190 A comparison of optical infrared camera and spirometry guided respiratory gating for liver radiotherapy

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This is a prospective radiological and pathological companion clinical trial to the Ontario Clinical Oncology Group (OCOG) PET evaluation studies in NSCLC. Eligible patients with stage I-III, resectable NSCLC enrolled on the OCOG PET studies, will have had a co-registered PET CT prior to tumour resection. The GTV and CIV will be contoured first on the CT and then on the PET CT by a radiation oncologist and radiologist. The surgical resection specimen will be insufflated when 'fixed' to more accurately reflect in vivo dimensions at the time of imaging, it will be serially sectioned. Contours representing gross tumour and gross + microscopic tumour will be identified on digital gross specimen and wholemount microscopy images respectively. Sequential contours will be 'stacked' to generate a 3-dimensional (3D) pathological GIV and CTV. The dimensions and volume of the CT and PET CT GTV and CTV and their pathological counterparts will be compared. 3D spatial matching will allow theoretical dosevolume histograms for 3D CRT plans derived from CT and PET CT contours to be compared for the adequacy of pathological GTV and CTV coverage. This is work in progress and available results will be presented. 188

Implementation and Workflow for a Clinical Tomotherapy Unit B. Clark, L. Montgomery, G. Fox, K. Carty, M. MacPherson, S. Malone, R. MacRae, L. Gerig, L. Grimard The Ottawa Hospital Regional Cancer Centre, Ottawa, Ontario mmacpherson@ottawahospital, on. ca Objectives: Helical tomotherapy is emerging as a solution for integrated image guided intensity modulated radiation therapy (IG-IMRT). The effectiveness of this technology will be at least partially governed by the time required to treat patients compared to competing modalities. We report implementation timelines, patient throughput and machine reliability baselines for a clinical TomoTherapy unit. Methods: We compare timelines for installation, acceptance testing, and commissioning of a helical tomotherapy machine (TomoTherapy Hi-ART) vs a conventional linear accelerator with MLC and EPID. Throughput was measured by recording the time spent for every patient at each stage of the treatment preparation and treatment delivery processes. A daily record of machine interrupts was maintained for future reporting of downtime. Results: Tomotherapy implementation was faster than a conventional single energy linac (23 vs 31 days), but training requirements for tomotherapy made the overall times comparable (28 vs 31 days). Quality assurance is currently more intensive, requiring up to 60 minutes daily. At our centre, three radiation therapists are responsible for all aspects of tomotherapy treatment planning and delivery. Mean time for treatment preparation per patient was 8.9 hours (median 6.6), while mean overall time for patient setup, daily MVCT, registration and treatment is 26.5 minutes (median 25.0). To date, a total of three days (out of 140) have been lost to machine failure. Minor interrupts requiring shutdown have been occurring at a rate of approximately three per day, removing nearly 30 minutes of available treatment time. Conclusions: Implementation timelines for the helical tomotherapy unit were shorter than for a conventional linac, and to-date uptime has been comparable. Our preliminary results suggest that three therapists can support a throughput of 16 patients per eight hour day, including treatment planning, delivery, and patient review. 189

Accuracy and Variability of Image-Guided Radiotherapy During Hypofractionated Treatment for Prostate Cancer L. Braithwaite ~, J. Wu ~, R. Karachewsky 1, D. Skarsgard ~, A. EIGayed 2, R. Pearcey 3, K, Joseph 4, C. Newcomb 1 Tom Baker Cancer Centre, University of Calgary, Calgary, Alberta'; Saskatoon Cancer Centre, University of Saskatchewan, Saskatoon, Saskatchewan2; Cross Cancer Institute, University of Alberta, Edmonton, Alberta3; Allan Blair Cancer Centre, Regina, Saskatchewan 4

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iackson, wuC~cancerboard, ab. ca Purpose: Hypofractionated conformal radiotherapy necessitates a high-precision delivery process. This study examines the accuracy of treatments delivered in a Phase I/II trial (55 Gy/16 fractions/4 weeks) being conducted in four cancer centres. Method: Low and intermediate risk prostate cancer patients are accrued and treated with daily online isocentre correction based on implanted fiducial (gold) markers. Patients are treated on LINACs with either megavoltage aSi (Varian Vision (tin)) or kilovoltage (kV) imaging systems (BrainLab ExacTracCtm)). If pre-treatment orthogonal images show target deviating above protocol threshold, table corrections are made in right-left (RL), ant-post (AP) and/or sup-inf (SI) directions without rotational adjustments. Post-delivery verification images are taken during or immediately after each fraction. Targeting variability, based on the post-delivery images, is expressed as standard deviations (SD in RL, AP, SI directions) over the 16 fractions for each patient. Results: Post-delivery verification images from 42 patients have been analyzed. The average SD in targeting in the RL, AP, and SI directions were 1.6mm, 1.7mm, and 1.7mm respectively (SDs range from 0.3 to 7.8mm). Fourteen patients treated on kV-imaging system had lower SDs (average SD RL 0.9mm, AP 1.3ram, SI 1.3mm) than the 28 patients treated on aSi-system (average SD RL 1.9mm, AP 1.9mm. SI 1.gram). Of the 665 fractions reviewed for the 42 patients, PTV violations were observed in 6 fractions in the posterior direction (>5 mm deviation) and 9 fractions in other directions (>10 mm deviation), resulting in a targeting accuracy of 98%. Conclusions: Image guided radiotherapy with daily isocentre correction results in highly accurate treatment delivery. An imaging system with integrated table correction function can avoid inadvertent human error during table adjustments. Potential factors that may influence targeting accuracy and variability will be reviewed. 190

