Optimal values of the Electron Monte Carlo dose engine parameters.

Background: The aim of this study was to indicate the most favorable - in terms of to the time of calculation and the uncertainty of determining the dose distribution - values of the parameters for the Electron Monte Carlo (eMC) algorithm in the Eclipse treatment planning system. Materials and methods: Using the eMC algorithm and the variability of the values of its individual parameters, calculations of the electron dose distribution in the full-scattering virtual water phantom were performed, obtaining percentage depth doses, beam profiles, absolute dose values in points and calculation times. The reference data included water tank measurements such as relative dose distributions and absolute point doses. Results: For 63 sets of calculation data created from selected values of the parameters for the eMC algorithm, calculation times were analyzed and the absolute calculated and measured doses were compared. Performing a statistical analysis made it possible to determine whether the differences in the values of deviations between the actual dose and the calculated dose in individual regions of the percentage depth dose curve and the beam profile are statistically significant between the analyzed sets of parameters. Conclusions: Taking into account obtained results from the analysis of the discrepancy between the distribution of the calculated and measured dose, the correspondence of the absolute value of the calculated and measured dose and the duration of the calculation of the dose distribution, the optimal set of parameters was indicated for the eMC algorithm which allows obtaining the dose distribution and the number of monitor units in an acceptable time.

Stereotactic management of arrhythmia - radiosurgery in treatment of ventricular tachycardia (SMART-VT). Results of a prospective safety trial.

BACKGROUND AND PURPOSE: Despite its increasing popularity, there are limited prospective data on stereotactic arrhythmia radioablation (STAR). In this trial, we assessed the safety and efficacy of STAR in patients with ventricular tachycardia (VT), focusing on early treatment-related grade ≥ 3 adverse events (AE). MATERIALS AND METHODS: This prospective trial was designed for adults with VT recurrence following catheter ablation (CA) despite adequate pharmacotherapy, or contraindications to CA. A single dose of 25 Gy was delivered to the arrhythmia substrate defined on electro-anatomic mapping and cardiac-gated CT. The primary endpoint was safety, defined as two or fewer treatment-related grade ≥ 3 AEs during the first three months in 11 patients. Additional endpoints included treatment efficacy, clinical and biological markers of cardiac injury, and quality of life. RESULTS: Eleven patients with a median age of 67 years, structural heart disease, and a clinically significant recurrence of VT despite adequate pharmacotherapy and 1-4 previous CAs were enrolled between 2020/09 and 2022/10. Following the treatment, one patient developed a possibly treatment-related grade ≥ 3 AE, a grade 4 heart failure exacerbation at 87 days, which resolved after conservative treatment. There was a total 84.3% reduction in VT burden in 10 evaluable patients; however, VT recurrence was eventually observed in eight, and three patients required additional CAs. Three deaths due to unrelated causes were recorded. CONCLUSIONS: STAR appears to be safe and efficient. It is a promising treatment for selected patients; however, long-term outcomes remain to be evaluated, and controlled trials comparing STAR with standards of care are missing.

Stereotactic Radiotherapy in Combination with Immunotherapy in Treatment of Advanced Recurrent Squamous Cell Carcinoma of the Larynx.

Squamous cell carcinoma (SCC) of the larynx in advanced stages is a challenging malignancy to treat with a high recurrence and death rate. An individualized approach to treatment is crucial in such patients. We present a 58-year-old male patient with SCC of the larynx in the T3N0M0 stage who was treated with concurrent radiochemotherapy. A total of 17 months after the radical treatment, the patient underwent a laryngectomy due to recurrence. A total of 11 months after the operation, local failure was diagnosed. In the next order, the patient received six cycles of palliative chemotherapy according to cisplatin 100 mg/m2 and 5-fluorouracil 1000 mg/m2. After three months, due to progression, Nivolumab-based immunotherapy was administered, ensuring disease stabilization. After the 56th cycle of Nivolumab, another progression was documented. The addition of stereotactic radiotherapy (18 Gy in three fractions) to immunotherapy led to significant regression of the disease and enabled the continuation of Nivolumab to the 70th cycle. The presented case demonstrates the usefulness of the combination of stereotactic radiotherapy with immunotherapy in prolonging the local control.

