Arc Therapy Technique Research Articles

Dosimetric and Patient Preference Analysis between 4-Dimension CT (4D CT) Scan and Deep Inspiration Breath Holding (DIBH) for SBRT in Lung Tumors

<h3>Purpose/Objective(s)</h3> Stereotactic body radiation therapy (SBRT) for early lung tumors and oligometastasis in the lung is a proven treatment technique. Motion management plays an essential role in very accurate treatment delivery. Among the various techniques available, the most widely implemented are Deep Inspiration Breath holding (DIBH) and 4 Dimensional CT (4DCT) scan. This study aims to compare the techniques mentioned above dosimetrically and according to patient preferences. This analysis would let us know the better motion management technique for each patient <h3>Materials/Methods</h3> All eligible patients for SBRT of lung treatment undergo both DIBH and 4D CT scans planning images. Contouring and planning are done on both these sets of images, and based on the dosimetric profile and patient preference, select the appropriate treatment. We retrospectively analyzed the initial five patients who were treated with SBRT for lung. All these patients underwent CT simulation using 4D CT and DIBH techniques. For the 4D CT, Maximum intensity projection (MIP) images were created, and contouring was done on these images. Planning Target Volume (PTV) was created, and planning was done on treatment planning system planning software. 6MV FFF beam (Dose rate of 1400MU/min) using Volumetric Modulated Arc Therapy (VMAT) technique was used for planning. The dose to the target volume was kept uniform and doses to normal tissue were noted for both the plans <h3>Results</h3> The dose to the PTV was 54 Gy in 3 fractions, and all were able to adapt to the deep breath-hold technique. With the DIBH increased lung volume, the mean right lung and left lung volumes were 1848.4 cc and 1636.2 cc, respectively, 1.49 times and 1.64 times more than the mean right lung (1237.5 cc) and left lung (993.46 cc) on 4D CT respectively. The mean GTV on DIBH was 30.62 cc, and that on 4D CT was 37.21 cc. This 4D CT GTV, in effect, was nearly 1.2 times more in volume than DIBH. The mean dose of the ipsilateral lung on DIBH was 5.35 Gy, and on 4D CT, it was 6.16 Gy, which is 1.15 times more than DIBH, both well within the tolerance limits of the lung. The Conformity index (CI) and homogeneity index (HI) for both the plans were similar. The dose to other normal tissue was the same for both plans. Peripheral lesions that are adherent to pleura GTV/ ITVs are almost the same in both DIBH and 4D CT <h3>Conclusion</h3> The volume of GTV was slightly lesser in DIBH because of the breath-holding. But for peripheral tumors (metastasis), which are adherent to pleura, given decreased movements of GTV/ ITV, are almost the same in both DIBH and 4D CT. The mean dose to the ipsilateral lung is less in DIBH than 4D CT. The analysis shows that SBRT in DIBH and 4D CT is an equally good technique with a dose to the normal tissues well within normal limits and can be individualized according to the patient's comfort and location of the tumor, with an overall preference for the DIBH technique

Investigation of Dosimetric Outcomes for Arteriovenous Malformations with Linac-Based SRS vs. Non-invasive Stereotactic Radiosurgery Planning

<h3>Purpose/Objective(s)</h3> Previous studies have established that higher doses of SRS may be associated with greater rates of closure of arteriovenous malformations (AVMs), but simultaneously may be associated with greater risk of toxicity. The purpose of this study is to compare the plan quality of non-invasive stereotactic radiosurgery vs linear accelerator (Linac)-based treatment for AVMs. <h3>Materials/Methods</h3> Sixty non-invasive stereotactic radiosurgery patients were identified for AVM treatment from 2011-2021. Of this list, 15 patients treated 20 Gy in a single fraction were selected. Plans for this sample were compared between two treatment planning systems (TPS). The plans used for the patient's non-invasive stereotactic radiosurgery treatment were developed using an MRI with a structure set including the CTV and relevant critical structures. Each plan was prescribed to the 50% isodose line (IDL) with the exception of one plan prescribed to the 54% IDL. The same MRIs and structure set from TPS were anonymized, converted to CT, and DICOM transferred. The converted MRIs were used to generate Linac-based SRS plans for a Linac with a high-definition multi-leaf collimator (HD-MLC), using the Volumetric Modulated Arc Therapy (VMAT) technique with non-coplanar arcs and no heterogeneity correction. A plan normalization was applied to each VMAT plan with the prescription dose covering 92-100% of the target volume to reproduce the coverage on LGP for each patient. The gradient index (GI), Paddick conformity index (PCI), V_20Gy, and V_12Gy were compared between each LGP and VMAT plan. <h3>Results</h3> The median CTV was 0.61cc (range: 0.07cc-5.91cc). The mean and standard deviation of PCI were 0.60±0.12 and 0.84±0.08 for non-invasive stereotactic radiosurgery and VMAT, respectively. The GI was 3.14±0.36 and 5.60±1.44, respectively; 1.57±1.96 and 1.56±1.99 for V_12Gy; 1.50±1.88 and 1.50±1.90 for V_20Gy. The differences were statistically significant with p<0.01 for all indexes. <h3>Conclusion</h3> A direct comparison of planning parameters was made to determine the risk of toxicity for AVMs treated with non-invasive stereotactic radiosurgery - vs Linac-based SRS. LGP gave the best dosimetric outcome in regards to GI, V_20Gy, and V_12Gy. VMAT outperformed LGP with the PCI, perhaps due to the better beam optimization on VMAT. VMAT was challenged by the delineation of the target volume in LGP and limitations of the HD-MLC at small volumes. Treating AVMs on non-invasive stereotactic radiosurgery is a better choice given the lower GI.

