Subtraction Fusion With Prior Images Helps Identify Additional Brain Metastases for Repeat RadiosurgeryKeywords: brain metastasis, brain tumor, gamma knife, radiosurgery, ImagingInteractive Manuscript
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What is the background behind your study?
Identification of all brain metastases present on planning stereotactic images is necessary to optimize control of brain metastases and limit the need for additional radiosurgery or radiotherapy to the brain.
What is the purpose of your study?
We hypothesized that subtraction fusion of new minus old
high-resolution stereotactic contrast enhanced magnetic resonance (MR)
images of brain metastasis patients for radiosurgery planning would
improve detection of small brain metastases.
Describe your patient group.
We studied 75 patients with 1-6 (median = 1) prior brain metastasis
radiosurgery procedures to 1-55 metastases (median = 4) at the time of
subsequent radiosurgery to 1-26 metastases (median= 4).
Describe what you did.
Prior high-resolution stereotactic contrast enhanced MR images were co-registered with new images to identify and outline all prior radiosurgery treatment volumes. All new brain metastases were outlined after review by at least one attending Neurosurgeon, one attending Radiation Oncologist and one Medical Physicist. Subtraction-fusion (new minus latest prior) images were constructed and reviewed to see if additional brain metastases could be identified. Two patients had two prior courses of whole-brain (WB) radiotherapy (XRT), 21 patients had one. 51 had none and one had partial brain XRT. The median interval since the latest prior radiosurgery imaging was 6 months (range: 2-29).
Describe your main findings.
Without the subtraction-fusion imaging 0-29 (median=3) new metastases were identified (3 patients had radiosurgery only to retreat metastases). After review of the subtraction-fusion (new-old) MR-images 16/75 (21 %) of patients had 1-5 additional brain metastases identified, measuring 3-176 cu-mm (median, 15 cu-mm, n=23). Stepwise linear-regression correlated increasing numbers of additional brain metastases identified by subtraction fusion with the total number of new and previously identified brain metastases (p=0.001) and prior WB-XRT (p=0.017). Logistic regression correlated an increasing rate of detecting any additional metastases by subtraction fusion with the number of previously identified brain metastases (p=0.029).
Describe the main limitation of this study.
This was a retrospective review.
Describe your main conclusion.
Subtraction-fusion of new minus prior contrast-enhanced high-resolution MR images appears to help identify additional brain metastases for radiosurgery planning, particularly with in patients with greater numbers of brain metastases.
Describe the importance of your findings and how they can be used by others.
The findings of this study show that subtraction imaging can affect dose planning.
Identification of all brain metastases present on planning stereotactic images is necessary to optimize control of brain metastases and limit the need for additional radiosurgery or radiotherapy to the brain.
We hypothesized that subtraction fusion of new minus old
high-resolution stereotactic contrast enhanced magnetic resonance (MR)
images of brain metastasis patients for radiosurgery planning would
improve detection of small brain metastases.
We studied 75 patients with 1-6 (median = 1) prior brain metastasis
radiosurgery procedures to 1-55 metastases (median = 4) at the time of
subsequent radiosurgery to 1-26 metastases (median= 4).
Prior high-resolution stereotactic contrast enhanced MR images were co-registered with new images to identify and outline all prior radiosurgery treatment volumes. All new brain metastases were outlined after review by at least one attending Neurosurgeon, one attending Radiation Oncologist and one Medical Physicist. Subtraction-fusion (new minus latest prior) images were constructed and reviewed to see if additional brain metastases could be identified. Two patients had two prior courses of whole-brain (WB) radiotherapy (XRT), 21 patients had one. 51 had none and one had partial brain XRT. The median interval since the latest prior radiosurgery imaging was 6 months (range: 2-29).
Without the subtraction-fusion imaging 0-29 (median=3) new metastases were identified (3 patients had radiosurgery only to retreat metastases). After review of the subtraction-fusion (new-old) MR-images 16/75 (21 %) of patients had 1-5 additional brain metastases identified, measuring 3-176 cu-mm (median, 15 cu-mm, n=23). Stepwise linear-regression correlated increasing numbers of additional brain metastases identified by subtraction fusion with the total number of new and previously identified brain metastases (p=0.001) and prior WB-XRT (p=0.017). Logistic regression correlated an increasing rate of detecting any additional metastases by subtraction fusion with the number of previously identified brain metastases (p=0.029).
This was a retrospective review.
Subtraction-fusion of new minus prior contrast-enhanced high-resolution MR images appears to help identify additional brain metastases for radiosurgery planning, particularly with in patients with greater numbers of brain metastases.
The findings of this study show that subtraction imaging can affect dose planning.
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