Log-file analysis of accuracy of beam localization for brain tumor treatment by CyberKnife

Robust and optimal dose distribution for brain metastases with robotic radiosurgery system: recipe for an inflection point

Purpose.This study aims to establish a robust dose prescription methodology in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) for brain metastases, considering geometrical uncertainty and minimising dose exposure to the surrounding normal brain tissue.Methods and Materials.Treatment plans employing 40%-90% isodose lines (IDL) at 10% IDL intervals were created for variously sized brain metastases. The plans were constructed to deliver 21 Gy in SRS. Robustness of each plan was analysed using parameters such as the near minimum dose to the tumour, the near maximum dose to the normal brain, and the volume of normal brain irradiated above 14 Gy.Results.Plans prescribed at 60% IDL demonstrated the least variation in the near minimum dose to the tumour and the near maximum dose to the normal brain under conditions of minimal geometrical uncertainty relative to tumour radius. When the IDL-percentage prescription was below 60%, geometrical uncertainties led to increases in these doses. Conversely, they decreased with IDL-percentage prescriptions above 60%. The volume of normal brain irradiated above 14 Gy was lowest at 60% IDL, regardless of geometrical uncertainty.Conclusions.To enhance robustness against geometrical uncertainty and to better spare healthy brain tissue, a 60% IDL prescription is recommended in SRS and SRT for brain metastases using a robotic radiosurgery system.

Dosimetric comparison of fractionated radiosurgery plans using frameless Gamma Knife ICON and CyberKnife systems with linear accelerator–based radiosurgery plans for multiple large brain metastases

OBJECTIVE

For patients with multiple large brain metastases with at least 1 target volume larger than 10 cm3, multifractionated stereotactic radiosurgery (MF-SRS) has commonly been delivered with a linear accelerator (LINAC). Recent advances of Gamma Knife (GK) units with kilovolt cone-beam CT and CyberKnife (CK) units with multileaf collimators also make them attractive choices. The purpose of this study was to compare the dosimetry of MF-SRS plans deliverable on GK, CK, and LINAC and to discuss related clinical issues.

METHODS

Ten patients with 2 or more large brain metastases who had been treated with MF-SRS on LINAC were identified. The median planning target volume was 18.31 cm3 (mean 21.31 cm3, range 3.42–49.97 cm3), and the median prescribed dose was 27.0 Gy (mean 26.7 Gy, range 21–30 Gy), administered in 3 to 5 fractions. Clinical LINAC treatment plans were generated using inverse planning with intensity modulation on a Pinnacle treatment planning system (version 9.10) for the Varian TrueBeam STx system. GK and CK planning were retrospectively performed using Leksell GammaPlan version 10.1 and Accuray Precision version 1.1.0.0 for the CK M6 system. Tumor coverage, Paddick conformity index (CI), gradient index (GI), and normal brain tissue receiving 4, 12, and 20 Gy were used to compare plan quality. Net beam-on time and approximate planning time were also collected for all cases.

RESULTS

Plans from all 3 modalities satisfied clinical requirements in target coverage and normal tissue sparing. The mean CI was comparable (0.79, 0.78, and 0.76) for the GK, CK, and LINAC plans. The mean GI was 3.1 for both the GK and the CK plans, whereas the mean GI of the LINAC plans was 4.1. The lower GI of the GK and CK plans would have resulted in significantly lower normal brain volumes receiving a medium or high dose. On average, GK and CK plans spared the normal brain volume receiving at least 12 Gy and 20 Gy by approximately 20% in comparison with the LINAC plans. However, the mean beam-on time of GK (∼ 64 minutes assuming a dose rate of 2.5 Gy/minute) plans was significantly longer than that of CK (∼ 31 minutes) or LINAC (∼ 4 minutes) plans.

CONCLUSIONS

All 3 modalities are capable of treating multiple large brain lesions with MF-SRS. GK has the most flexible workflow and excellent dosimetry, but could be limited by the treatment time. CK has dosimetry comparable to that of GK with a consistent treatment time of approximately 30 minutes. LINAC has a much shorter treatment time, but residual rotational error could be a concern.

Effect of testosterone on the expression of PPARγ mRNA in PCOS patients

Expression of peroxisome proliferator-activated receptor γ (PPARγ) mRNA in ovarian granulosa cells of patients with polycystic ovary syndrome (PCOS) were explored. Ovarian granulosa cells were extracted from 5 patients with PCOS and 30 normal controls. Expression of PPARγ mRNA in granulosa cells of the 5 PCOS patients (observation group) and 5 normal controls (control group) was detected by RT-qPCR. The remaining 25 cases of normal human ovarian granulosa cells were cultured in vitro for 48 h, followed by cell culture for another 24 h with different concentrations of testosterone, insulin (INS), and rosiglitazone (RGZ). After that, expression of PPARγ mRNA was detected by RT-qPCR. Relative expression level of PPARγ mRNA in the observation group was significantly lower than that in the control group. Compared with testosterone concentration at 10-2 mol/ml, testosterone concentration at 10-3 mol/ml significantly reduced the expression level of PPARγ mRNA. When the INS concentration was 10-5 mol/ml, relative expression level of PPARγ mRNA was significantly higher than that of the control group (P<0.01). Relative expression level of PPARγ mRNA was significantly higher than that of the control group when INS concentration was 10-4 mol/ml. When the concentration of RGZ was 10-4 mol/ml, the relative expression level of PPARγ mRNA was significantly higher than that of the control group (P<0.01). When concentration of RGZ was 10-3 mol/ml, expression level of PPARγ mRNA was significantly increased comparing to that under a RGZ concentration of 10-4 mol/ml or that of the control group (P<0.01). Appropriate concentrations of testosterone can inhibit the expression of PPARγ mRNA in ovarian granulosa cells, and certain concentrations of INS and RGZ can induce the expression of PPARγ mRNA in ovarian granulosa cells. Abnormal expression of PPARγ mRNA in ovarian granulosa cells may be related to the mechanism of PCOS.