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1.
The purpose was to evaluate the capacity of 1.5 T magnetic resonance (MR) imaging to assess articular cartilage in racehorses with naturally occurring metacarpophalangeal joint osteoarthritis. A sagittal, three‐dimensional spoiled gradient‐recalled echo (SPGR) with fat saturation (FS) sequence was acquired ex vivo on 20 joints. Following joint dissection, specific areas on the third metacarpal condyle were designated for subsequent sampling for histologic cartilage thickness measurement and modified Mankin scoring. Cartilage thickness was measured and cartilage signal intensity was also graded (0–3) on MR images at these selected metacarpal sites. Cartilage structure was graded (0–3) macroscopically and on MR images by two examiners in defined subregions of the proximal phalanx, third metacarpal, and proximal sesamoid bones. There was good precision (mean error 0.11 mm) and moderate correlation (r=0.44; P<0.0001) of cartilage thickness measurements between MR images (0.90±0.17 mm) and histology (0.79±0.16 mm). There was moderate correlation between modified Mankin histologic score and signal intensity of cartilage (r=0.36; P<0.01) or MR cartilage structure assessment (r=0.49, P>0.001) on SPGR‐FS. The sensitivity to detect full‐thickness cartilage erosion on MR was only moderate (0.56), and these lesions were often underestimated, particularly when linear in nature. However, the specificity to detect such lesions on MR was high (0.92). While few limitations were identified, the use of a clinically applicable SPGR‐FS sequence allows a reasonably accurate method to assess structural changes affecting the articular cartilage of the equine metacarpophalangeal joint.  相似文献   

2.
OBJECTIVE: To validate use of magnetic resonance images (MRIs) for measurement of equine articular cartilage and subchondral bone thickness by comparison with measurements in histologic specimens. SAMPLE POPULATION: 32 cadaveric carpal joints from 16 horses. PROCEDURE: Magnetic resonance imaging was performed by use of 3-dimensional fast spoiled gradient echo (SPGR) and T2* 3-dimensional fast gradient echo (GRE) pulse sequences with and without fat saturation. Standard sites on the medial and lateral facets of the intermediate, radial, and third carpal bones were used for subchondral bone and articular cartilage thickness measurements. Digital image analysis software was used for MRI measurements 10 mm from the dorsal extent and perpendicular to the articular surface. Histomorphometric measurements of hyaline, calcified cartilage, and subchondral bone thickness were obtained at selected sites. Comparisons between histomorphometric and MRI measurements and between magnetic resonance pulse sequences were evaluated. RESULTS: There were significant correlations between GRE and SPGR and SPGR and histologic measurements of articular cartilage, with no significant difference between measurements and good agreement. When calcified cartilage was excluded from the histologic measurement, MRI measurements were significantly greater than histologic measurements. For subchondral bone thickness, there was significant correlation between GRE and SPGR but GRE was significantly greater than SPGR measurements. Histomorphometric and MRI measurements were strongly correlated and not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: Magnetic resonance imaging provides a good representation of cartilage and subchondral bone thickness, supporting its use in the study and clinical diagnosis of osteochondral structure and alteration.  相似文献   

3.
Chronic laminitis is a severe disease affecting the equine digit. It was hypothesized that magnetic resonance (MR) imaging would improve visualization of structures within the foot and pathology associated with chronic laminitis. This study aimed to describe the MR imaging findings in chronic laminitis, compare different pulse sequences for visualization of pathology, and to compare MR imaging with standard radiography. Twenty (10 forelimb, 10 hindlimb) cadaver limbs from 10 horses clinically diagnosed with chronic laminitis (group L) and 10 limbs without laminitis (group N) were used. Lateromedial radiographs and sagittal and transverse MR images of the foot were obtained. Radiographs and MR images were evaluated for anatomic definition and evidence of pathology. Dorsal hoof wall thickness and angle of rotation and displacement distance of the distal phalanx were measured. Comparisons were made between group L and N, forelimb and hindlimb within each horse, and MR imaging and radiography. Features consistently noted with MR images in group L, but not detected using radiography, included laminar disruption, circumscribed areas of laminar gas, laminar fluid, and bone medullary fluid. Other findings seen only on MR images included increased size and number of vascular channels, alterations in the corium coronae, and distal interphalangeal joint distension. Magnetic resonance imaging allowed better definition of laminar gas lines and P3 surface irregularity observed on radiographs. Based on measurements, group L had a greater angle of rotation, distal displacement, and dorsal hoof wall thickness than group N; forelimb hoof wall thickness was greater than hindlimb; and distal displacement and hoof wall thickness measurements were smaller using MR imaging than radiography, but had a similar pattern. It is concluded that there are features of chronic laminitis consistently observed using MR imaging and that these may be additional to features observed radiographically.  相似文献   

