Reproducibility of Frame Positioning for Fractionated Stereotactic Radiosurgery
Tóm tắt
Fractionated stereotactic radiation therapy is a useful new approach for treating a number of intracranial neoplasms including meningiomas, pituitary adenomas, craniopharyngiomas, and recurrent gliomas. For the majority of these we employ a conventional fractionation scheme of 180 cGy per fraction for 25 to 30 fractions, using a modified Gill–Thomas–Cosman (GTC) relocatable frame to accommodate fractionated delivery. The GTC system uses a custom acrylic dental appliance to set the frame position and an occipital plate and Velcro straps fix the head in place. Daily reproducibility is evaluated through use of a “depth helmet,” a plastic hemispherical shell containing 25 holes at regularly spaced intervals. The depth helmet attaches to the GTC frame and the distance from the shell to the patient's head is recorded at each of the 25 positions. This paper describes a new simplified approach to the quantitative assessment of day-to-day variability in head fixation using the depth helmet measurements. This approach avoids the need to try and decide on the relative merit of 25 numerical differences at each fitting and provides a straightforward mathematical and conceptual framework for the description of fit and clinical decision making. The mathematical analysis and computer program we have developed uses all 25 measurements to provide a single three-dimensional displacement vector as well as displacement values in the three principal patient dimensions. Measurements at each of the 25 depth helmet positions are automatically separated into three principal axes corresponding to the patients left/right (x), anterior/posterior (y), and superior/inferior (z) using the spherical relations: x = r sin(Φ) cos(θ), y = r sin(Φ) sin(θ), z = r cos(Φ), where θ and Φ are the polar and azimuthal angles respectively and ris the distance from the center of the depth helmet to the surface of the patient's head. For each patient, a set of initial measurements is taken at the CT scanner with the patient in the treatment (supine) position. Because treatment planning is based on the CT scan, this serves as the baseline from which subsequent deviations are recorded. In an analysis of our first 30 patients representing over 750 fractions, the mean RMS deviation, that is, the mean three-dimensional displacement from baseline, was 0.468 ± 0.296 mm. Among individual patients the range was 0.169 mm to 1.438 mm. A closer analysis suggests that in-plane (AP/PA-lateral) deviations occur randomly. Deviations along the superior/inferior direction are greater than those in-plane, and in several patients a small shift along this axis, possibly due to a loosening or stretching of the Velcro straps, has been noted over time. We have found our method to be a useful indicator of day-to-day reproducibility, allowing ready identification and correction of three-dimensional shifts relative to the patient axes. Based on our initial analysis, we can now define quantitative limits of acceptability in repositioning for subsequent fractionated delivery.
Tài liệu tham khảo
Bova FJ, Buatti JM, Friedman WA, Mendenhall WM, Yang CC, Liu C: The University of Florida frameless high-precision stereotactic radiotherapy system. Int J Radiat Oncol Biol Phys 38(4):875–882, 1997
Delannes M, Daly-Schveitzer N, Sabatier J, Bonnet J: Fractionated brain stereotactic irradiation using a non-invasive frame: Technique and preliminary results. Radiat Oncol Invest 2:92–98, 1994
Gill SS, Thomas DGT, Warrington AP, Brada M: Relocatable frame for stereotactic external beam radiotherapy. Int J Radiat Oncol Biol Phys 20:599–603, 1991
