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McPartlin A, Hosni A, Alasti H, Catton C, Cho Y, Menard C. Potential Role of High-Dose Volumetric CT in Enabling MRI-CT Registration Based on Common Anatomical Landmarks. Int J Radiat Oncol Biol Phys 2015. [DOI: 10.1016/j.ijrobp.2015.07.1157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Alasti H, Islam M, Rink A, Carlone M, Breen S, Jaffray D. SU-E-J-165: Shielding Design for An MR Guided Radiotherapy (MRgRT) Suite. Med Phys 2013. [DOI: 10.1118/1.4814377] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Lamey M, Carlone M, Alasti H, Bissonnette JP, Borg J, Breen S, Coolens C, Heaton R, Islam M, van Proojen M, Sharpe M, Stanescu T, Jaffray D. Poster - Thur Eve - 05: Safety systems and failure modes and effects analysis for a magnetic resonance image guided radiation therapy system. Med Phys 2012; 39:4625. [DOI: 10.1118/1.4740112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Lamey M, Carlone M, Alasti H, Bissonnette J, Borg J, Breen S, Coolens C, Heaton R, Islam M, Sharpe M, Stanescu T, van Prooijen M, Jaffray D. SU-E-T-252: Safety Systems and Failure Modes and Effects Analysis for a Linear Accelerator - Magnetic Resonance Imager - Brachytherapy System. Med Phys 2011. [DOI: 10.1118/1.3612203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Markel D, Caldwell C, Alasti H, Sun A, Soliman H, Lee J, Ung Y, McGhee P, Webster D. TU-G-211-03: Automatic Segmentation of Non-Small Cell Lung Carcinoma Using 3D Texture Features in Co-Registered FDG PET/CT Images. Med Phys 2011. [DOI: 10.1118/1.3613253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Alasti H, Chow J, Markel D. TH-C-304A-08: Free-Form Deformation Algorithm: Validation and Dosimetric Corrections for Breathing Motion Using 4D-CT. Med Phys 2009. [DOI: 10.1118/1.3182644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Publicover J, Vandermeer A, Norrlinger B, Alasti H. SU-GG-T-305: Feasibility of Using a Programmable Respiratory Motion Phantom for QA and Assessment of Dosimetric Implications of Breathing Motion During Radiation Therapy. Med Phys 2008. [DOI: 10.1118/1.2962057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Alasti H, Chow J, Lochovsky C, Bezjak A. Evaluation of Lung IMRT Plan Using NTCP and gEUD Based on Internal Target Volume Delineated From Four-Dimensional Computed Tomography. Int J Radiat Oncol Biol Phys 2007. [DOI: 10.1016/j.ijrobp.2007.07.1717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Alasti H, Cho YB, Vandermeer AD, Abbas A, Norrlinger B, Shubbar S, Bezjak A. A novel four-dimensional radiotherapy method for lung cancer: imaging, treatment planning and delivery. Phys Med Biol 2006; 51:3251-67. [PMID: 16757875 DOI: 10.1088/0031-9155/51/12/017] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We present treatment planning methods based on four-dimensional computed tomography (4D-CT) to incorporate tumour motion using (1) a static field and (2) a dynamic field. Static 4D fields are determined to include the target in all breathing phases, whereas dynamic 4D fields are determined to follow the shape of the tumour assessed from 4D-CT images with a dynamic weighting factor. The weighting factor selection depends on the reliability of patient breathing and limitations of the delivery system. The static 4D method is compared with our standard protocol for gross tumour volume (GTV) coverage, mean lung dose and V20. It was found that the GTV delineated on helical CT without incorporating breathing motion does not adequately represent the target compared to the GTV delineated from 4D-CT. Dosimetric analysis indicates that the static 4D-CT based technique results in a reduction of the mean lung dose compared with the standard protocol. Measurements on a moving phantom and simulations indicated that 4D radiotherapy (4D-RT) synchronized with respiration-induced motion further reduces mean lung dose and V20, and may allow safe application of dose escalation and CRT/IMRT. The motions of the chest cavity, tumour and thoracic structures of 24 lung cancer patients are also analysed.
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Affiliation(s)
- H Alasti
- Department of Radiation Physics, Princess Margaret Hospital, Toronto, ON, Canada.