4.
Susceptibility artifacts caused by ferromagnetic implants compromise magnetic resonance imaging (MRI) of the canine stifle after tibial plateau leveling osteotomy (TPLO) procedures. The WARP‐turbo spin echo sequence is being developed to mitigate artifacts and utilizes slice encoding for metal artifact reduction. The aim of the current study was to evaluate the WARP‐turbo spin echo sequence for imaging post TPLO canine stifle joints. Proton density weighted images of 19 canine cadaver limbs were made post TPLO using a 3 Tesla MRI scanner. Susceptibility artifact sizes were recorded and compared for WARP vs. conventional turbo spin echo sequences. Three evaluators graded depiction quality for the tibial tuberosity, medial and lateral menisci, tibial osteotomy, and caudal cruciate ligament as sufficient or insufficient to make a diagnosis. Artifacts were subjectively smaller and local structures were better depicted in WARP‐turbo spin echo images. Signal void area was also reduced by 75% (sagittal) and 49% (dorsal) in WARP vs. conventional turbo spin echo images. Evaluators were significantly more likely to grade local anatomy depiction as adequate for making a diagnosis in WARP‐turbo spin echo images in the sagittal but not dorsal plane. The proportion of image sets with anatomic structure depiction graded adequate to make a diagnosis ranged from 28 to 68% in sagittal WARP‐turbo spin echo images compared to 0–19% in turbo spin echo images. Findings indicated that the WARP‐turbo spin echo sequence reduces the severity of susceptibility artifacts in canine stifle joints post TPLO. However, variable depiction of local anatomy warrants further refinement of the technique.  相似文献   

5.
Magnetic susceptibility artifacts as a result of metal debris from shoeing are a common problem in magnetic resonance imaging of the equine foot. Our purpose was to determine the suitability of radiography as a screening tool for the presence and location of metallic particles in the equine foot and to predict the size of the resultant magnetic susceptibility artifact. Radiography had 100% sensitivity for detection of metal particles ≥1 mm diameter. Metal particles of known diameter were placed within the hoof wall of 22 cadaver feet and scanned with a low‐field strength MR imaging unit (0.21 T). Magnetic resonance images were characterized by a signal void with a hyperintense rim and adjacent image distortion at the level of the known metal location. T2* weighted sequences were the most and fast spin echo (FSE) sequences the least affected. For all four sequences (T1 gradient echo [GRE]; T2*W GRE; T2 FSE; and short tau inversion recovery FSE), linear relationships were observed between particle and resultant artifact size. Magnetic susceptibility artifact size, location and superimposition on clinically relevant anatomic structures can be predicted radiographically for particles larger than 1 mm. If metal debris cannot be removed, the least artifact‐prone FSE sequences should be selected.  相似文献   

6.
Six cadaver forelimbs were imaged in two high‐field magnetic resonance (MR) systems and one low‐field MR system following the creation of osteochondral defects on the palmar distal aspect of the third metacarpal bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2* gradient echo (GRE), T2‐weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low‐field system. PD fat saturated and 3D T1‐weighted spoiled GRE images with and without fat suppression were acquired with the high‐field systems. Lesions were measured and assigned a confidence score. The images obtained using high‐field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low‐field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low‐field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low‐field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high‐field systems when compared with the low‐field system.  相似文献   