Quality of Life of Patients Treated with Radiotherapy in an Upper Middle-Income Country

<h3>Purpose/Objective(s)</h3> The utility of quality-of-life (QoL) measurements in daily clinical practice of cancer patients has been shown to influence decision making in 30.1% of medical interventions and in 63.2% of non-medical interventions. The purpose of our study was to assess the QoL of patients treated with radiotherapy at an upper middle-income country (UMIC). <h3>Materials/Methods</h3> Fifty-five patients that were treated with 3D-conformal, Intensity-modulated radiation therapy, or Volumetric Modulated Arc Therapy techniques from September 2021 to December 2021(four months). QoL was assessed using (QLQ-C30) in Spanish with the permission from the European Organization for Research and Treatment of Cancer (EORTC). This was administered in-person before radiotherapy (RT) and six weeks after treatment via phone. A linear transformation to standardize the raw score was applied according to the EORTC QLC-30 Scoring Manual. Data analysis was performed using Stata 12 to compare the global health status, functional scale, symptom scale, mean scores and standard deviations with the EORTC Reference Values for cancer patients. <h3>Results</h3> Of the 55 patients treated with RT, 42 (76.4%) were female, 35 (63.6%) were ≥50 years old, with most being diagnosed with cervical (32.7%) and breast cancer (14.5%). Compared with the pre-RT scores at 6 weeks after RT completion, patients had a significant increase in their global health status from 62.2 to 71.78 compared to the baseline assessment (p value 0.06). Emotional functioning, fatigue, pain and insomnia showed no significant differences compared to before treatment. <h3>Conclusion</h3> Further studies are needed in UMICs to understand how patient education and pretreatment information can help patients undergoing radiation therapy to cope with the process of therapy to better estimate predictors of quality of life after radiation therapy, and to see if patient reported QoL recovers over time at different timeline.

Evaluation of a hybrid automatic planning solution for rectal cancer

BackgroundScript-based planning and knowledge-based planning are two kinds of automatic planning solutions. Hybrid automatic planning may integrate the advantages of both solutions and provide a more robust automatic planning solution in the clinic. In this study, we evaluated and compared a commercially available hybrid planning solution with manual planning and script-based planning.MethodsIn total, 51 rectal cancer patients in our institution were enrolled in this study. Each patient generated 7 plans: one clinically accepted manual plan ({plan}_{manual}), three script-based plans and three hybrid plans generated with the volumetric-modulated arc therapy technique and 3 different clinical goal settings: easy, moderate and hard ({plan}_{hybrid}^{easy}, {plan}_{hybrid}^{moderate}, {plan}_{hybrid}^{hard}, {plan}_{script}^{easy}, {plan}_{script}^{moderate} and {plan}_{script}^{hard}). Planning goals included planning target volume (PTV) Dmax, bladder Dmean and femur head Dmean. The PTV prescription was the same (50.00 Gy) for the 3 goal settings. The hard setting required a lower PTV Dmax and stricter organ at risk (OAR) dose, while the easy setting was the opposite. Plans were compared using dose metrics and plan quality metric (PQM) scores, including bladder D15 and D50, left and right femur head D25 and D40, PTV D2, D98, CI (conformity index) and HI (homogeneity index).ResultsCompared to manual planning, hybrid planning with all settings significantly reduced the OAR dose (p < 0.05, paired t-test or Wilcoxon signed rank test) for all dose-volume indices, except D25 of the left femur head. For script-based planning, {plan}_{script}^{easy} significantly increased the OAR dose for the femur head and D2 and the PTV homogeneity index (p < 0.05, paired t-test or Wilcoxon signed rank test). Meanwhile, the maximum dose of the PTV was largely increased with hard script-based planning (D2 = 56.06 ± 7.57 Gy). For all three settings, the comparison of PQM between hybrid planning and script-based planning showed significant differences, except for D25 of the left femur head and PTV D2. The total PQM showed that hybrid planning could provide a better and more robust plan quality than script-based planning.ConclusionsThe hybrid planning solution was manual-planning comparable for rectal cancer. Hybrid planning can provide a better and more robust plan quality than script-based planning.