Stereotactic Radiotherapy Boost in Treatment of Persistent Periocular Sebaceous Carcinoma after Surgery.

Sebaceous carcinoma is a rare malignancy that should be treated with surgical resection. Nonetheless, a dynamic and aggressive course of the disease may disqualify a patient from this treatment. Applying radiotherapy with the escalation dose using a stereotactic boost is worthy of consideration as a radical treatment. In this paper, we present the case study of a young patient with a tumor localized in the periocular area. The patient was treated with operation two times without a satisfactory effect. Conventional radiotherapy, 60 Gy in 30 fractions, combined with chemotherapy based on cisplatin 40 mg/m2 and the addition of a stereotactic radiosurgery boost were administered. The tolerance of this treatment was acceptable. During the 2-year follow-up, local and distant recurrences were not diagnosed. The presented case shows the usefulness of an individualized approach in the radical treatment of sebaceous carcinoma with the use of the stereotactic radiotherapy boost. This is a subsequent example of the implementation of the boost in head and neck carcinoma, which yields a positive result.

The Effect of Radiotherapy on Cell Survival and Inflammatory Cytokine and Chemokine Secretion in a Co-Culture Model of Head and Neck Squamous Cell Carcinoma and Normal Cells.

Radiotherapy (RT) is one of the main treatments for head and neck squamous cell carcinomas (HNSCCs). Unfortunately, radioresistance is observed in many cases of HNSCCs. The effectiveness of RT depends on both the direct effect inducing cell death and the indirect effect of changing the tumor microenvironment (TME). Knowledge of interactions between TME components after RT may help to design a new combined treatment with RT. In the study, we investigated the effect of RT on cell survival and cell secretion in a co-culture model of HNSCCs in vitro. We examined changes in cell proliferation, colony formation, cell cycle phases, type of cell death, cell migration and secretion after irradiation. The obtained results suggest that the presence of fibroblasts and endothelial cells in co-culture with HNSCCs inhibits the function of cell cycle checkpoints G1/S and G2/M and allows cells to enter the next phase of the cell cycle. We showed an anti-apoptotic effect in co-culture of HNSCCs with fibroblasts or endothelial cells in relation to the execution phase of apoptosis, although we initially observed increased activation of the early phase of apoptosis in the co-cultures after irradiation. We hypothesize that the anti-apoptotic effect depends on increased secretion of IL-6 and MCP-1.

Influence of optional measurement parameters in the Eclipse treatment planning system on the quality of the dosimetric model of the biomedical accelerator using the Acuros XB algorithm.

Background: To properly configure a treatment planning system, a measurement data set is needed, which consists of the values required for its configuration. The aim is to obtain a dosimetric model of the beam that is as compatible as possible with the measured values. The set of required data can be supplemented with optional values. The aim of the study was to assess the influence of optional measurement data on the compliance of the calculations with the measurements. Materials and methods: Dosimetric measurements, model configuration and dose distribution calculations were performed for the photon radiation beams generated by the VMS TrueBeam® linear accelerator. Beams were configured on an Eclipse™ v. 15.6 system using the Acuros v. 15.6 algorithm. The measured and calculated data were entered into the Alfard™ software for comparison with the calculated dose distributions. In the last stage, the absolute dose values at the designated points were also compared. The obtained data were statistically analysed with Statistica™ v. 13.3. Results: The work showed that the differences in the shape of the beam profile, depth dose and the dose value in points were not related to the use of optional data. Differences in dose distributions are within the tolerance. It cannot be determined under which conditions the use of optional data has a more favourable effect on the reflection of the actual dose values. Conclusions: The use of optional data in modelling photon radiation beams does not significantly improve the compliance of the calculated and measured dose values.

