Correlation between apparent diffusion coefficient and viscoelasticity of articular cartilage in a porcine model.

OBJECTIVE: Quantitative MR imaging techniques of degenerative cartilage have been reported as useful indicators of degenerative changes in cartilage extracellular matrix, which consists of proteoglycans, collagen, non-collagenous proteins, and water. Apparent diffusion coefficient (ADC) mapping of cartilage has been shown to correlate mainly with the water content of the cartilage. As the water content of the cartilage in turn correlates with its viscoelasticity, which directly affects the mechanical strength of articular cartilage, ADC can serve as a potentially useful indicator of the mechanical strength of cartilage. The aim of this study was to investigate the correlation between ADC and viscoelasticity as measured by indentation testing. MATERIALS AND METHODS: Fresh porcine knee joints (n = 20, age 6 months) were obtained from a local abattoir. ADC of porcine knee cartilage was measured using a 3-Tesla MRI. Indentation testing was performed on an electromechanical precision-controlled system, and viscosity coefficient and relaxation time were measured as additional indicators of the viscoelasticity of cartilage. The relationship between ADC and viscosity coefficient as well as that between ADC and relaxation time were assessed. RESULTS: ADC was correlated with relaxation time and viscosity coefficient (R(2) = 0.75 and 0.69, respectively, p < 0.01). The mean relaxation time values in the weight-bearing and non-weight-bearing regions were 0.61 ± 0.17 ms and 0.14 ± 0.08 ms, respectively. CONCLUSIONS: This study found a moderate correlation between ADC and viscoelasticity in the superficial articular cartilage. Both molecular diffusion and viscoelasticity were higher in weight bearing than non-weight-bearing articular cartilage areas.

Evaluation of human muscle hardness after dynamic exercise with ultrasound real-time tissue elastography: a feasibility study.

AIM: To assess the feasibility of ultrasound real-time tissue elastography (RTE) for measuring exercise-induced changes in muscle hardness and to compare the findings of RTE with those of a tissue hardness meter for semi-quantitative assessment of the hardness of exercised muscles. MATERIALS AND METHODS: Nine male participants performed an arm-curl exercise. RTE measurements were performed by manually applying repetitive compression with the transducer on the scan position before exercise, immediately after exercise, and at 30 min after exercise; strain ratios between muscle and a reference material (hydrogel) were calculated (muscle strain/material strain). A tissue hardness meter was also used to evaluate muscle hardness. The intraclass correlation coefficients (ICCs) for the three repeated measurements at each measurement time were calculated to evaluate the intra-observer reproducibility of each technique. RESULTS: Immediately after exercise, the strain ratio and the value obtained using the tissue hardness meter significantly decreased (from 1.65 to 1.35) and increased (from 51.8 to 54.3), respectively. Both parameters returned to their pre-exercise value 30 min after exercise. The ICCs of the RTE (and the ICCs of the muscle hardness meter) were 0.971 (0.816) before exercise, 0.939 (0.776) immediately after exercise, and 0.959 (0.882) at 30 min after exercise. CONCLUSION: Similar to the muscle hardness meter, RTE revealed the exercise-induced changes of muscle hardness semi-quantitatively. The intra-observer reproducibility of RTE was very high at each measurement time. These findings suggest that RTE is a clinically useful technique for assessing hardness of specific exercised muscles.

Value of subtraction in fat-saturated three-dimensional contrast-enhanced magnetic resonance angiography of the hemodialysis fistula.

PURPOSE: To evaluate image subtraction in a three-dimensional contrast-enhanced magnetic resonance angiography (3D CE-MRA) using fat suppression for the hemodialysis fistula. MATERIAL AND METHODS: Fifteen patients suffering from hemodialysis fistula dysfunction were imaged with 3D CE-MRA using fat suppression and digital subtraction angiography (DSA). Non-subtracted and subtracted MRA images using maximum intensity projection (MIP) were constructed and the validity of the MRA interpretations of the degree of vascular stenoses was evaluated using DSA as the standard of reference. Image quality was assessed using qualitative analysis (vessel contrast) and quantitative analysis (contrast-to-noise ratio (CNR) of the vessel versus the background). RESULTS: In the vessels with stenosis of 50% or greater, the sensitivity and specificity of the non-subtracted MRA were 89.5% and 81.8%, respectively, and of the subtracted MRA 89.5% and 86.4%, respectively. There was no significant difference in the detectability of stenoses between either MRA. The vessel contrast of the anterior interosseous artery and the CNR of the anterior interosseous artery versus the background on the subtracted MRA were significantly superior to those on the non-subtracted MRA. With regard to the radial artery and cephalic vein, there was no significant difference in the vessel contrast and CNR between either MRA. CONCLUSION: Both subtracted and non-subtracted MRA techniques are useful in detecting hemodialysis fistula dysfunction.

