753 原著 Code No. 490 kv-cone beam CT 1, 2 河野友宏 3 荒木不次男 4 中口裕二大野 3 剛緒言 intensity modulated radiotherapy: IMRT volumetric

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1 753 原著 de No. 490 kv-cone beam CT 1, 2 河野友宏 3 荒木不次男 4 中口裕二大野 3 剛緒言 intensity modulated radiotherapy: IMRT volumetric modulated arc radiotherapy: VMAT image-guided radiotherapy: IGRT 1 4 IGRT 2 X kv-cone beam computed tomography CBCT MV-CBCT MV-fan beam computed tomography FBCT IGRT 5, 6 kv-cbct kv-cbct The American Association of Physicists in Medicine: Dose Distribution from kv-ne Beam mputed Tomography in Image-guided Radiotherapy Tomohiro Kouno 1, 2, Fujio Araki 3, Yuji Nakaguchi 4, and Takeshi Oono 3 1 Graduate School of Health Sciences, Kumamoto University 2 Current address: Department of Radiological, Isahaya Health Insurance General Hospital 3 Faculty of Life Sciences, Kumamoto University 4 Department of Radiological Technology, Kumamoto University Hospital Received October 27, 2012; Revision accepted May 21, 2013 de No. 490 Summary Image-guided radiotherapy (IGRT) is an increasingly commonly adopted technique. As a result, however, total patient dose is increasing rapidly, especially when kv-cone beam computed tomography (CBCT) is applied. This study investigated the dosimetry of kv-cbct using a Farmer ionization chamber with a absorbed-dose calibration factor. The absorbed-dose measurements were performed using an I mrt phantom (RW3, IBA) which is employed for dose verification of intensity-modulated radiotherapy (IMRT). The I mrt phantom was used as a substitute for head and pelvis phantoms. The kv-cbct absorbed dose was evaluated from a beam quality conversion factor of kv to and the ionization ratio of the I mrt phantom and water, calculated using the Monte Carlo method. The dose distribution in the I mrt phantom was also measured using a radiophotoluminescent glass dosimeter (RGD). The absorbed doses for the pelvis phantom (full scan) ranged from cgy for kv-cbct and 4 8 cgy for MV-CBCT. TomoTherapy resulted in a lower dose of approximately 1.3 cgy due to fan-beam. For the head phantom (half scan), the doses ranged from cgy for kv-cbct and 3 5 cgy for MVCBCT. The results for RGD were similar to ion chamber measurements. It is necessary to decrease the absorbed dose of the organs at risk every time IGRT is applied. Key words: kv-cone beam computed tomography, image-guided radiotherapy (IGRT), ion chamber dosimetry, Monte Carlo simulation *Proceeding author Vol. 69 No. 7 Jul 2013

2 754 AAPM Task Group 61 TG IGRT AAPM TG CBCT AAPM TG Song 9 Elekta X-ray Volume Imaging XVI Varian On-Board Imager OBI kv-cbct XVI OBI Wen 10 thermoluminescent dosimeter: TLD kv-cbct Ding 11, 12 CT Monte Carlo: dose volume histogram: DVH 4 kv-cbct kv-cbct IGRT IGRT kv-cbct I mrt RW3 IBA IGRT MV-CBCT Siemens MV-FBCT TomoTherapy radiophotoluminescent glass dosimeter: RGD 1. 方法 IGRT kv-cbct kv-cbct 1-1 kv-cbct OBI ver1.5 kv-cbct EGSnrc 18 /BEAMnrc 19 X bowtie Half-bowtie Full-bowtie 125 kv 100 kv phase space file PSF Varian Medical systems percent depth dose: PDD off-center ratio: OCR EGSnrc/DOSXYZnrc cm 3 PDD 1 cm cm 3 5 cm cm cm 3 OCR cm 3 PDD OCR PTW cm 3 PDD 20 cm OCR 1 cm 5 cm Half-bowtie cm 2 Full-bowtie cm 2 AE=512 kev ECUT=516 kev AP=PCUT=1 kev 11 AE AP ECUT PCUT IGRT-CT IGRT-CT Fig. 1 a I mrt Fig. 1 b 36 cm 16 cm 16 cm 16 cm 16 cm 16 cm =16 cm 4 8 cm 4 9 IGRT-CT Table 1 Varian kv-cbct Siemens TomoTherapy MV-CT cone beam fan beam TomoTherapy kv-cbct N Dw, kv-cbct

755 Fig. 1 Absorbed-dose measurement points with an ionization chamber and RGD in (a) an I mrt phantom (front view). The illustrations show pelvis (b) and head (c) phantoms.