7.
Pulsatile venous flow in the internal vertebral venous plexus of the cervical spine can lead to vertical, linear T2‐hyperintensities in the spinal cord at the cranial aspect of C3 and C4 in transverse T2‐weighted images in large breed dogs that are not accompanied by ghosting. The artifact is more conspicuous in pre‐ and postcontrast transverse T1‐weighted images and is accompanied by ghosting in that sequence, typical of a pulsatility artifact. A flow‐related artifact was confirmed as the cause for this appearance by noting its absence after either exchange of phase and frequency encoding direction or by flow compensation. Care should be exercised to avoid misdiagnosing this pulsatility artifact seen in transverse T2‐weighted images of the midcervical spine in large dogs as an intramedullary lesion when T1‐images or phase‐swap images are not available to confirm its artifactual origin.  相似文献   

8.
Magnetic resonance (MR) imaging of the canine brain is commonly acquired at field strengths ranging from 0.2 to 1.5 T. Our purpose was to compare the MR image quality of the canine brain acquired at 3 vs. 7 T in dogs. Low‐resolution turbo spin echo (TSE) T2‐weighted images (T2W) were obtained in transverse, dorsal, and sagittal planes, and high‐resolution TSE T2W and turbo spin echo proton density‐weighted images were obtained in the transverse and dorsal planes, at both 3 and 7 T. Three experienced reviewers evaluated 32 predetermined brain structures independently and without knowledge of field strength for spatial resolution and contrast. Overall image quality and evidence of artifacts were also evaluated. Contrast of gray and white matter was assessed quantitatively by measuring signal intensity in regions of interest for transverse plane images for the three pulse sequences obtained. Overall, 19 of the 32 neuroanatomic structures had comparable spatial resolution and contrast at both field strengths. The overall image quality for low‐resolution T2W images was comparable at 3 and 7 T. High‐resolution T2W was characterized by superior image quality at 3 vs. 7 T. Magnetic susceptibility and chemical shift artifacts were slightly more noticeable at 7 T. MR imaging at 3 and at 7 T provides high spatial resolution and contrast images of the canine brain. The use of 3 and 7 T MR imaging may assist in the elucidation of the pathogenesis of brain disorders, such as epilepsy.  相似文献   

9.
Tendon injuries are common in athletic humans and horses. Ultrasonography is the diagnostic method of choice in horses with tendon injuries but there is increasing application of magnetic resonance (MR) imaging to monitor and follow‐up tendon healing. A core lesion was created in the superficial digital flexor tendon (SDFT) of each forelimb of four horses. One of the four horses was euthanized at 2, 4, 8, and 12 weeks after creation of the lesion. MR examinations of the SDFT were performed immediately post mortem in a 1.5 T Siemens Symphony magnet and compared with histologic findings. Measurements from the MR images were also compared to ultrasonographic measurements available from the same lesions. Tendon lesions appeared as well‐circumscribed hyperintensities in the core of the SDFT on all pulse sequences. Lesions were most conspicuous on fat‐suppressed fast low angle shot (FLASH) sequences and least conspicuous on T2 transverse dual turbo spin echo (T2 TSE) sequences. The signal‐difference‐to‐noise ratio decreased with the age of the lesion in all sequences in this study. Twelve‐week‐old lesions were not visible on T2 TSE images but in all other sequences the lesion remained hyperintense. The lesion volume and maximum cross‐sectional area of core lesions were significantly smaller in T2 TSE images than in other MR sequences. The lesion volume and maximum cross‐sectional area of core lesions were significantly larger in proton density, T1, and FLASH sequences and significantly smaller in T2 sequences than when measured from ultrasonographic images. Through comparison between sequences, MR imaging may be able to provide information on various stages of tendon healing.  相似文献   

10.
Magnetic resonance (MR) imaging is important in diagnosing musculoskeletal injuries in horses. However, there is still much to learn regarding the significance of lesions identified in equine MR images. Of particular importance is the clinical significance of signal change as a function of pulse sequence. We hypothesized that a resolution of tendon, ligament, and bone marrow lesions on short‐tau inversion recovery (STIR) images would be associated with a return to soundness, and that a persistence of tendon and ligament lesions on only T1‐weighted (T1w) gradient recalled echo (GRE) images would not be associated with persistent lameness. The medical records and MR images of 27 horses that had a hyperintense lesion in initial STIR MR images followed by a subsequent follow‐up MR imaging examination were reviewed. Horses whose tendon or ligament lesions had resolved on STIR images at the time of the recheck examination were significantly more likely to be sound than horses whose lesions persisted on STIR images (P=0.039). This association did not exist in horses with bone marrow lesions (P=1.00). Horses whose tendon or ligament lesions persisted only on T1w GRE images were no more likely to be sound than horses whose lesion persisted on at least one other sequence type (P=0.26). However, the low number of horses included in this analysis may have precluded identification of a significant difference in lameness status. Tendon or ligament lesions visualized on STIR images may represent active lesions that may contribute to lameness in the horse.  相似文献   