Escalating a Biological Dose of Radiation in the Target Volume Applying Stereotactic Radiosurgery in Patients with Head and Neck Region Tumours.

Background: The treatment of head and neck tumours is a complicated process usually involving surgery, radiation therapy, and systemic treatment. Despite the multidisciplinary approach, treatment outcomes are still unsatisfactory, especially considering malignant tumours such as squamous cell carcinoma or sarcoma, where the frequency of recurrence has reached 50% of cases. The implementation of modern and precise methods of radiotherapy, such as a radiosurgery boost, may allow for the escalation of the biologically effective dose in the gross tumour volume and improve the results of treatment. Methods: The administration of a stereotactic radiotherapy boost can be done in two ways: an upfront boost followed by conventional radio(chemo)therapy or a direct boost after conventional radio(chemo)therapy. The boost dose depends on the primary or nodal tumour volume and localization regarding the organs at risk. It falls within the range of 10-18 Gy. Discussion: The collection of detailed data on the response of the disease to the radiosurgery boost combined with conventional radiotherapy as well as an assessment of early and late toxicities will contribute crucial information to the prospective modification of fractionated radiotherapy. In the case of beneficial findings, the stereotactic radiosurgery boost in the course of radio(chemo)therapy in patients with head and neck tumours will be able to replace traditional techniques of radiation, and radical schemes of treatment will be possible for future development.

High-dose stereotactic radiotherapy boost in the treatment of squamous cell carcinoma of the head and neck region.

BACKGROUND: Surgical resection with adjuvant concurrent radiochemotherapy is the standard of care for stage III-IV oral cavity cancer. In some cases, the dynamic course of the disease is out of the prepared schedule of treatment. In that event, a stereotactic radiosurgery boost might be the only chance for disease control. CASE PRESENTATION: Here, we present a case study of a patient with oral cancer who underwent surgery. During adjuvant radiotherapy, a metastatic cervical lymph node was diagnosed based on fine-needle aspiration biopsy. To increase the total dose to the metastatic tumor, a stereotactic radiosurgery boost of 1 × 18 Gy was performed two days after the last fraction of conventional radiotherapy. The early and late tolerance of this treatment were positive. During the 18-month follow-up, locoregional recurrence was not detected. The patient died due to secondary malignancy. CONCLUSIONS: This paper shows that a stereotactic radiosurgery boost added to adjuvant conventional radiotherapy is an effective approach permitting the maintenance of good local control in well-selected patients.

Stereotactic radiotherapy is a useful treatment option for patients with medullary thyroid cancer.

The role of radiotherapy in advanced medullary thyroid carcinoma (MTC) is confined to patients in whom surgical treatment or the administration of tyrosine kinase inhibitors are not possible or contraindicated. High fractionated radiation doses during radiosurgery or fractionated stereotactic radiotherapy are applied to reduce cancer-related symptoms and stabilize irradiated lesions. This study aimed to retrospectively evaluate the therapeutic effect of stereotactic radiotherapy in MTC patients. MATERIAL AND METHODS: The study group involved 11 MTC patients, treated due to 16 cancer lesions, mainly bone metastases (10 lesions), lymph node (2 lesions) metastases, or liver metastases (2 lesions), one primary thyroid tumor, and one MTC recurrence in the thyroid bed. The fractionated and total radiation doses ranged between 5 and 12 Gy and 8-44 Gy, respectively. Six lesions were treated with a single radiation fraction, three lesions with 2 fractions, another 6 lesions with 3 fractions, whereas the remaining one metastatic lesion with 9 fractions of stereotactic radiosurgery. RESULTS: The beneficial effect of stereotactic radiosurgery was obtained in all treated lesions. None of treated lesions progressed in the further disease course. Fourteen lesions were stable (87.5 %), including eight lesions showing progression before radiosurgery (good response). Disease control was obtained in all soft-tissue metastases. Regarding bone metastases, partial regression was achieved in 20 % lesions, whereas in 30 % lesions progressive before radiotherapy, the treatment led to disease stabilization. CONCLUSIONS: Our data pointed to the effectiveness of high-dose fractionated radiotherapy in MTC. However, an observation of a larger group of patients is required to confirm it.