A Comparison of Optical Infrared Camera and Spirometry Guided Respiratory Gating for Liver Radiotherapy M. Lock 1, E. Wong 1, A. Shuk On Leung 1, S. Gaede ~, G. Rodrigues ~, R, Dinniwell2, D. D'Souza ~, G. Berryhill I, J. Van Dyk 1 London Regional Cancer Program, University of Western Ontario, London, Ontario'; Princess Margaret Hospital, University of Toronto, Toronto, Ontario 2 michael. Iock~lhsc. on. ca Background: Optical infrared guidance and spirometry/lung volume-based systems are used to track liver lesions. The goal of this study is to determine which of these systems would better localize lesions in real-time. The best placement of the infrared markers to account for both rib-cage displacement and diaphragm motion was also determined. Methods: Eight lung cancer patients had 4DCT scans with infrared markers. Markers on the sternum (where the sternum and xyphoid process join), and the abdomen (midway between the xyphoid process and umbilicus) were used to define ribcage displacement and diaphragm motion, respectively. Four respiratory phases were tracked: end expiration (EE), 50% end inspiration (50 EI), end inspiration (EI), and 50% end expiration (50 EE). The right and left lungs were contoured both manually and auto-contoured. Lung volumes were calculated for each phase. Motion of the diaphragm served as a surrogate for liver lesion movement. Results: The r-squared values for total lung volume vs motion of the diaphragm in the superior-inferior direction ranged from 0.82-0.99. The average was 0.94 with a standard deviation of 0.007. Five of eight patients had r-squared values over 0.95. The motion of the markers on the abdomen versus the sternum was patient dependent. R-squared valued ranged from 0 to 0.96. Within patient correlation suggest that there were two types of breathers: diaphragm and rib-cage/chest breathers. Infrared markers may be useful when placed on the abdomen

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for diaphragm breathers and on the sternum for rib-cage breathers. Conclusions: Total lung volume appears to correlate well with motion of the liver compared to infrared markers. This establishes a strong motivation to use spirometry in respiratory-gating for liver metastases. 191 Adaptive Planning Using Helical Tomotherapy M. MacKenzie, A. Murtha, C. Field, D. Drabik, G. Fallone University of Alberta, Edmonton, Alberta rnarcrnack@cancerboard, ab. ca The manner in which helical tomotherapy (HT) is used in image guided adaptive radiotherapy (IGAR) is mostly for patient setup, with motion assessed using vendor image fusion software to fuse the megavoltage CT (MVCT) to the planning kilovoltage CT (kVCT). Using the MVCT to recompute the daily dose delivered, however, has long been a goal for tomotherapy. Beta test software at our centre allows for this recomputation and adaptive replanning of HT treatments. Dose delivered for a given fraction is recomputed using an input delivery pattern and a merged kVCT - MVCT data set (kVCT filling areas not scanned by MVCT). Doses recomputed for individual fractions can be summed, although deformable dose summation is not currently available. Adaptive plans can be based on merged data, using summed dose or changing patient anatomy as the basis for replanning. Results are presented for the first Canadian patient to be adaptively replanned in this way. The tumour, a C-spine benign meningioma, was immediately adjacent to the spinal cord, so cord sparing was the primary goal followed by tumour dose homogeneity. The plan was reoptimized after 18 of 28 fractions in response to concerns over set up reproducibility, patient complaints of dry mouth and to add thyroid sparing. As the course of treatment progressed, daily delivered doses were computed and summed. At the end of treatment, each of the 28 fraction daily doses were computed and summed as delivered. For comparison, the total dose was also computed using the original un-adapted delivery pattern to compute the last 10 fractions. The adaptive plan reduced median dose to the contra lateral parotid gland by 13.3 % (22.6 Gy to 19.6 Gy), and to the thyroid by 25.9% (37.4 Gy to 27.7 Gy). The cord maximum dose was only 3.3% lower (44.5 Gy to 42.9 Gy). 192 Implementation of a Standardized Head and Neck Structure Nomenclature and Contouring Terminology for IMRT Planning and Quality Assurance J. Kim, S.L. Breen, J. Waldron, A.J. Bayley, B.J. Cummings, J. Ringash, L.A. Dawson, B. O'Sullivan Princess Margaret Hospital, University of Toronto, Toronto, Ontario iohn. kirn @rrnp. uhn. on. ca IMRT is now standard treatment for head and neck (H&N) cancer patients at our institute. Approximately 45 IMRT cases are planned monthly. In 2004, standardized H&N structure nomenclature and contouring terminology was implemented to facilitate planning, quality assurance (QA) and future outcome audits of IMRT. A flexible system conforming to ICRU 50 and 62 was developed which is applicable to all H&N sites and presentations. Case-sensitive terminology for normal structures, gross disease and target volumes are unique and descriptive e.g. CORD (spinal cord), Rfacial (right facial node). Guidelines were developed to handle separate, multiple or combined targets. Physicians contour primary, nodal gross disease and CTVs PTVs and PRVs are planner-generated. The term 'GTV' refers only to the primary disease. The term 'CTV' without prefix refers to a volume surrounding GTV. All gross nodes are contoured and localized to specific areas of the neck by applying Consensus Guidelines terminology except that Arabic script and capital letters are used. A laterality prefix 'R' or 'L' is used for gross or elective neck nodal targets e.g. R2A (right level IIa node). A suffix for dose is applied to all CTVs, RCTVs and LCTVs and corresponding PTVs, LPTVs and RPTVs