11.
Reasons for performing study: To determine the reliability of 2 magnetic resonance imaging (MRI) systems for detection of cartilage and bone lesions of the equine fetlock. Objectives: To test the hypotheses that lesions in cartilage, subchondral and trabecular bone of the equine fetlock verified using histopathology can be detected on high‐ and low‐field MR images with a low incidence of false positive or negative results; that low‐field images are less reliable than high‐field images for detection of cartilage lesions; and that combining results of interpretation from different pulse sequences increases detection of cartilage lesions. Methods: High‐ and low‐field MRI was performed on 19 limbs from horses identified with fetlock lameness prior to euthanasia. Grading systems were used to score cartilage, subchondral and trabecular bone on MR images and histopathology. Sensitivity and specificity were calculated for images. Results: High‐field T2*‐weighted gradient echo (T2*W‐GRE) and low‐field T2‐weighted fast spin echo (T2W‐FSE) images had high sensitivity but low specificity for detection of cartilage lesions. All pulse sequences had high sensitivity and low–moderate specificity for detection of subchondral bone lesions and moderate sensitivity and moderate–high specificity for detection of trabecular bone lesions (histopathology as gold standard). For detection of lesions of trabecular bone low‐field T2*W‐GRE images had higher sensitivity and specificity than T2W‐FSE images. Conclusions: There is high likelihood of false positive results using high‐ or low‐field MRI for detection of cartilage lesions and moderate–high likelihood of false positive results for detection of subchondral bone lesions compared with histopathology. Combining results of interpretation from different pulse sequences did not increase detection of cartilage lesions. MRI interpretation of trabecular bone was more reliable than cartilage or subchondral bone in both MR systems. Potential relevance: Independent interpretation of a variety of pulse sequences may maximise detection of cartilage and bone lesions in the fetlock. Clinicians should be aware of potential false positive and negative results.  相似文献   

12.
Intracranial diseases are common in dogs and improved noninvasive diagnostic tests are needed. Magnetic resonance (MR) spectroscopy is a technique used in conjunction with conventional MR imaging to characterize focal and diffuse pathology, especially in the brain. As with conventional MR imaging, there are numerous technical factors that must be considered to optimize image quality. This study was performed to develop an MR spectroscopy protocol for routine use in dogs undergoing MR imaging of the brain. Fifteen canine cadavers were used for protocol development. Technical factors evaluated included use of single‐voxel or multivoxel acquisitions, manual placement of saturation bands, echo time (TE), phase‐ and frequency‐encoding matrix size, radiofrequency coil, and placement of the volume of interest relative to the calvaria. Spectrum quality was found to be best when utilizing a multivoxel acquisition with the volume of interest placed entirely within the brain parenchyma without use of manually placed saturation bands, TE = 144 ms, and a quadrature extremity radiofrequency coil. An 18 × 18 phase‐ and frequency‐encoding matrix size also proved optimal for image quality, specificity of voxel placement, and imaging time.  相似文献   