Dosimetric comparison of mDCAT and VMAT techniques according to 6MV-FFF and 10MV-FFF energies in patients with single adrenal metastasis.

To compare dosimetric and radiobiological terms of modified dynamic conformal arc therapy (mDCAT) and volumetric modulated arc therapy (VMAT) techniques using different flattening-filter free (FFF) energies in patients with single adrenal metastasis. In this study, plans were prepared for 10 patients drawing on the mDCAT and VMAT techniques with 6MV-FFF and 10MV-FFF energies. Target volume doses, biological effective doses (BED), quality indices, Monitor Unit (MU), number of segments, beam-on time and critical organ doses were compared in the plans. Plans with the significantly lower gradient index (GI) and conformity index (CI) values were obtained with 6MV-FFF energy VMAT planning (p < 0.05). The higher values were obtained for dose to 95% of internal target volume (ITVD95), ITVD95-BED10 with 10MV-FFF energy VMAT planning, whereas lower results were obtained for high dose spillage (HDS%) values (p < 0,05). With 10MV-FFF energy, HDS% values were 21.1% lower in VMAT plans and 5.6% lower in mDCAT plans compared to 6MV-FFF energy. Plans with approximately 50% fewer segments were obtained in mDCAT plans than VMAT plans (p < 0,05). Beam-on time values with mDCAT was 1.84 times lower when 6MV-FFF energies were analyzed, and 2.11 times lower when 10MV-FFF was analyzed (p < 0,05). Additionally, when 6MV-FFF and 10MV-FFF energies were examined, MU values with mDCAT were 2.1 and 2.5 times lower (p < 0,05). In general, the smaller the target volume size, the greater the differences between MU and beam-on time values mDCAT and VMAT. The study results implied that VMAT enabled to offer significantly more conformal SBRT plans with steeper dose fall-off beyond the target volume for single adrenal metastasis than the mDCAT, which attained at the cost of significantly higher MU and beam-on times. Especially with 10MV-FFF energy mDCAT plans, low-dose-bath zones can be reduced, and shorter-term treatments can be implemented with large segments. In adrenal gland SBRT, higher effective doses can be achieved with the right energy and technique, critical organ doses can be reduced, thus increasing the possibility of local control of the tumor with low toxicity.

Stereotactic Radiosurgery for Lung Cancer with a Risk-Adapted Strategy Using the Volumetric Modulated Arc Therapy Technique: A Single Arm Phase II Study.

Simple SummaryStereotactic radiosurgery (SRS) for lung cancer has an attractive schedule. In this study, we focused on the efficacy of SRS, and the primary endpoint of this study was the 3-year local recurrence rate. The results showed that the 3-year local recurrence rate was 5.3% (95% confidence interval: 0.3–22.2%), and this rate was less than the expected rate. Good results were obtained in this study and this regimen of SRS is a candidate for a future phase III trial.Purpose: A phase II study carried out to assess the efficacy of a risk-adapted strategy of stereotactic radiosurgery (SRS) for lung cancer. The primary endpoint was 3-year local recurrence, and the secondary endpoints were overall survival (OS), disease-free survival (DFS), rate of start of systemic therapy or best supportive care (SST-BSC), and toxicity. Materials and Methods: Eligible patients fulfilled the following criteria: performance status of 2 or less, forced expiratory volume in 1 s of 700 mL or more, and tumor not located in central or attached to the chest wall. Twenty-eight Gy was prescribed for primary lung cancers with diameters of 3 cm or less and 30 Gy was prescribed for primary lung cancers with diameters of 3.1–5.0 cm or solitary metastatic lung cancer diameters of 5 cm or less. Results: Twenty-one patients were analyzed. The patients included 7 patients with adenocarcinoma, 2 patients with squamous cell carcinoma, 1 patient with metastasis, and 11 patients with clinical diagnosis. The median tumor diameter was 1.9 cm. SRS was prescribed at 28 Gy for 18 tumors and 30 Gy for 3 tumors. During the median follow-up period of 38.9 months for survivors, 1 patient had local recurrence, 7 patients had regional or distant metastasis, and 5 patients died. The 3-year local recurrence, SST-BSC, DFS, and OS rates were 5.3% (95% confidence interval [CI]: 0.3–22.2%), 20.1% (95% CI: 6.0–40.2%), 59.2% (95% CI: 34.4–77.3%), and 78.2% (95% CI: 51.4–91.3%), respectively. The 95% CI upper value of local recurrence was lower than the null local recurrence probability. There was no severe toxicity, and grade 2 radiation pneumonitis occurred in 1 patient. Conclusions: Patients who received SRS for lung cancer had a low rate of 3-year local recurrence and tolerable toxicity.

