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1 Department of Radiology, University of Vienna, Waehringer Guertel 18-20,
A-1090 Vienna, Austria.
2 Institute of Anatomy, University of Vienna, Waehringer Str. 13, A-1090 Vienna,
Austria.
3 Department of Psychoanalysis and Psychotherapy, Documentation and Statistics
Branch, University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna,
Austria.
Received June 25, 2001;
accepted after revision January 22, 2002.
Address correspondence to B. Partik.
Abstract
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SUBJECTS AND METHODS. The study included 18 healthy subjects (nine men, nine women; age range, 24-34 years; mean age, 30.8 years). We obtained coronal T1-weighted spin-echo images with fat suppression before and after IV administration of gadopentetate dimeglumine and additional axial T1-weighted spin-echo images after contrast administration. Patterns of signal-intensity enhancement in and around the radiocarpal joints were evaluated qualitatively and quantitatively.
RESULTS. In eight (44.4%) of 18 healthy subjects, enhancement of the radiocarpal joints was seen and exclusively located in the region of the prestyloid recess. Enhancement patterns were bandlike in three (16.7%) of 18 healthy subjects, homogeneous in another three (16.7%) of 18, and nodular in two (11.1%) of 18.
CONCLUSION. After IV administration of gadopentetate, signal-intensity enhancement in the radiocarpal joint is frequently seen in healthy subjects and is not predictive of inflammatory joint disease. If contrast enhancement is present, three distinct patterns are usually revealed, all invariably located in the region of the prestyloid recess.
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MR imaging has shown great accuracy in the evaluation of synovitis in patients who have rheumatoid arthritis [3,4,5,6,7,8,9,10,11]. Recently, Sugimoto et al. [12] recommended contrast-enhanced MR imaging of the wrist for a more accurate diagnosis of patients suspected of having rheumatoid arthritis, thus enabling the initiation of a therapeutic regimen early in the course of the disease. Previous studies have advocated contrast-enhanced MR imaging to detect synovial inflammation and have described a correlation between the degree of synovial enhancement and disease activity [13, 14]. MR imaging in healthy subjects has been given only limited attention in the literature. Rand et al. [15] described contrast enhancement in the atlantoaxial joints in healthy subjects. To our knowledge, no dedicated study dealing with contrast enhancement in the radiocarpal joints of healthy subjects has been performed. However, the hands and wrists are the most frequently involved joints both in patients with elderly onset rheumatoid arthritis (age of onset > 60 years) and younger onset rheumatoid arthritis [16].
Thus, the aim of our study was to evaluate whether gadopentetate enhancement in the radiocarpal joint occurs in healthy subjects and whether different patterns and grades of enhancement are present.
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MR Imaging
MR images were obtained using a 1.0-T MR imaging unit (Gyroscan T10-NT
Powertrak 3000; Philips, Best, The Netherlands) equipped with a C3 surface
coil 14 cm in diameter. Before each volunteer underwent MR imaging, an IV
catheter was inserted into a cubital vein of the contralateral arm for
injection of contrast material. Volunteers were placed in the prone position
with the arm to be examined extended overhead toward the midline and the hand
positioned in the center of the coil. The wrist was positioned palm downward
and secured with restraining bands.
Multiple MR images were obtained using a short tau inversion recovery (STIR) sequence (TR/TE, 1200/16; inversion time, 130 msec; section thickness, 2.4 mm; interslice gap, 0.4 mm; matrix size, 256 x 256 pixels; field of view, 12 cm) in the axial plane from the distal radius to the distal carpal bones. Further images were obtained using a T1-weighted spin-echo sequence (500/20; section thickness, 2.4 mm; interslice gap, 0.4 mm; matrix size, 256 x 256 pixels; signals acquired, 2; field of view, 12 cm) with fat suppression by spectral presaturation by inversion recovery (SPIR) in the coronal plane covering the entire radiocarpal joint before and after administration of contrast material [12]. In addition, contrast-enhanced images with the same parameters were acquired in the axial plane. To reduce the possible effects of contrast diffusion into the joint fluid, we obtained contrast-enhanced images immediately after a manually applied IV bolus injection (approximately 2 mL/sec) of 0.1 mmol gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany) per kilogram of body mass via a venous catheter in the contralateral arm followed by a final bolus of 20 mL of physiologic saline that was administered without moving the volunteer during the entire procedure [17]. The mean time interval between injection and complete image acquisition was 4 min 51 sec.
