P. Munck af Rosenschöld

Doses to head and neck normal tissues for early stage Hodgkin lymphoma after involved node radiotherapy.

PURPOSE To evaluate dose plans for head and neck organs at risk (OARs) for classical Hodgkin lymphoma (HL) patients using involved node radiotherapy (INRT) delivered as 3D conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), and intensity modulated proton therapy (PT), in comparison to the past mantle field (MF). MATERIALS AND METHODS Data from 37 patients with cervical lymph node involvement were used. All patients originally received chemotherapy followed by 3DCRT-INRT (30.6 Gy). A VMAT-INRT, PT-INRT (both 30.6 Gy), and a MF plan (36 Gy) were simulated. Doses to head and neck OARs were compared with cumulative DVHs and repeated measures ANOVA. RESULTS The estimated median mean doses were 15.3, 19.3, 15.4, and 37.3 Gy (thyroid), 10.9, 12.0, 7.9, and 34.5 Gy (neck muscles), 2.3, 11.1, 1.8, and 37.1 Gy (larynx), 1.7, 5.1, 1.3, and 23.8 Gy (pharynx), 0.5, 0.8, 0.01, and 32.3 Gy (ipsilateral parotid), and 2.4, 3.8, 0.7, and 34.7 Gy (ipsilateral submandibular) with 3DCRT, VMAT, PT, and MF (all p<0.0001), respectively. CONCLUSION The use of INRT significantly lowered the estimated radiation dose to the head and neck OARs. VMAT appeared suboptimal compared to 3DCRT and PT, and for some patients, PT offered an additional gain.

OC-0162: Liquid fiducial markers' performance in non small cell lung cancer during radiotherapy

Conclusion: Within the limitations of a retrospective study, our results show that the growth and shift of brain metastasis over time can be significant and may vary over patient groups. Given the typical steep dose gradient in SRS treatments (>10%/mm), tumour growths and shifts may have a significant impact on the tumour dose. Therefore, this phenomenon must be considered if the workup and treatment of SRS for brain metastasis is encompassing multiple days.

A biological comparison of epithermal neutron beams for BNCT.

Breast radiotherapy is planned on image data acquired pre-treatment, however the delivered distribution of radiation may vary from the plan due to changes in position and shape of the breast at the different fractions of treatment. This study uses anatomical information from repeated cone beam CT (CBCT) imaging at the point of treatment to assess the delivered dose distribution at different fractions of treatment.

PO-0651: Pattern of failure in glioblastoma patients after FET-PET and MRI-guided chemo-radiotherapy

Results: The median overall DBMFS was 12.9 months. A significant difference in median DBMFS was observed for patients with squamous cell vs. adenocarcinoma primary histology (4.57 months vs. 15.9 months, respectively, p <0.015). The initial number of metastases, total initial metastasis volume, ECD status, KPS scores, EGFR mutation status, or ALK gene rearrangement status, made no significant difference on DBMFS. None of the analyzed parameters displayed significant impact on ODBF. WBRT had no significant effect on DBMFS or ODBF in the study population, but patients with history of WBRT prior to SRS had an increased DBFR (0.396 vs. 0.089) which was borderline significant (p=0.05). There was an insufficient number of patients receiving combined WBRT with SRS to determine an effect on distant brain failure vs. SRS alone.

PO-0946: A new liquid fiducial marker formulation for image-guided pencil beam scanning proton radiotherapy

Material and Methods: The hyperthermia device is equipped with double arms, operating at a radiofrequency of 434 MHz, with a water automatic superficial cooling device. For temperature measures, it is equipped with an integrated Multichannel thermometer. The antennas are designed to cover areas from 7.2 × 19.7 cm2 up to 20.7 × 28.7 cm2. The applicators geometry have been reproduced in the CAD environment with a professional software based on the FDTD processing methods. In order to identify the distribution of specific absorption power rate in different types of tissues, several simulations have been performed, varying the relative thicknesses of a model consisting of skin, fat and muscle. Working incident power has been set equal to 100 watt. Waterbolus temperature is assumed to be equal to 38 °C

PO-0964: Artefact quantification of liquid and solid fiducial marker in single and dual energy CT with MAR

Corresponding author: per.jonas.scherman.rydhoeg@regionh.dk Purpose The aim of this study was to evaluate artefacts of liquid and solid fiducial markers for radiotherapy. Specifically in single energy CT (SECT) and dual energy CT (DECT) with different metal artefact reduction (MAR) algorithms on a clinical CTscanner. The artefacts were quantified by severity and streaking Index (SI) on SECT and DECT with eight different MAR algorithms and with no MAR.

