Yu, Amy
(Department of Radiation Oncology, Stanford University School of Medicine)
,
Fahimian, Benjamin
(Department of Radiation Oncology, Stanford University School of Medicine)
,
Million, Lynn
(Department of Radiation Oncology, Stanford University School of Medicine)
,
Hsu, Annie
(Department of Radiation Oncology, Stanford University School of Medicine)
Purpose Radiotherapy treatment planning of extended volume typically necessitates the utilization of multiple field isocenters and abutting dosimetrically matched fields in order to enable coverage beyond the field size limits. A common example includes total lymphoid irradiation (TLI) treatments, w...
Purpose Radiotherapy treatment planning of extended volume typically necessitates the utilization of multiple field isocenters and abutting dosimetrically matched fields in order to enable coverage beyond the field size limits. A common example includes total lymphoid irradiation (TLI) treatments, which are conventionally planned using dosimetric matching of the mantle, para-aortic/spleen, and pelvic fields. Due to the large irradiated volume and system limitations, such as field size and couch extension, a combination of couch shifts and sliding of patients are necessary to be correctly executed for accurate delivery of the plan. However, shifting of patients presents a substantial safety issue and has been shown to be prone to errors ranging from minor deviations to geometrical misses warranting a medical event. To address this complex setup and mitigate the safety issues relating to delivery, a practical technique for couch indexing of TLI treatments has been developed and evaluated through a retrospective analysis of couch position.MethodsThe indexing technique is based on the modification of the commonly available slide board to enable indexing of the patient position. Modifications include notching to enable coupling with indexing bars, and the addition of a headrest used to fixate the head of the patient relative to the slide board. For the clinical setup, a Varian Exact CouchTM (Varian Medical Systems, Inc, Palo Alto, CA) was utilized. Two groups of patients were treated: 20 patients with table indexing and 10 patients without. The standard deviations (SDs) of the couch positions in longitudinal, lateral, and vertical directions through the entire treatment cycle for each patient were calculated and differences in both groups were analyzed with Student's t-test.ResultsThe longitudinal direction showed the largest improvement. In the non-indexed group, the positioning SD ranged from 2.0 to 7.9 cm. With the indexing device, the positioning SD was reduced to a range of 0.4 to 1.3 cm (p < 0.05 with 95% confidence level). The lateral positioning was slightly improved (p < 0.05 with 95% confidence level), while no improvement was observed in the vertical direction.ConclusionsThe conventional matched field TLI treatment is error-prone to geometrical setup error. The feasibility of full indexing TLI treatments was validated and shown to result in a significant reduction of positioning and shifting errors.
Purpose Radiotherapy treatment planning of extended volume typically necessitates the utilization of multiple field isocenters and abutting dosimetrically matched fields in order to enable coverage beyond the field size limits. A common example includes total lymphoid irradiation (TLI) treatments, which are conventionally planned using dosimetric matching of the mantle, para-aortic/spleen, and pelvic fields. Due to the large irradiated volume and system limitations, such as field size and couch extension, a combination of couch shifts and sliding of patients are necessary to be correctly executed for accurate delivery of the plan. However, shifting of patients presents a substantial safety issue and has been shown to be prone to errors ranging from minor deviations to geometrical misses warranting a medical event. To address this complex setup and mitigate the safety issues relating to delivery, a practical technique for couch indexing of TLI treatments has been developed and evaluated through a retrospective analysis of couch position.MethodsThe indexing technique is based on the modification of the commonly available slide board to enable indexing of the patient position. Modifications include notching to enable coupling with indexing bars, and the addition of a headrest used to fixate the head of the patient relative to the slide board. For the clinical setup, a Varian Exact CouchTM (Varian Medical Systems, Inc, Palo Alto, CA) was utilized. Two groups of patients were treated: 20 patients with table indexing and 10 patients without. The standard deviations (SDs) of the couch positions in longitudinal, lateral, and vertical directions through the entire treatment cycle for each patient were calculated and differences in both groups were analyzed with Student's t-test.ResultsThe longitudinal direction showed the largest improvement. In the non-indexed group, the positioning SD ranged from 2.0 to 7.9 cm. With the indexing device, the positioning SD was reduced to a range of 0.4 to 1.3 cm (p < 0.05 with 95% confidence level). The lateral positioning was slightly improved (p < 0.05 with 95% confidence level), while no improvement was observed in the vertical direction.ConclusionsThe conventional matched field TLI treatment is error-prone to geometrical setup error. The feasibility of full indexing TLI treatments was validated and shown to result in a significant reduction of positioning and shifting errors.
1 The Physical Aspects of Total and Half Body Photon Irradiation Physicists in Medicine Van Dyk J Galvin J Glasgow GP Podgorsak EB 17 New York American Institute of Physics 1986 http://www.aapm.org/pubs/reports/RPT_17.pdf
2 The matching of adjacent fields in radiotherapy Radiology Armstrong DI Tait JJ 419 422 108 1973 4719048
3 Physical and dosimetric aspects of the radiotherapy of malignant lymphomas. II. The inverted-Y technique Radiology Page V Gardner A Karzmark CJ 619 626 96 1970 5456317
4 Site-specific tolerance tables and indexing device to improve patient setup reproducibility J Appl Clin Med Phys McCullough KT James JA Cetnar AJ McCullough MA Wang B 378 388 College 16 2015
5 Analysis of couch position tolerance limits to detect mistakes in patient setup J Appl Clin Med Phys Hadley SW Balter JM Lam KL 207 219 College 10 2009
6 Physical and dosimetric aspects of the radiotherapy of malignant lymphomas. I. The mantle technique Radiology Page V Gardner A Karzmark CJ 609 618 96 1970 5456316
7 Immunosuppression and tolerance after total lymphoid irradiation (TLI) Transplant Proc Strober S Gottlieb M Slavin S King DP Hoppe RT Fuks ZU Bieber CP Kaplan HS 477 482 12 1980 http://inis.iaea.org/search/search.aspx?orig_q=RN:12581399 6452725
8 Dosimetric effects caused by couch tops and immobilization devices: report of AAPM Task Group 176 Med Phys Olch AJ Gerig L Li H Mihaylov I Morgan A 61501 41 2014
9 Fractionated total-body irradiation, etoposide, and cyclophosphamide plus autografting in Hodgkin's disease and non-Hodgkin's lymphoma J Clin Oncol Horning SJ Negrin RS Chao JC Long GD Hoppe RT Blume KG 2552 2558 12 1994 7989928
10 A computerized record and verify system for radiation treatments Int J Radiat Oncol Biol Phys Mohan R Podmaniczky KC Caley R Lapidus A Laughlin JS 1975 1985 10 1984 6490426
11 Facilitation of radiotherapeutic error by computerized record and verify systems Int J Radiat Oncol Biol Phys Patton GA Gaffney DK Moeller JH 50 57 56 2003 12694823
12 The use of Varian Delta Couch Shift functionality during treatment set-up: A radiation therapists' perspective Royal Australian and New Zealand College of Radiologists (RANZCR) Faulkner K 0 300 2014
13 Reproducibility of patient positioning for fractionated extracranial stereotactic radiotherapy using a double-vacuum technique Strahlenther Onkol Nevinny-Stickel M Sweeney RA Bale RJ Posch A Auberger T Lukas P 117 122 180 2004 14762665
14 Effect of a carbon fiber tabletop on the surface dose and attenuation for high-energy photon beams Radiat Med Meydanci TP Kemikler G 539 544 26 2008 19030962
AI-Helper
※ AI-Helper는 부적절한 답변을 할 수 있습니다.