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Jean Pouliot, Ph.D.
ProfessorUCSF Comprehensive Cancer Center
San Francisco
Daily Localization:
MV Cone-Beam CT
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Course Objectives
1. Understand the basics of MV Cone-Beam CT imaging
2. Understand the possibilities of daily 3D Imaging for patient alignment and other applications
3. Understand the clinical roles of Image-Guided (IGRT) and Dose-Guided (DGRT) Radiation Therapy
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Description of MVCBCT Fan Beam vs Cone Beam Basic Principles and Characteristics Image Samples
Workflow of IGRT with MVCBCT Acquisition, Reconstruction & Registration Absolute Positioning & Alignment Presicion
Clinical Applications Patient positioning Monitoring of anatomical changes Target delineation with CT non-compatible
objects Tomosynthesis, Brachytherapy, etc. Dose calculation to assess dosimetrical
impact
Dose-Guided Radiation Therapy
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Basic Principles of MV CBCT
1 slice per rotation Entire volume in 1 rotation
Fan beam CT Cone-beam CT
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Basic Principles of MV CBCT
MVisionTM generates a 3D image of the patient anatomy from the same x-ray beam (6MV) used for treatment.
Image and x-ray beam share the same isocenter.
Patient 3D anatomy in treatment position, moments before dose delivery.
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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2001
21 MU
2002
16 MU
2003
16 MU
2004
1 MU
2005
10 MU
2006
6 MU
2007
1-2 MU ?
2004
15 MU
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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On Board CT
Courtesy of K. Langen Courtesy of F.F. Yin
MV CT MV CB CT kV CB CT
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Basic Characteristicsof MV CBCT
Half rotation: 200 degrees Acquisition ~ 45 seconds Acquisition + Reconstruction < 2 min. 27 cm x 27 cm x 27 cm Field of View Volume of 256 x 256 x 270 Pixel size (0.5 mm)3
Typical dose: 2 to 9 cGy Accurate Electron Density
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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MV CBCT
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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a)
b)
c)
Prostate
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Dose from Imaging
MV CT: < 2 cGy
kV CBCT1: < 4 cGy
MV CBCT: < 9 cGy
kV CBCT2: < 12 cGy
Islam M. et al., Patient dose from kilovoltage cone beam computed tomograhy imaging in radiation therapy, Med. Phys. 33 (6), pp1573-1582, June 2006.
Wen. N., Skin and dose measurement measurement for Cone-Beam CT during IMRT for prostate patient, TH-D-ValB-02
Hendee WR, Ritenour ER. Medical Imaging Physics, Fourth Edition. NewYork: Wiley-Liss; 2002.
Morin et al., Patient Dose Considerations for Routine Megavoltage Cone-Beam CT Imaging, Med. Phys. 34(5), 1819-1827; 2007.
Meeks SL et al., Performance Characterization of megavoltage computed tomography imaging on a helical tomotherapy unit.
Wen N, Guan H, Hammoud R, et al. TH-D-VaIB-02: Skin and Body Dose Measurements for Varian Cone-Beam CT (CBCT) During IMRT for Prostate Cancer. Med Phys 2006;33:2280.
Hill M.A., Variation in Biological Effectiveness of X-Rays and Gamma Rays with Energy, Radiation Protection Dosimetry (2004), Vol. 112, No. 4, pp.471-481
RBE .... x 1 < 2 cSv
.... x 1.8 to 4 < 7 cSv
.... x 1 < 9 cSv
.... x 1.8 to 4 < 21 cSv
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Description of MVCBCT Fan Beam vs Cone Beam Basic Principles and Characteristics Image Samples
Workflow of IGRT with MVCBCT Acquisition, Reconstruction & Registration Absolute Positioning & Alignment Presicion
Clinical Applications Patient positioning Monitoring of anatomical changes Target delineation with CT non-compatible
objects Tomosynthesis, Brachytherapy, etc. Dose calculation to assess dosimetrical
impact
Dose-Guided Radiation Therapy
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Workflow of IGRT with MV CBCT
1) The patient and the cone-beam acquisition mode are selected at the treatment console.
2) The linac gantry is placed in starting position, namely 270 degrees.
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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MV Cone-Beam CT Acquisition and Reconstruction
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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MV CBCT - CT Registration4) Upon completion of the reconstruction image, the cone-beam image is automatically loaded in the Adaptive Targeting SofwareTM, and the CB to CT image registration is performed automatically in few seconds using a mutual information algorithm.