13.
The purpose of this study was to describe the normal magnetic resonance (MR) imaging characteristics of the palmar structures of the equine podotrochlear apparatus by means of retrospective evaluation of MR imaging studies of 16 cadaver limbs. The articular aspect of the distal sesamoid bone was not evaluated in this study. Equine digits were imaged with a human knee radiofrequency coil in a 1.5 T magnetic field, using spin echo (SE) T1-weighted, turbo spin echo proton density (TSE PD)-weighted with and without fat saturation (FS), and FS TSE T2-weighted sequences. The limbs were dissected after imaging to validate the absence of gross abnormalities of the flexor aspect of the distal sesamoid bone, of the deep digital flexor tendon, and the distal impar sesamoidean ligament. Seven deep digital flexor tendons were subjected to histologic examination to exclude any microscopic tendon pathology. The anatomic structures of the podotrochlear apparatus were easily identified on MR images. Compact bone of the flexor cortex of the distal sesamoid bone had low intensity signal on all sequences. In 11 digits an increased signal was seen within the thickness of the sagittal eminence of the flexor cortex in SE T1-weighted images and in TSE PD-weighted images without FS. Trabecular bone had a granular appearance and high signal in SE T1-weighted sequences and TSE images without FS. The deep digital flexor tendon had low signal on FS T2-weighted images, while on short echo time sequences (T1- and PD-weighted sequences), the tendon signal varied depending on the relative orientation between its fibers and the static magnetic field. Seven tendons had stippled appearance due to small intratendonous foci of slightly increased signal on transverse T1-weighted images. MR imaging provides a thorough evaluation of the anatomical structure of the podotrochlear apparatus: A good knowledge of the MR imaging appearance and anatomy and an awareness of potential pitfalls will improve diagnostic specificity for the detection of pathologic changes.  相似文献   

14.
T2*‐weighted magnetic resonance imaging (MRI) has been reported to help improve detection of intracranial hemorrhage and is widely used in human neuroimaging. To assess the utility of this technique in small animals, interpretations based on this sequence were compared with those based on paired T2‐weighted and fluid‐attenuated inversion recovery (FLAIR) sequences in 200 dogs and cats that underwent brain MRI for suspected intracranial disease. Two sets of images (T2 + FLAIR and T2*) were reviewed separately in random order unaccompanied by patient information and were interpreted as normal or abnormal based on whether intracranial abnormalities were seen. The number and location of intracranial lesions were recorded. Eighty‐five studies were considered normal and 88 were considered abnormal based on both sets of images, with good agreement (κ = 0.731) between the two. Susceptibility artifact was present in 33 cases (16.5%) on T2*‐weighted images. In 12 cases (6%) a total of 69 lesions were seen on T2*‐weighted images that were not seen on T2/FLAIR, all of which were associated with susceptibility artifact caused by presumed intracranial hemorrhage. Pseudolesions were seen on T2*‐weighted images in five cases, none of which were associated with susceptibility artifact. Abnormalities were seen on T2/FLAIR images that were not seen on T2*‐weighted images in 35 cases, confirming that T2* does not replace standard spin echo sequences. These results support inclusion of T2*‐weighted sequences in small animal brain MRI studies and indicate that that a large number of abnormalities (especially hemorrhagic lesions) can go undetected if it is not performed.  相似文献   

15.
The widths of spaces between the thoracolumbar processi spinosi (interspinous spaces) are frequently assessed using radiography in sports horses; however effects of varying X‐ray beam angles and geometric distortion have not been previously described. The aim of this prospective, observational study was to determine whether X‐ray beam angle has an effect on apparent widths of interspinous spaces. Thoracolumbar spine specimens were collected from six equine cadavers and left‐right lateral radiographs and sagittal and dorsal reconstructed computed tomographic (CT) images were acquired. Sequential radiographs were acquired with each interspinous space in focus. Measurements were performed for each interspinous space in the focus position and up to eight angled positions as the interspinous space moved away from focus (±). Focus position measurements were compared to matching sagittal CT measurements. Effect of geometric distortion was evaluated by comparing the interspinous space in radiographs with sagittal and dorsal reconstructed CT images. A total of 49 interspinous spaces were sampled, yielding 274 measurements. X‐ray beam angle significantly affected measured width of interspinous spaces in position +3 (P = 0.038). Changes in width did not follow a consistent pattern. Interspinous space widths in focus position were significantly smaller in radiographs compared to matching reconstructed CT images for backs diagnosed with kissing spine syndrome (P < 0.001). Geometric distortion markedly affected appearance of interspinous space width between planes. In conclusion, X‐ray beam angle and geometric distortion influence radiographically measured widths of interspinous spaces in the equine thoracolumbar spine, and this should be taken into consideration when evaluating sport horses.  相似文献   