Clinical outcome in metastatic prostate cancer after primary radiotherapy

PurposeTo describe a local radio-oncological treatment for patients with prostate cancer that metastasized to either the lymph nodes or distant regions.Methods and materialsWe included 133 patients with prostate cancer that displayed either distant metastases (DM) or lymph node metastases alone (NM) and were treated between 2004 and 2019. All patients underwent computed tomography and a bone scan or 18F- or prostate-specific membrane antigen-targeted positron emission tomography. Patients received local external beam radiation therapy to the prostate to achieve local control (60–81.4 Gy to the prostate, and 45–50.4 Gy to pelvic lymph nodes), with either the 3D conformal (4-field box) or volumetric modulated arc therapy technique. A urologist prescribed additional therapy.ResultsWe included 51 patients with DM and 82 patients with NM. The mean follow-up was 42 months for all patients. The groups were similar in T stage, initial prostate-specific antigen, histology, androgen deprivation therapy, age, treatment techniques, and prescribed doses, but different in lymph node inclusion and follow-up times. In the NM and DM groups, the 5‑year biochemical recurrence-free rates were 52% and 24%, respectively (p < 0.0001); the 5‑year disease-specific survival rates were 92% and 61%, respectively (p = 0.001); and the 5‑year OS rates were 77% and 48%, respectively (p = 0.01). The groups had similar acute and late gastrointestinal and genitourinary side effects, except that late genitourinary side effects occurred significantly more frequently in the NM group (p = 0.01).ConclusionsDM was associated with significantly worse outcomes than NM. The long-term survival of patients with metastatic prostate cancer was low.

Dosimetric Evaluation of Commercially Available Flat vs. Self-Produced 3D-Conformal Silicone Boluses for the Head and Neck Region.

BackgroundBoluses are routinely used in radiotherapy to modify surface doses. Nevertheless, considerable dose discrepancies may occur in some cases due to fit inaccuracy of commercially available standard flat boluses. Moreover, due to the simple geometric design of conventional boluses, also surrounding healthy skin areas may be unintentionally covered, resulting in the unwanted dose buildup. With the fused deposition modeling (FDM) technique, there is a simple and possibly cost-effective way to solve these problems in routine clinical practice. This paper presents a procedure of self-manufacturing bespoke patient-specific silicone boluses and the evaluation of buildup and fit accuracy in comparison to standard rectangular commercially available silicone boluses.Methods3D-conformal silicone boluses were custom-built to cover the surgical scar region of 25 patients who received adjuvant radiotherapy of head and neck cancer at the University Hospital Würzburg. During a standard CT-based planning procedure, a 5-mm-thick 3D bolus contour was generated to cover the radiopaque marked surgical scar with an additional safety margin. From these digital contours, molds were 3D printed and poured with silicone. Dose measurements for both types of boluses were performed with radiochromic films (EBT3) at three points per patient—at least one aimed to be in the high-dose area (scar) and one in the lower-dose area (spared healthy skin). Surface–bolus distance, which ideally should not be present, was determined from cone-beam CT performed for positioning control. The dosimetric influence of surface–bolus distance was also determined on slab phantom for different field sizes. The trial was performed with hardware that may be routinely available in every radiotherapy department, with the exception of the 3D printer. The required number of patients was determined based on the results of preparatory measurements with the help of the statistical consultancy of the University of Würzburg. The number of measuring points represents the total number of patients.ResultsIn the high-dose area of the scar, there was a significantly better intended dose buildup of 2.45% (95%CI 0.0014–0.0477, p = 0.038, N = 30) in favor of a 3D-conformal bolus. Median distances between the body surface and bolus differed significantly between 3D-conformal and commercially available boluses (3.5 vs. 7.9 mm, p = 0.001). The surface dose at the slab phantom did not differ between commercially available and 3D-conformal boluses. Increasing the surface–bolus distance from 5 to 10 mm decreased the surface dose by approximately 2% and 11% in the 6 × 6- and 3 × 3-cm2 fields, respectively. In comparison to the commercially available bolus, an unintended dose buildup in the healthy skin areas was reduced by 25.9% (95%CI 19.5–32.3, p < 0.01, N = 37) using the 3D-conformal bolus limited to the region surrounding the surgical scar.ConclusionsUsing 3D-conformal boluses allows a comparison to the commercially available boluses’ dose buildup in the covered areas. Smaller field size is prone to a larger surface–bolus distance effect. Higher conformity of 3D-conformal boluses reduces this effect. This may be especially relevant for volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) techniques with a huge number of smaller fields. High conformity of 3D-conformal boluses reduces an unintended dose buildup in healthy skin. The limiting factor in the conformity of 3D-conformal boluses in our setting was the immobilization mask, which was produced primarily for the 3D boluses. The mask itself limited tight contact of subsequently produced 3D-conformal boluses to the mask-covered body areas. In this respect, bolus adjustment before mask fabrication will be done in the future setting.