Using beam profile inflection point in process of treatment planning system verification.

BACKGROUND: The comparison between profiles during the commissioning of the treatment planning system is an essential procedure. It is impossible to designate a field size for off-axis, wedged, and FFF beams directly by using the definition of the on-axis symmetric field size. This work proposes the use of different characteristic points as indicators of the field size for commissioning and QA purposes. This work aimed to search for the beam profile's characteristic points and use them for the TPS commissioning purposes. MATERIALS AND METHODS: The proposal is to use profile inflection points as the beam profile characteristic points. The usage of dedicated software allowed for comparing distances between inflection points and between points of 50% intensity. For the off-axis, wedged, and FFF fields, comparisons were made to the nominal field sizes. RESULTS: Distances between inflection points proved to be different by less than 1 mm from nominal field sizes for all kinds of investigated beams. CONCLUSIONS: Inflection points are convenient for comparing the off-axis, wedged, and FFF field sizes because of their independence from profile normalization. With finite accuracy, the inflection points could be used for the above kind of beam sizes designation.

Successful Treatment of Adenoid Cystic Carcinoma with the Application of a High-Dose Stereotactic Body Radiotherapy Boost.

BACKGROUND: Adenoid cystic carcinoma (ACC) should be treated with a surgical procedure. Unfortunately, in some cases, such procedures are impossible to perform. In that event, radiotherapy can be used as a form of radical treatment, although ACC is established as a radio- and chemoresistant tumour. Therefore, unconventional fractionated radiotherapy needs to be considered. CASE PRESENTATION: Here, we present a case study of a patient with an unresectable tumour of the choanae and nasopharynx treated with a stereotactic radiotherapy boost in combination with conventional radiotherapy. We achieved complete clinical regression after application of a 1 × 18 Gy boost followed by conventional radiotherapy at 50 Gy in 25 fractions. The early and late tolerance of this treatment were positive. During the 2-year follow-up, local and distant recurrence were not detected. CONCLUSIONS: This case represents an individualized, modern and safe approach to unresectable ACC. This is one of the first cases to show the use of a combination of stereotactic and conventional radiotherapy in radical, conservative cancer treatment.

Portal dosimetry in radiotherapy repeatability evaluation.

The accuracy of radiotherapy is the subject of continuous discussion, and dosimetry methods, particularly in dynamic techniques, are being developed. At the same time, many oncology centers develop quality procedures, including pretreatment and online dose verification and proper patient tracking methods. This work aims to present the possibility of using portal dosimetry in the assessment of radiotherapy repeatability. The analysis was conducted on 74 cases treated with dynamic techniques. Transit dosimetry was made for each collision-free radiation beam. It allowed the comparison of summary fluence maps, obtained for fractions with the corresponding summary maps from all other treatment fractions. For evaluation of the compatibility in the fluence map pairs (6798), the gamma coefficient was calculated. The results were considered in four groups, depending on the used radiotherapy technique: stereotactic fractionated radiotherapy, breath-hold, free-breathing, and conventionally fractionated other cases. The chi2 or Fisher's exact test was made depending on the size of the analyzed set and also Mann-Whitney U-test was used to compare treatment repeatability of different techniques. The aim was to test whether the null hypothesis of error-free therapy was met. The patient is treated repeatedly if the P-value in all the fluence maps sets is higher than the level of 0.01. The best compatibility between treatment fractions was obtained for the stereotactic technique. The technique with breath-holding gave the lowest percentage of compliance of the analyzed fluence pairs. The results indicate that the repeatability of the treatment is associated with the radiotherapy technique. Treated volume location is also an essential factor found in the evaluation of treatment accuracy. The EPID device is a useful tool in assessing the repeatability of radiotherapy. The proposed method of fluence maps comparison also allows us to assess in which therapeutic session the patient was treated differently from the other fractions.