PET/CT-guided treatment planning for paediatric cancer patients: a simulation study of proton and conventional photon therapy

OBJECTIVE To investigate the impact of including fluorine-18 fludeoxyglucose ((18)F-FDG) positron emission tomography (PET) scanning in the planning of paediatric radiotherapy (RT). METHODS Target volumes were first delineated without and subsequently re-delineated with access to (18)F-FDG PET scan information, on duplicate CT sets. RT plans were generated for three-dimensional conformal photon RT (3DCRT) and intensity-modulated proton therapy (IMPT). The results were evaluated by comparison of target volumes, target dose coverage parameters, normal tissue complication probability (NTCP) and estimated risk of secondary cancer (SC). RESULTS Considerable deviations between CT- and PET/CT-guided target volumes were seen in 3 out of the 11 patients studied. However, averaging over the whole cohort, CT or PET/CT guidance introduced no significant difference in the shape or size of the target volumes, target dose coverage, irradiated volumes, estimated NTCP or SC risk, neither for IMPT nor 3DCRT. CONCLUSION Our results imply that the inclusion of PET/CT scans in the RT planning process could have considerable impact for individual patients. There were no general trends of increasing or decreasing irradiated volumes, suggesting that the long-term morbidity of RT in childhood would on average remain largely unaffected. ADVANCES IN KNOWLEDGE (18)F-FDG PET-based RT planning does not systematically change NTCP or SC risk for paediatric cancer patients compared with CT only. 3 out of 11 patients had a distinct change of target volumes when PET-guided planning was introduced. Dice and mismatch metrics are not sufficient to assess the consequences of target volume differences in the context of RT.

EP-1247: Simulating intra-fraction prostate motion using random walk and conditional Gaussian based Gibbs sampling models

the exhalation phase. Before the treatment delivery, the RPM block was put on patient’s abdominal surface and the gating signal was generated by the RPM system. Then, the patient’s position was set based on cone beam computed tomography (CBCT) compare with ITV. During the treatment, kv images were acquired at each exhalation phase of the breathing cycle and the positions of the fiducial markers were compared with their expected positions. We reported here for the five first fractions the differences between expected and real fiducial position, treatment planning parameters such as the prescription, conformity index CIPTV = (VITV95% (cc) / VPTV (cc)) * (VITV95% (cc) / Viso95% (cc)), homogeneity index HIPTV = (D2% D98%) / Dmedian and the number of Monitor Unit (UM) per Gray. The treatment delivery parameters such as kv images acquired per fraction, the fraction’s time and the room occupation’s time were also mentioned. Results: For the eight PTV patients, the average (±SD) conformity index was 0,93 ± 0,02 and homogeneity index was 0,09 ± 0,02. Average MU/Gy was 147 ± 25.

Spatially varying Riemannian elasticity regularization: Application to thoracic CT registration in image-guided radiotherapy

For deformable registration of computed tomography (CT) scans in image guided radiation therapy (IGRT) we apply Riemannian elasticity regularization. We explore the use of spatially varying elasticity parameters to encourage bone rigidity and local tissue volume change only in the gross tumor volume (GTV) and the lungs. We evaluate the method on the point-validated 4DCT breathing thorax POPI-model and demonstrate its use and properties in registration of pre- and post-chemo CT scans for contour propagation in a Hodgkin lymphoma (HL) case showing significant tumor shrinkage. For the POPI-model we achieved a total mean target registration error (TRE) of 0.92 ± 0.49 mm. Using spatially varying regularization for the HL case, deformation was limited to the GTV and lungs.

PD-0212 SURVIVAL AFTER PET/CT PLANNED CONCOMITANT BOOST (IMRT) TO LYMPH NODE METASTASIS IN PATIENTS WITH CERVICAL CANCER

Purpose/Objective: In cancer of the uterine cervix, lymph node metastasis (LN) has been associated with a poor prognosis. The purpose of the current study was to evaluate the effect of the introduction of PET/CT-planned Intensity Modulated Radiotherapy (IMRT) on survival in patients with cervical cancer with LN Materials and Methods: A single institution retrospective analysis of survival and characteristics in cervical cancer patients with LN Inclusion criteria: Histopatological diagnose of cervical cancer, approved curative intended IMRT plan for patients with pelvic and/or para aortic fields, lymph node metastasis verified by CT, PET/CT and/or lymph node biopsy. Cisplatin based chemotherapy concomitant to IMRT. Consecutive patients from 1. January 2000 to 15. September 2011 with primary pelvicor para aortic LN, or recurrence of para aortic LN after primary treatment were included. IMRT was given as a sliding window technique and PET/CT planed on an Eclipse (Varian) doseplanning system. Doses to CTV: 50 Gy and a concomitant boost to LN: 60-64 Gy. Furthermore, patients with primary tumors received PDR brachytherapy 17.5 Gy x 2 Survival statistics and Kaplan Meier plots were calculated using SPSS. The distribution of patient characteristics was also tested. Results: Eighty-three patients were included. Patient characteristics are listed in Table 1. The statistical analysis indicated significant differences in the distributions of histopathology between the three groups. For both age and stage, no significant differences was found.