Bimin Chen1,2, Hongda Shao1, Michael Carl3, Arthur Kavanaugh4, Graeme M Bydder1, and Jiang Du1
1Radiology Department, UCSD, San Diego, CA, United States, 2Radiology Department, The first affiliated hospital of Jinan University, Guangzhou, China, People's Republic of, 3GE Healthcare, San Diego, CA, United States, 4Center for Innovative Therapy Division of Rheumatology, Allergy, and Immunology, UCSD, San Diego, CA, United States
Synopsis
Achilles tendon enthesitis is the source of the the heel pain of PsA patients. The current measures based on pressure being placed on various entheses during physical examination are both insensitive and non-specific.Also it’s very time consuming and poorly reproducible.MR imaging with ultrashort echo time (UTE) sequences provides a good option for assessing entheses, which has a relatively short T2 and largely “invisible” with clinical MR sequence.Introduction
Enthesitis is a common and characteristic
component of psoriatic arthropathy (PsA). Although there are several clinical
indices that have been developed 1, there is a major unmet clinical
need for better methods to assess enthesial inflammation. The current measures
based on pressure being placed on various entheses during physical examination
are both insensitive and non-specific. Physical examination is very time
consuming and poorly reproducible 2. Clinical enthesitis measures
are nonspecific insofar as the only readout is pain on palpation, and it cannot
be determined that enthesial inflammation is indeed the source of the
pain. Magnetic resonance imaging
provides another option. However, entheses has a relatively short T2 and are largely “invisible” with clinical MR sequences. In this study we aim to
study entheses in healthy volunteers and
PsA patients using ultrashort echo time (UTE) sequences at 3T
Methods and Materials
Fig 2 3D Cones imaging of a 33y old healthy volunteer
with a TE of 32 µs (A) and 4.4 ms (B), and 3D Cones UTE imaging of a 65y
old PsA patient with a TE of 32 µs (C) and 4.4 ms (D) as well as the
corresponding T1-FSE image (E) which shows no signal from the
Achilles tendon enthesis. Increased signal was observed for the abnormal
tendon enthesis, consistent with increased T2* values.
We have
developed a 3D UTE Cones sequence a GE 3T Signa TwinSpeed MR scanner (GE
Healthcare Technologies, Milwaukee, MI). The 3D Cones sequence (Fig 1A) employs a short rectangular
pulse excitation (duration = 14-26 µs) followed by a 3D Cones trajectory (Fig 1B) 3. The 3D k-space is
divided into multiple cones, with twisted radial trajectories along each cone.
It allows anisotropic field of view (FOV) and spatial resolution as well as
multi-echo acquisitions, which vastly reduce the scan time to a few minutes for
in vivo studies. In total 8 volunteers (male=6, female=2, 27-42yrs average 34.4 yrs) and 4
diagnosed PsA patients (male=4, 37-62yrs, average 49.5yrs) were recruited for this study. T2*, T1 and
magnetization transfer ratio (MTR) were measured for each subject. T2* was
measured with four sets of dual echo Cones data acquisitions (TEs = 0.03/4.4;
0.4/6.6; 0.8/8.8; 2.2/11 ms). T1 was measured with variable TR Cones data
acquisitions (TRs = 7.4, 10, 15, 20, 30 ms). MTR was measured with Cones-MT
data acquisitions with a MT power of 1000º and frequency offset of 1.5 kHz.
Clinical gradient echo MTR was also measured. Other Cones imaging parameters
included a flip angle of 20o, a bandwidth of 90 kHz, a FOV of 6 cm,
a slice thickness of 2 mm, 20 slices, reconstruction matrix of 256×256. T-tests were performed and p values
were calculated
for
enthesis of volunteer and PsA patients .
Results
Fig 2 shows
representative 3D UTE Cones imaging and quantification of the tendon enthesis
of a 33y old healthy volunteer and a 65y old PsA patient. High resolution
morphological images of the Achilles tendon enthesis were depicted with 3D
Cones while near zero signal was shown in the clinical FSE images. The
increased signal intensity in later echoes of 3D Cones images shows evidence of increased T2* in
the abnormal tendon enthesis.
Table 1. Mean and standard
deviation in T2*, T1 and MTR measurements of the Achilles tendon enthesis
in healthy volunteers (n=8) and PsA patients (n=4). T-tests were conducted
to evaluate the significance of each measurements.
Table 1 summarizes T1, T2* and
MTR measurements. T-tests showed significant difference of T2* value (p value of
0.00047),T1 value (p value of 0.042608) ,GRE-MTR (p value of 0.000) and
Cones-MTR (p value of 0.000) between volunteers and PsA patients. Increased T2* and T1 and decreased MTR were
observed for the PsA patient, suggesting that 3D UTE Cones biomarkers can be
used to evaluate enthesis disease.
Discussion
Our
results show that there are significant differences in T2* and T1 as well as
GRE-MTR and Cones-MTR between PsA patients and volunteers. Patients with PsA
have the symptoms attributable to autoimmune inflammation 4,5. Inflammation causes
increased cytokines and other inflammatory exudates as well as increased free water content. This is likely to be responsible for the
increased T2* and T1 and reduced MTR. More volunteers and PsA patients are
under investigation to further validate these findings.
References
Acknowledgements
No acknowledgement found.References
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