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Alasti H, Vandermeer A, Cho YB, Norrlinger B. SU-FF-J-90: Investigating Factors Affecting Weight Selection for Safe Delivery of Four Dimensional Weighted Radiotherapy (4D-WRT). Med Phys 2006. [DOI: 10.1118/1.2240866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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McGibney C, Abbas A, Chan B, Ubhi R, Mosseri A, Kane G, Lee M, Chhin V, Koch A, Alasti H, Jaffray D, Vallis K. Evaluation of 4D Computed Tomography for Planning Boost Radiation Therapy in Breast-Conserving Therapy. Int J Radiat Oncol Biol Phys 2005. [DOI: 10.1016/j.ijrobp.2005.07.425] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Wiltshire K, Wong R, Alasti H, Abbas A, Cheung F, Ringash J, Brierley J. 57 GTV motion in oesophageal cancer. Radiother Oncol 2005. [DOI: 10.1016/s0167-8140(05)80218-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Alasti H, Cho Y, Abbas A, Norrlinger B. SU-FF-J-17: Free Breathing Synchronized 4D Radiotherapy: Imaging, Treatment Planning, and Delivery. Med Phys 2005. [DOI: 10.1118/1.1997563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Kirilova A, Nichol A, Alasti H, Damyanovich A, Warde P, Catton C, Jaffray D. Magnetic resonance imaging of the pelvic organs for planning of prostate radiotherapy. Int J Radiat Oncol Biol Phys 2004. [DOI: 10.1016/j.ijrobp.2004.07.331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Moseley D, White E, Haycocks T, Sharpe M, Siewerdsen J, Bissonnette J, Alasti H, Gospodarowicz M, Warde P, Catton C, Jaffray D. Comparison of implanted fiducial markers and cone-beam computed tomography for on-line image-guided radiotherapy of the prostate. Int J Radiat Oncol Biol Phys 2004. [DOI: 10.1016/j.ijrobp.2004.07.152] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Catton C, Chung P, Haycocks T, Warde P, Alasti H, Bayley A, Bristow R, Crook J, Gospodarowicz M, McLean M, Milosevic M. Hypofractionated intensity modulated radiation therapy for prostate cancer. Int J Radiat Oncol Biol Phys 2002. [DOI: 10.1016/s0360-3016(02)03382-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Bayley A, Giovinazzo J, Rakaric P, Kelly V, Haycocks T, Lam T, Alasti H, Kim J, O’Sullivan B, Ringash J, Waldron J, Warde P. Med-Tek type-S immobilization system: calculating the set-up margin for radiotherapy of head and neck cancer patients. Int J Radiat Oncol Biol Phys 2002. [DOI: 10.1016/s0360-3016(02)03558-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Wu J, Haycocks T, Alasti H, Ottewell G, Middlemiss N, Abdolell M, Warde P, Toi A, Catton C. Positioning errors and prostate motion during conformal prostate radiotherapy using on-line isocentre set-up verification and implanted prostate markers. Radiother Oncol 2001; 61:127-33. [PMID: 11690677 DOI: 10.1016/s0167-8140(01)00452-2] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To evaluate treatment errors from set-up and inter-fraction prostatic motion with port films and implanted prostate fiducial markers during conformal radiotherapy for localized prostate cancer. METHODS Errors from isocentre positioning and inter-fraction prostate motion were investigated in 13 men treated with escalated dose conformal radiotherapy for localized prostate cancer. To limit the effect of inter-fraction prostate motion, patients were planned and treated with an empty rectum and a comfortably full bladder, and were instructed regarding dietary management, fluid intake and laxative use. Field placement was determined and corrected with daily on-line portal imaging. A lateral portal film was taken three times weekly over the course of therapy. From these films, random and systematic placement errors were measured by matching corresponding bony landmarks to the simulator film. Superior-inferior and anterior-posterior prostate motion was measured from the displacement of three gold pins implanted into the prostate before planning. A planning target volume (PTV) was derived to account for the measured prostate motion and field placement errors. RESULTS From 272 port films the random and systematic isocentre positioning error was 2.2 mm (range 0.2-7.3 mm) and 1.4 mm (range 0.2-3.3 mm), respectively. Prostate motion was largest at the base compared to the apex. Base: anterior, standard deviation (SD) 2.9 mm; superior, SD 2.1 mm. Apex: anterior, SD 2.1 mm; superior, SD 2.1 mm. The margin of PTV required to give a 99% probability of the gland remaining within the 95% isodose line during the course of therapy is superior 5.8 mm, and inferior 5.6 mm. In the anterior and posterior direction, this margin is 7.2 mm at the base, 6.5 mm at the mid-gland and 6.0 mm at the apex. CONCLUSIONS Systematic set-up errors were small using real-time isocentre placement corrections. Patient instruction to help control variation in bladder and rectal distension during therapy may explain the observed small SD for prostate motion in this group of patients. Inter-fraction prostate motion remained the largest source of treatment error, and observed motion was greatest at the gland base. In the absence of real-time pre-treatment imaging of prostate position, sequential portal films of implanted prostatic markers should improve quality assurance by confirming organ position within the treatment field over the course of therapy.
