Impact of beam complexity on plan delivery accuracy verification of a transmission detector in volumetric modulated arc therapy.

OBJECTIVE: To study the effect of beam complexity on VMAT delivery accuracy evaluated by means of a transmission detector, together with the possibility of scoring plan complexity. METHODS: 43 clinical VMAT plans delivered by a TrueBeam linear accelerator to both Delta4 Discover and Delta4 Phantom+ for patient-specific quality assurance were evaluated. Global Dose-γ analysis, MLC-γ analysis, percentage of leaves with a deviation between planned and measured leaf tip position lower than 1 mm (LD) were computed. Modulation complexity score (MCSv), average leaf travel (LT), a multiplicative combination of LT and MCSv (LTMCS), percentage of leaves with speed lower than 5 mm/s (LS), from 5 to 20 mm/s (MS), higher than 20 mm/s (HS) and the average value of leaf speed (MLCSav) were evaluated by means of an home-made Matlab script. RESULTS: Dose-γ passing rate showed a moderate correlation with MCSv, LT, MLCSav, LS and HS, while a stronger positive correlation was found with LTMCS. A strong correlation was observed between LD and both LT and leaves speed, while a weak correlation was observed with MCSv. A correlation between MLC-γ pass rate and plan complexity parameters was found except for MCSv; a moderate correlation with LS was observed, while all other parameters showed weak correlations. CONCLUSIONS: The study confirmed the possibility to establish correlations between plan complexity indices versus dose distribution and MLC parameters measured by a transmissive detector. Further investigation is necessary to define specific values of the complexity indices to evaluate whether a VMAT plan is deliverable as intended.

Clinical evaluation of a deep learning CBCT auto-segmentation software for prostate adaptive radiation therapy.

Purpose: Aim of the present study is to characterize a deep learning-based auto-segmentation software (DL) for prostate cone beam computed tomography (CBCT) images and to evaluate its applicability in clinical adaptive radiation therapy routine. Materials and methods: Ten patients, who received exclusive radiation therapy with definitive intent on the prostate gland and seminal vesicles, were selected. Femoral heads, bladder, rectum, prostate, and seminal vesicles were retrospectively contoured by four different expert radiation oncologists on patients CBCT, acquired during treatment. Consensus contours (CC) were generated starting from these data and compared with those created by DL with different algorithms, trained on CBCT (DL-CBCT) or computed tomography (DL-CT). Dice similarity coefficient (DSC), centre of mass (COM) shift and volume relative variation (VRV) were chosen as comparison metrics. Since no tolerance limit can be defined, results were also compared with the inter-operator variability (IOV), using the same metrics. Results: The best agreement between DL and CC was observed for femoral heads (DSC of 0.96 for both DL-CBCT and DL-CT). Performance worsened for low-contrast soft tissue organs: the worst results were found for seminal vesicles (DSC of 0.70 and 0.59 for DL-CBCT and DL-CT, respectively). The analysis shows that it is appropriate to use algorithms trained on the specific imaging modality. Furthermore, the statistical analysis showed that, for almost all considered structures, there is no significant difference between DL-CBCT and human operator in terms of IOV. Conclusions: The accuracy of DL-CBCT is in accordance with CC; its use in clinical practice is justified by the comparison with the inter-operator variability.

Dosimetric characterization and use of GAFCHROMIC EBT3 film for IMRT dose verification.

Radiochromic film has become an important tool to verify dose distributions in highly conformal radiation therapy such as IMRT. Recently, a new generation of these films, EBT3, has become available. EBT3 has the same composition and thickness of the sensitive layer of the previous EBT2 films, but its symmetric layer configuration allows the user to eliminate side orientation dependence, which is reported for EBT2 films. The most important EBT3 characteristics have been investigated, such as response at high-dose levels, sensitivity to scanner orientation and postirradiation coloration, energy and dose rate dependence, and orientation dependence with respect to film side. Additionally, different IMRT fields were measured with both EBT3 and EBT2 films and evaluated using gamma index analysis. The results obtained show that most of the characteristics of EBT3 film are similar to the EBT2 film, but the orientation dependence with respect to film side is completely eliminated in EBT3 films. The study confirms that EBT3 film can be used for clinical practice in the same way as the previous EBT2 film.

Preliminary evaluation of a novel secondary check tool for intensity modulated radiotherapy treatment planning.