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Geometric Calibration
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ReconstructionProgram
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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1) Place a small fiducial marker at isocenter
2) MV CBCT Imaging
3) Verify position of the fiducial in the reconstruction space
Should be: [-0.1, 0.1] cm
Absolute positioning
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
Monthly Calibration
No re-calibration for 8 months
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2D (EPID) vs 3D (MVCBCT) Setup Methods
2D method: DRR with EPI
3D method: CT with MV CBCT
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Description of MVCBCT Fan Beam vs Cone Beam Basic Principles and Characteristics Image Samples
Workflow of IGRT with MVCBCT Acquisition, Reconstruction & Registration Absolute Positioning & Alignment Presicion
Clinical Applications Patient positioning Monitoring of anatomical changes Target delineation with CT non-compatible
objects Tomosynthesis, Brachytherapy, etc. Dose calculation to assess dosimetrical
impact
Dose-Guided Radiation Therapy
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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• Head & Neck• Lung• Spine• Chest• Breast• Prostate
Patient positioning
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Patient AlignmentDaily or weekly imaging
Planning or DGRTImaging once or twice
Head and neck
Exposure (MU): 5-8 (bone).Recon Size: 256 x 256Slice Thickness: 1 or 3 mmFOVz: exclude eyes if possibleKernel: Smoothing -H&N
Exposure: 10-20 MURecon Size: 512 x 512Slice Thickness: (1) to 5 mm*FOVz: exclude eyes if possibleKernel: Smoothing -H&N
Chest or Breast
Exposure (MU): 5-10 (bone).Recon Size: 256 x 256Slice Thickness: 1 mmFOVz: full lengthKernel: Smoothing -Pelvis
Exposure: 15-20 MURecon Size: 512 x 512Slice Thickness: (1) to 5 mm*FOVz: full lengthKernel: Smoothing -Pelvis
Pelvis Exposure (MU): 3-4 (seeds), 4-7 (bone), 8-12 (soft-tissue).
Recon Size: 256 x 256Slice Thickness: 1 mmFOVz: full lengthKernel: Smoothing -Pelvis
Exposure: 15-20 MURecon Size: 512 x 512Slice Thickness: (1) to 5 mm*FOVz: full lengthKernel: Smoothing -Pelvis
* Best to reconstruct with 1 mm slice thickness and resample images to 3 or 5 mm for planning applications.1 mm will produce too many slices for most planing systems.
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
Acquisition Protocols
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Patient alignment with gold markers since 1994 Off line verification (1997) On line verification (Daily alignment since 2001) > 800 patients -> Clinical routine
Daily Prostate AlignmentEPID + Markers
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Prostate Motion Management at UCSFEPID + Markers
Accuracy (Aubin et al. 2002): . . . . . . . . . . . . . . Global accuracy ~ 1.5 mm
Patient tolerance to implant (Downs et al. 2002): . . . .Side effects < biopsy
BAT vs. EPID (Langen et al. 2003): . . . . . . . . . . . . . . . . . . . User variability
Visibility of Markers (Aubin et al. 2003): . . . . . . . . . . . . . . . . . . . 1 x 3 mm
Migration & Positional Stability (Pouliot et al. 2003): . . . . . sigma ~ 1.3 mm
Obese patients (Millender et al. 2004): . . . . . Patient setup > organ motion
Post-Prostatectomy (Schniffer et al. 2005): . . .Prostate bed moves, but less
Long-term f-up w/ MRS (Pickett et al. 2006): . . . Shorter metabolic atrophy
Intra-fractional motion (Lometti et al. 2006): . . . . . . . Minutes, not seconds
Dual Target Adaptive Strategy (Xia et al., 2007): . . . Lymph nodes Boost
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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38
MVCBCT Acquisition -Pelvis
SUPERIOR
INFERIOR
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Measuring Prostate Motion
Intra-Fractional Prostate Motion Study
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Intra-Fractional Prostate Motion Study
Between Setup and Dose Delivery
32% > 2 mm10% > 4 mm
All Displacements> 2 mm
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Prostate is stable during short time periods (i.e. radiation delivery)
Prostate motion more likely during longer time periods (i.e. between setup and radiation delivery)
Motion appears to be due mostly to gas in the colon/rectum
Respiration has little effect on organ motion
Intra-Fractional Prostate Motion Study
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Prostate Alignment with MV CBCTReference CT MV CBCT
50% BlendCT-MV CBCT
As fast, objective and less dose than EPID+markers,
