Angular/Depth Dependent Analysis

Abstract #: TR05
In-vivo T2 and T1ρ Mapping of Femoral Cartilage at
3T: Angular/Depth Dependent Analysis
(Category: Technical Report)
Hon J. Yu1,2 (hjyu@uci.edu), Eiko Yamabe2, Peter Huy Pham4, Kayleigh Kaneshiro2,
Ran Schwarzkopf3, Dave Hitt5, Hiroshi Yoshioka2
1Tu & Yuen Center for Functional Onco-Imaging, and
2Department of Radiological Sciences, 3Department of Orthopaedic Surgery, University of
California, Irvine, CA, USA
4Loma Linda University Medical Center, Loma Linda, CA, USA
5Philips Healthcare, U.S. Clinical Science Department, Cleveland, OH, USA
Disclosures
Nothing to disclose:
All authors
Background and Aims
T1ρ-map via MRI is shown to be sensitive to
proteoglycan content and promises to be a
valuable quantitative tool along with T2-map
for early detection of cartilage degeneration.
Unknown, however, is whether or not the
T1ρ value of normal cartilage is dependent
on the angular/depth factors affecting T2
value, such as magic angle effect and
laminar anisotropy.
Methods – Acquisition
Utilization of a clinical 3T scanner (Philips) and an
8-channel knee receive-only RF-coil.
Both T2 and T1ρ in geometrically matched sagittal
slices with following parameters – T2: Multi-echo
TSE sequence (TR=2700; TE=13-91); T1ρ: Multi-shot
3D T1-FFE sequence for read-out with a rotary echo
based T1ρ preparatory pulses for 4 different spin
lock durations (TSL=10,20,40,60 ms).;
Reconstructed voxel size: 0.3x0.3x3 mm.
Methods – Processing
Image alignment assessed and performed
separately with respect to the first series of T2 and
T1ρ via a rigid-body transformation using SPM
package in Matlab.
Mono-exponential, pixel-by-pixel fitting for both T2
and T1ρ map using a custom program in Matlab.
Manual segmentation of entire medial femoral
condyle cartilage followed by a semi-automatic
angular/depth segmentation of cartilage using a
custom program.
T2 and T1ρ map
T2 (w/ TE=13)
T2-map
T1ρ-map
T1ρ (w/ TSL=10)
0
50
100 (ms)
Angular/depth segmentation
_
+
0˚
Angular convention with respect to B0 at 0˚
Angular/depth profile
T2
Full-thickness
Deep-Layer
SuperficialLayer
70
60
50
40
30
-50
0
50
100
150
Orientation to B0 (degree)
80
T1r value (ms)
T2 value (ms)
80
T1ρ
70
60
50
40
30
-50 -30 -10 10 30 50 70 90 110 130 150
Orientation to B0 (degree)
* Based on a single slice of medial femoral condyle cartilage in normal volunteers
analyzed thus far with no major mis-alignment observed between T2 and T1ρ series
(n=12; age: 23-35 yrs.)
Summary
The results demonstrate the potential of a novel
segmentation methodology for quantitative assessment
of cartilage in vivo using T2 and T1ρ mapping.
A very robust co-registration technique, however, is
critical for a reliable cartilage-only profile assessment
when it is based on a single ROI-drawing and
angular/depth segmentation in presence of subject
motion between T2 and T1ρ series.