Dosimetric effect of modelling non-homogeneous LINAC couch using cone-beam computed tomography on quality assurance (QA) results

Abstract Aim: To evaluate the dosimetric effect of modelling a non-homogeneous couch on patients’ quality assurance (QA) gamma pass rates for intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques. Materials and Methods: A non-homogeneous treatment couch (TxT 550 TTM, CIVCO, USA) was imaged using the LINAC mounted cone-beam computer tomography (CBCT) system. Modelling this couch in different situations, including incomplete (homogeneous model), correct model and not defined situations in the treatment planning system (TPS), was performed based on the geometrical and material densities data extracted from the CBCT images. Calculated gamma pass rates between TPS dose calculations and the measurements in a phantom for different couch models were obtained and compared at two gamma criteria (2%-2 mm and 3%-3 mm). Results: Comparing TPS calculations for the correct modelled couch and the measurements showed high gamma pass rates for both the IMRT and VMAT techniques (96·5 ± 0·9%, 99·2 ± 0·5% for IMRT in 2%-2 mm and 3%-3 mm criteria; 97·5 ± 0·8%, 99·4 ± 0·5% for VMAT). The overall gamma pass rate of the IMRT plan QAs was reduced by about 2% and 3% on average for incomplete and no couch modelling, respectively. These reductions for VMAT techniques were 2·5% and 4·3%, respectively. Conclusions: Non-homogeneous couches have different parts with different attenuations, which can be correctly defined using LINAC CBCT. Modelling of treatment couch has a significant effect on patient QA results for VMAT and IMRT plans, especially in radiation fields/subfield transmitting from the couch. We suggest using LINAC CBCTs as an appropriate device for couch modelling in modulated radiotherapy techniques.

Association between the cardiac contact distance and the maximum dose at the left anterior descending coronary artery in post mastectomized patients.

The clinical information on the relationship between the cardiac contact distance (CCD), the maximum dose (Dmax) delivered to the left anterior descending (LAD) coronary artery and the mean heart dose has mostly focused on patients with breast-conserving surgery (BCS), being scarce in postmastectomy patients. The aim of this study is to determine the association between the CCD and the Dmax delivered to the LAD. The secondary objective was to evaluate the dosimetric results of comparing three-dimensional conformal radiotherapy (3D-CRT) to intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques for post mastectomized breast cancer patients with irradiation to the left chest wall. 53 cases of women who received adjuvant standard fractionated postmastectomy radiotherapy (PMRT) were used. Three types of plans were created for each patient: 3D-CRT, seven equidistant IMRT fields, and four partial VMAT arcs. Correlations were evaluated using Pearson's correlation coefficient. Plans made with IMRT and VMAT showed improved homogeneity and conformity. Associations between CCD and Dmax to LAD were positive for all three plan types. Compared to 3D-CRT, the modulated intensity plans obtained better dose homogeneity and conformity to the target volume. The LAD and heart doses were significantly lower for IMRT and VMAT plans. The CCD can be used as a predictor of the maximum and mean doses of the LAD. Modulated intensity techniques allow for better dose distribution and dose reduction to the heart and LAD.

"Sequential Volumetric Modulated Arc Therapy (VMAT) Boost in Hy- brid Plan With Tangential Beams for Whole Breast Treatment: a Do- simetric Study "

"Purpose: Whole breast radiation therapy (WBRT) with a boost to the tumor bed following con-servative primary surgery in women with breast cancer (BC) plays a central role in reducing local recurrences and mortality. Volumetric modulated arc therapy (VMAT) technique has been shown to allow better dose conformation with low dose levels to organs at risk (OARs), compared to static fields three-dimensional Conformal Radiotherapy (3D-CRT). The aim of this study was to evaluate the feasibility and dosimetric advantages of sequential boost (SB), administered with VMAT tech-nique in hybrid plans with tangential beams for whole breast treatment. Material and methods: BC patients undergoing adjuvant RT from June to October 2020 were selected. ESTRO guidelines for the Clinical Target Volume (CTV) delineation were used. Total delivered dose was 60-66 Gy; 50 Gy in 2 Gy daily fractions for whole breast and 10-16 in 2 Gy daily fractions Gy to tumor bed was 10-16 Gy in 2 Gy daily fractions. Results: The analysis included 31 patients with BC treated with adjuvant RT following con-servative surgery. Hybrid treatment plans characterized by a 3D-CRT plan using tangential medi-olateral and lateromedial fields for the irradiation of the whole breast Planning Target Volume (PTV) and a sequential VMAT plan with 2 coplanar arches for boost PTV irradiation were gener-ated. Dosimetric analysis resulted in homogeneous target volumes coverage and OARs constraints compliance. As regarding to organs at risks (OARs), contralateral breast, ipsi- and contralateral lung and heart constraints values were analysed. Conclusions: In the frame BC RT, this dosimetric study showed that hybrid plans performed with 3D-CRT and VMAT techniques are feasible in terms of dosimetric outcomes. "

