treatment plans were obtained as 0.09 and 0.12 using 3D CRT and IMRT, respectively. Moreover, the conformity number of the treatment plans was reported as 0.79 using 3D CRT and 0.81 applying IMRT.
The density of the MWB head cast was 1.05 g/cm3 which is closer to that of the equivalent tissue than the existing helmet type bolus material. In addition, it reduces the processing time and associated pain during custom manufacturing and has little air gaps. Therefore, it can be considered an effective method for the treatment of patients with scalp malignant tumors.

At present, there is a lack of evidence concerning urinary complications caused by intensity-modulated radiation therapy (IMRT) used for the management of prostate cancer (PCa).

This study aimed at identifying the nature and severity of post-IMRT urinary symptoms in patients with PCa.

This prospective study was performed with consecutive patients, who had clinically localized PCa (cT1c-cT2c) and had undergone IMRT treatment from 2016 to 2019. At 1, 6, and 12 months of follow-up, medical history, physical information, prostate-specific antigen values, International Prostate Symptom Score (IPSS), medication use, Radiation Therapy Oncology Group (RTOG), acute and late toxicity, and Q max were collected.

A total of 127 patients with a mean age of 71.04 ± 7.1 years received IMRT and underwent 12 months of follow-up. The mean IPSSs at baseline versus those at 1, 6, and 12 months after IMRT was 14.5 ± 6.8 versus 13.3 ± 6.1, 12.3 ± 5.3, and 10.4 ± 4.2, respectively (P < 0.000). The mean prostate volume was 38.2 ± 12.1 cc. At the last follow-up, 31 patients (24.4%) took genitourinary (GU) medications.

This study showed that the majority of GU side effects caused by primary IMRT for PCa treatment are transient. Treatment triggered an acute increase in obstructive urinary symptoms, which peaked during the first month after IMRT. In most patients, in the course of 6 months, symptoms returned to baseline.

This study aims to investigate the effect of reference dose calculation grid size (RDCGS) on gamma passing rate (GPR) for patient-specific quality assurance of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT).

A total of 20 patients were retrospectively selected. Both IMRT and VMAT plans were generated for each patient. Reference dose distributions for gamma analysis were calculated with RDCGS of 1–5 mm at intervals of 1 mm. Dose distributions were measured using MapCHECK2 and ArcCHECK dosimeters. Both global and local gamma analyses with gamma criteria of 3%/3 mm, 2%/3 mm, 2%/2 mm, and 2%/1 mm were performed with various RDCGS.

As the RDCGS increased from 1 mm to 5 mm, the average global GPRs with 2%/2 mm for VMAT with MapCHECK2 and ArcCHECK decreased by 9.3% and 5.9%, respectively. The average local GPRs decreased by 14% and 11.7%, respectively. For IMRT, the global GPRs decreased by 4.8% and 6%, respectively, whereas the local GPRs decreased by 10.5% and 8.6%, respectively. The effect of the RDCGS on the GPRs became larger when performing local gamma analysis as well as when applying small distance-to-agreement (DTA). As the RDCGS increased, the average changes in the GPR per mm of DTA change increased regardless of the type of radiotherapy, detector, or gamma analysis.

For an accurate verification of the IMRT and VMAT plans, it is recommended that the reference dose distribution must be calculated with the smallest possible RDCGS.

The current study aimed to compare the tumor control probability (TCP) and normal tissue complication probability (NTCP) of three-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) for left-sided breast cancer using radiobiological models.

This study was conducted on 30 patients with left-sided breast cancer, who were planned for 3D-CRT and 6-9 fields IMRT treatments using the PROWESS treatment planning system.  The planning target volume (PTV) dose of 50 Gy was administered for the 3D-CRT and IMRT plans, respectively.  The Niemierko’s equivalent uniform dose (EUD) model was utilized for the estimation of tumor control probability (TCP) and normal tissue complication probability (NTCP). 

According to the results, the mean TCP values for 3D-CRT, 6-fields IMRT, and 9-fields IMRT plans were 99.07 ±0.07, 99.24 ±0.05 and 99.28 ±0.04, respectively, showing no statistically significant difference. The NTCPs of the lung and heart were considerably lower in the IMRT plans, compared to those in the 3D-CRT plans.

From the radiobiological point of view, our results indicated that 3D-CRT produces a lower NTCP for ipsilateral lung. In contrast, for TCP calculations, there was a higher gain with IMRT plans compared to 3D-CRT plans.

The incidence of internal lymph node (IMN) involvement was 4- 65% in breast cancer patients. Despite studies indicating the positive effects of IMNRT on the oncological results, most of the clinicians avoided IMNRT because of the toxicity related to the increased dose of organs at risk (OAR). We aimed to compare the dosimetric results of RT plans with and without IMN containing planning target volumes (PTVs) using helical tomotherapy (HT) in obese patients.

The PMRT data of 23 obese patients were evaluated retrospectively / dosimetrically. Two PTVs with and without IMN were defined and two separate plans were made with HT. Dose received by IMN and OAR were compared.