Provides additional information - Volumetric info: Rectum, bladder, etc. - Prostate contours -> Dose recalculation
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Daily Prostate Alignment with MVCBCT
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Problems in concurrent IMRT treatment of prostate with pelvic lymph nodes: Independent movements of prostate vs nodes
ADAPTIVE STRATEGYfor Pelvic Nodal Irradiation in the Treatment of Prostate Cancer
Daily MVCBCT
1- CT-MVCBCT registered on bony structures: patient aligned accordingly2- CT-MVCBCT registered on gold markers
-> prostate shift is the difference between these two alignments
3- Select and treat with a (pre-calculated) plan according to prostate shift
Courtesy of Ping Xia, UCSF 2007AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Patient Setup: Prostate BedIrradiation of postprostatectomy patient
Markers are distinguished from surgical clips for daily alignment
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Hip ProsthesisComplementing CT with MVCBCT for planning purpose
MV CBCT
CT MVCBCT
Regular CT MVCB CT
� Make the target delineation difficult� Disturb the Hounsfield Number� Hide the gold markers on EPID
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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The MV CBCT images are particularly useful to help delineating:
• The anterior rectum wall.
• The lateral extension of the prostate in the median plane.
• The bladder neck
The prostate volume contoured with the help of MV CBCT was often smaller than what could be guessed from the regular CT in presence of artifacts, preventing overdosage of the rectum.
US News Magazine
“In 2005, in Europe and U.S., more than
500,000 hip joints have been replaced.”
The US Academy of Orthopedic Surgeon
Organ Segmentation with Hip Prosthesis
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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HDR Brachytherapyfor Prostate patient withBilateral Hip Prostheses
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
M. Descovich, ABS-2006,MVCBCT procedure for HDR Brachytherapy
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KVCT MVCBCT
X-ray film
H&N Patient with Dental Implants
6 M.U. ~ 3 cGy
MRI
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Paraspinous TumorsCase report
Surgery + supporting hardware + post-op IMRT Spinal cord tolerance limits Dx (palliative) Image hardware artifact
impairs target delineation hinders treatment verification
MV CBCT -> Target definition -> Daily 3D patient alignment -> Improved confidence Px (curative)
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Spinal cord delineation with MVCBCT registered to CT for planning purpose,for a patient with a metallic supporting structure
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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IGRT with MVCBCT of Paraspinous Tumorsin the Presence of Orthopedic Hardware
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Paraspinous Tumors: Patient SetupCase Report
Mean magnitude of setup errors:
- Lateral: 3.6 mm (95% C.I., 2.6-4.6 mm)
- Longitudinal: 4.1 mm (95% C.I., 3.2-5.0 mm)
- Vertical: 1.0 mm (95% C.I., 0.6-1.3 mm)
Daily Setup Errors (cm)
AAPM 2006, Session: CE: Daily Localization - EPID, MVCBCT, Jean Pouliot - U.C.S.F.
Hansen et al., Int. J. Radio. Biol. Phys. 2006, in press
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AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
Hypo-fractionated: 8 Gy x 5 fractionsLung Patient with non-small lung tumor treated with IMRT
Tumor position fairly stable on fluoroscopy
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Head and neck patient
Planning CT MV CBCT
Fusion
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Positioning: H&N Patients
Gillis, A., et al. IJROBP, Volume 63, 1 October 2005, Pages S351-S352
68% of the 2D and 3D isocenter shifts agree within 2mm
Overall, MV CBCT resulted in more clinical shifts than portal imaging
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Patient setup: Head & Neck
6 mm
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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DRREPID (1.M.U.) 50%/50%
Patient setup with EPID
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Anatomic Change: Weight Loss
Day 0 Day 24 Day 37
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Anatomic Changes
Day 1
Day 23
Bucci, K., Gillis, A., et al. IJROBP, Volume 63, October 2005, Pages S357-S358
Tumor shrinkage
Weight Loss
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Monitor Anatomical Changes
Is the initial plan still valid?When to replan?What is the dosimetrical impact?