3 755 Fig. 1 Absorbed-dose measurement points with an ionization chamber and RGD in (a) an I mrt phantom (front view). The illustrations show pelvis (b) and head (c) phantoms. a b c Table 1 Clinical exposure conditions of kv-cbct, MV-CBCT, and MV-FBCT kv-cbct MV-CBCT MV-FBCT Varian OBI Siemens TomoTherapy Pelvis Head Pelvis Head Normal X-ray voltage 125 kv 100 kv 4 MV 4 MV 3.5 MV X-ray current per projection 80 ma 80 ma Exposure time 13 ms 25 ms 50 MU/min 50 MU/min 17 MU/min Number of projections /min 222 /min 51/rot Total mas or MU 680 mas 720 mas 8 MU 5 MU 43 MU Filter Half bowtie Full bowtie FOV 45 cm 25 cm 27.4 cm 27.4 cm 40 cm Gantry rotation range Gantry rotation angle Helical ND,air N = N D, air D, w ( D ) air w D w 1 (D air)w 5 cm Dw kv-cbct D kv w Mw 1 kv air w M, Dw, w Dw kv Dw D = N M N w D air w = ( D ) air w k D N M k Dw D = ( ) Dw ( D ) air w kv kv air w Q kv kv = w D, w w Q Dw ( D ) ( D ) kv air w 2 3 k kv Q PTW30013 kv-cbct k kv Q k Q I mrt pl w Mpl Mw kpl kv kv = w D, w pl pl Q D N M k k 4 kpl=mw/m pl k pl M N M D w D, air w ( ) air w = = = M N M ( D ) pl D, air pl air pl kv 5 (D air)pl I mrt (D air)w (D air)pl k kv Q kpl 1.5 cm 5 cm 10 cm MV-CT Vol. 69 No. 7 Jul 2013

4 756 Fig. 2 Geometrical alignment of RGD in an I mrt phantom for (a) kv-cbct and (b) MV-CT (top view of slab). a b RGD I mrt kv-cbct Siemens MV-CBCT TomoTherapy MV-FBCT RGD RGD 1.5 mmφ 12 mm g/cm 3 kv GD-352M 4.3mmφ 14.5 mm Sn MV GD-302M 2.8 mmφ 13 mm I mrt RGD kv-cbct 4 cm 7 cm MV-CT 7 cm Fig. 2 a, b 3 RGD CBCT 7 cm Fig. 2 a b RGD RGD D GD I mrt 5 D IC,center D GD = M GD D M IC,center GD,center 6 M GD M GD,center RGD 2. 結果 2-1 kv-cbct Fig. 3 kv-cbct Half-bowtie filter PDD OCR 125 kv source-to-surface distance: SSD 100 cm PDD 15 cm 220 cm 3OCR 1 cm 5 cm 5 Fig. 3 mparison of Monte Carlocalculated and measured dose distributions with a half-bowtie filter and 125-kV photon beam: (a) central axis percentage depth dose and (b) dose profiles along the x-axis at depths of 1 and 5 cm and SSD 100 cm. Fig. 4 Full-bowtie filter PDD OCR 3 5 Half-bowtie Full-bowtie 3 5 mm 100 kv bowtie filter PDD OCR 2-2 IGRT-CT Table 2 kv-cbct kq I mrt PTW30013 k pl kv Half-bowtie filter cm kq 0.887± kv

5 757 a b Fig. 4 mparison of Monte Carlo calculated and measured dose distributions with a full-bowtie filter for a 125-kV photon beam: (a) central axis percentage depth dose and (b) dose profiles along the x-axis at depths of 1 and 5 cm and SSD 100 cm. Table 2 Beam quality conversion factor kq of a PTW30013 ion chamber and the ionization ratio kpl (Mw/Mpl) of water to I mrt phantom for kv-cbct 125 kv CBCT 100 kv CBCT Depth (cm) Half-bowtie Full-bowtie kq kpl kq kpl ±0.34% 1.003±0.39% 0.870±0.32% 1.003±0.35% ±0.40% 1.002±0.45% 0.871±0.39% 1.000±0.43% ±0.55% 1.007±0.63% 0.885±0.55% 1.008±0.61% Average 0.887±0.82% 1.004±0.29% 0.875±0.97% 1.004±0.42% k Q and k pl are derived using Monte Carlo calculation. Full-bowtie filter 0.875±1.0 kq kv-cbct kq 1.8 kq kpl 125 kv Half-bowtie filter kpl 1.004± kv Fullbowtie filter 1.004±0.4 I mrt Fig. 5 kv-cbct MV-CBCT MV-FBCT kv-cbct cgy Siemens MV-CBCT 4 8 cgy kv-cbct 2 Siemens MV-CBCT TomoTherapy MV-FBCT 1.3 cgy kv-cbct 1/2 1/3 Fig. 6 kv-cbct Siemens MV-CBCT kv-cbct 1 cgy cgy Siemens MV-CBCT 3 5 cgy CBCT clockwise: CW counterclockwise: CCW Table 3 kv-cbct MV-CBCT MV-FBCT RGD kv-cbct MV-CBCT MV-FBCT Table 4 kv-cbct MV-CBCT Vol. 69 No. 7 Jul 2013