The untargeted IMN V40 were calculated between 0% to 99%. When the plans are evaluated in terms of critical organs, the inclusion of the IMN into the target volume, the most significant adverse effect was observed in heart doses in the left chest wall (CW) irradiation. The significant increases in cardiac V5 (%62.6 vs %48.6 p=0.007), V10 (%38.2 vs %23.2 p=0.011), V20 (%14.15 vs %9.06 p=0.045) and maximum heart dose (48.04 vs 43.2 p=0.043) were observed in the left-side CW irradiations that involving the IMN. In CW irradiation on the right side with IMN, only a significant increase in mean heart dose (5.44 vs 4.52 p=0.036) was observed. Lung V5 doses were increased by inclusion with IMN in both sides. There was no difference in the contralateral breast doses in both plans for both sides.

If the IMN is not targeted, some of the patients are getting appropriate doses in obese patients.

Presence of artifacts, caused by dental filling high-Z materials (DFM), on intensity-modulated radiation therapy (IMRT) treatment plan CT images may lead to uncertainty in head and neck calculated dose distributions. Hence, the purpose of this study was to investigate the effects of DFM on the IMRT calculated dose distribution and consequent radiobiological derived outcomes for nasopharyngeal cancer patients. IMRT optimization of two groups (15 patients in each) of nasopharyngeal cancer (NPC) patients with (group I) and without (group II) dental amalgam was performed by using the Prowess Panther treatment planning system (TPS). For all the patients, target prescribed dose was 70 Gy to planning target volume. We used 3 sets of treatment plans including; nine fields arrangement (F9E) and two plans of seven fields (namely: F7 and F7E) at different angles. The dose volume histograms (DVHs), monitor units (MUs), Homogeneity index (HI), conformity index (CI), Tumor control probability (TCP) and normal tissue complication probability (NTCP) of main organs at risk (OARs) were analyzed. According to the results, the TCP of PTV70 due to presence of dental filling material was significantly decreased (p=0.031). On the other hand received dose by mandible, left cochlea, both eyes and right optic nerve were considerably different between patients with and without artifacts (p<0.05), whereas mandible showed the maximum differences (up to 315.65 cGy) compared to the other studied OARs. Results Presence of dental artifact in patients with nasopharyngeal carcinoma leads to uncertainty in calculated dose of IMRT treatment plans, especially for mandible as an OAR.

This study aimed to evaluate the overall accuracy of the beam commissioning criteria of targeted image‑guided radiation therapy (TiGRT) treatment planning system (TPS) based on the American Association of Physicists in Medicine (AAPM) Task Group Report 119 (TG‑119). The work was performed using 6 MV energy LINAC with a variable dose rate of 200 MU/min which equipped with the high‑quality external TiGRT dynamic multileaf collimator model H. The AAPM TG‑119 intensity‑modulated radiation therapy (IMRT) commissioning tests are composed of two preliminary tests and four clinical test cases. The clinical tests consisted of mock prostate, mock head and neck, C‑shaped target, and multitarget. EDR2 flm was used for evaluating the IMRT plans and point dose measured by a Pinpoint chamber positioned in slab phantom. The flm analysis was done with the Sun Nuclear Corporation patient software. The dose prescription for each fraction was 200 cGy in mock prostate, mock head and neck, C‑shaped target, and multitarget. Dose distributions were analyzed using gamma criteria of 3% and 2% dose difference (DD) and 3 and 2 mm distance to agreement. In all test cases, the gamma criteria for 2%/2 and 3%/3 were found to be 94% and 98%, respectively. Results showed that the average gamma criteria result was in the range of 99.1% to 93% (3%/3, 2%/2) overall test cases. Findings were favorable and in some tests were comparable with the other studies. The dose point values were within the mean values of the range reported by TG‑119. Overall, the TiGRT TPS is needed to apply IMRT technique in radiation therapy centers.

Intensity Modulated Radiation Therapy (IMRT) has made a significant progress in radiation therapy centers in recent years. In this method, each radiation beam is divided into many subfields that create a field with a modulated intensity. Considering the complexity of this method, the quality control for IMRT is a topic of interest for researchers. This article is about the various steps of planning and quality control of Siemens linear accelerators for IMRT, using film dosimetry. This article in addition to review of the techniques, discusses the details of experiments and possible sources of errors which are not mentioned in the protocols and other references. This project was carried out in Isfahan Milad hospital which has two Siemens ONCOR linear accelerators.Both accelerators are equipped with Multi-Leaf Collimators (MLC) which enables us to perform IMRT delivery in the step-and-shoot method. The quality control consists of various experiments related to the sections of radiation therapy. In these experiments, the accuracy of some components such as treatment planning system, imaging device (CT), MLC, control system of accelerator, and stability of the output are evaluated. The dose verification is performed using film dosimetry method. The films were KODAK-EDR2, which were calibrated before the experiments. One of the important steps is the comparison of the calculated dose with planning system and the measured dose in experiments. The results of the experiments in various steps have been acceptable according to the standard protocols. The calibration of MLC and evaluation of the leakage through the leaves of MLC was performed by using the film dosimetry and visual check. In comparison with calculated and measured dose, more that 80% of the points have to be in agreement within 3% of the value. In our experiments, between 85 and 90% of the points had such an agreement with IMRT delivery.The EDR2 films are suitable for quality control of IMRT. According to complexity of the quality control for IMRT, the physicists of each center have to develop specific guidelines according to their equipments and limitations. An accurate treatment planning system with capability of inverse planning is an essential need for IMRT. The result of the planning system has to be compared with experiments in various situations.