Day 1 Day 23
3D rendering of CT 3D rendering of MV CBCT
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Dose Calculation with MVCBCT
Dose Calculation better than 3% and 3 mm
Morin et al., Dose Calculation using Megavoltage Cone-Beam CT,Int. J. Radiation Oncology Biol. Phys. 67(4),1202-1210; 2007.
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Comparing dose distributions
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Dosimetrical Impact of Weight Loss
Week 1 Week 3
Δ(%) >5% >10%
Differences in dose distribution due to anatomical changes
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Availability of theDose Distribution “of the Day”
Global quality assurance “in-vivo”e.g. Treatment documentation
More Precise (Delivered-)Dose Response vs Outcomes
Enables Dose-Guided Radiation Therapy:DGRT is an extension of ART where dosimetric considerations constitute the basis of treatment modification and validation.
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Description of MVCBCT Fan Beam vs Cone Beam Basic Principles and Characteristics Image Samples
Workflow of IGRT with MVCBCT Acquisition, Reconstruction & Registration Absolute Positioning & Alignment Presicion
Clinical Applications Patient positioning Monitoring of anatomical changes Target delineation with CT non-compatible
objects Tomosynthesis, Brachytherapy, etc. Dose calculation to assess dosimetrical
impact
Dose-Guided Radiation Therapy
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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MVCBCT1 MVCBCT2
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Dose Comparison
MVCBCT1 MVCBCT2
Right Parotid dose increased from 26 Gy to 42 Gy
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Day 1
Pt#3
Day 24
VD5+(%)
0
5
10
15
20
25
Wee
k 1
Wee
k 3
20
3
VD
5+
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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MV CBCT: Summary MVision is a reliable, fast and efficient IGRT tool
-> Has been used >3000 times on patients
Provide 3D anatomy of patient in treatment position-> Patient Setup-> Monitoring of anatomical changes-> Tumor evolution
Accurate electron density for dose calculation-> Assess dosimetric Impact-> Planning in presence of high-Z material
Allows dose re-calculation for DGRT
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Main Collaborators UCSF Michelle Aubin Jean-Francois Aubry Josephine Chen Hong Chen Cynthia Chuang Martina Descovich Bruce Faddegon Amy Gillis Alex Gottschalk Olivier Morin Mack Roach III Joycelyn Speight Lynn Verhey Ping Xia and several others...
Siemens• Ali Bani-Hashemi• Fahard Ghelmansarai• Paco Hernandez• Dimitre Histrov• Bijumon Gangadharan• Matthias Mitschke
This work is supportedby
Siemens O.C.S.
AAPM 2007, Session: CE: Daily Localization - MVCBCT, Jean Pouliot - U.C.S.F.
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Langen K., Meeks S.L. and Pouliot J., Quality Assurance of Onboard MV CT Imaging and Target Localization Systems for On- and Off-line Image Guided Radiation Therapy, Int. J. of Radiation Oncology, Biol, Phys. 2007, in press
Morin O, Gillis A, Chen J, et al. Patient Dose Considerations for Routine Megavoltage Cone-Beam CT IMaging. Med. Phys. 2007; 34, 1819-1827.
Morin O, Chen J, Aubin M, et al. Dose Calculation using Megavoltage Cone-Beam CT. Int J Radiat Oncol Biol Phys 2007; 67, 1201-1210.
Pouliot J., Aubin M., Aubry J.F., et. al. Megavoltage cone-beam CT: Récents développements et applications cliniques pour l’IMRT, Cancer et Radiothérapie, France, 10, 258-268 ; 2006.
Aubin M, Morin O, Chen J, et al. The use of Megavoltage Cone-Beam CT to complement CT for target definition in pelvic radiotherapy in presence of hip replacement. Br J Radiol 2006;79:918-921.
Hansen EK, Larson DA, Aubin M, et al. IGRT using MVCBCT for treatment of paraspinous tumors in the presence of orthopedic hardware. Int J Radiat Oncol Biol Phys 2006;66:323.
Morin O, Gillis A, Chen J, et al. Megavoltage Cone-Beam CT: system description and clinical applications. Med Dosim 2006;31:51-61.
Chen J, Morin O, Aubin M, et al. Dose-Guided Radiation Therapy using Megavoltage Cone-Beam CT. Br J Radiol 2006;79:S87-S98.
Pouliot J, Bani-Hashemi A, Chen J, et al. Low-dose megavoltage cone-beam CT for radiation therapy. Int J Radiat Oncol Biol Phys 2005;61:552-560.
References on MVCBCT