Michael Drabkin MD Lauren Senior Uma Kanth Allison Rubin MD Steven Lev MD ASNR 2015 Annual Meeting eEdE eEdE85 Control 772 Disclosures Nothing to disclose Purpose To provide the radiologist with a pattern approach to head CT interpretation based on templates of interconne ID: 650639
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Slide1
Geometric Modeling as a Foundation for Head CT Interpretation
Michael Drabkin MDLauren Senior, Uma Kanth, Allison Rubin MD, Steven Lev MD
ASNR 2015 Annual
Meeting
eEdE
#: eEdE-85
Control #: 772 Slide2
DisclosuresNothing to disclose.Slide3
Purpose
To provide the radiologist with a pattern approach to head CT interpretation based on templates of interconnected geometric shapes. The viewer is encouraged to think from general to specific and consider spatial relationships. Cases will demonstrate the utility of this framework to everyday practice.Slide4
Approach/Methods
Utilizing graphic software, we construct transparencies of geometric shapes which are superimposed over sequential normal and abnormal axial CT images. Larger shapes are successively subdivided into smaller ones. Selective colorization is based on variable tissue densities and anatomical considerations. Slide5
Approach/Methods
The assorted shapes and variations thereof have zero (circular) to six (hexagonal) vertices. Circular constructs include ovals (thalami), sectors (posterior fossa), lenses and lunes (extra-axial spaces). We present a broad array of challenging cases from our Level I trauma center to demonstrate how a geometric approach can elucidate subtle findings.Slide6
Color Codes and Shapes
Geometrical shapes and colors can help clarify understanding of head CT interpretation. The genu and
splenium
of the corpus callosum (yellow) are represented by annular sectors. The cortex (red), arachnoid (green),
dura
(brown) and
calvarium
(light blue) can be simplified as ovoid simple annuli. The internal, external and extreme capsules, together with the basal ganglia, are sector shapes contained within a single larger sector (pink). The caudate and thalamus (both blue) are ovals and are bounded laterally by the ventricles, represented by crescent (
lune
) forms (purple). Slide7
Discussion
Shapes are the foundation of how we perceive the world. Studies have shown that building blocks can help children better absorb math and language concepts; art schools emphasize simplifying the body into component geometric forms. Similarly shapes can serve as a scaffold for interpreting neuroanatomy. The axial sections of the original CT and our model are homeomorphic to each other, therefore one can be readily modified into the other. Slide8
Discussion
Each slice represents a new packing problem, in which we optimize the arrangement of non-overlapping shapes. Mathematical concepts essential to our model are symmetry and connectivity (the latter concerning the number of neighbors adjacent to a single shape). Distortion of one shape by pathology will predictably affect all surrounding shapes. Slide9
Posterior
FossaSlide10Slide11
The sector form (yellow) is disrupted by an oval shape (red). The surrounding annulus (blue) represents a CSF cleft indicating that this is an extraxial
mass. This is a meningioma.Slide12
Fourth VentricleSlide13Slide14
In the image on the left The pons is expanded and the 4
th ventricle (blue) is obliterated in this case of brain stem glioma causing obstructive hydrocephalus.Slide15
PonsSlide16Slide17
The basilar cisterns are completely effaced in the image on the right. The circle (yellow) formed by these CSF spaces is entirely lost amidst the diffuse cerebral edemaSlide18
Mid BrainSlide19Slide20
A circle (blue) is seen within the
suprasellar
cistern (yellow pentagon). This was a pituitary adenoma.Slide21
A circle (blue) is seen within the
suprasellar
cistern (yellow pentagon). This was a pituitary adenoma.Slide22
Lateral VentriclesSlide23Slide24
When the template of the cortex (red) is superimposed on the image, the right frontal extra-axial
isodense
lesion becomes more apparent.Slide25
When the template of the cortex (red) is superimposed on the image, the right frontal extra-axial
isodense
lesion becomes more apparent.Slide26
Isodense
MeningiomaSlide27
Lateral VentriclesSlide28
Did you notice the absence of
sulci
on the right? There is subtle ventricular asymmetry with slight mass effect on the right frontal horn. Slide29
Initially, the cortex appears expanded.Slide30
However, in the setting of trauma, this likely represents an
isodense
subdural hematoma.Slide31
MR
T1W and T2W images clearly depict a subdural hemorrhage in the late subacute stage, corresponding to the isodense appearance on CTSlide32
Lateral VentriclesSlide33
Did you notice the absence of
sulci on the right? There is subtle ventricular asymmetry with slight mass effect on the right frontal horn. Slide34
The large colloid cyst (blue) at the foramen of
Monro produces a life-threatening obstructive hydrocephalus. The ventricles (purple) assume a more rounded formSlide35
Centrum
OvaleSlide36Slide37
Note the cerebral hemi-atrophy. There is
calvarial
thickening , highlighted by an annulus (blue), which is much thicker on the left. This combination is
pathognamonic
for Dyke-DavidoffSlide38
Summary/Conclusion
While interpreting head CTs, radiologists often overlook the big picture and instead are too quick to focus on minor or insignificant details. This novel geometric framework, based on component interrelated shapes, can assist in lesion detection, increasing the radiologist’s accuracy and confidence.