Data Analysis
Two board-certified radiologists who were experienced in skeletal radiology
independently evaluated the unenhanced and contrast-enhanced images. First,
any enhancement in the four anatomic regions (prestyloid recess,
lunotriquetral region, scapholunate region, and radial region) containing a
synovial layer (Fig. 1) was
noted. Enhancement was defined as an increase in signal intensity with
comparison of images before and after administration of contrast material.
Second, the type of synovial enhancement was assessed qualitatively using a
three-grade scale as follows: A, nodular enhancement; B, bandlike enhancement;
and C, homogeneous enhancement. Third, the degree of synovial enhancement was
ranked quantitatively using a three-grade scale as follows: mild, moderate,
and strong enhancement. In the STIR sequence, the presence of other findings
(e.g., fluid in the joint space and changes in signal intensity of soft
tissues and bones) was noted. For ambiguous cases, agreement was by consensus
in a second image review session.
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Statistics
Interobserver concordance on the synovial enhancement rank data was
assessed with Cohen's weighted kappa coefficient for partial credit agreement
between two ordered measurements along with the exact 95% confidence interval
(CI) [18].
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No enhancement in the radiocarpal joint was observed in the remaining 10 (55.6%) of 18 healthy subjects. Neither soft-tissue enhancement nor signs of marrow edema or presence of fluid in the joint space were seen in any healthy subject on T1-weighted spin-echo sequences, unenhanced or contrast-enhanced administration, or on the STIR sequence.
In 16 (88.9%) of the 18 subjects, the two observers were concordant
regarding the evaluation of type and degree of enhancement (
= 0.90;
exact 95% CI, 0.71-1.00).
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Our study revealed that in 44.4% of healthy subjects, predominantly mild signalintensity enhancement after administration of gadopentetate occurs in the region of the prestyloid recess of the radiocarpal joint.
In previous studies researchers have advocated contrast-enhanced MR imaging to detect synovial inflammation and have described a correlation between the degree of synovial enhancement and disease activity [13, 14]. Although contrast-enhanced MR imaging may be helpful in the detection of the early stages of synovitis, as in rheumatoid arthritis, the patterns of signal-intensity enhancement seen in our healthy subjects may mimic those observed in patients with low-grade synovitis [12]. In our study, soft-tissue signal intensity with enhancement and marrow edema were not observed. Thus, concomitant findings in inflammatory joint diseases, such as soft-tissue enhancement and bone marrow edema, may be more accurate in identifying early stages of synovitis.
Other authors have discussed the limitations of synovial imaging, primarily the diffusion of contrast agent from the synovial membrane to the joint fluid, observed most commonly in the knee joint [26, 27]. Winalski et al. [26] observed an initial peripheral rim of enhancement in the peripheral joint fluid that appeared to be related to early diffusion of gadopentetate from the synovial membrane. König et al. [17] did not describe enhancement of signal intensity in the synovial membrane or joint fluid after IV gadopentetate administration in healthy subjects. Other authors have indicated that the healthy synovial membrane does not enhance and therefore remains invisible after IV gadopentetate administration [28,29,30]. However, contrast enhancement in the atlantoaxial joints of healthy subjects was described by Rand et al. [15], in which the authors found different patterns of enhancement. Our findings are in accordance with these observations, showing three patterns of enhancement in the radiocarpal joints of healthy subjects.