Skin Surface Dose for Whole Breast Radiotherapy Using Personalized Breast Holder: Comparison with Various Radiotherapy Techniques and Clinical Experiences.

Simple SummaryBreast immobilization with personalized breast holder (PERSBRA) is a promising approach to reduce the toxicity in the lungs and heart during whole breast radiotherapy. In this study, we designed PERSBRA with three different mesh sizes (large, fine and solid) and applied them on a Rando phantom. Hybrid, intensity modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) techniques were used to deliver a prescribed dose. The dose measurement with EBT3 film and TLD were taken on Rando phantom with no PERSBRA, large mesh, fine mesh, and solid PERSBRA for tumor doses and surface doses. This innovative PERSBRA provides another radiotherapy option for patients with left breast cancer.Purpose: Breast immobilization with personalized breast holder (PERSBRA) is a promising approach for normal organ protection during whole breast radiotherapy. The aim of this study is to evaluate the skin surface dose for breast radiotherapy with PERSBRA using different radiotherapy techniques. Materials and methods: We designed PERSBRA with three different mesh sizes (large, fine and solid) and applied them on an anthropomorphic(Rando) phantom. Treatment planning was generated using hybrid, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques to deliver a prescribed dose of 5000 cGy in 25 fractions accordingly. Dose measurement with EBT3 film and TLD were taken on Rando phantom without PERSBRA, large mesh, fine mesh and solid PERSBRA for (a) tumor doses, (b) surface doses for medial field and lateral field irradiation undergoing hybrid, IMRT, VMAT techniques. Results: The tumor dose deviation was less than five percent between the measured doses of the EBT3 film and the TLD among the different techniques. The application of a PERSBRA was associated with a higher dose of the skin surface. A large mesh size of PERSBRA was associated with a lower surface dose. The findings were consistent among hybrid, IMRT, or VMAT techniques. Conclusions: Breast immobilization with PERSBRA can reduce heart toxicity but leads to a build-up of skin surface doses, which can be improved with a larger mesh design for common radiotherapy techniques.

Comparison of plan dosimetry on multi-targeted lung radiotherapy: A phantom-based computational study using IMRT and VMAT

This work analyzed the dosimetric difference between the intensity modulated radiotherapy (IMRT), partial/single/double-arc volumetric modulated arc therapy (PA/SA/DA-VMAT) techniques in treatment planning for treating more than one target of lung cancer at different isocenters. IMRT and VMAT plans at different isocenters were created systematically using a Harold heterogeneous lung phantom. The conformity index (CI), homogeneity index (HI), gradient index (GI), dose-volume histogram and mean and maximum dose of the PTV were calculated and analyzed. Furthermore, the dose-volume histogram and mean and maximum doses of the OARs such as right lung, contralateral lung and non GTV were determined from the plans. The IMRT plans showed the superior target dose coverage, higher mean and maximum values than other VMAT techniques. PA-VMAT technique shows more lung sparing and DA-VMAT increases the V5/10/20 values of contralateral lung than other VMAT and IMRT techniques. The IMRT technique achieves highly conformal dose distribution to the target than other VMAT techniques. Comparing to the IMRT plans, the higher V5/10/20 and mean lung dose were observed in the contralateral lung in the DA-VMAT.

Treatment Planning Comparison of Intensity Modulated Arc Therapy and CyberKnife Techniques in Early Stage Glottic Larynx Radiotherapy

We aimed to compare two radiotherapy techniques (the robotic-based linear accelerator Stereotactic Body Radiotherapy (SBRT) and linear accelerator-based Intensity Modulated Arc Therapy (IMAT)) dosimetrically on Early Glottic Larynx Cancerx (EGL) treatment plans in the terms of target volume and critical organ doses. The computerized tomography (CT) images of 15 patients treated with EGL diagnosis were used retrospectively. The Planning Target Volumes (PTV) was generated with a margin of 0.5 cm from the laryngeal volume. The PTV dose was defined as 45 Gy delivered in 10 fractions within each of treatment plans. At least 95% of PTV treatment volumes (D95%) were to receive the treatment dose. The average PTV volume was 95.56 cm3 (range: 68.8 cm3 - 142.6 cm3). The average D98%, D2% and Dmean values of PTV were lower in IMAT plan than in CK plan. In CK plans, the mean of the spinal cord maximum dose (Dmax) for all patients was statistically significantly lower than in IMAT plans. Dmax and Dmean values for the right and left carotid arteries was significantly lower in IMAT plans. Also, the Dmean value of thyroid gland was significantly lower in IMAT plans. Our dosimetric comparison study made using images of 15 EGL cancer patients shows that the desired critria for the critical organ doses can not reached with CK plans, especially when the treatment volume is large.

