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Musculoskeletal Imaging |
1 From the Departments of Radiology (C.A.B., M.Z., J.H.) and Orthopedic Surgery (C.G.), University Hospital Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland. Received July 6, 2000; revision requested August 19; final revision received January 8, 2001; accepted January 16. Address correspondence to C.A.B., Dotter Interventional Institute, Oregon Health Sciences University, L605, 3181 SW Sam Jackson Park Rd, Portland, OR 97201-3098 (e-mail: binkert@compuserve.com).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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MATERIALS AND METHODS: One hundred fifty-six consecutive MR arthrograms were randomly obtained with either 2 mmol/L gadoteridol (n = 52), 4 mmol/L gadoteridol (n = 52), or Ringer solution (n = 52). MR arthrograms were assessed quantitatively (for contrast-to-noise ratio [CNR]) and qualitatively (for overall image quality, image contrast, degree of joint distention, and motion artifacts). MR diagnoses were compared with arthroscopic or surgical reports in 88 patients.
RESULTS: The mean CNR at imaging was 40.4 with 2 mmol/L gadoteridol, 45.6 with 4 mmol/L gadoteridol, and 48.7 with Ringer solution. The CNR with 2 mmol/L gadoteridol was significantly lower than that with 4 mmol/L gadoteridol (P = .025) and Ringer solution (P = .012). Qualitative differences between the two gadoteridol concentrations were not significant. Ringer solution was significantly worse with regard to overall quality, motion artifacts, image contrast, and joint distention compared with both gadoteridol concentrations. Ringer solution was slightly more sensitive and less specific than the gadoteridol solutions in the detection of supraspinatus tears and less sensitive and more specific in enabling diagnosis of superior labrum anteroposterior lesions.
CONCLUSION: MR arthrograms of the shoulder obtained with gadoteridol and those obtained with Ringer solution provided equivalent diagnostic accuracy. The authors, however, preferred the image quality of the gadoteridol-enhanced arthrograms.
Index terms: Arthrography, contrast media, 414.122 • Contrast media, comparative studies • Gadolinium • Magnetic resonance (MR), arthrography, 414.121411, 414.121415, 414.12143 • Shoulder, arthrography, 414.122 • Tendons, injuries, 414.41, 414.481
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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The purpose of the present investigation was to compare two concentrations of a gadolinium-based contrast material with Ringer solution for MR arthrography of the shoulder by assessing quantitative and qualitative image parameters and diagnostic efficacy, with surgery or arthroscopy as the standard of reference.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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MR Arthrography
MR arthrography was performed with a 20-gauge needle and fluoroscopic guidance. Local anesthesia was induced. The intraarticular position of the needle tip was confirmed by injecting 1 mL of iopamidol (Iopamiro 200; Bracco Diagnostics, Milan, Italy). One milliliter of mepivacain (Scandicain 2%; AstraZeneca, Södertälje, Sweden) was then injected, followed by 10 mL of contrast material. The total injected volume was 12 mL. On the basis of our experience, this standardized volume enables delineation of the relevant structures without leakage in the majority of patients.
The contrast material used was either 2 mmol/L gadoteridol (ProHance; Bracco Diagnostics), 4 mmol/L gadoteridol, or Ringer solution (sodium chloride 0.9%, potassium chloride 0.03%, calcium chloride 0.015%, sodium hydrocarbonate 0.017%; Braun Medical, Melsungen, Germany). The two gadoteridol solutions were prepackaged by the manufacturer and did not require additional dilution. The three types of contrast material were administered in 52 patients each. They were assigned to the patients randomly by using the random number function of a spreadsheet (EXCEL 97; Microsoft, Redmond, Wash). The orthopedic surgeons at our hospital prefer Ringer solution over saline for irrigation during arthroscopy. The results of an in vitro study (7) involving the use of rat articular cartilage demonstrated that Ringer solution is the best agent for joint irrigation during arthroscopy or other procedures.
MR imaging was performed by using a 1.0-T unit (Siemens Expert; Siemens Medical Systems, Erlangen, Germany) equipped with a dedicated receive-only shoulder coil. For the gadoteridol-enhanced arthrograms, T1-weighted transverse (580/20 [repetition time msec/echo time msec], 4-mm section thickness, 140 x 160-mm field of view, 224 x 512 matrix) and parasagittal (700/12; 5-mm section thickness, 160 x 160-mm field of view, 192 x 256 matrix) images, as well as angled coronal dual-spin-echo (3,500/14 and 85, 4-mm section thickness, 184 x 210-mm field of view, 230 x 512 matrix) and T1-weighted fat-suppressed (800/20, 4-mm section thickness, 160 x 160-mm field of view, 192 x 256 matrix) images were obtained. For the arthrograms obtained with Ringer solution, the dual-spin-echo sequence was performed in all three planes. An angled coronal T2-weighted fat-suppressed spin-echo sequence (4,500/96, 4-mm section thickness, 160 x 160-mm field of view, 196 x 256 matrix) was added. The total imaging time was 16 minutes 1 second for the gadoteridol-enhanced arthrograms compared with 20 minutes 48 seconds for the Ringer solution–enhanced arthrograms.