Two possible explanations exist for our findings. On the one hand, the observed enhancement may be related to early diffusion of gadopentetate into the joint fluid from the synovial membrane [26]. On the other hand, the synovial membrane itself may contribute to the appearance of the areas of increased signal intensity. The anatomy of the radiocarpal joint may explain the distribution of enhancement in our study. As shown in Figure 1, synovia is present in four anatomic regions of the radiocarpal joint. However, the increase of signal intensity after administration of gadopentetate was seen invariably in the region of the prestyloid recess. We hypothesize that enhancement in this site is related to redundant synovium in the prestyloid recess, which increases the relative volume of enhancing tissue, thereby making it more conspicuous. Furthermore, these findings are supported by the fact that no supplying vessels are found anatomically in that area. Enhancement seen in regions other than the prestyloid recess could indicate inflammatory disease.
In agreement with Rand et al. [15], we were unable to prove that the regions of high signal intensity are primarily related to contrast agent in the synovial membrane, the joint fluid, or both. However, Sugimoto et al. [12] assessed the effect of contrast diffusion into the joint within a time range of a few minutes as negligible.
In general, fat may also yield high signal intensity on T1-weighted images. However, fatsuppression techniques (STIR and SPIR) were used in our study. With a very small field of view, inhomogeneities of the static magnetic field, which could contribute to incomplete fat saturation, were minimized [31]. Although fat suppression is possibly not 100%, fat does not seem to be the reason for hyperintense signal intensity in the region of the prestyloid recess on contrast-enhanced images. On T1-weighted images, hyperintense signal potentially may relate to venous blood flow [32]. However, because a venous complex the size of the high-signal patterns observed in our study is not described in the region of the prestyloid recess, our findings do not reflect slow venous blood flow.
Our study had some possible limitations. First, the volunteers were
relatively young, and rheumatoid arthritis is most common in the elderly.
However, onset of the disease can occur at any age, and young onset rheumatoid
arthritis especially affects a younger age group
[1]. Of course, it would be of
interest to explore the enhancement patterns of the radiocarpal joint in the
asymptomatic older age group. Contrast enhancement in the atlantoaxial joints
of an older age group of healthy subjects has been shown
[15]. We expect similar
results in the radiocarpal joints of elderly patients. Second, because of
subtle findings in some volunteers, we could not define an exact region of
interest for quantitative measurements of signal-intensity enhancement in the
prestyloid recess. Thus, our results are based on the subjective impressions
of two observers. However, we assume that our data are valid because of the
high interobserver concordance ( = 0.90), which is also above the
interobserver agreement percentage (88.9%), indicative of only negligible
disagreement between observers. Furthermore, the 2.4-mm section thickness of
the T1-weighted MR images is on the same spatial scale as the enhancement
observed in the region of the prestyloid recess, which could cause volume
averaging effects. However, this finding might be an underestimation of the
number of volunteers whose images showed contrast enhancement in the
radiocarpal joint. Third, some authors advocate the use of dynamic MR imaging
in rheumatoid arthritis, particularly in monitoring disease activity
[10,
11,
13,
14,
17]. Although static
contrast-enhanced MR imaging has been reported to yield a sensitivity,
specificity, and accuracy in the diagnosis of rheumatoid arthritis of 96%,
86%, and 94%, respectively, dynamic MR imaging might further improve
diagnostic accuracy [12].
However, an experimental animal study
[33] advocates the
administration of macromolecular contrast medium in dynamic MR imaging.
Therefore, we consider that the routine use of dynamic MR imaging in the
diagnosis of early rheumatoid arthritis may be more useful when macromolecular
contrast medium is commercially available.
We conclude that after IV administration of gadopentetate, signal-intensity enhancement in the radiocarpal joint is frequently seen in healthy subjects and is not predictive of inflammatory joint disease. If contrast enhancement is present, characteristically, three distinct patterns are revealed, all invariably located in the region of the prestyloid recess.
Acknowledgments
We thank Petra Peischl for her efforts in performing all examinations and
all the volunteers who made this study possible.
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  F McQueen, M Ostergaard, C Peterfy, M Lassere, B Ejbjerg, P Bird, P O'Connor, H Genant, R Shnier, P Emery, et al. Pitfalls in scoring MR images of rheumatoid arthritis wrist and metacarpophalangeal joints Ann Rheum Dis, February 1, 2005; 64(suppl_1): i48 - i55. [Abstract] [Full Text] [PDF]
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