The document provides guidance on contouring the hippocampus on MRI images for radiation treatment planning. It describes in detail how to contour each section of the hippocampus - the head, body, and tail - on axial MRI slices from inferior to superior. Landmarks used to define the boundaries include the temporal horn of the lateral ventricle, uncal recess, quadrigeminal cistern, and atrium of the lateral ventricle. A 5mm expansion of the hippocampus contour is used to create the hippocampal avoidance zone.

1. TARGET DELINEATION OF
HIPPOCAMPUS
DR KANHU CHARAN PATRO
MD,DNB(Radiation Oncology),MBA,FICRO,FAROI(USA),PDCR,CEPC
HOD,RADIATION ONCOLOGY
Mahatma Gandhi Cancer Hospital And Research Institute, Visakhapatnam
drkcpatro@gmail.com /M- +91-9160470564 1

2. Hippocampal Contouring:
A Contouring Atlas for RTOG 0933
Vinai Gondi, M.D.1
Wolfgang A. Tome, Ph.D. 1
Howard A. Rowley, M.D.2
Minesh P. Mehta, M.D. 3
Departments of 1Human Oncology and 2Neuroradiology, University of
Wisconsin Comprehensive Cancer Center
3Department of Radiation Oncology, Northwestern University Feinberg
School of Medicine 2

3. HA WBRT
VINAI GONDI PAUL D BROWN
3

4. 4

5. 5

6. MRI-CT Fusion
• MRI:
– (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
accurately. 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 accurate 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. 6

7. General 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 the temporal horn.
7

8. MR 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: Hippocampus
Begin contouring at the most caudal (inferior) extent of the crescentic-shaped floor of the
temporal horn of the lateral ventricle and contour the hypointense grey matter located medial to
the CSF hypointensity, not the white, bright white matter.
8
Temporal Horn

9. Red: Hippocampus
MR 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)
Fimbriae
9
Continue 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.

10. Red: Hippocampus
MR 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)
10
Continue contouring in a cephalad (superior) direction. Avoid contouring the fimbriae, the T1-
hyperintense structures located superomedial to the hippocampus.
Fimbria

11. Red: Hippocampus
MR 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)
11
Continue 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. 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) located anterior to the tip of the temporal horn of the ventricles.

12. Red: Hippocampus
MR 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)
12
As contouring proceeds postero-cranially, the anterior 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” uncus
Amygdala Uncus

13. Red: Hippocampus
MR 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)
13
Uncal
Recess
Uncal
Recess
Continue contouring in a cephalad (superior) direction, medial to the temporal 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.

14. Red: Hippocampus
MR 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)
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.
14
Medial edge of
Uncal Recess
Uncal recess

15. Red: Hippocampus
MR 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)
15
Continue contouring in a cephalad (superior) direction, medial to the temporal 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.

16. Red: Hippocampus
MR 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)
Postero-cranially, the medial boundary of the hippocampus is defined by the lateral edge of the
quadrageminal cistern which is the CSF containing space lateral to the pons.
16
Quadrageminal cistern

17. Red: Hippocampus
MR 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)
17
Continue contouring in a cephalad (superior) direction; note that at this level, the temporal horn
of the lateral ventricle may no longer be visible on every slice, but the quadrigeminal cistern
serves as a medial reference landmark. Contour only the hypointense grey matter, not the bright
white matter.
Quadrageminal cistern

18. Red: Hippocampus
MR 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)
The hippocampus remains medial to the temporal horn of the lateral ventricle throughout its
extent, and so on slices where you can visualize it, use it as a consistent reference. The
quadrigeminal cistern remains a good medial landmark.
18
Temporal horn of
the lateral ventricle
Quadrageminal cistern

19. Red: Hippocampus
MR 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)
19
Quadrageminal cistern
The hippocampus remains medial to the temporal horn of the lateral ventricle throughout its
extent, and so on slices where you can visualize it, use it as a consistent reference. The
quadrigeminal cistern remains a good medial landmark.
Temporal horn of
the lateral ventricle

20. Red: Hippocampus
MR 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)
20
The hippocampal tail remains posterior to the thalamus as it curves medially toward the
splenium of the corpus callosum. Note that it is still medially located relative to the lateral
ventricle. Also note that the thalamus, basal ganglia and internal capsule now become visible.
Thalamus
Quadrageminal cistern
Caudate
Putamen

21. Red: Hippocampus
MR 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)
21
Internal
Capsule
The hippocampal tail remains posterior to the thalamus as it curves medially toward the
splenium of the corpus callosum. Note that it is still medially located relative to the lateral
ventricle. Also note that the thalamus, basal ganglia and internal capsule now become visible.