PURPOSE: To evaluate the dosimetric accuracy of the Delta4 Insight (DI) secondary-check dosimetry system. METHODS: Absolute dosimetry in reference conditions, output factors, percent depth doses normalized and off-axis dose profiles for different field sizes calculated by DI were compared with measurements. Dose calculations for 20 clinical IMRT/VMAT plans generated in the TPS using both AAA or AcurosXB algorithms were compared with measurements. The average difference between calculated and measured point dose in high-dose region was calculated for all cases. 3D dose measurements were performed in Delta4 Phantom+ and a comparison between calculated and measured dose distributions was performed by means of the gamma analysis with 3 %/2 mm criteria. The dose distributions calculated by DI for 20 IMRT/VMAT plans were compared with those calculated by the TPS. RESULTS: The absolute dosimetry computed by DI showed dose value in agreement with the measured one within 0.3 %. The average differences between measured and calculated output factors were less than 2.5 %. The average PDD differences were less than 0.6 %. An excellent agreement between calculations and off-axis measurements is found. The point doses calculated for the 20 recalculated plan showed good agreement with measurements with average differences less than 0.5 %. The average gamma pass rate values for the Delta4 Phantom + 3D dose analysis was greater than 97.%. The comparison of DI with theTPS showed good agreement for the used metrics. CONCLUSIONS: Delta4 Insight may provide a useful independent secondary dose verification system for IMRT/VMAT plans, complementing the traditional global QA protocols.

Interventional radiology at a single institution over 9 years: a comprehensive evaluation of procedures and an estimation of collective effective dose.

PURPOSE: To investigate the exposure parameters, effective dose, frequency, and collective dose for interventional radiology (IR) procedures performed at a single institution during a 9-year period. MATERIALS AND METHODS: According to the anatomic region imaged, seven diagnostic and 16 therapeutic IR procedures performed between 2002 and 2010 were retrospectively investigated with regard to exposure setting parameters and frequency. Dose-area products (DAPs), cumulative doses (CDs), and irradiation time values were analyzed on a sample of 1,100 examinations. DAP distributions (median, mean, and percentiles) were adjunctively determined by using bootstrap resampling in PCXMC software to estimate patient effective dose. Data provided by the Radiological Information System allowed collective effective and per-capita doses to obtained. RESULTS: The exposure parameters showed widespread variability. The median DAP values for pelvic arteriography and pelvic arterial angioplasty/stent placement were 10,015 and 19,424 cGy·cm(2), respectively. For the 23 procedures studied, the estimated average per-procedure effective dose ranged from 0.34 to 104.9 mSv. The pelvis (37%) was the region most often imaged in diagnostic procedures, and angioplasty/stent treatment of vessels was the most frequently performed therapeutic procedure (44%). During the study period, IR procedures increased in frequency (+137%), with a consequent increase in the per-capita dose (0.172 to 0.461 mSv) and collective dose (21 to 58 man-Sv/y). CONCLUSIONS: A comprehensive Monte Carlo-aided analysis, which allowed evaluation of contributions in terms of per-procedure and collective doses to the population for the practice of IR, showed a significant growth rate during the study period.

Accelerated hypofractionated adjuvant whole breast radiotherapy with concomitant photon boost after conserving surgery for early stage breast cancer: a prospective evaluation on 463 patients.