Outcomes of carotid sparing intensity-modulated radiotherapy for early stage glottic cancer in 201 patients: Multicenter study of Turkish Radiation Oncology Society/TROD-01-007.

To assess and report clinical outcomes after carotid sparing intensity-modulated radiotherapy for early stage laryngeal cancer. We retrospectively analyzed 201 patients with early stage glottic laryngeal cancer treated with carotid sparing intensity-modulated radiotherapy (IMRT)/volumetric modulated arc therapy (VMAT) techniques in six TROD centers. After a median follow-up of 31 months the actuarial 1- and 3-year local and locoregional control rates were 99.4% and 94.7%, 98.4% and 93%, respectively. T classification, anterior commissure involvement, IMRT technique, and type of fractionation were not found to be prognostic for local control. Overall, eight patients had lost their organ function due to recurrence or toxicity. Grade 3 and 4 acute laryngeal edema was seen in eight (4%) and one (0.5%) of patients, respectively. Grade 3 and 4 late laryngeal edema developed in two (1%) and one patient (0.5%), respectively. Oncologic outcomes of patients treated with carotid sparing IMRT were excellent; comparable with historical series, with acceptable side effects. Longer follow-up is needed to estimate long term effect on stroke.

Comparison of pre-treatment and in-vivo dosimetry for advanced radiotherapy of prostate cancer.

BackgroundThe usage of advanced radiotherapy techniques requires validation of a previously calculated dose with the precise delivery with a linear accelerator. This study aimed to review and evaluate new verification methods of dose distribution. Moreover, our purpose was to define an internal protocol of acceptance for in-vivo measurements of dose distribution.Materials and methodsThis study included 43 treatment plans of prostate cancer calculated using the Monte Carlo algorithm. All plans were delivered using the Volumetric Modulated Arc Therapy (VMAT) technique of advanced radiotherapy by the linear accelerator Elekta VersaHD. The dose distribution was verified using: MatriXX, iViewDose, and in-vivo measurements. The verification also included recalculation of fluence maps of quality assurance plans in another independent algorithm.ResultsThe acceptance criterion of 95% points of dose in agreement was found for pre-treatment verification using MatriXX; the average γ value was 99.09 ± 0.93 (SD) and 99.64 ± 0.35 (SD) for recalculation in the Collapse Cone algorithm. Moreover, using the second algorithm in the verification process showed a positive correlation ρ = 0.58, p < 0.001. However, verification using iViewDose in a phantom and in-vivo did not meet this γ-pass rate.ConclusionsEvaluation of gamma values for in-vivo measurements utilizing iViewDose software was helpful to establish an internal dosimetry protocol for prostate cancer treatments. We assumed value at a minimum of 50% points of the dose in agreement with the 3%/3 mm criterion as an acceptable compliance level. The recalculated dose distribution of QA plans in regard to the Collapse Cone algorithm in the other treatment planning system can be used as a pre-treatment verification method used by a medical physicist in their daily work. The effectiveness of use in iViewDose software, as a pre-treatment tool, is still debatable, unlike the MatriXX device.

In Situ Real-Time Dosimetric Studies for Spine Stereotactic Body Radiation Therapy in a Cadaver Implanted with Carbon-Fiber and Titanium Instrumentation

We sought to compare the dosimetric accuracy of postoperative stereotactic body radiation therapy in a carbon-fiber (CF) versus titanium instrumented spine using a cadaveric model. In situ cadaveric implantation of titanium and CF instrumentation and dosimeter chips in a thoracic spine. The cadaver underwent stereotactic body radiation therapy, and a dose of radiation therapy was calculated, measured, and compared. The sensors were placed in positions to provide data on dosimetry near the screws (within 1 cm) and between the screws. The differences between calculated and measured doses were reported as percentages. There was a significant difference in the dosimetry from calculated versus measured values near the screws of CF compared with titanium (P= 0.0057) with a mean percentage difference of only 2.93 for CF and a much higher value of 19.32 for titanium near the screws. There was also greater variability in the percent difference for the 2 screw types, with differences ranging from-16.54% to 35.20% near titanium screws and-3.37% to 1.66% near CF screws. More accurate dosimetry and radiation therapy delivery with CF screws compared with traditional titanium screws may have implications on optimal radiation delivery, as well as complication avoidance. This may be due to reduced scatter and thus lower variability in radiation delivery with the volumetric modulated arc therapy technique.