16.
Motion artifact is an important limiting factor for abdominal magnetic resonance imaging (MRI) in veterinary patients. The purpose of this study was to determine the effects of pulse sequence on abdominal MRI diagnostic quality in dogs. Ten normal dogs were each scanned using 16 MRI pulse sequences. Sequences included breath‐holding sequences, respiratory navigation sequences, and traditional spin‐echo sequences. Four observers independently scored diagnostic quality for each sequence based on the appearance of specific organs, overall diagnostic quality, and degree of artifactual interference. Signal‐to‐noise ratio and contrast‐to‐noise ratio were also calculated for each sequence. The sequence with the highest overall mean diagnostic quality score was the dorsal T2 turbo spin echo (TSE) with fat saturation and breath‐holding. The sequence with the lowest mean diagnostic quality score was the dorsal T2 fast spin echo. The sequence with the highest signal‐to‐noise ratio for all evaluated organs was the sagittal T1 spin echo. Signal‐to‐noise and contrast‐to‐noise ratios did not correlate with subjective assessment of overall diagnostic quality for the majority of the sequences evaluated (P < 0.05). The three sequences considered to have the highest diagnostic quality for the cranial abdomen were the dorsal T2 TSE with fat saturation and breath‐hold, transverse T1 turbo fast low‐angle shot gradient echo with breath‐hold, and dorsal T2 half‐Fourier acquisition single shot TSE with respiratory navigation. These sequences had short acquisition times, yielded studies of similar diagnostic quality, provided complementary information, and are therefore recommended for routine canine abdominal MRI protocols.  相似文献   

17.
We compared the ability of 1.5 T magnetic resonance imaging (MRI), computed tomography (CT), and computed radiography (CR) to evaluate noncartilaginous structures of the equine metacarpophalangeal joint (MCP), and the association of imaging changes with gross cartilage damage in the context of osteoarthritis. Four CR projections, helical single‐slice CT, and MRI (T1‐weighted gradient recalled echo [GRE], T2*‐weighted GRE with fast imaging employing steady‐state acquisition [FIESTA], T2‐weighted fast spin echo with fat saturation, and spoiled gradient recalled echo with fat saturation [SPGR‐FS]) were performed on 20 racehorse cadaver forelimbs. Osteophytosis, synovial effusion, subchondral bone lysis and sclerosis, supracondylar lysis, joint fragments, bone marrow lesions, and collateral desmopathy were assessed with each modality. Interexaminer agreement was inferior to intraexaminer agreement and was generally moderate (i.e., 0.4<κ<0.6). Subchondral bone sclerosis scores using CT or MRI were correlated significantly with the reference quantitative CT technique used to assess bone mineral density (P<0.0001). Scores for subchondral lysis and osteophytosis were higher with MRI or CT vs. CR (P<0.0001). Although differences between modalities were noted, osteophytosis, subchondral sclerosis, and lysis as well as synovial effusion were all associated with the degree of cartilage damage and should be further evaluated as potential criteria to be included in a whole‐organ scoring system. This study highlights the capacity of MRI to evaluate noncartilaginous changes in the osteoarthritic equine MCP joint.  相似文献   