The current standard therapeutic option for early stage breast cancer (EBC) employs a multimodality treatment approach including conservative surgery, radiotherapy, chemotherapy, and hormone therapy. The most common adjuvant radiotherapeutic strategy consists of external beam radiation therapy (EBRT) delivered to the whole breast using 1.8-2 Gy fractions given five times a week, up to a total dose of 45-50 Gy over a period of 5 weeks. In recent years, altered schedules employing larger dose per fraction delivered in fewer treatment sessions over a shorter overall treatment time began to be explored. We herein present clinical data on accelerated hypofractionated adjuvant whole-breast radiotherapy delivered on a daily basis for a total treatment time of 20 fractions. Between February 2005 and June 2009, a total of 463 patients underwent hypofractionated accelerated adjuvant radiation after conservative surgery for early breast cancer (pathological stage pTis, pT1 or pT2, pN0-N1). The basic course of radiotherapy consisted of 45 Gy, to the whole breast in 20 fractions with 2.25 Gy/fraction; an additional daily boost dose of 0.25 Gy was concomitantly delivered, to the lumpectomy cavity, for an additional total dose of 5 Gy. The cumulative nominal dose was 50 Gy. At follow-up, patients were examined at 3 and 6 months after the end of radiotherapy and twice a year afterward. Toxicity was scored according to the Common Terminology Criteria for Adverse Events, using the Radiation Therapy Oncology Group /European Organization for Research and Treatment of Cancer toxicity scale. Cosmetic results were assessed in agreement with the Harvard criteria. All the 463 patients treated with the accelerated hypofractionated adjuvant whole-breast radiotherapy schedule achieved at least 6 months' follow-up and subsequently were considered for the present analysis. With a median follow-up of 27 months, 5-year DFS is 93.1%. Only three patients experienced disease recurrence: two of them with an axillary nodal relapse; one patient with systemic spread. No local relapse occurred. No major toxicities (grade 3 or more) were detected during follow-up. Only 2% of the patients experienced grade 3 skin toxicity at the very end of the radiotherapy course. Cosmetic result was assessed and scored at 6 months, 1 year, 2 years: 100% of patients showed excellent or good cosmetic result. The explored accelerated hypofractionated adjuvant radiotherapeutic approach for early breast cancer with concomitant photon boost seems to be feasible providing consistent clinical results with excellent short-to-medium-term toxicity profile.

Delta4 Discover transmission detector: A comprehensive characterization for in-vivo VMAT monitoring.

OBJECTIVE: To investigate the dosimetric behaviour, influence on photon beam fluence and error detection capability of Delta4 Discover transmission detector. METHODS: The transmission detector (TRD) was characterized on a TrueBeam linear accelerator with 6 MV beams. Linearity, reproducibility and dose rate dependence were investigated. The effect on photon beam fluence was evaluated in terms of beam profiles, percentage depth dose, transmission factor and surface dose for different open field sizes. The transmission factor of the 10x10 cm2 field was entered in the TPS's configuration and its correct use in the dose calculation was verified recalculating 17 clinical IMRT/VMAT plans. Surface dose was measured for 20 IMRT fields. The capability to detect different delivery errors was investigated evaluating dose gamma index, MLC gamma index and leaf position of 15 manually modified VMAT plans. RESULTS: TRD showed a linear dependence on MU. No dose rate dependence was observed. Short-term and long-term reproducibility were within 0.1% and 0.5%. The presence of the TRD did not significantly affect PDDs and profiles. The transmission factor of the 10x10 cm2 field size was 0.985 and 0.983, for FF and FFF beams respectively. The 17 recalculated plans met our clinical gamma-index passing rate, confirming the correct use of the transmission factor by the TPS. The surface dose differences for the open fields increase for shorter SSDs and greater field size. Differences in surface dose for the IMRT beams were less than 2%. Output variation ≥2%, collimator angle variations within 0.3°, gantry angle errors of 1°, jaw tracking and leaf position errors were detected. CONCLUSIONS: Delta4 Discover shows good linearity and reproducibility, is not dependent on dose rate and does not affect beam quality and dose profiles. It is also capable to detect dosimetric and geometric errors and therefore it is suitable for monitoring VMAT delivery.

Performance of Radiologists in the Evaluation of the Chest Radiography with the Use of a "new software score" in Coronavirus Disease 2019 Pneumonia Suspected Patients.

OBJECTIVES: The purpose of this study is to assess the performance of radiologists using a new software called "COVID-19 score" when performing chest radiography on patients potentially infected by coronavirus disease 2019 (COVID-19) pneumonia. Chest radiography (or chest X-ray, CXR) and CT are important for the imaging diagnosis of the coronavirus pneumonia (COVID-19). CXR mobile devices are efficient during epidemies, because allow to reduce the risk of contagion and are easy to sanitize. MATERIAL AND METHODS: From February-April 2020, 14 radiologists retrospectively evaluated a pool of 312 chest X-ray exams to test a new software function for lung imaging analysis based on radiological features and graded on a three-point scale. This tool automatically generates a cumulative score (0-18). The intra- rater agreement (evaluated with Fleiss's method) and the average time for the compilation of the banner were calculated. RESULTS: Fourteen radiologists evaluated 312 chest radiographs of COVID-19 pneumonia suspected patients (80 males and 38 females) with an average age of 64, 47 years. The inter-rater agreement showed a Fleiss' kappa value of 0.53 and the intra-group agreement varied from Fleiss' Kappa value between 0.49 and 0.59, indicating a moderate agreement (considering as "moderate" ranges 0.4-0.6). The years of work experience were irrelevant. The average time for obtaining the result with the automatic software was between 7 s (e.g., zero COVID-19 score) and 21 s (e.g., with COVID-19 score from 6 to 12). CONCLUSION: The use of automatic software for the generation of a CXR "COVID-19 score" has proven to be simple, fast, and replicable. Implementing this tool with scores weighed on the number of lung pathological areas, a useful parameter for clinical monitoring could be available.

