Abstract
Background and PurposeThis study aimed to quantify the differences between pre- and post-contrast agent (CA) CT for CyberKnife brain SRS plans.Materials and MethodsTwenty-five patients were retrospectively analyzed. They were divided into two categories, inhomogeneous cases (13 patients) and homogeneous cases (12 patients), according to whether the tumor was close to the cavity and inhomogeneous tissues or not. The pre-CA and post-CA plans were designed and calculated using the same monitor unit and paths as those in the ray-tracing algorithm, respectively.ResultsThe CT number difference of tumor between pre- and post-CA was significant (on average, 24.78 ± 18.56 HU, P-value < 0.01). The deviation value of the target was the largest at approximately 37 HU (inhomo-) and 13 HU (homo-) (P < 0.01), and the values of the organs at risk (OARs) were not statistically significant (P-value > 0.05). However, it was not statistically significant for the dose difference between the two groups with the injection of CA (P-value > 0.05). The absolute effective depth difference generally remained at a level of 1 mm, but the dose difference was quitely fluctuated sometimes more than 20%. The absolute effective depth difference of the inhomo-case (0.62 mm) was larger than that of the homo-case (0.37 mm) on median, as well as the variation amplitude (P-value < 0.05). Moreover, the relative dose differences between the two cases were 0.38% (inhomo-) and 0.2% (homo-), respectively (P-value < 0.05). At the criterion of 1 mm/1%, the gamma pass rate of the homo-case (95.89%) was larger than that of the inhomo-case (93.79%). For the OARs, except for the cochlea, the two cases were almost the same (>98.85%). The tumor control probability of the target was over 99.99% before and after injection of a CA, as well as the results for the homo-case and inhomo-case.ConclusionsConsidering the difference of evaluation indexes between pre- and post-CA images, we recommended plain CT to be employed as the primary image for improving the CK treatment accuracy of brain SRS, especially when the target was close to CA-sensitive OARs and cavity.
Highlights
Stereotactic radiosurgery (SRS), such as single-fraction or hypofractionated cranial radiosurgery, is commonly used to treat various primary and metastatic brain tumors [1]
According to whether the tumor was close to the cavity anatomical structure or not, the patients were dichotomized into homo-case and inhomo-case
The deviation value of the target was largest at approximately 37 Hounsfield unit (HU) and 13 HU (P < 0.05), and the values of the organ at risk (OAR) were not statistically significant (P-value > 0.05)
Summary
Stereotactic radiosurgery (SRS), such as single-fraction or hypofractionated (two to five fractions) cranial radiosurgery, is commonly used to treat various primary and metastatic brain tumors [1]. Unlike other treatment planning systems (TPS), MultiPlan needs to select only one of the CT scans as the primary image on which the 3D dose distribution is calculated. The delineation error caused by the limitation of the MultiPlan, to some degree, is reduced This has the potential to improve outcomes via disease control and to increase safety. The aim of this paper is to quantify the difference between pre-CA and post-CA brain SRS radiosurgery treatment plan, supplying evidence whether enhanced CT can be used to calculate the dose. This paper on brain tumors sought, for homo- and inhomo-cases between pre-CA and post-CA the following:. This study aimed to quantify the differences between preand post-contrast agent (CA) CT for CyberKnife brain SRS plans
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