Dosimetric feasibility of an “off-target isocenter” technique for cranial intensity-modulated radiosurgery

Journal Article · Thu Jan 01 04:00:00 EST 2015 · Medical Dosimetry

DOI:https://doi.org/10.1016/J.MEDDOS.2015.02.003· OSTI ID:22577837

Moragues, Sandra; Pozo, Miquel; Delgado, David; Casals, Joan

To evaluate the dosimetric effect of placing the isocenter away from the planning target volume (PTV) on intensity-modulated radiosurgery (IMRS) plans to treat brain lesions. A total of 15 patients who received cranial IMRS at our institution were randomly selected. Each patient was treated with an IMRS plan designed with the isocenter located at the target center (plan A). A second off-target isocenter plan (plan B) was generated for each case. In all the plans,100% of the prescription dose covered 99% of the target volume. The plans A and B were compared for the target dosage (conformity index [CI] and homogeneity index) and organs-at-risk (OAR) dose sparing. Peripheral dose falloff was compared by using the metrics volume of normal brain receiving more than 12-Gy dose (V12) and CI at the level of the 50% of the prescription dose (CI 50%). The values found for each metric (plan B vs plan A) were (mean ± standard deviation [SD]) as follows—CI: 1.28 ± 0.15 vs 1.28 ± 0.15, p = 0.978; homogeneity index (HI): 1.29 ± 0.14 vs 1.34 ± 0.17, p = 0.079; maximum dose to the brainstem: 2.95 ± 2.11 vs 2.89 ± 1.88 Gy, p = 0.813; maximum dose to the optical pathway: 2.65 ± 4.18 vs 2.44 ± 4.03 Gy, p = 0.195; and maximum dose to the eye lens: 0.33 ± 0.73 vs 0.33 ± 0.53 Gy, p = 0.970. The values of the peripheral dose falloff were (plan B vs plan A) as follows—V12: 5.98 ± 4.95 vs 6.06 ± 4.92 cm{sup 3}, p = 0.622, and CI 50%: 6.08 ± 2.77 vs 6.28 ± 3.01, p = 0.119. The off-target isocenter solution resulted in dosimetrically comparable plans as the center-target isocenter technique, by avoiding the risk of gantry-couch collision during the cone beam computed tomography (CBCT) acquisition.

• OSTI ID: 22577837
• Journal Information: Medical Dosimetry, Journal Name: Medical Dosimetry Journal Issue: 4 Vol. 40; ISSN 0958-3947
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
62 RADIOLOGY AND NUCLEAR MEDICINE
BRAIN
COMPARATIVE EVALUATIONS
COMPUTERIZED TOMOGRAPHY
CRYSTALLINE LENS
HAZARDS
PATIENTS
PLANNING
RADIATION DOSES
RADIOTHERAPY
SURGERY