Moderately Hypofractionated Radiotherapy with Simultaneous Integrated Boost in Prostate Cancer: A Comparative Study with Conventionally Fractionated Radiation.

BACKGROUND: To report 5-year clinical outcomes and toxicity in organ-confined prostate cancer (PCa) for low- and intermediate-risk patients treated with a moderately hypofractionated schedule of radiotherapy (RT) delivered with simultaneous integrated boost (SIB) compared to a conventionally fractionated RT regimen. METHODS: Data of 384 patients with PCa treated between August 2006 and June 2017 were retrospectively reviewed. The treatment schedule consisted of hypofractionated RT (HYPO FR) with SIB up to 70 Gy to the prostate gland and 63 Gy to seminal vesicles delivered in 28 fractions or in conventionally fractionated RT (CONV FR) up to a total dose of 80 Gy in 40 fractions. Patient allocation to treatment was based on the time period considered. For intermediate-risk patients, androgen deprivation was given for a median duration of 6 months. The 5-year biochemical relapse-free survival (bRFS), cancer-specific survival (CSS), and overall survival (OS) were assessed. Furthermore, we evaluated gastrointestinal (GI) and genitourinary (GU) toxicities. Uni- and multivariate Cox regression analyses were used to test the impact of clinical variables on both outcome and toxicity. RESULTS: A total of 198 patients was treated with hypofractionated RT and 186 with the conventional schedule. At a median follow-up of 5 years, no significant differences were observed in terms of GI toxicity and outcome between the two groups. Early GU toxicity was significantly increased in HYPO FR, while late GU toxicity was significantly higher in CONV FR. In HYPO FR, a biochemical relapse occurred in 12 patients (6.1%), and 9 patients (4.5%) reported a clinical relapse (4 local, 2 locoregional, and 3 systemic recurrence). In CONV FR, 15 patients (8.1%) experienced a biochemical relapse and 11 patients (5.9%) showed a clinical relapse (5 local, 4 locoregional, and 3 systemic recurrences). Early grades 1-2 GU and GI toxicities were observed in 60 (30.3%) and 37 (18.7%) patients, respectively, in the hypofractionated group and in 33 (17.7%) and 27 (14.5%) patients, respectively, in the conventionally fractionated RT group. Late GU and GI toxicities occurred in 1 (0.51%) and 8 (4.1%) patients, respectively, in HYPO FR. In CONV FR, 5 (2.7%) and 6 (3.2%) patients experienced late GU and GI toxicities, respectively. The 5-year OS, bRFS, and CSS were 98.9%, 94.1%, and 99.5%, respectively, in HYPO FR, and 94.5%, 92.1%, and 99.0%, respectively, in CONV FR. CONCLUSIONS: Results obtained in this study showed that moderately hypofractionated RT employing SIB can be an effective approach providing valuable clinical outcomes with an acceptable toxicity profile.

The use of a diode matrix in commissioning activities for electron energies > or = 9 MeV: a feasibility study.