Technical Efficacy
For quantitative assessment, the angled coronal image closest to the center of the humeral head was chosen. The fat-suppressed T1-weighted sequence was selected for evaluation of the gadoteridol-enhanced arthrograms, and the fat-suppressed T2-weighted sequence was selected for evaluation of the Ringer solution–enhanced arthrograms. These sequences were chosen because we believe that they are the most useful for assessment of intraarticular abnormalities on MR arthrograms. Contrast-to-noise ratios were calculated as follows: Signal intensities were measured by the first author (C.A.B.) by using the standard MR console and the MR unit manufacturer’s software (Siemens Medical Systems). Circular regions of interest were drawn in the areas of the axillary recess, the most normal part of the supraspinatus tendon, and the air lateral to the body. The region-of-interest sizes in the axillary recess and supraspinatus tendon were made as large as possible without including adjacent structures. The region of interest in the air was 10 cm2. Contrast-to-noise ratios were calculated by dividing the difference in mean signal intensity of fluid between the axillary recess and the supraspinatus tendon by the SD of the background signal intensity (8).
Two staff radiologists (M.Z., J.H.) specializing in musculoskeletal radiology independently performed a qualitative evaluation. They had not been involved in the quantitative assessment. The readers were blinded to the gadoteridol concentration used; however, blinding with regard to the Ringer solution protocol was not possible because of differences in the sequences used.
Several image aspects were graded on a scale of 1–5, with 1 defined as worst quality and 5 defined as perfect quality: (a) For overall image quality, a score of 5 meant excellent—that is, perfect contrast between the relevant structures, crisp images, and no artifacts; 3, moderate—that is, contrast not perfect for some structures, some blurring, and some artifacts, but diagnosis still possible; and 1, inferior—that is, contrast insufficient for all structures, severe blurring, and/or severe artifacts, and diagnosis may not be possible. (b) For subjective contrast between joint fluid and adjacent structures, a score of 5 meant excellent—that is, best signal intensity difference; 3, moderate—that is, visible signal intensity difference and still sufficient for diagnostic purposes; and 1, inferior—that is, no visible signal intensity difference. (c) For degree of glenohumeral joint distention, a score of 5 meant full distension—that is, complete delineation of the undersurface of the supraspinatus tendon and separation of the joint capsule from the labrum; 3, moderate distension—that is, either supraspinatus tendon or labrum not delineated, or both structures partially delineated; and 1, poor distension—that is, neither the supraspinatus tendon nor the labrum delineated. (d) For extent of motion artifacts, 5 meant no motion artifacts; 3, moderate artifacts—that is, diagnosis still possible; and 1, severe artifacts—that is, diagnosis may not be possible. 
statistics were used to calculate interobserver agreement (9): a value less than 0.20 indicated poor agreement; 0.21–0.40, fair agreement; 0.41–0.60, moderate agreement; 0.61–0.80, good agreement; and 0.81–1.00, very good agreement.
Diagnostic Efficacy
In addition to the quantitative and qualitative evaluations of image quality, the diagnostic efficacy of the different contrast material concentrations was assessed. The same two readers who performed the qualitative grading made a diagnosis regarding the supraspinatus, infraspinatus, and subscapularis tendons; the superior and anteroinferior labra; and the intraarticular part of the long biceps tendon. The two readers performed this evaluation independently and were blinded with regard to clinical and intraoperative findings. For the rotator cuff tendons, the following diagnoses were made: normal, partial tear, or full thickness tear. For the biceps tendon, a diagnosis of normal, tendinopathy, or tear was made. For the anteroinferior labrum, a diagnosis of normal, degeneration, or tear was made. For the superior labrum, a diagnosis of normal, degeneration, or superior labrum anteroposterior (SLAP) lesion was made. Established criteria from the literature (1–3,10–14) were used to differentiate the various abnormalities. MR findings were compared with those of arthroscopy (n = 62) or open surgery (n = 26). Sensitivity, specificity, categorical agreement, and interobserver agreement were calculated.
