Endobiliary Stent: Marker for Patient Alignment in Image-Guided Radiotherapy in Pancreatic and Periampullary Cancers
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ORIGINAL RESEARCH
Endobiliary Stent: Marker for Patient Alignment in Image-Guided Radiotherapy in Pancreatic and Periampullary Cancers Pragya Shukla & Reena Engineer & Supriya Chopra & Shyam Kishore Shrivastava
# Springer Science+Business Media New York 2013
Abstract Purpose The aim of this study was to analyse the possibility of using stent in pretreatment megavoltage computed tomography (MVCT) images with respect to that on planning kilovoltage computed tomography as tumour surrogate during matching for daily registration in cases of pancreatic and periampullary cancer treated on a TomoTherapy Hi-Art system. Methods Planning CT and pretreatment MVCT of the first and then after every three fractions were transferred to a FocalSim workstation for ten patients. Planning CT of each patient was independently fused with each of the seven MVCT images of that patient. The stent was contoured on all of the eight images for each patient. The difference between the three co-ordinates of centre of mass (CM) of the stent on the planning CT and seven MVCT images was found. The difference between CM of the liver and stents on the planning CT as well as on the MVCT for all seven fractions was also calculated. The mean of these differences across all patients was calculated and analysed. Results The mean difference in planning and MVCT CMs for stents in the X, Y and Z directions was 0.13 cm (±0.4), 0.16 cm (±2.2) and 0.35 cm (±0.7), respectively. Average difference between CM of the liver and stent on the planning CT in the X, Y and Z directions was found to be 1.832 cm (±1.64), 5.34 cm (±1.33) and 0.54 cm (±0.26), respectively. P. Shukla : R. Engineer (*) : S. K. Shrivastava Departments of Radiation Oncology and Medical Physics, Tata Memorial Hospital, Tata Memorial Centre, Parel, Mumbai 400012, India e-mail: [email protected] R. Engineer e-mail: [email protected] S. Chopra Department of Radiation Oncology, Advanced Centre for Treatment, Research and Education in Cancer, Tata Memorial Centre, Navi, Mumbai, India
Average difference between CM of the liver and CM of stent on the MVCT for that day in the X, Y and Z directions was found to be 1.93 cm (±1.5), 4.6 cm (±1.03) and 0.654 cm (±0.35), respectively. Conclusions Endobiliary stents are stable tumour localisation surrogates and can be used to correct for interfraction target motion. Keywords Endobiliary stents . Pancreatic and periampullary cancers . Image-guided radiotherapy . Tumour localisation
Introduction Pancreatic carcinoma is a highly lethal disease. For locally advanced tumours which are borderline resectable or unresectable, neoadjuvant chemoradiation is given for downsizing and improving resectability rates [1, 2]. To achieve a desired downsizing, radiation dose escalation beyond 50 Gy has been recommended, and the proximity of dose-limiting critical organs like the duodenum, liver and kidneys warrants the use of improved tumour- or target-conformal radiation [3]. Intensity-modulated radiation therapy (IMRT) has steep dose gradients, which ac
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