In silico assessment of the dosimetric quality of a novel, automated radiation treatment planning strategy for linac-based radiosurgery of multiple brain metastases and a comparison with robotic methods.

BACKGROUND: To appraise the dosimetric features and the quality of the treatment plan for radiosurgery of multiple brain metastases optimized with a novel automated engine and to compare with plans optimized for robotic-based delivery. METHODS: A set of 15 patients with multiple brain metastases was selected for this in silico study. The technique under investigation is the recently introduced HyperArc. For all patients, three treatment plans were computed and compared: i: a HyperArc; ii: a standard VMAT; iii) a CyberKnife. Dosimetric features were computed for the clinical target volumes as well as for the healthy brain tissue and the organs at risk. RESULTS: The data showed that the best dose homogeneity was achieved with the VMAT technique. HyperArc allowed to minimize the volume of brain receiving 4Gy (as well as for the mean dose and the volume receiving 12Gy, although not statistically significant). The smallest dose on 1 cm3 volume for all organs at risk is for CK techniques, and the biggest for VMAT (p < 0.05). The Radiation Planning Index coefficient indicates that, there are no significant differences among the techniques investigated, suggesting an equivalence among these. CONCLUSION: At treatment planning level, the study demonstrates that the use of HyperArc technique can significantly improve the sparing of the healthy brain while maintaining a full coverage of the target volumes.

Determination of boundaries between ranges of high and low gradient of beam profile.

AIM: This work addresses the problem of treatment planning system commissioning by introducing a new method of determination of boundaries between high and low gradient in beam profile. BACKGROUND: The commissioning of a treatment planning system is a very important task in the radiation therapy. One of the main goals of this task is to compare two field profiles: measured and calculated. Applying points of 80% and 120% of nominal field size can lead to the incorrect determination of boundaries, especially for small field sizes. MATERIALS AND METHODS: The method that is based on the beam profile gradient allows for proper assignment of boundaries between high and low gradient regions even for small fields. TRS 430 recommendations for commissioning were used. RESULTS: The described method allows a separation between high and low gradient, because it directly uses the value of the gradient of a profile. For small fields, the boundaries determined by the new method allow a commissioning of a treatment planning system according to the TRS 430, while the point of 80% of nominal field size is already in the high gradient region. CONCLUSIONS: The method of determining the boundaries by using the beam profile gradient can be extremely helpful during the commissioning of the treatment planning system for Intensity Modulated Radiation Therapy or for other techniques which require very small field sizes.

Tolerance and efficacy of palliative radiotherapy for advanced pancreatic cancer: A retrospective analysis of single-institutional experiences.

This study was conducted to investigate hypofractionated radiotherapy (RT) in patients with locally advanced or metastatic adenocarcinoma of the pancreas. A total of 31 patients were enrolled in this study, 26 of whom had locally advanced (M0) pancreatic cancer and 5 had metastatic (M1) disease. The patients were treated with palliative RT (6-30 Gy in 1-10 fractions over a period of 1 day-2 weeks). Treatment-related toxicity was classified according to the Common Terminology Criteria for Adverse Events, version 3.0. Early mild toxicity was observed. A total of 17 patients (55%) achieved good pain control without pharmacological therapy, and 12 patients (39%) reduced their use of analgesics; in the remaining 2 patients (6%), there was no change in analgesic use. Late high-grade (>3) toxicity was not observed. The average survival time for the 31 patients was 9 months. The 1-year overall survival rate was 16%. Palliative RT was well-tolerated and was able to prolong the survival time. The majority of the patients achieved better pain control with palliative RT.

Integral dose: Comparison between four techniques for prostate radiotherapy.

