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Abstract Purpose Analysis of dose-of-the-day (DoDa) for patients during treatment represents the first step to Adaptive-radiotherapy (ART). In our Institute DoDa for Tomotherapy plans is computed for first fraction for all patients, daily for SRT, weekly for all other treatments. This workflow aiming to ensure a control of delivered dose, check inter-fraction patient set-up and follow patient anatomical changes that may require a replanning. In this work we retrospectively reviewed DoDa of last 100 therapy courses in order to have an insights of efficacy and effectiveness of procedure. Methods Patients included were 83. For each patient the associated plans (different courses and corresponding adaptive plans) were included (total of 137 plans included). For each plan, delivered fractions number, computed DoDa number, DoDa passed and failed numbers were reported. Results 1507 delivered fraction were considered, 23% were checked computing DoDa. Passing rate was 78%. 10.9% DoDa outlined problems that need a plan reevaluation, while 10.3% showed problems of set-up but doses were adequately comparable to planned dose. All results are summarized in table. Conclusions Although DoDa analysis process is demanding in terms of workload and computation time, our results show that may have a high impact on daily dose delivery quality shifting the paradigma from planned dose to actual delivered dose. [ABSTRACT FROM AUTHOR]

Purpose Patient who underwent stereotactic body radiation therapy (SBRT) for liver cancer show a signal intensity alteration in follow-up imaging known as focal liver reaction (FLR). Accurate image registration between planning and follow-up imaging is crucial for estimating relationship between planned dose and radiation-induced FLR. This study aims to compare three different strategies of imaging for follow-up studies. Methods 22 patients (13 metastasis, 9 hepatocellular carcinomas [hcc]) underwent SBRT with an abdominal compressor. After therapy patients had follow-up studies at 3, 6, 9, 12, 18, 24 and 30 months. Imaging was performed using either CT (12 cases), MRI with a water-only Dixon sequence (34 cases) or MRI with a T1-weighted, fat-suppressed sequence (19 cases). For each follow-up the liver was contoured and the planning images were registered to the follow up using deformable registration. The registration quality was evaluated by computing the conformal index between the liver in the two image sets. Results the figure shows the computed conformal indices as a function if the follow-up imaging type. The overall average value is 90% (range 79–94%), and CT images have less variability compared to MRI's. An ANOVA analysis does not show any statistically significant difference between the three imaging modalities (p = 0.06). Conclusions The average registration quality is not optimal, with any image type used. The main reason is the amount of distortion caused by the abdominal compressor used for immobilization in treatment planning and delivery. Beside this issue, the three different methods of follow-up imaging can be registered to the planning CT with similar results. Therefore, the imaging modality that allows better delineation of FLR can be safely chosen for follow-ups. Moreover, MRI can be chosen over CT to avoid unjustified use of ionizing radiation. [ABSTRACT FROM AUTHOR]

Purpose Patient who underwent liver stereotactic body radiation therapy (SBRT) show a signal intensity alteration in follow-up imaging known as focal liver reaction (FLR). This study aims at evaluating dose threshold for FLR after SBRT. Methods 22 patients (13 metastasis, 9 hepatocellular carcinomas [hcc]) underwent SBRT with 48 or 60 Gy in 3 fractions. After therapy patients had, according to clinical protocols, follow-up imaging studies (12 CT and 32 MRI) at 3, 6, 9, 12, 18, 24 and 30 months. For each follow-up the region of signal alteration, if present, was classified as FLR, residual or recurrent disease, and contoured. In case of FLR, the planning images were registered to the follow up using deformable registration, and planning dose was mapped to the follow up applying the registration matrix. The isodose that better fits the FLR (dose threshold) was found, and the conformality index between dose threshold and FLR computed. The figure shows the dose threshold as a function of cancer type and follow up time. Results Threshold dose is higher for metastasis than for hcc (8 Gy at 3–6 months, 12 Gy at 9–12 months), and shows an increase up to 9 months followed by a decrease at 12 month. Cases at 18 or more months are too few or broad to be significant. The table shows threshold doses with their uncertainties – cases with just one samples are excluded. Conclusions hcc's show FLR for lower doses, which can be justified by pre-existing cirrhosis. Since higher isodoses are embedded in lower ones, follow-up lesion size has an inverse correlation with dose threshold; therefore, there is a decrease of the lesion in the first 9 months followed by an increase 3 months later. Threshold doses are consistent with literature data. [ABSTRACT FROM AUTHOR]