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e.g. CTVS0 (50 Gy CTV surrounding GTV), R2ACTV70 (70 Gy CTV encompassing a right level IIa node). For patients who have undergone surgery, there may be no gross tumour objects. Site(s) of preoperative tumour may be considered high risk. Currently, there is no ICRU terminology for this principle. We have applied principles and developed terminology that enables physicians to contour high risk regions. The implementation of this nomenclature system has facilitated multidisciplinary communication between radiation oncologists, planners, and physicists; facilitated quality assurance review of H&N planning; and enabled the automation of complex programming tasks within our planning system. 193 Segment Weighted Post Midline Block Planning Technique for External Radiotherapy of Cervix and Corpus Carcinoma K-M. Lain, Y-B. Cho, M. Milosevic, G. Chaulk Princess Margaret Hospital, Toronto, Ontario Tony. Larn @rrnp. uhn. on. ca

Purposes: For cervix and corpus carcinoma patients who receive brachytherapy after externat radiotherapy, mid-line block with thickness of two half-value layers (HVL) has been used for posterior field to reduce rectal dose. In order to show the dosimetric effect of block (2 HVL) in current version of Pinnacle (7.6c), segmented fields are used to replace the physical block (2 HVL). This work presents a segment weighted post midline block planning technique that delivers adequate dose distribution to treatment fields and maintains dose constraints of rectum for external radiotherapy of cervix and corpus carcinoma. Methods and Materials: Pinnacle 7.6c planning system was used. For 18MV two-field and four-field technique, a posterior field was divided into seven segments. Segment-weight optimization was used to obtain a dose distribution with dosimetric effect similar to a posterior field with midline block of two HVLs. A script of three junctions in seven segment posterior field was developed for Elekta machine. The idea of three junctions is a practical implementation of the moving junction. Fluence map was taken for segmented posterior field and dose profile across junctions was reviewed. Field parameters, segment weighting, prescription point location and rectal dose will be detailed on the poster. Results: Five cases were investigated with this technique. Ninety-five percent isodose of prescribed dose could adequately cover treatment fields. Average dose under MLC junction at dmax was 1.5% and 0.7% for two-field and four-field and hotspot of 2cm 3 was 108% on average. Conclusions: This technique delivers adequate dose distribution to treatment fields with acceptable dose variation under MLC junction. It reduces set-up time and effort for Treatment Therapists by avoiding the use of physical block (2 HVL). It documents full picture of dose distribution including rectal dose and allows favourable biological effect on rectum sparing in 2-field plan. 194 Superficial Hyperthermia Plus Radiotherapy as Palliative Treatment of Lymph Nodes and Skin Cancer Metastases L. Miszczyk, G. Owczarek Centre of Oncology, M. Sklodowska-Curie Memorial Institute, Branch Gliwice, Poland leszek@io, qliwice, pl

Purpose: The aim of this study was an evaluation of hyperthermia plus radiotherapy as a treatment of lymph nodes and skin cancer metastases. Materials and Methods: The material comprised of 48 metastatic lymph nodes and 17 skin metastases. The most common pathological and clinical diagnoses were adenocarcinoma (n=27) and lung cancer (n=17) respectively. Mean follow-up was 3.5 months. Hyperthermia of 43°C was used twice a week, through 45 minutes, using 915 MHz microwaves. Patients were irradiated five times a week (fd=2-4