Modified volumetric modulated arc therapy technique with reduced planning and treatment time for craniospinal irradiation utilising two isocentres.

IntroductionPaediatric patients (individuals below 18 years of age) requiring cranial‐spinal irradiation (CSI) at our institution are commonly planned and treated using a three isocentre (3‐ISO) volumetric modulated arc therapy (VMAT) technique. A modified two isocentre (2‐ISO) VMAT technique was investigated with the aim to improve workflow and reduce planning and treatment time.MethodsFive CSI paediatric patients previously treated with a 3‐ISO VMAT technique were retrospectively replanned using a 2‐ISO VMAT technique. The 2‐ISO VMAT plans were reviewed and approved by a radiation oncologist (RO) before undergoing patient‐specific quality assurance (QA) procedures, performed by a radiation oncology medical physicist (ROMP). Planning target volume (PTV) coverage, organ‐at‐risk (OAR) dose as well as planning and treatment durations of the first five patients utilising 2‐ISO technique were compared with 3‐ISO technique.ResultsThe average percentage difference in PTV coverage by 95% reference dose between the 2‐ISO and 3‐ISO is 0.14%, and the average difference in OAR median dose is 0.68 Gy. Conformity and homogeneity indices have the same averages at 1.18 and 0.4 respectively. Patient‐specific physics QA results were all comparable with the 3‐ISO averages at 98.84% and the 2‐ISO at 98.71%. Planning duration for the 2‐ISO was reduced by up to 75%, and daily treatment duration was reduced by up to 50%. Of all the previously treated CSI patients using a 3‐ISO technique, 45% were suitable for the 2‐ISO technique.ConclusionThe 2‐ISO VMAT technique provided comparable dose distribution based on PTV coverage, OAR dose and plan metric indices. Reduced planning and treatment duration with the 2‐ISO technique facilitated improved workflow with decreased sedation time for paediatric patients requiring a general anaesthesia.

Radiosurgery in Treatment of Ventricular Tachycardia – Initial Experience Within the Polish SMART-VT Trial

BackgroundStereotactic Arrhythmia Radioablation (STAR) is an emerging treatment modality for patients with sustained ventricular tachycardia (VT) and refractory to treatment with drugs and radiofrequency catheter ablation (RFA). It is believed that up to 12–17% of patients experience recurrence of VT within 1 year of follow-up; thus, novel therapeutic options are needed. The aim of this article is to present initial experience within a novel treatment modality for VT.Case SummaryTwo patients with a medical history of coronary artery disease and heart failure with reduced left ventricle (LV) ejection fraction, after implantation of cardioverter-defibrillator (ICD) and previous unsuccessful RFAs owing to sustained VT were admitted to the cardiology department due to recurrence of sustained VT episodes. With electroanatomical mapping (EAM), the VT substrate in LV has been confirmed and specified. In order to determine the target volume for radioablation, contrast-enhanced computed tomography was performed and the arrhythmia substrate was contoured using EAM data. Using the Volumetric Modulated Arc Therapy technique and three 6 MeV flattening filter-free photon beam fields, a single dose of 25 Gy was delivered to the target volume structure located in the apex and anterior apical segments of LV in the first patient and in the apex, anterolateral and inferior apical segments of the second patient. In both cases, volumes of the target structures were comparable. Interrogation of the implanted ICD at follow-up visits throughout 6 months after the treatment revealed no VT episodes in the first patient and sudden periprocedural increase in VT burden with a subsequent gradual decrease of ventricular arrhythmia to only two non-sustained episodes at the end of the follow-up period in case of the second patient. A significant reduction in premature ventricular contractions burden was observed compared to the pre-treatment period. No noticeable deterioration in LV function was noted, nor any adverse effects of radiosurgery associated with the implanted device.ConclusionThe early response to STAR can be unpredictable and probably does not reflect the final outcome of irradiation. Close monitoring of patients, especially in the early period after irradiation is crucial to properly handle potentially harmful early reactions to STAR.

Introduction of deep inspirational breath-hold and Butterfly-VMAT techniques into clinical practice for the treatment of mediastinal lymphoma - Lessons learned from an experienced centre.

Deep inspiration breath-hold, butterfly volumetric modulated arc therapy and daily imaging techniques for mediastinal lymphoma patients have been introduced in a single department. Whilst introducing these techniques, there were many practical lessons to be learned across the patient pathway, from pre-treatment through to treatment delivery.Therapeutic radiographers were key members of the multi-disciplinary team implementing these techniques. This work reflects on the experience of introducing these advanced techniques for mediastinal lymphoma patients and the lessons learnt.