AIM: Comparisons of integral dose delivered to the treatment planning volume and to the whole patient body during stereotactic, helical and intensity modulated radiotherapy of prostate. BACKGROUND: Multifield techniques produce large volumes of low dose inside the patient body. Delivered dose could be the result of the cytotoxic injuries of the cells even away from the treatment field. We calculated the total dose absorbed in the patient body for four radiotherapy techniques to investigate whether some methods have a potential to reduce the exposure to the patient. MATERIALS AND METHODS: We analyzed CyberKnife plans for 10 patients with localized prostate cancer. Five alternative plans for each patient were calculated with the VMAT, IMRT and TomoTherapy techniques. Alternative dose distributions were calculated to achieve the same coverage for PTV. Integral Dose formula was used to calculate the total dose delivered to the PTV and whole patient body. RESULTS: Analysis showed that the same amount of dose was deposited to the treated volume despite different methods of treatment delivery. The mean values of total dose delivered to the whole patient body differed significantly for each treatment technique. The highest integral dose in the patient's body was at the TomoTherapy and CyberKnife treatment session. VMAT was characterized by the lowest integral dose deposited in the patient body. CONCLUSIONS: The highest total dose absorbed in normal tissue was observed with the use of a robotic radiosurgery system and TomoTherapy. These results demonstrate that the exposure of healthy tissue is a dosimetric factor which differentiates the dose delivery methods.

Robotic radiosurgery versus micro-multileaf collimator: a dosimetric comparison for large or critically located arteriovenous malformations.

BACKGROUND: Stereotactic irradiation of large or critically located arteriovenous malformations (AVMs) is a special challenge for clinicians and radiation physicists. To date, no comprehensive comparison of two linac-based radiosurgery systems used for hypofractionated radiotherapy of large AVMs was published. The aim of the study was to compare dose distributions between CyberKnife (CK) system and linac with a micro-multileaf collimator (L-mMLC) in high-grade or critically located cerebral AVMs. METHODS: Two sets of plans made for 15 different patients with at least 95% target coverage were selected for comparisons. Conformity (CI), homogeneity (HI) and gradient score (GSI) indices, conformity index proposed by Lomax (CIL), conformation number (CN), quality of coverage (Q), volumes of brain receiving 12,10,8,6,4, and 2 Gy, minimum and maximum doses for critical structures in both treatment planning systems (TPS) were compared. Finally, the number of monitor units needed to deliver the prescribed dose was compared. RESULTS: The mean minimum doses in the target volume were 93.3% (CK) and 90.7% (L-mMLC),p=n.s, maximum: 119.7 and 110%, respectively (p=0.004). The mean CI was 1.46 and 1.86, HI: 1.2, and 1.11, CIL 0.7, and 0.6, CN: 0.68 and 0.58 for CK and mMLC, respectively (p<0.05). The values of GSI and Q were not significantly different. The volumes of the brain receiving low doses (4 Gy and 2 Gy) were significantly lower in the CK system. The number of monitor units necessary to deliver the prescribed dose was significantly greater in case of the CK system. CONCLUSIONS: Better conformity can favor the CK system for treatment of large AVMs at the cost of higher maximum doses and worse homogeneity. L-mMLC is superior when shorter treatment time is required. Neither system can assure satisfying dose gradients outside large targets surrounded by numerous critical structures.

Beam rate influence on dose distribution and fluence map in IMRT dynamic technique.