22. Red: Hippocampus
MR 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)
22
The postero-cranial extent of the hippocampal tail is located just antero-medially to the atrium of
the lateral ventricle.
Atrium of the
lateral ventricle
Hippocampal tail

23. Red: Hippocampus
MR 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)
23
The postero-cranial extent of the hippocampal tail is located just antero-medially to the atrium of
the lateral ventricle.
Atrium of the
lateral ventricle
Hippocampal tail

24. Red: Hippocampus
MR 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)
Even in its cephalad (superior) extent, the hippocampal tail remains lateral to the lateral edge of
the quadrageminal cistern.
24
Quadrageminal cistern

25. Red: Hippocampus
MR 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)
25
Even in its cephalad (superior) extent, the hippocampal tail remains lateral to the lateral edge of
the quadrageminal cistern.
Quadrageminal cistern

26. Red: Hippocampus
MR 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)
Terminate hippocampal contours at the point where the T1-hypointense structure no longer
borders the atrium of the lateral ventricle. At this point, the crux of the fornix emerges anteriorly
and the splenium of the corpus callosum can be visualized posteriorly.
26
Splenium

27. Red: Hippocampus
MR 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)
27
The grey signal from the hippocampus is no longer visible. Do not contour any further.

28. MR 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)
Generate the hippocampal avoidance zone using a 5mm volumetric expansion on the
hippocampus.
28
Red: Hippocampus Green: Hippocampal Avoidance Zone

29. Red: Hippocampus Green: Hippocampal Avoidance Zone
MR 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)
29
Hippocampal
1) Tail
2) Body
3) Head
Generate the hippocampal avoidance zone using a 5mm volumetric expansion on the
hippocampus.

30. MR 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)
30
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
Hippocampal
1) Tail
2) Body
3) Head
The hippocampus has three anatomic subdivisions: the head, body, and tail; note that the head
is inferior or caudad, the body is superoposterior and the tail is most cephalad (superior) and
posterior, and an overall “banana” shape emerges on sagittal images, located in the plane of the
lateral ventricle.

31. MR 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)
31
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
The hippocampus has three anatomic subdivisions: the head, body, and tail; note that the head
is inferior or caudad, the body is superoposterior and the tail is most cephalad (superior) and
posterior, and an overall “banana” shape emerges on sagittal images, located in the plane of the
lateral ventricle.

32. MR 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)
On sagittal sections, confirm delineation of the hippocampus separate from neighboring
structures, such as the amygdala.
32
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
Amygdala

33. MR 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)
33
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
On sagittal sections, confirm delineation of the hippocampus separate from neighboring
structures, such as the amygdala.
Amygdala

34. MR 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)
34
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
On coronal sections, confirm delineation of the hippocampus separate from neighboring
structures, such as the parahippocampal gyrus, which has different signal intensity.
Parahippocampal Gyrus

35. MR 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)
35
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
On coronal sections, confirm delineation of the hippocampus separate from neighboring
structures, such as the parahippocampal gyrus, which has different signal intensity.
Parahippocampal Gyrus

36. MR 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)
On sagittal and coronal sections, confirm separation between the hippocampal tail and the crus
of the fornix. Note the location of the hippocampii medial to the ventricles on the coronal
images.
36
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
Crus of the fornix Crus of the fornix

37. MR 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)
37
Hippocampal
1) Tail
2) Body
3) Head
Red: Hippocampus Green: Hippocampal Avoidance Zone
On sagittal and coronal sections, confirm separation between the hippocampal tail and the crus
of the fornix. Note the location of the hippocampii medial to the ventricles on the coronal
images.

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44. Holistic approach
• Cochlea
• Parotid
• Optic apparatus
• Lacrimal gland
• Dysphagia structures
• Scalp
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