The Effect of Dose Grid Resolution on Dose Volume Histograms for Slender Organs at Risk during Pelvic Intensity-modulated Radiotherapy
| Autor: | Vickie Kong, Geoffrey M. Currie, Michael Milosevic, Tara Rosewall, Robert K. Heaton, Janelle Wheat |
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| Rok vydání: | 2014 |
| Předmět: |
Radiological and Ultrasound Technology
business.industry medicine.medical_treatment Resolution (electron density) Grid Radiation therapy medicine.anatomical_structure Prostate Histogram Medicine Radiology Nuclear Medicine and imaging Intensity modulated radiotherapy Radiation treatment planning Nuclear medicine business Volume (compression) |
| Zdroj: | Journal of Medical Imaging and Radiation Sciences. 45:204-209 |
| ISSN: | 1939-8654 |
| Popis: | Purpose There are enduring uncertainties regarding the optimal dose grid resolution for use with pelvic intensity-modulated radiotherapy (IMRT) plans in which the adjacent organs at risk are slender and transect the field edge. Therefore, this study evaluated the effect of dose grid resolution on bladder wall dose-volume histogram (DVH) calculations for prostate IMRT plans. Materials and Methods The planning computed tomography scans and clinical plans from 15 prostate cancer patients were included in this analysis. For each study computed tomography, the entire inner and outer bladder surfaces were delineated. Nine versions of the clinical plan were created, varying interval between the dose grid calculation points uniformly in three dimensions, whereas all other plan parameters were kept constant. The dose grid increments tested were 1–10 mm. The plans were recalculated and the bladder wall DVH compared against the study benchmark (1 mm grid). Results All the dose grid increments evaluated resulted in a systematic overestimation of the bladder wall volume receiving low doses and an underestimation of the volume receiving high doses. Grid increments 5.0 mm resulted in mean volume differences greater than 2 cm3. Individual patient analysis revealed that only the 1.5 mm increment resulted in maximum volume differences ≤1 cm3 for every patient across the full length of the DVH curve. Bladder wall thickness ranged from 1.7 to 4.4 mm and displayed no correlation with the magnitude of the dose grid effect. Conclusions For an accurate DVH calculation for bladder wall during IMRT planning for prostate cancer, a 1.5 mm dose grid increment is recommended. This finding was unaffected by a normal range in bladder wall thickness. It is suggested that the application of any new treatment planning technique or organ delineation method be accompanied with an evaluation of optimal dose grid resolution. |
| Databáze: | OpenAIRE |
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