AIM: To examine the impact of beam rate on dose distribution in IMRT plans and then to evaluate agreement of calculated and measured dose distributions for various beam rate values. BACKGROUND: Accelerators used in radiotherapy utilize some beam rate modes which can shorten irradiation time and thus reduce ability of patient movement during a treatment session. This aspect should be considered in high conformal dynamic techniques. MATERIALS AND METHODS: Dose calculation was done for two different beam rates (100 MU/min and 600 MU/min) in an IMRT plan. For both, a comparison of Radiation Planning Index (RPI) and MU was conducted. Secondly, the comparison of optimal fluence maps and corresponding actual fluence maps was done. Next, actual fluence maps were measured and compared with the calculated ones. Gamma index was used for that assessment. Additionally, positions of each leaf of the MLC were controlled by home made software. RESULTS: Dose distribution obtained for lower beam rates was slightly better than for higher beam rates in terms of target coverage and risk structure protection. Lower numbers of MUs were achieved in 100 MU/min plans than in 600 MU/min plans. Actual fluence maps converted from optimal ones demonstrated more similarity in 100 MU/min plans. Better conformity of the measured maps to the calculated ones was obtained when a lower beam rate was applied. However, these differences were small. No correlation was found between quality of fluence map conversion and leaf motion accuracy. CONCLUSION: Execution of dynamic techniques is dependent on beam rate. However, these differences are minor. Analysis shows a slight superiority of a lower beam rate. It does not significantly affect treatment accuracy.

EPID in vivo dosimetry in RapidArc technique.

AIM: The aim of the study was to estimate the dose at the reference point applying an aSi-EPID device in the course of patient treatment. MATERIALS AND METHODS: The method assumes direct proportionality between EPID signal and dose delivered to the patient reference point during the treatment session. The procedure consists of treatment plan calculation for the actual patient in the arc technique. The plan was realized with an elliptic water-equivalent phantom. An ionization chamber inside the phantom measured the dose delivered to the reference point. Simultaneously, the EPID matrix measured the CU distribution. EPID signal was also registered during patient irradiation with the same treatment plan. The formula for in vivo dose calculation was based on the CU(g) function, EPID signal registered during therapy and the relation between the dose and EPID signal level measured for the phantom. In vivo dose was compared with dose planned with the treatment planning system. Irradiation was performed with a Clinac accelerator by Varian Medical Systems in the RapidArc technique. The Clinac was equipped with an EPID matrix (electronic portal image device) of aSi-1000. Treatment plans were calculated with the Eclipse/Helios system. The phantom was a Scanditronix/Wellhöfer Slab phantom, and the ionization chamber was a 0.6 ccm PTW chamber. RESULTS: In vivo dose calculations were performed for five patients. Planned dose at the reference point was 2 Gy for each treatment plan. Mean in vivo dose was in the range of 1.96-2.09. CONCLUSIONS: Our method was shown to be appropriate for in vivo dose evaluation in the RapidArc technique.

Linear array measurements of enhanced dynamic wedge and treatment planning system (TPS) calculation for 15 MV photon beam and comparison with electronic portal imaging device (EPID) measurements.

INTRODUCTION: Enhanced dynamic wedges (EDW) are known to increase drastically the radiation therapy treatment efficiency. This paper has the aim to compare linear array measurements of EDW with the calculations of treatment planning system (TPS) and the electronic portal imaging device (EPID) for 15 MV photon energy. MATERIALS AND METHODS: The range of different field sizes and wedge angles (for 15 MV photon beam) were measured by the linear chamber array CA 24 in Blue water phantom. The measurement conditions were applied to the calculations of the commercial treatment planning system XIO CMS v.4.2.0 using convolution algorithm. EPID measurements were done on EPID-focus distance of 100 cm, and beam parameters being the same as for CA24 measurements. RESULTS: Both depth doses and profiles were measured. EDW linear array measurements of profiles to XIO CMS TPS calculation differ around 0.5%. Profiles in non-wedged direction and open field profiles practically do not differ. Percentage depth doses (PDDs) for all EDW measurements show the difference of not more than 0.2%, while the open field PDD is almost the same as EDW PDD. Wedge factors for 60 deg wedge angle were also examined, and the difference is up to 4%. EPID to linear array differs up to 5%. CONCLUSIONS: The implementation of EDW in radiation therapy treatments provides clinicians with an effective tool for the conformal radiotherapy treatment planning. If modelling of EDW beam in TPS is done correctly, a very good agreement between measurements and calculation is obtained, but EPID cannot be used for reference measurements.