Purpose Careful evaluation of the heart-absorbed dose has to be adopted in any Radiotherapy Center and although a risk of cardiac death <1% after breast RT is considered acceptable, the QUANTEC constraint V 25 Gy < 10 % is not sufficient to limit the excess cardiac mortality risk for each patient and for every RT schedule of tangential beams left sided breast RT. Aim of this work is to find a group of patient for which the dose constraint, above mentioned, is respected, but at a further investigation the excess cardiac mortality probability results greater than 1%. Than a correlation between these results and the dose volume histogram (DVH) has to be investigated and verified on a control group of patients. Methods and materials Analyzing the DVHs on TPS Philips Pinnacle3 of 240 women, who underwent to left sided breast tangential beams RT, came out that the constraint V 25 Gy < 10 % was respected. By inspecting the integral DVHs some patients were individuated as "probable false negatives". The Relative Seriality model (α / β = 3 Gy , s = 1 , D 50 = 52.4 Gy and g = 1.28) was used as method to evaluate the probability of late cardiac mortality. Results For 19 patients the V 25 Gy was satisfied, but the probability of long-term cardiac mortality was found > 1% and up to 6%. The dosimetric heart constraints V 40 Gy and D 2 % showed a good correlation (R = 0.97 and R = 0.90 respectively) with the risk of cardiac death. To keep the probability lower than 1%, the cut off levels were determined by the simultaneous occurrence of the conditions: V 40 Gy < 2 % , and D 2 % < 38 Gy. The generalized gEUD was also valuated with an a = 5.7 For all calculations considering the EQD2Gy dose correction was considered. Conclusions This probability was only a calculation and not an observation of mortality. Anyway modern TPSs should promote, even more, the use of either radiobiological DVHs or algorithm optimization, especially in the era of hypofractionation. [ABSTRACT FROM AUTHOR]

Abstract Purpose In Vivo EPID dosimetry, is a time-consuming procedure. This paper reports a time workload analysis of SOFTDISO software (SW) (Best Medical Italy) obtained in our center. Methods the time workload analysis was subdivided into two phases: the first regard pre-clinical mounting in particular the creation of communication DICOM nodes ( t links) , the SW commissioning time ( t commissioning) and the radiology technician training time ( t training) ; the second refer to clinical routine. This last phase was divided in four steps: single patient's loading times, t load , (import patient from TPS to SW, t TPS-SW , and from TPS to EPID management device, t TPS - EPID) ; single patient's daily synchronization time on SW, t synchro ; single patient's setting time, t set-up ; time of troubles, t troubles . In our center the TPS was Pinnacle 9.10 (Philips) and EPID device was IViewGT (Elekta). Results The pre-clinical phase required about three weeks where a multi-disciplinary team (medical physicist, product specialist and system administrator) has worked to interface all devices, the medical physicist has performed the SW commissioning measure and along with the product specialist they trained the staff. For a single patient by the clinical times shows in Table 1 we can calculate the daily time, t daily , equal to (240 ± 135) s and the insertion time, t load , equal to (180 ± 30) s. This time analysis was performed overall 30 patient. The daily workload was estimated from 10 of 20 patients treated per day who undergo to in vivo dosimetry checks and was equal to 45 min. Conclusions After a month a medium sized radiotherapy center gets these results with a dedicated medical physicist and a radiology technician. Additional clinical time is required to discuss the out of tolerance value provided by the SW. This time was estimated in 1 h per week. [ABSTRACT FROM AUTHOR]

Poster discussion: CL: Lung PD-0416: Daily adaptive strategy simulation in lung cancer pts treated with RTCHT with reduced CTV-PTV MARGIN M.L. Bonu, P. Borgetti, L. Spiazzi, A. Taddeo, G. Volpi, A. Guaineri, G. Costantino, A. Donofrio, A. Guerini, D. Tomasini, C. Toraci, J. Imbrescia, S.M. Magrini. [Extracted from the article]

Poster: Physics track: Radiobiological and predictive modelling, and radiomics PO-1572: Use of intravoxel incoherent motion (IVIM) MRI for predicting dysphagia in oropharyngeal carcinoma M. Maddalo, L. Altabella, L. Pegurri, A. Guerini, G. Peretto, A. Alghisi, O. Turla, A. Guaineri, G. Costantino, L. Spiazzi, L. Costa, C. Mozzetti, N. Pasinetti, M. Buglione. [Extracted from the article]

Poster: Clinical track: Head and Neck PO-0843: Assessment of weight loss and subjective dysphagia after radiotherapy for head and neck cancer M. Maddalo, G. Costantino, M. Buglione, L. Spiazzi, G. Volpi, A. Premi, A. Donofrio, A. Guerini, A. Alghisi, S. Pedretti, L. Costa, D. Greco, C. Cominardi, L. Pegurri, S.M. Magrini. [Extracted from the article]

Poster: Clinical track: Lung PO-1022: Clinical-dosimetric assessment with Prodvh software after adjuvant radiotherapy for MPM E. Salah ElDin Tantawi, P. Borghetti, C. Cozzaglio, M. Bonù, N. Pasinetti, D. Greco, M. Maddalo, A. Baiguini, P. Vitali, E. Ranghetti, A. Guerini, M. Buglione, L. Spiazzi, S.M. Magrini. [Extracted from the article]

Poster: Clinical track: CNS PO-0903: Cellular phones radiofrequency exposure and malignant brain tumor:sistematic review and metaanalisys A. Guaineri, G. Peretto, L. Triggiani, A. Alghisi, D. Tomasini, P. Borghetti, M. Maddalo, S. Pedretti, C. Tomasi, L. Spiazzi, S.M. Magrini, M. Buglione. [Extracted from the article]