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Purpose: Given tissue inhomogeneity and lack of backscatter media, superficial brachytherapy necessitates more accurate dosimetry than TG-43 formalism. However, the introduction of modern model-based dose calculation algorithms into clinical practice should be carefully evaluated. The aim of this work was to compare dose distributions calculated with TG-43 and advanced collapsed cone engine (ACE) algorithms for individual multi-catheter moulds, and investigate the impact of target size and the lack of bolus to differences between plans. Material and methods: Eleven treatment plans for individual mould multi-catheter high-dose-rate brachytherapy (IMM HDR) were selected for retrospective analysis. All treatment plans were initially calculated with TG-43 formula and re-calculated using ACE algorithm. Plan re-calculation with ACE was repeated for each plan in order to assess the impact of bolus. To evaluate differences between TG-43 and ACE dose distributions, dose-volume histogram (DVH) parameters for each ROI were compared. Dmax (maximal point dose), D0.1cc, and D2cc were calculated for each risk's organ (OARs) and for external contour. For clinical target volume (CTV), D98, D90, D50, CTV coverage (CTV-V100), and dose delivered to reference point were compared between the plans. Results: A significantly lower values (p < 0.05) of CTV parameters were observed for treatment plans calculated with ACE algorithm comparing to TG-43. Further analysis showed that differences between CTV-V100 for ACE and TG-43 plans depended on CTV volume. Dosimetric parameters for OARs were significantly lower in ACE plans than those of TG-43. Only D2cc for external and D0.1cc for both eye lenses in ACE plans were insignificantly different comparing to TG-43 plans. Conclusions: Results show that differences between dosimetric parameters are statistically significant. However, their clinical relevance is still undetermined. Careful re-evaluation of the clinical results based on long-term research on TG-43 is necessary to safely introduce modern algorithms to clinical practice. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study includes four years of our clinical trials to improve implant quality in multicatheter accelerated partial breast irradiation (APBI). The progress in dosimetric and volumetric parameters of the treatment plans was evaluated. One hundred and ninety-one women, for whom treatment plans were made based on three dimensional imaging, were selected for the study. To evaluate progress made in our APBI procedure, following parameters and indices were taken into account: percentage of the target volume receiving the reference dose (PTVref), minimum dose in the target volume expressed as a percentage of reference dose (PTVmin), dose homogeneity index (DHI), and conformity index (COIN). Additionally, the plan quality index was calculated for every group as the sum of mean values of four evaluated parameters. PTVref have increased from the mean value of 83.4% at the beginning to recent 94.8%. The maximum value equals to 95.4%. The same trend can be observed with PTVmin value, which has been improved from 51.7% to 70.1%, maximally. DHI and COIN mean values present similar progress. DHI value increased from 0.53 level to 0.68, and COIN from 0.58 in 2009 to 0.74. Plan quality index has increased from 2.46 in 2009 to 3.06, recently. The implant quality is crucial for the accurate dose distribution. This paper shows the progress that was made in APBI procedure to improve implant quality. Nowadays, our implant technique is based on three-dimensional CT imaging results in acceptable dose distributions. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The aim was to provide a dosimetric comparison between IMRT and RapidArc treatment plans with RPI index with simultaneous comparison of the treatment delivery time. Background: IMRT and RapidArc provide highly conformal dose distribution with good sparing of normal tissues. However, a complex spatial dosimetry of IMRT and RapidArc plans hampers the evaluation and comparison between plans calculated for the two modalities. RPI was used in this paper for treatment plan comparisons. The duration of the therapeutic session in RapidArc is reported to be shorter in comparison to therapeutic time of the other dynamic techniques. For this reasons, total treatment delivery time in both techniques was compared and discussed. Materials and methods: 15 patients with prostate carcinoma were randomly selected for the analysis. Two competitive treatment plans using respectively the IMRT and RapidArc techniques were computed for each patient in Eclipse planning system v. 8.6.15. RPIwin® application was used for RPI calculations for each treatment plan. Additionally, total treatment time was compared between IMRT and RapidArc plans. Total treatment time was a sum of monitor units (MU) for each treated field. Results: The mean values of the RPI indices were insignificantly higher for IMRT plans in comparison to rotational therapy. Comparison of the mean numbers of monitor units confirmed that the use of rotational technique instead of conventional static field IMRT can significantly reduce the treatment time. Conclusion: Analysis presented in this paper, demonstrated that RapidArc can compete with the IMRT technique in the field of treatment plan dosimetry reducing the time required for dose delivery. [Copyright &y& Elsevier]

