IMRT: Improvement in treatment planning efficiency using NTCP calculation independent of the dose-volume-histogram

Journal Article · Mon May 15 04:00:00 EDT 2006 · Medical Physics

DOI:https://doi.org/10.1118/1.2181301· OSTI ID:20775196

Grigorov, Grigor N; Chow, James C.L.; Grigorov, Lenko; Jiang, Runqing; Barnett, Rob B ^[1]

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1. Medical Physics Department, Grand River Regional Cancer Centre, 835 King Street West, N2G 1G3, Kitchener, ON (Canada)

The normal tissue complication probability (NTCP) is a predictor of radiobiological effect for organs at risk (OAR). The calculation of the NTCP is based on the dose-volume-histogram (DVH) which is generated by the treatment planning system after calculation of the 3D dose distribution. Including the NTCP in the objective function for intensity modulated radiation therapy (IMRT) plan optimization would make the planning more effective in reducing the postradiation effects. However, doing so would lengthen the total planning time. The purpose of this work is to establish a method for NTCP determination, independent of a DVH calculation, as a quality assurance check and also as a mean of improving the treatment planning efficiency. In the study, the CTs of ten randomly selected prostate patients were used. IMRT optimization was performed with a PINNACLE3 V 6.2b planning system, using planning target volume (PTV) with margins in the range of 2 to 10 mm. The DVH control points of the PTV and OAR were adapted from the prescriptions of Radiation Therapy Oncology Group protocol P-0126 for an escalated prescribed dose of 82 Gy. This paper presents a new model for the determination of the rectal NTCP ({sub R}NTCP). The method uses a special function, named GVN (from Gy, Volume, NTCP), which describes the {sub R}NTCP if 1 cm{sup 3} of the volume of intersection of the PTV and rectum (R{sub int}) is irradiated uniformly by a dose of 1 Gy. The function was 'geometrically' normalized using a prostate-prostate ratio (PPR) of the patients' prostates. A correction of the {sub R}NTCP for different prescribed doses, ranging from 70 to 82 Gy, was employed in our model. The argument of the normalized function is the R{sub int}, and parameters are the prescribed dose, prostate volume, PTV margin, and PPR. The {sub R}NTCPs of another group of patients were calculated by the new method and the resulting difference was <{+-}5% in comparison to the NTCP calculated by the PINNACLE3 software where Kutcher's dose-response model for NTCP calculation is adopted.

• OSTI ID: 20775196
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 5 Vol. 33; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
COMPUTER CODES
DOSIMETRY
EFFICIENCY
OPTIMIZATION
PATIENTS
PLANNING
PROBABILITY
PROSTATE
QUALITY ASSURANCE
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOTHERAPY
RECTUM