Graham JD, Warrington AP, Gill SS, Brada M: A non-invasive, relocatable stereotactic frame for fractionated radiotherapy and multiple imaging. Radiother Oncol 21:60–62, 1991
Hariz MI, Henriksson R, Lofroth PO, Laitinen LV, Saterborg NE: A non-invasive method for fractionated stereotactic irradiation of brain tumors with linear accelerator. Radiother Oncol 17:57–72, 1990
Hirato M, Inoue H, Nakamura M, Ohye C, Hirato J, Shibazaki T, Andou, Y: Gamma knife radiosurgery for acoustic schwannoma: Early effects and preservation of hearing. Neurologia Medico-Chirurgica 35(10):737–741, 1995
Hunt MA, Kutcher GJ, Burman C, Fass D, Harrison, L, Leibel S, Fuks Z: The effect of setup uncertainties on the treatment of nasopharynx cancer. Int J Radiat Oncol Biol Phys 27(2):437–447, 1993
Jones D, Christopherson DA, Washington JT, Hafermann MD, Rieke JW, Travaglini JJ, Vermeulen SS: A frameless method for stereotactic radiotherapy. Br J Radiol 66:1142–1150, 1993
Kooy HM, Dunbar SF, Tarbell NJ, Mannarino E, Ferarro N, Shusterman S, Bellerive M, Finn L, McDonough CV, Loeffler JS: Adaptation and verification of the relocatable Gill-Thomas-Cosman frame in stereotactic radiotherapy. Int J Radiat Oncol Biol Phys 30:685–691, 1994
Laing RW, Thompson V, Warrington AP, Brada M: Feasibility of patient immobilization for conventional cranial irradiation with a relocatable stereotactic frame. Br J Radiol 66:1020–1024, 1993
Laing RW, Warrington AP, Graham J, Britton J, Hines F, Brada M: Efficacy and toxicity of fractionated stereotactic radiotherapy in the treatment of recurrent gliomas (phase I/II study). Radiother Oncol 30:239–246, 1994
Menke M, Hirschfeld F, Mack T, Pastyr O, Sturm V, Schlegel W: Photogrammetric accuracy measurements of head holder systems used for fractionated radiotherapy. Int J Radiat Oncol Biol Phys 29:1147–1155, 1994
Niewald M, Lehmann W, Uhlmann U, Schnabel K, Leetz HK: Plastic material used to optimize radiotherapy of head and neck tumors and the mammary carcinoma. Radiother Oncol 11(1):55–63, 1988
Ogunrinde OK, Lunsford LD, Flickinger JC, Kondziolka D: Stereotactic radiosurgery for acoustic nerve tumors in patients with useful preoperative hearing: Results at 2-year follow-up examination. J Neurosurg 80(6):1011–1017, 1994
Rosenthal SJ, Gall KP, Jackson M, Thornton AF Jr: A precision cranial immobilization system for conformal stereotactic fractionated radiation therapy. Int J Radiat Oncol Biol Phys 33:1239–1245, 1995
Schlegel W, Pastyr O, Bortfeld T, Gademann G, Menke M, Maier-Borst W: Stereotactically guided fractionated radiotherapy: Technical aspects. Radiother Oncol 29:197–204, 1993
Shrieve DC, Tarbell NJ, Goumnerova L, Loeffler JS: Hyperfractionated stereotactic radiotherapy for recurrent gliomas in children and adults: A biological compromise between radiosurgery and conventionally fractionated radiotherapy. In Radiosurgery 1995. D Kondziolka (ed). Basel, S. Karger AG, pp 158–164, 1995
Thornton AF Jr, Ten Haken RK, Gerhardsson A, Correll M: Three-dimensional motion analysis of an improved head immobilization system for simulation, CT, MRI, and PET imaging. Radiother Oncol 20:224–228, 1991
Tsujii H, Kamada T, Matsuoka Y, Takamura A, Akazawa T, Irie G: The value of treatment planning using CT and an immobilizing shell in radiotherapy for paranasal sinus carcinomas. Int J Radiat Oncol Biol Phys 16:243–249, 1989
Varlotto JM, Shrieve DC, Alexander III E, Kooy HM, Black PM, Loeffler JS: Fractionated stereotactic radiotherapy for the treatment of acoustic neuromas: Preliminary results. Int J Radiat Oncol Biol Phys 36:141–145, 1996
Verhey LJ, Goitein M, McNulty P, Munzenrider JE, Suit HD: Precise positioning of patients for radiation therapy. Int J Radiat Oncol Biol Phys 8:289–294, 1982
Warrington AP, Laing RW, Brada M: Quality assurance in fractionated stereotactic radiotherapy. Radiother Oncol 30:239–246, 1994