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Affiliation(s)
- J Wu
- The Princess Margaret Hospital, Toronto, Canada
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Alasti H, Petric MP, Catton CN, Warde PR. Portal imaging for evaluation of daily on-line setup errors and off-line organ motion during conformal irradiation of carcinoma of the prostate. Int J Radiat Oncol Biol Phys 2001; 49:869-84. [PMID: 11172971 DOI: 10.1016/s0360-3016(00)01446-2] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE To use portal imaging to measure daily on-line setup error and off-line prostatic motion in patients treated with conformal radiotherapy to determine an optimum planning target volume (PTV) margin incorporating both setup error and organ motion. RESULTS A total of 2549 portal images from 33 patients were acquired over the course of the study. Of these patients, 23 were analyzed for setup errors while the remaining 10 were analyzed for prostatic motion. Setup errors were characterized by standard deviations of 1.8 mm in the anterior-posterior (AP) direction and 1.4 mm in the superior-inferior (SI) direction. Displacements due to prostatic motion, with standard deviations of 5.8 mm AP and 3.3 mm SI, were found to be more significant than setup errors. CONCLUSIONS Taking into account both setup errors and target organ motion, optimum PTV margins to ensure 95% coverage are 10.0 mm AP and 5.9 mm SI. The portal imaging protocol established in this study allows radiation therapists to accept or adjust a treatment setup based upon daily on-line image matching results. The successful localization of radiopaque fiducial markers on a significant number of portal images acquired in the study gives hope that more accurate on-line targeting verification may soon be possible through the visualization of the prostate itself as opposed to the surrounding bony structures of the pelvis.
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Affiliation(s)
- H Alasti
- Princess Margaret Hospital, Department of Radiation Physics, 601 University Avenue, Toronto, Ontario, Canada.
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Milosevic M, Voruganti S, Blend R, Alasti H, Warde P, McLean M, Catton P, Catton C, Gospodarowicz M. Magnetic resonance imaging (MRI) for localization of the prostatic apex: comparison to computed tomography (CT) and urethrography. Radiother Oncol 1998; 47:277-84. [PMID: 9681891 DOI: 10.1016/s0167-8140(97)00232-6] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND AND PURPOSE It is necessary to include the entire prostate in the high dose treatment volume when planning radical radiation for patients with prostate cancer. We prospectively compared magnetic resonance imaging (MRI) to computed tomography (CT) and urethrography as means of localizing the prostatic apex. MATERIALS AND METHODS Thirty patients with clinically localized prostate cancer had a sagittal T2-weighted MRI scan and a conventional axial CT scan performed in the treatment position prior to the start of radiotherapy. Twenty of these patients had a static retrograde urethrogram performed at simulation. The position of the MRI and CT apices were localized independently by two radiation oncologists. In addition, the MRI apex was localized independently by a diagnostic radiologist. The urethrogram apex, defined as the tip of the urethral contrast cone, was easily identified and was therefore localized by only one observer. RESULTS There was good interobserver agreement in the position of the MRI apex. Interobserver agreement was significantly better with MRI than with CT. There were no systematic differences in the position of the MRI and CT apices. However, the MRI apex was located significantly above and behind the urethrogram apex. There was poor correlation between MRI and CT and between MRI and urethrogram in the height of the apex above the ischial tuberosities. There was 83% agreement between MRI and CT and 80% agreement between MRI and urethrogram in the identification of patients with a low-lying apex. The apex, as determined by MRI, was <2 cm above the ischial tuberosities and therefore potentially under-treated in 17% of the patients. CONCLUSIONS MRI is superior to CT and urethrography for localization of the prostatic apex. All patients undergoing radiotherapy for prostate cancer should have localization of the apex using MRI or a technique of equal precision to assure adequate dose delivery to the entire prostate and to minimize the unnecessary irradiation of normal tissues.
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Affiliation(s)
- M Milosevic
- Department of Radiation Oncology, Ontario Cancer Institute/Princess Margaret Hospital and University of Toronto, Canada
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Alasti H, Catton C, Middlemiss N, Ottewell G, Green L, Warde P. Portal imaging for evaluation of daily on-line set up errors and off-line organ motion for radiotherapy of carcinoma of prostate. Int J Radiat Oncol Biol Phys 1998. [DOI: 10.1016/s0360-3016(98)80439-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
A common problem with low-energy electron beams (< 15 MeV) is their low surface dose when the incident electrons are monodirectional. This makes it difficult to deliver a uniform dose to tumor with any precision, limiting the clinical usefulness of such beams. A practical method is presented for greatly increasing the tissue depth enclosed by the 95% isodose region, while delivering the entire dose in a single uninterrupted treatment. Beam modification is achieved by placing a wire mesh of high atomic number (Z) on the treatment surface throughout the treatment. Electron beams of energies 6, 9, and 13 MeV are modified to produce a near uniform dose from the surface to the original depth of maximum, approximately doubling the depth enclosed by the 95% isodose. These beams have a step-function-like depth dose and can be arranged to deliver a constant dose to tumor located at varying depths while simultaneously sparing deeper tissues which are also located at varying depths. A single mesh design was found to be suitable for all energies.
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Affiliation(s)
- H Alasti
- Princess Margaret Hospital, Toronto, Ontario, Canada
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