TY - JOUR
T1 - The effect of the number of computed tomographic slices on dose distributions and evaluation of treatment planning systems for radiation therapy of intact breast
AU - Cheng, Chee Wai
AU - Das, Indra J.
AU - Stea, Baldassarre
PY - 1994/8/30
Y1 - 1994/8/30
N2 - Purpose: This study was undertaken to answer the following questions in breast irradiation: (a) How many calculation planes are sufficient for three-dimensional (3-D) treatment planning? (b) Is pseudo-3-D planning system sufficiently accurate for 3-D treatment planning of a breast? Methods and Materials: We carried out dose calculations and differential dose-volume analysis on three representative patients covering the range of breast size encountered in a clinic. The breast volumes were reconstructed from computed tomography (CT) scans using three slices, five slices and the full CT scan respectively. An established 3-D dose algorithm and two pseudo-3-D commercial systems were used in the calculations. Comparison of isodose distributions were made between the central axis plane, a cephalic and a caudal plane 6 cm above or below the central axis respectively. Results: When comparing isodose distributions generated with conventional two-dimensional treatment planning with 3-D dose calculations, the former underestimated the size and magnitude of the hot spots in the medial and the lateral subcutaneous (SC) regions. When comparing the three-slice with the full CT model, while the three-slice model was found to be adequate for the "small" and the "medium" size patients, the full CT model provided a more accurate representation of dose distributions for the "large" patient. Comparison of a true 3-D algorithm with pseudo-3-D algorithms showed that while the latter systems were adequate for the "small" and the "medium" patients, significant differences were noted between the true 3-D and the pseudo-3-D algorithms for the "large" patient. Conclusion: For patients whose breast contours vary slowly within the tangential fields, a three-slice CT scan as well as a pseudo-3-1) approach appears to be adequate for clinical decision. However, for patients with large variation of contours within the tangential fields, a full scale CT scan with a true 3-D dose algorithm is more accurate than either the three-slice or the five-slice model.
AB - Purpose: This study was undertaken to answer the following questions in breast irradiation: (a) How many calculation planes are sufficient for three-dimensional (3-D) treatment planning? (b) Is pseudo-3-D planning system sufficiently accurate for 3-D treatment planning of a breast? Methods and Materials: We carried out dose calculations and differential dose-volume analysis on three representative patients covering the range of breast size encountered in a clinic. The breast volumes were reconstructed from computed tomography (CT) scans using three slices, five slices and the full CT scan respectively. An established 3-D dose algorithm and two pseudo-3-D commercial systems were used in the calculations. Comparison of isodose distributions were made between the central axis plane, a cephalic and a caudal plane 6 cm above or below the central axis respectively. Results: When comparing isodose distributions generated with conventional two-dimensional treatment planning with 3-D dose calculations, the former underestimated the size and magnitude of the hot spots in the medial and the lateral subcutaneous (SC) regions. When comparing the three-slice with the full CT model, while the three-slice model was found to be adequate for the "small" and the "medium" size patients, the full CT model provided a more accurate representation of dose distributions for the "large" patient. Comparison of a true 3-D algorithm with pseudo-3-D algorithms showed that while the latter systems were adequate for the "small" and the "medium" patients, significant differences were noted between the true 3-D and the pseudo-3-D algorithms for the "large" patient. Conclusion: For patients whose breast contours vary slowly within the tangential fields, a three-slice CT scan as well as a pseudo-3-1) approach appears to be adequate for clinical decision. However, for patients with large variation of contours within the tangential fields, a full scale CT scan with a true 3-D dose algorithm is more accurate than either the three-slice or the five-slice model.
KW - Breast
KW - Computed tomography
KW - Dose volume histogram
KW - Three-dimensional
KW - Treatment planning
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U2 - 10.1016/0360-3016(94)90534-7
DO - 10.1016/0360-3016(94)90534-7
M3 - Article
C2 - 8083113
AN - SCOPUS:0027991507
SN - 0360-3016
VL - 30
SP - 183
EP - 195
JO - International Journal of Radiation Oncology, Biology, Physics
JF - International Journal of Radiation Oncology, Biology, Physics
IS - 1
ER -