6 758 Fig. 5 mparison of absorbed doses in a pelvis phantom for kv-cbct, MV-CBCT, and MV-FBCT. Fig. 6 mparison of absorbed doses in a head phantom for kv-cbct and MV-CBCT. Table 3 mparison of pelvis doses between an ionization chamber and RGD for kv-cbct, MV-CBCT, and MV-FBCT at measurement points 1 9 Measurement points kv-cbct MV-CBCT MV-FBCT RGD a RGD b RGD b ±2.6% ±0.8% ±5.3% ±3.3% ±1.5% ±3.7% ±0.2% ±1.0% ±0.2% ±3.7% ±0.6% ±3.5% ±1.7% ±0.9% ±1.9% ±1.9% ±1.3% ±0.6% ±0.2% ±1.1% ±0.5% ±3.1% ±1.4% ±0.9% ±1.5% ±0.7% ±3.0% Unit: cgy a : RGD-352M, b : RGD-302M Table 4 mparison of head doses between an ionization chamber and RGD for kv-cbct and MV-CBCT at measurement points 1 9 Measurement points kv-cbct MV-CBCT RGD a RGD b ±1.3% ±1.5% ±2.4% ±1.2% ±0.1% ±1.4% ±6.0% ±0.8% ±4.0% ±0.9% ±0.9% ±0.5% ±0.0% ±0.5% ±1.5% ±1.7% ±3.1% ±1.1% Unit: cgy a : RGD-352M, b : RGD-302M

7 759 RGD kv-cbct MV-CBCT 考察 3-1 kv-cbct kv-cbct X PDD OCR kv-cbct bowtie filter 0.6 cc PDD OCR OCR cm 6 mmφ OCR bowtie filter kv-cbct Half-bowtie Full-bowtie filter PDD 5 cm cm Half-bowtie filter kv-cbct Ding 11, 12 PDD OCR kv AAPM TG-61 7 kv-x kv-cbct PTW kv 100 kv 0.887± ± kv-x / / cm bowtie filter I mrt kpl 125 kv 100 kv 1 kv-cbct cgy IMRT 30 1 Gy 22 Siemens MV-CBCT TomoTherapy MV-FBCT kv-cbct 1/2 1/3 TomoTherapy MV-FBCT Siemens MV-CBCT MU 2 mm fan beam CT Shah 15 MV-FBCT cgy RGD RGD kv-x 21 RGD I mrt RGD 4. 結論 kv-cbct Vol. 69 No. 7 Jul 2013

