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1、Hippocampal Contouring:A Contouring Atlas for RTOG 0933Vinai Gondi,M.D.1Wolfgang A.Tome,Ph.D.1Howard A.Rowley,M.D.2Minesh P.Mehta,M.D.3Departments of 1Human Oncology and 2Neuroradiology,University of Wisconsin Comprehensive Cancer Center3Department of Radiation Oncology,Northwestern University Feinb
2、erg School of Medicine1MRI-CT FusionMRI:Three-dimensional spoiled gradient(3D-SPGR)axial MRI scan of the head with standard axial and coronal FLAIR,axial T2-weighted and gadolinium contrast-enhanced T1-weighted sequence acquisitions.1.25mm slice thickness is preferred to contour the hippocampus accu
3、rately.Slice thickness of 1.5mm or less is permitted.Obtain in supine position;immobilization devices used for CT simulation and daily radiation treatments not necessary.CT Simulation:Non-contrast treatment-planning CT scan of the entire head region.1.25-1.5mm slice thickness is preferred for accura
4、te hippocampal sparing planning.Slice thickness of 2.5mm or less is permitted.Immobilize patient in supine position using an immobilization device such as an Aquaplast mask over the head.Treat patients in the immobilization device.MRI-CT Fusion:Fuse the 3D-SPGR MRI and the treatment-planning CT.2Gen
5、eral Principles Please note that we are not contouring the entire hippocampus,but focusing mostly on the subgranular zone(SGZ)Contour the hippocampus on T1-weighted MRI axial sequences.Given the preponderance of gray matter in the hippocampus,focus contouring on the T1-hypointense signal medial to t
6、he temporal horn.3MR Images courtesy of:Holmes CJ,Hoge R,Collins L,et al.Enhancement of MR Images Using Registration for Signal Averaging Journal of Computer Assisted Tomography 22,324-333(1998)Red:HippocampusBegin contouring at the most caudal(inferior)extent of the crescentic-shaped floor of the t
7、emporal horn of the lateral ventricle and contour the hypointense grey matter located medial to the CSF hypointensity,not the white,bright white matter.4Temporal HornRed:HippocampusMR Images courtesy of:Holmes CJ,Hoge R,Collins L,et al.Enhancement of MR Images Using Registration for Signal Averaging
8、 Journal of Computer Assisted Tomography 22,324-333(1998)Fimbriae5Continue contouring in a cephalad(superior)direction,medial to the temporal horn of the lateral ventricle and contour the hypointense grey matter,not the white,bright white matter.Red:HippocampusMR Images courtesy of:Holmes CJ,Hoge R,
9、Collins L,et al.Enhancement of MR Images Using Registration for Signal Averaging Journal of Computer Assisted Tomography 22,324-333(1998)6Continue contouring in a cephalad(superior)direction.Avoid contouring the fimbriae,the T1-hyperintense structures located superomedial to the hippocampus.FimbriaR
10、ed:HippocampusMR Images courtesy of:Holmes CJ,Hoge R,Collins L,et al.Enhancement of MR Images Using Registration for Signal Averaging Journal of Computer Assisted Tomography 22,324-333(1998)7Continue contouring in a cephalad(superior)direction,medial to the temporal horn of the lateral ventricle and
11、 contour the hypointense grey matter,not the white,bright white matter.Note that the contours are progressively moving in a supero-posterior direction,keeping in line with the curved banana shaped structure of the hippocampus.Avoid the fimbriae and also avoid the grey matter(amygdala and uncus)locat
12、ed anterior to the tip of the temporal horn of the ventricles.Red:HippocampusMR Images courtesy of:Holmes CJ,Hoge R,Collins L,et al.Enhancement of MR Images Using Registration for Signal Averaging Journal of Computer Assisted Tomography 22,324-333(1998)8As contouring proceeds postero-cranially,the a
13、nterior boundary of the hippocampus is defined by the anterior edge of the temporal horn,to distinguish the hippocampus from the T1-hypointense gray matter of the amygdala,lying anterior and superior to the hippocampus.The medial boundary of the hippocampus is defined by the“boomerang-shaped”uncusAm
14、ygdala UncusRed:HippocampusMR Images courtesy of:Holmes CJ,Hoge R,Collins L,et al.Enhancement of MR Images Using Registration for Signal Averaging Journal of Computer Assisted Tomography 22,324-333(1998)9Uncal RecessUncal RecessContinue contouring in a cephalad(superior)direction,medial to the tempo
15、ral horn of the lateral ventricle and contour only the hypointense grey matter,not the white,bright white matter.Continue to avoid the fimbriae and also avoid the grey matter(amygdala and uncus)located anterior to the tip of the temporal horn of the ventricles.Red:HippocampusMR Images courtesy of:Ho
16、lmes CJ,Hoge R,Collins L,et al.Enhancement of MR Images Using Registration for Signal Averaging Journal of Computer Assisted Tomography 22,324-333(1998)The emergence of the uncal recess of the temporal horn defines the anterior boundary of the hippocampus.This may not be seen on all axial image sets due to its limited size.The medial boundary of the hippocampus becomes defined by the medial edge of the uncal recess.10Medial edge of Uncal RecessUncal recessRed:HippocampusMR Images courtesy of:Hol