The contribution of a commercially available diode matrix (MapCHECK, provided by Sun Nuclear, Melbourne, FL) for the commissioning procedures of the voxel based Monte Carlo (VMC++) algorithm for electron beams of MasterPlan treatment planning system was investigated. The attention is mainly focused on the calculation in homogeneous and heterogeneous phantoms. With this aim, following a data set similar to that proposed by Electron Collaborative Working Group (ECWG), the dose profiles and two-dimensional (2D) dose distributions measured by the diode matrix were compared with the calculated ones using the gamma analysis method with acceptance criteria for the dose difference and the distance to agreement equal to 4% and 4 mm, respectively. The average and standard deviation of the percentage of points satisfying the constraint gamma < or = 1 are 98.3 +/- 4.1% and 99.3 +/- 1.7% for the 9 and 12 MeV electron beam, respectively, showing that the accuracy of MasterPlan electron beam algorithm is good for simple two-dimensional geometries as well as for more complicated three-dimensional ones. The results are in agreement with those reported in literature by Cygler et al. ["Evaluation of the first commercial Monte Carlo dose calculation engine for electron beam treatment planning," Med. Phys. 31, 142-153 (2004)]. In addition, the authors have also analyzed the response of the 2D array in terms of dose profiles at different depths, comparing the results with those obtained in water phantom using an electron diode. The results show that in the low gradient regions there were no deviations larger than the criteria of acceptability set by Van Dyk et al. ["Commissioning and quality assurance of treatment planning computers," Int. J. Radiat. Oncol. Biol. Phys. 26, 261-273 (1993)]; in the high gradient region, the maximum deviations are less than 2 mm with most of the values less than 1 mm. The present article shows that MapCHECK can play a useful role in the commissioning of electron algorithms of treatment planning systems in the evaluation of the 2D dose distributions in homogeneous and heterogeneous phantoms. In fact, it provides accurate results with the merit of expediting the commissioning process by using measuring device that requires minimal setup time and data processing time.

Verification of Varian Enhanced Dynamic Wedge implementation in masterplan treatment planning system.

This paper investigates the accuracy of the two available calculation algorithms of the Oncentra MasterPlan three-dimensional treatment planning system (TPS)-- the pencil beam method and collapsed-cone convolution--in modeling the Varian enhanced dynamic wedge (EDW). Measurements were carried out for a dual high energy (6-15 MV) Varian DHX-S linear accelerator using ionization chambers for beam axis measurements (wedge factors and depth doses), film dosimetry for off-axis dose profiles measurements, and a diode matrix detector for two dimensional absolute dose distributions. Using both calculation algorithms, different configuration of symmetric and asymmetric fields varying the wedge's angle were tested. Accuracy of the treatment planning system was evaluated in terms of percentage differences between measured and calculated values for wedge factors, depth doses, and profiles. As far as the absolute dose distribution was concerned, the gamma index method (Low et al.) was used with 3% and 3 mm as acceptance criteria for dose difference and distance-to-agreement, respectively. Wedge factors and percentage depth doses were within 1% deviation between calculated and measured values. The comparison of measured and calculated dose profiles shows that the Van Dyk's acceptance criteria (Van Dyk et al.) are generally met; a disagreement can be noted for large wedge angles and field size limited to the low dose-low gradient region only. The 2D absolute dose distribution analysis confirms the good accuracy of the two calculation algorithms in modeling the enhanced dynamic wedge.

PET-CT post therapy dosimetry in radioembolization with resin 90Y microspheres: Comparison with pre-treatment SPECT-CT 99mTc-MAA results.

Resin microspheres radioembolization is an effective treatment for liver tumors when the surgical option is not feasible. Doses delivered to tumor and normal liver can be assess in the pre-therapy phase by means of a 99mTc-MAA SPECT-CT simulation and after the treatment with 90Y PET-CT acquisition. The optimal therapeutic 90Y activity is determined on 99mTc-MAA SPECT-CT dose results in order to avoid healthy parenchyma toxicity and to effectively irradiate the tumor. The assumption of identical radiopharmaceutical distribution between simulation and verification is still under debate and literature data showed controversial results. In this study 10 HCC patient's dosimetry performed on 99mTc SPECT-CT and 90Y PET-CT were compared. Patients were selected when a good agreement between the pre and post-therapy distribution was observed in order to investigate the intrinsic dosimetric variations between the two imaging modalities. Mean doses (MIRD and Voxel approaches) showed a good correlation (Pearson's coefficient r > 0.90) both for tumor and normal liver. Dose Volume Histogram curves were compared with a good agreement particularly for normal liver (D50). Goal doses were achieved for 90% of patients. Bland-Altman analysis indicates lower variations for healthy parenchyma than for tumor (1.96 SD equal to 9.1 Gy and 68 Gy respectively) confirming the robustness of the dose-toxicity approach. PET-CT dosimetry well correlates with SPECT-CT doses (under assumption of same catheter position and 90Y activity). Better agreement was showed for 7/10 and 8/10 patients for T and NL respectively, confirming dosimetry as effective tool to optimize and individualize the treatment.

Patient dose in angiographic interventional procedures: A multicentre study in Italy.