The unpaired Student t test was performed to compare contrast-to-noise ratios. The Wilcoxon rank sum test was performed to compare gradings; the mean grade of the two observers was used. A P value of less than .05 indicated a statistically significant difference.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Diagnostic Efficacy
Contrary to the results found with regard to technical efficacy, no major differences in diagnostic performance were found among the different intraarticular contrast materials. On all three types of arthrograms, the prevalences of abnormalities were low for several anatomic structures, which, therefore, were not evaluated in depth. The prevalence of a subscapularis tendon tear was two (7%) of 30 at 2 mmol/L gadoteridol arthrography, one (4%) of 26 at 4 mmol/L gadoteridol arthrography, and zero of 32 at Ringer solution arthrography. Infraspinatus tendon tear was seen during surgery in four (13%) of 30 cases with 2 mmol/L gadoteridol, in two (8%) of 26 with 4 mmol/L gadoteridol, and in one (3%) of 32 with Ringer solution. A long biceps tendon tear was surgically confirmed in two (7%) of 30 surgical cases with 2 mmol/L gadoteridol, in two (8%) of 26 with 4 mmol/L gadoteridol, and in zero of 32 with Ringer solution. During arthroscopy, an anteroinferior labrum tear was found in two (10%) of 20 patients by using 2 mmol/L gadoteridol, in one (6%) of 17 patients by using 4 mmol/L gadoteridol, and in two (8%) of 25 patients by using Ringer solution.
Higher prevalences were found for supraspinatus tendon tears and SLAP lesions, so these were further analyzed (Table 2). For detection of supraspinatus tears (Figs 1–3), sensitivity was excellent for all the contrast materials and for both readers (91%–100%). The specificity of the gadoteridol-enhanced arthrograms (87%–100%) was higher than that of the Ringer solution–enhanced arthrograms (reader 1, 79%; reader 2, 88%). On the basis of categorical agreement data, the Ringer solution–enhanced arthrograms (reader 1, 66%; reader 2, 72%) did not differ consistently from the gadoteridol-enhanced arthrograms (63%–80%). Interobserver agreement was better for the gadoteridol-enhanced arthrograms ( = 0.59 for 2 mmol/L and = 0.64 for 4 mmol/L) than for the Ringer arthrograms ( = 0.51).
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= 0.56), followed by 2 mmol/L gadoteridol ( = 0.52) and Ringer solution ( = 0.48) arthrograms, although the differences were not large.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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Most clinical studies focusing on evaluation of MR arthrograms of the glenohumeral joint have involved an intraarticular gadolinium-based contrast material concentration of 2 mmol/L (1–3, 16). A few authors (14,18) have used a higher concentration (4 mmol/L). Our data indicate that despite objectively better contrast (measured as the contrast-to-noise ratio) with 4 mmol/L versus 2 mmol/L gadoteridol, the differences are not relevant according to qualitative criteria. The focus of our investigation, however, was not to determine the appropriate contrast material concentration but rather to compare gadoteridol with Ringer solution, a potentially inexpensive and safe agent, similar to pure saline. The diagnostic performance of saline-enhanced arthrograms for detection of anterior glenohumeral instability has proved to be good (4,5). Such arthrograms may be less useful for distinguishing partial- from full-thickness tears of the rotator cuff, because it is not possible to differentiate between preexisting fluid in the subacromial-subdeltoid bursa and contrast material leaking from the joint. To our knowledge, only one comparative investigation (6) based on differences in signal intensity and the qualitative assessment of image quality has been performed.
It is not easy to perform such an investigation, however. Because of ethical considerations, it is not feasible to perform three arthrographic examinations with three different contrast materials in the same patient. Therefore, we used a randomized study setup and a relatively large number of patients to reduce the effects of interindividual differences.
Another problem of investigations to assess intraarticular contrast materials is that the inclusion of patients on the basis of available surgical reports creates a bias toward severe, and therefore easy to diagnose, disease. We believe that our study, with 88 of 156 shoulders, included a relatively large proportion of patients with independent standards of reference, without excluding patients who had not undergone surgery and thus had presumably less pronounced disease.
With the standardized sequences used for this investigation, the Ringer solution–enhanced arthrograms performed best on the basis of mean contrast-to-noise ratios measured for intraarticular fluid versus supraspinatus tendon. Considering the experience reported by Zanetti and Hodler (6), this was not anticipated. In their study, however, a T2*-weighted gradient-echo sequence was used to obtain the saline solution arthrograms and a T1-weighted gradient-echo sequence was used to obtain the gadolinium-enhanced arthrograms. Their results, therefore, cannot be directly compared with those of this study.
In the current study, the mean contrast-to-noise ratio for the Ringer solution–enhanced arthrograms was higher than that for the gadoteridol-enhanced arthrograms. This has to be considered together with the SDs, however, which indicated higher variability on the Ringer solution–enhanced arthrograms. Uniform image quality is important for a consistent diagnosis to not only the radiologist but also the clinicians.