Abstract: Background: During a proper execution of dMLC plans, there occurs an undesired but frequent effect of the dose locally accumulated by tissue being significantly different than expected. The conventional dosimetric QA procedures give only a partial picture of the quality of IMRT treatment, because their solely quantitative outcomes usually correspond more to the total area of the detector than the actually irradiated volume. Aim: The aim of this investigation was to develop a procedure of dynamic plans verification which would be able to visualize the potential anomalies of dose distribution and specify which tissue they exactly refer to. Materials & methods: The paper presents a method discovered and clinically examined in our department. It is based on a Gamma Evaluation concept and allows accurate localization of deviations between predicted and acquired dose distributions, which were registered by portal as well as film dosimetry. All the calculations were performed on the self-made software GammaEval, the γ-images (2-dimensional distribution of γ-values) and γ-histograms were created as quantitative outcomes of verification. Results: Over 150 maps of dose distribution have been analyzed and the cross-examination of the gamma images with DRRs was performed. Conclusions: It seems, that the complex monitoring of treatment would be possible owing to the images obtained as a cross-examination of γ-images and corresponding DRRs. [Copyright &y& Elsevier]

Summary: Background: In HDR brachytherapy precision of catheter implantation is crucial for conformal treatment planning as a starting point for better optimization process. Aim: The aim was to investigate differences between virtual and real needle position and the effect of needle displacement on dosimetric parameters as a function of prostate volume for better evaluation of “real” implant with respect to final dose distribution. Materials/Methods: Thirty treatment plans calculated by Nucletron SWIFT™ were randomly selected. Dosimetric data including V100 for prostate gland and D10 for urethra were analyzed as a function of prostate volume and needle displacement. Needle displacement was determined by measuring the distance between virtual and real positions of respective needles in three sectional images: at the base, apex of the prostate gland and reference image. Dosimetric parameters were determined for consecutive computer plans: virtual (before implantation), live (after implantation and renewed optimization). For the purpose of this study a new parameter, VD (Volume-Dose), was created. Results: VD indicates the quality of “real” dose distribution with respect to “virtual” treatment plan. In order to realize the assumption of virtual plan (VD<1) for a given prostate volume, mean values of needle displacement r should not exceed racceptable according to the formula: racceptable (Vp) ∝ Vp 2. For larger glands (above 30cc) final dose distribution is less dependent on needle displacement than smaller ones. Conclusions: The experiment determined maximum values of needle displacement for a given Vp parameter, allowing one to take advantage of optimization algorithms and to improve the final dose distribution. [Copyright &y& Elsevier]

Summary: Background: The electronic portal imaging device (EPID) is used for patient setup during radiotherapy sessions. Dosimetric verification is done using ion chambers, diodes and thermoluminescence detectors. In intensity-modulated radiation therapy (IMRT) the dosimetry is a sophisticated and time-consuming task. The simultaneous use of amorphous silicon (aSi) detectors and the transit dosimetry (TD) option in the treatment planning system (TPS) (Eclipse, Varian) enables dosimetric pre-treatment verification of the IMRT plans. Aim: The purpose of this study was to calibrate the EPID and TPS and to evaluate the usefulness of that method for dose verification in IMRT technique. Materials/Methods: The first step was calibration of the aSi EPID mounted on three linear accelerators (Clianc23EXS, Varian). Afterwards, configuration of the calculation algorithm in TPS was carried out. Then dosimetric characteristics of the EPID were investigated. The EPID response depending on the beam mode, treatment time and static square field size was measured. The same measurements were repeated twice for three accelerators and analyzed. Additionally, three IMRT plans were treated for the pre-treatment dose evaluation. The calculated dose matrix was compared with the delivered one. The similarity of the calculated and measured fluency maps was evaluated by means of gamma index and score factor in Eclipse. Results: The linearity of the EPID signal was proven. For both beam modes EPID response is proportional to treatment time and field size, within the considered field size range. Conclusions: The gamma evaluation indicates good correlation between predicted and acquired EPID image, although some differences in a high gradient area were found. We found the EPID-based pre-treatment IMRT verification method to be a good quality assurance (QA) procedure. Quite frequent control of the method and periodic recalibration of the used device are required. [Copyright &y& Elsevier]