PURPOSE: The Council Directive 2013/59/EURATOM considers interventional radiology to be a special practice involving high doses of radiation and requiring strict monitoring to ensure the best quality assurance programs. This work reports the early experience of managing dose data from patients undergoing angiography in a multicentre study. MATERIALS AND METHODS: The study was based on a survey of about 15,200 sample procedures performed in 21 Italian hospitals centres involved on a voluntary basis. The survey concerned the collection of data related to different interventional radiology procedures: interventional cardiology, radiology, neuroradiology, vascular surgery, urology, endoscopy and pain therapy from a C-Arm and fixed units. The analysis included 11 types of procedures and for each procedure, air-kerma, kerma-area product and fluoroscopy time were collected. RESULTS: The duration and dose values of fluoroscopic exposure for each procedure is strongly dependent on individual clinical circumstances including the complexity of the procedure; the observed distribution of patient doses was very wide, even for a specified protocol. The median values of the parameters were compared with the diagnostic reference levels (DRL) proposed for some procedures in Italy (ISTISAN) or internationally. This work proposes local DRL values for three procedures. CONCLUSION: This first data collection serves to take stock of the situation on patient's dosimetry in several sectors and is the starting point for obtaining and updating DRL recalling that these levels are dependent on experience and technology available.

Dosimetric characterization of small fields using a plastic scintillator detector: A large multicenter study.

PURPOSE: In modern radiation therapy accurate small fields dosimetry is a challenge and its standardization is fundamental to harmonize delivered dose in different institutions. This study presents a multicenter characterization of MLC-defined small field for Elekta and Varian linear accelerators. Measurements were performed using the Exradin W1 plastic scintillator detector. MATERIALS AND METHODS: The project enrolled 24 Italian centers. Each center performed Tissue Phantom Ratio (TPR), in-plane and cross-plane dose profiles of 0.8×0.8cm2 field, and Output Factor (OF) measurements for square field sizes ranging from 0.8 to 10cm. Set-up conditions were 10cm depth in water phantom at SSD 90cm. Measurements were performed using two twin Exradin W1 plastic scintillator detectors (PSD) correcting for the Cerenkov effect as proposed by the manufacturer. RESULTS: Data analysis from 12 Varian and 12 Elekta centers was performed. Measurements of 7 centers were not included due to cable problems. TPR measurements showed standard deviations (SD)<1%; SD<0.4mm for the profile penumbra was obtained, while FWHM measurements showed SD<0.5mm. OF measurements showed SD<1.5% for field size greater than 2×2cm2. Median OFs values were in agreement with the recent bibliography. CONCLUSIONS: High degree of consistency was registered for all the considered parameters. This work confirmed the importance of multicenter dosimetric intercomparison. W1 PSD could be considered as a good candidate for small field measurements.

Dosimetric characterization and behaviour in small X-ray fields of a microchamber and a plastic scintillator detector.

OBJECTIVE: The aim of this work was to investigate the main dosimetric characteristics and the performance of an A26 Exradin ionization microchamber (A26 IC) and a W1 Exradin plastic scintillation detector (W1 PSD) in small photon beam dosimetry for treatment planning system commissioning and quality assurance programme. METHODS: Detector characterization measurements (short-term stability, dose linearity, angular dependence and energy dependence) were performed in water for field sizes up to 10 × 10 cm2. Polarity effect (Ppol) was examined for the A26 IC. The behaviour of the detectors in small field relative dosimetry [percentage depth dose, dose profiles often called the off-axis ratio and output factors (OFs)] was investigated for field sizes ranging from 1 × 1 to 3 × 3 cm2. RESULTS: Results were compared with those obtained with other detectors we already use for small photon beam dosimetry. A26 IC and W1 PSD showed a linear dose response. While the A26 IC showed no energy dependence, the W1 PSD showed energy dependence within 2%; no angular dependence was registered. Ppol values for A26 IC were below 0.9% (0.5% for field size >2 × 2 cm2). A26 IC and W1 PSD depth-dose curves and lateral profiles agreed with those obtained with an EDGE diode. No differences were observed among the detectors in OF measurement for field sizes larger than 1 × 1 cm2, with average differences <1%. For field sizes <1 × 1 cm2, the effective volume of ionization chamber and non-water equivalence of EDGE diode become significant. A26 IC OF values were significantly lower than EDGE diode and W1 PSD values, with percentage differences of about -23 and -13% for the smallest field, respectively. W1 PSD OF values lay between ion chambers and diode values, with a maximum percentage difference of about -10% with respect to the EDGE diode, for a 6 × 6-mm2 field size. CONCLUSION: The results of our investigation confirm that A26 IC and W1 PSD could play an important role in small field relative dosimetry. Advances in knowledge: Dosimetric characteristics of Exradin A26 ionization microchamber and W1 plastic scintillation detector for small field dosimetry.