The qualitative evaluations did not reveal significant differences between the two concentrations of gadoteridol. Ringer solution–enhanced MR arthrograms, however, had significantly lower scores for all four graded features—that is, overall image quality, image contrast, joint distention, and motion artifacts. There may have been relevant observer bias, especially because these results in part contradicted the quantitative evaluation results. This argument is strengthened by the fact that interobserver variability for image quality was high. However, the lower scores for joint distention suggest that the iso-osmolar Ringer solution is absorbed more rapidly than is gadolinium-based contrast materials. At our institution, MR imaging usually is performed within 5–15 minutes after arthrography. At institutions where there are longer delays between contrast material administration and MR imaging, this aspect may become even more relevant. Adding epinephrin or using higher volumes may solve this problem. Willemsen et al (5) injected up to 40 mL of saline in patients with an expanded articular capsule after recurrent anterior dislocation of the shoulder. Repetitive shoulder dislocation leads to an enlarged shoulder capsule; this partly explains the volume difference—40 mL versus the 12 mL used in our study (with few patients with glenohumeral instability)—and the similar contrast material doses recommended by other investigators (5,16,18).
Motion artifacts are not directly dependent on the type of intraarticular contrast material, but rather they are related to differences in the sequences used. The slightly lower grade for motion artifacts on the Ringer solution–enhanced arthrograms was probably due to a higher sensitivity to motion associated with the high fluid-to-background signal intensity difference and to the longer acquisition time associated with the fat-suppressed T2-weighted spin-echo sequence.
In those study patients who underwent either open surgery or arthroscopy, the prevalence of infraspinatus, subscapularis, biceps, and anteroinferior labral abnormalities was too low for a more detailed analysis. For this reason, the following discussion is focused on supraspinatus and superior labral lesions. This is reflective of the referral habits of the shoulder surgeons at our institution, who order MR arthrography to help distinguish partial from small full-thickness tears of the rotator cuff, SLAP lesions, and biceps tendon abnormalities but not to identify shoulder instability (which is assessed with computed tomographic arthrography owing to the better demonstration of small fragments at the anteroinferior glenoid rim).
All three types of arthrograms (Figs 1–3) were excellent in depicting supraspinatus tears, as indicated by the high sensitivities. However, the gadoteridol-enhanced MR arthrograms were slightly more specific (Figs 1, 2). This is probably explained by the fact that on Ringer solution–enhanced arthrograms, leaked intraarticular contrast material cannot be distinguished from preexisting fluid relating to bursitis (Fig 3). It is also interesting that the lower concentration of gadoteridol was slightly more specific than the higher concentration. Occasionally, continuous but degenerated rotator cuff tendons may be imbibed by contrast material, and this may lead to false-positive diagnoses. Such effects may be stronger with higher contrast material concentrations.
The results for SLAP lesion detection were not very good, probably because of the previously discussed problem in differentiating between a normal recess and a detachment (Figs 4–7) (18). For SLAP lesions, the findings for sensitivity and specificity were the opposite of those for supraspinatus tendon lesions: The gadoteridol-enhanced arthrograms (Figs 4, 6) were more sensitive but less specific than the Ringer solution–enhanced arthrograms (Figs 5, 7). There are potentially confounding factors at the base of the superior labrum, including undercutting by hyaline articular cartilage, basal labral degeneration, and loose connective tissue connecting the labrum to the glenoid bone, all of which may cause increased signal intensity on MR images. Such aspects may be more pronounced on T1-weighted images than on T2-weighted images. Therefore, the higher specificity of Ringer solution may not be related specifically to the contrast material but rather to the image sequence used with it.
values for diagnostic accuracy were slightly but consistently higher for the gadoteridol-enhanced arthrograms. This is another indication—in addition to the contrast-to-noise ratio variability–that gadoteridol-enhanced arthrograms may lead to more consistent image characteristics. There may have been bias in this respect, however, because the readers were used to reading MR arthrograms obtained with intraarticular gadolinium-based contrast material.
In conclusion, MR arthrograms of the shoulder obtained with gadoteridol and those obtained with Ringer solution provide equivalent diagnostic accuracy. However, the image quality of the gadoteridol-enhanced arthrograms was preferred by the authors.
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FOOTNOTES |
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Author contributions: Guarantor of integrity of entire study, C.A.B.; study concepts, C.A.B., J.H.; study design, M.Z., C.A.B., J.H.; literature research, C.A.B.; clinical studies, all authors; data acquisition, C.A.B., C.G.; data analysis/interpretation, M.Z., J.H.; statistical analysis, C.A.B., J.H.; manuscript preparation, C.A.B.; manuscript definition of intellectual content, J.H.; manuscript editing and revision/review, M.Z., J.H.; manuscript final version approval, all authors.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTS DISCUSSIONREFERENCES |
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