8 7 kv-cbct MV-CBCT MV-FBCT kv-cbct cgy 1 cgy MV-CBCT cgy 3 5 cgy TomoTherapy 1.3 cgy IGRT CT 謝辞 kv-cbct MV-CBCT TomoTherapy 参考文献 1 Barney BM, Lee RJ, Handrahan D, et al. Image-guided radiotherapy (IGRT) for prostate cancer comparing kv imaging of fiducial markers with cone beam computed tomography (CBCT). Int J Radiat Oncol Biol Phys 2011; 80(1): Yartsev S, Kron T, Van Dyk J. Tomotherapy as a tool in image-guided radiation therapy (IGRT): current clinical experience and outcomes. Biomed Imaging Interv J 2007; 3(1): e17. 3 Webster GJ, Rowbottom CG, Mackay RI. Accuracy and precision of an IGRT solution. Med Dosim 2009; 34(2): Potters L, Gaspar LE, Kavanagh B, et al. American Society for Therapeutic Radiology and Oncology (ASTRO) and American llege of Radiology (ACR) practice guidelines for image-guided radiation therapy (IGRT). Int J Radiat Oncol Biol Phys 2010; 76(2): Gu J, Bednarz B, Xu XG, et al. Assessment of patient organ doses and effective doses using the VIP-Man adult male phantom for selected cone-beam CT imaging procedures during image guided radiation therapy. Radiat Prot Dosimetry 2008; 131(4): Ay MR, Shahriari M, Sarkar S, et al. Measurement of organ dose in abdomen-pelvis CT exam as a function of ma, KV and scanner type by Monte Carlo method. Iran J Radiat Res 2004; 1(4): Ma CM, ffey CW, DeWerd LA, et al. AAPM protocol for kv x-ray beam dosimetry in radiotherapy and radiobiology. Med Phys 2001; 28(6): Hyer DE, Serago CF, Kim S, et al. An organ and effective dose study of XVI and OBI cone-beam CT systems. J Appl Clin Med Phys 2010; 11 (2): Song WY, Kamath S, Ozawa S, et al. A dose comparison study between XVI and OBI CBCT systems. Med Phys 2008; 35(2): Wen N, Guan H, Hammoud R, et al. Dose delivered from Varian s CBCT to patients receiving IMRT for prostate cancer. Phys Med Biol 2007; 52(8): Ding GX, Duggan DM, ffey CW. Accurate patient dosimetry of kilovoltage cone-beam CT in radiation therapy. Med Phys 2008; 35(3): Ding GX, Duggan DM, ffey CW. Characteristics of kilovoltage x-ray beams used for cone-beam computed tomography in radiation therapy. Phys Med Biol 2007; 52(6): Ding GX, Duggan DM, ffey CW. Accurate patient dosimetry of kilovoltage cone-beam CT in radiation therapy. Med Phys 2008; 35(3): Deng J, Chen Z, Roberts KB, et al. Kilovoltage imaging doses in the radiotherapy of pediatric cancer patients. Int J Radiat Oncol Biol Phys 2012; 82(5): Shah AP, Langen KM, Ruchala KJ, et al. Patient dose from megavoltage computed tomography imaging. Int J Radiat Oncol Biol Phys 2008; 70(5): Deng J, Chen Z, Yu JB, et al. Testicular doses in imageguided radiotherapy of prostate cancer. Int J Radiat Oncol Biol Phys 2012; 82(1): e39-e Murphy MJ, Balter J, Balter S, et al. The management of imaging dose during image-guided radiotherapy: report of the AAPM Task Group 75. Med Phys 2007; 34(10): Bissonnette JP, Balter PA, Dong L, et al. Quality assurance for image-guided radiation therapy utilizing CT-based technologies: a report of the AAPM TG-179. Med Phys 2012; 39(4): Rogers DW, Faddegon BA, Ding GX, et al. BEAM: a Monte Carlo code to simulate radiotherapy treatment units. Med Phys 1995; 22(5): Rogers DW, Walters B, Kawrakow I. BEAMnrc users manual, 2009: NRCC Report PIRS-0509 (A) rev L. 21 Walters B, Kawrakow I, Rogers DW. DOSXYZnrc users manual, 2009: NRCC Report PIRS-794 rev B IMRT CBCT 2011; 67(3): ; (7): Araki F, Moribe N, Shimonobou T, et al. Dosimetric properties of radiophotoluminescent glass rod detector in highenergy photon beams from a linear accelerator and cyberknife. Med Phys 2004; 31(7): Hsu SM, Lee JH, Hsu FY, et al. Dose measurements for gamma knife with radiophotoluminescent glass dosimeter and radiochromic film. Radiat Prot Dosimetry 2011; 146(1-3):

491 原著 kv-cbct 川村哲朗 2 宮脇大輔 1 村上直基 1 木村邦彦 1 岡村佳明土師 1 守 2 西村英輝 2 佐々木良平 Code No 緒言 image-guided radiation therapy: IGRT kv

491 原著 kv-cbct 川村哲朗 2 宮脇大輔 1 村上直基 1 木村邦彦 1 岡村佳明土師 1 守 2 西村英輝 2 佐々木良平 Code No 緒言 image-guided radiation therapy: IGRT kv 49 原著 kv-cbct 202 3 27 川村哲朗 2 宮脇大輔村上直基木村邦彦岡村佳明土師守 2 西村英輝 2 佐々木良平 203 3 2 Code No. 754 2 緒言 image-guided radiation therapy: IGRT kv cone-beam computed tomography kv-cbct, 2 kv-cbct CT dose index CTDI

753 原著 Code No. 490 kv-cone beam CT 1, 2 河野友宏 3 荒木不次男 4 中口裕二 大野 3 剛 緒言 intensity modulated radiotherapy: IMRT volumetric

753 原著 Code No. 490 kv-cone beam CT 1, 2 河野友宏 3 荒木不次男 4 中口裕二大野 3 剛緒言 intensity modulated radiotherapy: IMRT volumetric