Ten-year results of accelerated hypofractionated adjuvant whole-breast radiation with concomitant boost to the lumpectomy cavity after conserving surgery for early breast cancer.

Accelerated hypofractionated whole-breast radiotherapy (WBRT) is considered a standard therapeutic option for early breast cancer (EBC) in the postoperative setting after breast conservation (BCS). A boost to the lumpectomy cavity may further increase local control. We herein report on the 10-year results of a series of EBC patients treated after BCS with hypofractionated WBRT with a concomitant photon boost to the surgical bed over 4 weeks. Between 2005 and 2007, 178 EBC patients were treated with a basic course of radiotherapy consisting of 45 Gy to the whole breast in 20 fractions (2.25 Gy daily) with an additional boost dose of 0.25 Gy delivered concomitantly to the lumpectomy cavity, for an additional dose of 5 Gy. Median follow-up period was 117 months. At 10-year, overall, cancer-specific, disease-free survival and local control were 92.2% (95% CI 88.7-93.4%), 99.2% (95% CI 96.7-99.7%), 95.5% (95% CI 91.2-97.2%) and 97.3% (95% CI 94.5-98.9%), respectively. Only eight patients recurred. Four in-breast recurrences, two axillary node relapses and two metastatic localizations were observed. Fourteen patients died during the observation period due to other causes while breast cancer-related deaths were eight. At last follow-up, ≥G2 fibrosis and telangiectasia were seen in 7% and 5% of patients. No major lung and heart toxicities were observed. Cosmetic results were excellent/good in 87.8% of patients and fair/poor in 12.2%. Hypofractionated WBRT with concomitant boost to the lumpectomy cavity after BCS in EBC led to consistent clinical results at 10 years. Hence, it can be considered a valid treatment option in this setting.

Correction to: Ten-year results of accelerated hypofractionated adjuvant whole-breast radiation with concomitant boost to the lumpectomy cavity after conserving surgery for early breast cancer.

An error inadvertently occurred in the discussion of the original publication when citing the local relapse rates of the EORTC 22881-10882 trial ('boost vs no boost trial').

Emptying the rectum before treatment delivery limits the variations of rectal dose - volume parameters during 3DCRT of prostate cancer.

PURPOSE: To investigate the impact of rectum motion on dose - volume histograms of the rectum including filling and of the wall (DVH and DWH, respectively), during 3D-conformal radiotherapy (3DCRT) for localized prostate cancer. MATERIALS AND METHODS: Ten patients received a planning CT scan (CT(0)) and 11-14 CT during 3DCRT for prostate cancer (total CT scans=126). CT images were 3D matched using bony anatomy. A single observer drew the external contours of rectum and rectum wall and the CTV (prostate + seminal vesicles) on CT(0). Patients were asked to empty their rectum before every CT, as generally performed at the Institute for Cancer Research and Treatment (IRCC) before treatment delivery. Bladder was kept full by drinking 500 cm(3) of water 60 min before the scan, according to our protocol. A 4-field box 3DCRT technique was planned and dose statistics/dose - volume histograms of the rectum were calculated for each contour referred to CT(0),CT(1),...,CT(n) for each patient. Average DVHs during treatment were calculated along with their standard deviation (SD(rand)) and compared to the planned DVH. The analyses on the patient population included the assessment of systematic deviation (average difference and SD, named SD(sys)) as well as the average SD(rand) value expressing the random component of organ motion. Rectum shifts were also assessed by anterior and lateral BEV projections. RESULTS: As to the rectum, 8/10 patients showed a "better" average DVH than DVH on CT(0). Wilcoxon test showed a statistically significant reduction when correlating the difference Delta between the average DVH during therapy and planning DVH at CT(0): for instance V(70)Delta = -3.6% and p = 0.022, V(50)Delta = -5.5% and p = 0.022, D(med)Delta = -3.2 Gy and p = 0.007. Average values of DVH systematic difference (average difference between planning scan and treatment), standard deviations (SD(sys)) and average standard deviations of the random fluctuation (SD(random)) were -4.0%, 4.7% and 6.6%, respectively. Whilst the fluctuation results were slightly smaller for DWH. Volume analysis showed a slight systematic variation of the rectal volume between planning and treatment BEV. The average rectal volume during therapy was larger than at the planning CT in 8/10 patients. The systematic shifts of the rectal wall between the planning phase and the treatment were rather small, both below and above the flexure. The larger random fluctuation of the rectum shape was found to be in the cranial half (1 SD=4.4 mm). CONCLUSIONS: The practice of carefully emptying the rectum during simulation and therapy for prostate cancer, which is a safe and simple procedure, reduces the impact of organ motion on dose - volume parameters of the rectum.

