The Actual Whole Brain Dose Measurement Under The Protocol Of Limiting The Skull Dose To 12 JKeywords: gamma knife, radiosurgery, brain metastasis, Radiation Therapy, dose deliveryInteractive Manuscript
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What is the background behind your study?
The safe skull dose is considered 10-12J that is equivalent to 3Gy of whole brain radiation. However, the cumulative irradiation dose to the whole brain (WB dose) under this protocol has not been measured in the common Gamma knife (GK) planning.
What is the purpose of your study?
We studied the difference between the WB dose and the skull dose, and estimated the dose distribution on the normal brain about all procedures.
Describe your patient group.
Among 89 patients (96 procedures) who underwent GK surgery between January 2009 and October 2009, 82 patients (89 procedures) could have the WB CT or MRI images.
Describe what you did.
The skull dose in all procedures was under 12 J. In all procedures taken the WB images, the WB dose was computed using a Gamma Plan. The cases of brain metastasis were studied in detail because of the possibility of the re-treatment.
Describe your main findings.
The mean skull dose was 3.9 (range 0.5-11.2) J. The mean WB dose was 2.7 (range 0.3-7.0) J. The mean proportion of the WB dose to the skull dose was 0.57(range 0.28-0.75). In the cases of brain metastasis (52 procedures), the mean numbers of tumors were 6 (range 1-32), the mean total volume of all tumors was 7.7 (range 0.05-26.5) cc, and the mean WB dose was 2.69(range 0.28-6.41) J. The mean proportion of the WB dose to the skull dose was 0.56 (range 0.28-0.64). The mean proportion of volumes receiving >3Gy, >6Gy, >10Gy in the WB was 19.5 (range 0.2-86.2) %., 5.8 (0.1-21.7) %, 1.9 (range 0.0-7.9) %. In cases (8 procedures) with more than 10 (range 12-32) tumors, the mean WB dose was 5.4 (range 3.68-6.41) J.
Describe the main limitation of this study.
This is a retrospective study.
Describe your main conclusion.
This result assures that the effect of GK to the normal brain is low under this protocol.
Describe the importance of your findings and how they can be used by others.
It may be said that repeated GK could be performed with small risk.
The safe skull dose is considered 10-12J that is equivalent to 3Gy of whole brain radiation. However, the cumulative irradiation dose to the whole brain (WB dose) under this protocol has not been measured in the common Gamma knife (GK) planning.
We studied the difference between the WB dose and the skull dose, and estimated the dose distribution on the normal brain about all procedures.
Among 89 patients (96 procedures) who underwent GK surgery between January 2009 and October 2009, 82 patients (89 procedures) could have the WB CT or MRI images.
The skull dose in all procedures was under 12 J. In all procedures taken the WB images, the WB dose was computed using a Gamma Plan. The cases of brain metastasis were studied in detail because of the possibility of the re-treatment.
The mean skull dose was 3.9 (range 0.5-11.2) J. The mean WB dose was 2.7 (range 0.3-7.0) J. The mean proportion of the WB dose to the skull dose was 0.57(range 0.28-0.75). In the cases of brain metastasis (52 procedures), the mean numbers of tumors were 6 (range 1-32), the mean total volume of all tumors was 7.7 (range 0.05-26.5) cc, and the mean WB dose was 2.69(range 0.28-6.41) J. The mean proportion of the WB dose to the skull dose was 0.56 (range 0.28-0.64). The mean proportion of volumes receiving >3Gy, >6Gy, >10Gy in the WB was 19.5 (range 0.2-86.2) %., 5.8 (0.1-21.7) %, 1.9 (range 0.0-7.9) %. In cases (8 procedures) with more than 10 (range 12-32) tumors, the mean WB dose was 5.4 (range 3.68-6.41) J.
This is a retrospective study.
This result assures that the effect of GK to the normal brain is low under this protocol.
It may be said that repeated GK could be performed with small risk.
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