Dataset Information

Operation and calibration of the novel PTW 1600SRS detector for the verification of single isocenter stereotactic radiosurgery treatments of multiple small brain metastases.

ABSTRACT:

Objectives

The aim of this work was to evaluate the operation of the 1600SRS detector and to develop a calibration procedure for verifying the dose delivered by a single isocenter stereotactic radiosurgery (SRS) treatment of small multiple brain metastases (BM).

Methods

14 clinical treatment cases were selected with the number of BM ranging from 2 to 11. The dosimetric agreement was investigated between the calculated and the measured dose by an OCTAVIUS 1600SRS array detector in an OCTAVIUS 4D phantom equipped with dedicated SRS top. The cross-calibration procedure deviated from the manufacturer's as it applied field sizes and dose rates corresponding to the volumetric modulated arc therapy segments in each plan.

Results

Measurements with a plan specific cross-calibration showed mean ± standard deviation (SD) agreement scores for cut-off values 50%, 80%, 95%, of 98.6 ± 1.7%, 96.5 ± 4.6%, 97.3 ± 4.4% for the 6 MV plans respectively, and 98.6 ± 1.5%, 96.6 ± 4.0% 96.4 ± 6.3%, for the 6 MV flattening filter free (FFF) plans respectively. Using the default calibration procedure instead of the plan specific calibration could lead to a combined systematic dose offset of 4.1% for our treatment plans.

Conclusion

The 1600SRS detector array with the 4D phantom offers an accurate solution to perform routine quality assurance measurements of single isocenter SRS treatments of multiple BM. This work points out the necessity of an adapted cross-calibration procedure.

Advances in knowledge

A dedicated calibration procedure enables accurate dosimetry with the 1600SRS detector for small field single isocenter SRS treatment of multiple brain metastases for a large amount of BM.

SUBMITTER: Decabooter E

PROVIDER: S-EPMC8248213 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Introduction:Due to the neurocognitive side effects of whole brain radiation therapy (WBRT), stereotactic radiosurgery (SRS) is being used with increasing frequency. The use of SRS is expanding for patients with multiple (>4) brain metastases (BM). This study summarizes our institutional experience with single-fraction, linear-accelerator-based SRS for multiple BM. Methods and materials:All patients who were treated between January 1, 2013, and September 30, 2015, with single-fraction SRS for ?4 BM were included in this institutional review board-approved, retrospective, single-institution study. Patients were treated with linear accelerator-based image guided SRS. Results:A total of 59 patients with ?4 BM were treated with single-fraction SRS. The median follow-up was 15.2 months, and the median overall survival for the entire cohort was 5.8 months. The median number of treated lesions per patient was 5 (range, 4-23). Per patient, the median planning target volume (PTV) was 4.8?cc (range, 0.7-28.8?cc). The prescribed dose across all 380 BM for the 59 patients ranged from 7 to 20?Gy. The median of the mean dose to the total PTV was 19.5?Gy. Although the number of treated lesions (4-5 vs ?6) did not influence survival, better survival was noted for a total PTV <10?cc versus ?10?cc (7.1 vs 4.2 months, respectively; P?=?.0001). A mean dose of ?19?Gy to the entire PTV was also associated with increased survival (6.6 vs 5.0 months, respectively; P?=?.0172). Patients receiving a dose of >12?Gy to ?10?cc of normal brain had worse survival (5.1 vs 8.6 months, respectively; P?=?.0028). Conclusion:In single-fraction SRS for patients with multiple BM, smaller total tumor volume, higher total dose, and lower volume of normal brain receiving >12?Gy were associated with increased survival. These data suggest that using SRS for the treatment of multiple BM is efficacious and that outcomes may be affected more by total tumor volume than by the number of lesions.