Transmission, penumbra and leaf positional accuracy in commissioning and quality assurance program of a multileaf collimator for step-and-shoot IMRT treatments.

AIMS AND BACKGROUND: The performance characteristics of a commercial multileaf collimator (MLC) for intensity modulated radiation therapy (IMRT) and a comprehensive quality assurance program (QA) to be performed during the commissioning of the MLC were investigated. MATERIALS AND METHODS: The midleaf transmission and interleaf leakage, the in-plane penumbra and its in-plane/cross-plane variation, the cross-plane penumbra and its in-plane/cross-plane variation, and the leaf positional accuracy of a high-energy photon (6 MV) Sli Precise Elekta linear accelerator were measured. Kodak EDR2 Ready Pack film was used for MLC transmission measurement; for the other characterization measurements we used Kodak X-Omat XV2 Ready Pack film placed at 5 cm depth in a solid RW3 phantom. Each film was digitized with a laser scanning photodensitometer VXR-12 Plus using the Omni Pro-Accept 6.OA film dosimetry system and converted to dose by means of H&D curves. The dose calibration measurements were performed with a Farmer ionization chamber according to the guidelines of the IAEA Technical Report No. 277. RESULTS: The average midleaf transmission and interleaf leakage were 1.8% +/- 0.1% and 2.1% +/- 0.2%, respectively. The average value of the cross-plane penumbra was 5.4 mm +/- 0.3 mm with maximum variation less than 0.4 mm and 1.0 mm in the in-plane and cross-plane direction, respectively. The average value of the in-plane penumbra was 3.2 mm +/- 0.2 mm and 3.5 mm +/- 0.2 mm for the step side and groove side of the leaves, respectively. A dose profile perpendicular to the direction of the leaf travel passing through the central axis shows a tongue-and-groove effect of about 33%. The positional accuracy of the leaves was investigated according to AAPM Report No. 72 TG50; the deviation of the net optical density along all the match lines was less than +/- 20%. Moreover, the results obtained with a step field technique showed a positional accuracy of less than 1 mm. CONCLUSIONS: The results suggest the necessity of extensive knowledge of the MLC dosimetric characteristics for IMRT applications in order to allow physicists to study their influence on treatment delivery and to perform a comprehensive routine QA program of the investigated parameters.

Hypofractionated whole-breast radiotherapy and concomitant boost after breast conservation in elderly patients.

AIMS: To report the 5- and 10-year results of accelerated hypofractionated whole-breast radiotherapy (WBRT) with concomitant boost to the tumor bed in 83 consecutive patients with early breast cancer aged >70 years. METHODS: All patients were treated with breast conservation and hypofractionated WBRT. The prescription dose to the whole breast was 45 Gy (2.25 Gy/20 fractions) with an additional daily concomitant boost of 0.25 Gy to the surgical cavity (2.5 Gy/20 fractions up to 50 Gy). The maximum detected toxicity was scored according to the Common Terminology Criteria for Adverse Events, version 3.0. We considered as skin toxicity: erythema, edema, desquamation, ulceration, hemorrhage, necrosis, telangiectasia, fibrosis-induration, hyperpigmentation, retraction and atrophy. Cosmetic results were assessed as set by the Harvard criteria. RESULTS: With a median follow-up of 60 months (range 36-88), no local recurrence was observed. The maximum detected acute skin toxicity was G0 in 57% of patients, G1 in 40% and G2 in 3%. Late skin and subcutaneous toxicity was generally mild with no ≥G3 events. The cosmetic results were excellent in 69% of patients, good in 22%, fair in 5%, and poor in 4%. CONCLUSIONS: The present results support the use of hypofractionation employing a concomitant boost to the lumpectomy cavity in women aged >70 years. This is a convenient treatment option for both this type of population and health-care providers.