18.
Reasons for performing study: Erosion of the palmar (flexor) aspect of the navicular bone is difficult to diagnose with conventional imaging techniques. Objectives: To review the clinical, magnetic resonance (MR) and pathological features of deep erosions of the palmar aspect of the navicular bone. Methods: Cases of deep erosions of the palmar aspect of the navicular bone, diagnosed by standing low field MR imaging, were selected. Clinical details, results of diagnostic procedures, MR features and pathological findings were reviewed. Results: Deep erosions of the palmar aspect of the navicular bone were diagnosed in 16 mature horses, 6 of which were bilaterally lame. Sudden onset of lameness was recorded in 63%. Radiography prior to MR imaging showed equivocal changes in 7 horses. The MR features consisted of focal areas of intermediate or high signal intensity on T1‐, T2*‐ and T2‐weighted images and STIR images affecting the dorsal aspect of the deep digital flexor tendon, the fibrocartilage of the palmar aspect, subchondral compact bone and medulla of the navicular bone. On follow‐up, 7/16 horses (44%) had been subjected to euthanasia and only one was being worked at its previous level. Erosions of the palmar aspect of the navicular bone were confirmed post mortem in 2 horses. Histologically, the lesions were characterised by localised degeneration of fibrocartilage with underlying focal osteonecrosis and fibroplasia. The adjacent deep digital flexor tendon showed fibril formation and fibrocartilaginous metaplasia. Conclusions: Deep erosions of the palmar aspect of the navicular bone are more easily diagnosed by standing low field MR imaging than by conventional radiography. The lesions involve degeneration of the palmar fibrocartilage with underlying osteonecrosis and fibroplasia affecting the subchondral compact bone and medulla, and carry a poor prognosis for return to performance. Potential relevance: Diagnosis of shallow erosive lesions of the palmar fibrocartilage may allow therapeutic intervention earlier in the disease process, thereby preventing progression to deep erosive lesions.  相似文献   

19.
Gadoxetate disodium (Gd‐EOB‐DTPA; gadolinium‐ethoxybenzyl‐diethylene triamine penta‐acetic acid) is a newly developed paramagnetic contrast agent reported to have a high specificity for the hepatobiliary system in humans. The purpose of this prospective study was to describe effects of Gd‐EOB‐DTPA contrast administration on MRI characteristics of the liver in eight clinically healthy dogs. Precontrast dorsal and transverse T1‐weighted spin echo, T2‐weighted fast spin echo, and transverse T1‐weighted 3D gradient echo (VIBE; volume‐interpolated body examination) pulse sequences were acquired for each dog. Dogs were assigned to four groups based on contrast dose administered (0.0125 mmol/kg or 0.025 mmol/kg), and pulse sequences acquired after contrast administration (T1‐weighted spin echo and T1‐weighted 3D gradient echo). Liver signal intensity ratios were calculated and compared between the two contrast dose groups and two postcontrast pulse sequence groups using ANOVA. No adverse effects of contrast administration were observed. All dogs exhibited homogeneous contrast enhancement of the liver with no statistical difference in enhancement between the two different contrast doses. Contrast enhancement in all dogs peaked between 1 and 10 min after intravenous injection. There was a significant difference in mean signal intensity ratios between sequences (P = 0.035) but not between doses (P = 0.421). Postcontrast signal intensities of the liver parenchyma were significantly higher for the T1‐weighted 3D gradient echo images when compared to the T1‐weighted spin echo sequences. Findings indicated that Gd‐EOB‐DTPA contrast administration is safe in healthy dogs and causes homogeneous enhancement of the liver that is more pronounced in T1‐weighted 3D gradient echo MRI pulse sequences.  相似文献   

20.
The suitability of low‐field magnetic resonance (MR) imaging for assessment of articular cartilage has been questioned, based on insufficient image quality. The purposes of this study were to describe the MR anatomy of the normal distal interphalangeal (DIP) cartilage, and to evaluate the sensitivity and accuracy of low‐field MR imaging for identification of cartilage erosions that were created ex vivo. Imaging sequences included sagittal and dorsal multiple‐oblique T1‐weighted gradient‐recalled echo (GRE) and sagittal dual echo sequences. In the thickest regions, normal cartilage appeared as a trilaminar structure on high‐resolution T1‐weighted GRE sequences. All 8 mm large full‐thickness erosions were correctly identified (100% sensitivity and accuracy) using T1‐weighted GRE sequences. Sensitivity and accuracy ranged from 80% to 100% and 10% to 80%, respectively, for detecting focal full‐thickness erosions and from 35% to 80% and 35% to 60%, respectively, for detecting partial thickness erosions, using T1‐weighted GRE sequences. Superficial irregularities were not diagnosed using any sequence. Overall, fewer cartilage alterations were detected with sagittal dual echo sequences than with sagittal T1‐weighted GRE sequences. The dorsal multiple‐oblique plane was useful to detect linear dorsopalmar erosions. A combination of T1‐weighted GRE sequences in two planes has potential for identification of severe DIP cartilage erosion in anesthetized horses using low‐field MR imaging.  相似文献   

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