Magnetic resonance microscopic images with 50-mm field-of-view of the medial aspect of the knee.

PURPOSE: To demonstrate the utility of microscopic images with field-of-view of 50 mm in delineation of the medial aspect of the knee, including fascial plane, superficial and deep layers of the medial collateral ligament (MCL), and the medial meniscus. MATERIAL AND METHODS: Using a phantom, the signal-to-noise ratio (SNR) of a magnetic resonance (MR) microscopy coil with a diameter of 47 mm was calculated and compared with that of a regular coil. Four cadaveric knees were imaged by microscopy and resected to confirm the morphologies. Sixty-nine patients with internal derangement were examined by routine and microscopic imaging. Comparing the paired images for delineation of the above-mentioned structures, a qualitative image analysis was performed. RESULTS: SNRs of the MR microscopy coil were higher than those of the regular coil. MR microscopy readily demonstrated the multilayered appearance of the fascial plane and both layers of the MCL in cadavers and patients. In cases with MCL tears, ruptured stumps were identified by microscopy. MR microscopy delineated tiny cleavages in cases with meniscal tears. The mean values of qualitative evaluation of the MR microscopy were significantly higher than those of the routine imaging. CONCLUSION: High-resolution imaging delineated fine structures of the medial aspect of the knee.

The effects of various therapeutic measures on shoulder range of motion and cross-sectional areas of rotator cuff muscles after baseball pitching.

AIM: The purpose of this study was to investigate the effects of various therapeutic measures on the shoulder range of motion (ROM) and muscle cross-sectional area (mCSA) of rotator cuff muscles after baseball pitching. EXPERIMENTAL DESIGN: a mode of therapeutic measures was classified in 4 groups; the control (CON), ice treatment (IT), light shoulder exercise (LSE) and ice treatment with LSE (ILSE) groups. Each therapeutic measure was performed after pitching. PARTICIPANTS: 7 healthy, skilled baseball pitchers. MEASURES: ROM and mCSA were measured before pitching, immediately after pitching, at the time of the therapeutic measure, and 24 hours after pitching. Shoulder ROM at 90 inverted exclamation mark of abduction included internal rotation (IROM), maximum internal rotation (IMROM), external rotation (EROM) and maximum external rotation (EMROM). RESULTS: In all groups, both IROM and IMROM were significantly decreased after pitching compared with the pre-exercise values and conversely both EROM and EMROM were significantly increased. The mCSA of all rotator cuff muscles were increased significantly after pitching. For IMROM, ILSE showed a significant recovery at the post-therapeutic measure compared with the others and at 24 hours after pitching compared with IT, respectively. For IROM, both LSE and ILSE showed significant recovery compared with CON at the post-therapeutic measure. For the mCSA of external muscles, ILSE showed a greater decrease at the post-therapeutic measure than the others, and at 24 hours after pitching than CON. CONCLUSION: This study suggested the possibility that ILSE was more effective to recover ROM and decrease mCSA than the other methods.

Routine MR examination of the knee using parallel imaging.

AIM: To demonstrate the feasibility and the clinical value of parallel imaging of the knee. METHODS: A pair of flex coils was used for the parallel imaging. Before optimization of the protocol, qualitative and quantitative analysis was performed by volunteer and phantom study. Two separate consecutive groups of 80 patients were examined with or without parallel imaging and compared with the arthroscopic results. RESULTS: Parallel imaging obtained a total of 164 images of six series in less than 20 min. Compared with conventional imaging, the parallel imaging appeared slightly noisy with an 83% relative signal-to-noise ratio. Demarcation of the cruciate ligaments and menisci were rated equivalent. For the patients study, the parallel imaging delineated ligament and meniscus pathologies with accuracies of over 93%. CONCLUSION: Parallel MR imaging of the knee enables significant reduction of scan time as well as preserving diagnostic results.

The effects of various therapeutic measures on shoulder strength and muscle soreness after baseball pitching.

AIM: This study was intended as an investigation of the effects of various therapeutic measures on the shoulder strength and muscle soreness after baseball pitching. EXPERIMENTAL DESIGN: participants threw 98 pitches in a simulated single game. The mode of the therapeutic measures after pitching were classified into 4 groups; the control group (CON), the ice treatment group (IT), the light shoulder exercise group (LSE) and the ice treatment with LSE group (ILSE). Each therapeutic measure was applied to the dominant shoulder immediately after pitching. PARTICIPANTS: 7 healthy, skilled baseball pitchers. MEASURES: both shoulder strength and muscle soreness were measured before pitching, immediately after pitching (Post-P), at the time of the therapeutic measure (Post-TM), and 24 hours after pitching (Post-24 h). RESULTS: All 4 groups showed shoulder strength losses in shoulder abduction, internal/external rotation with no shoulder abduction or with the shoulder abducted to 90 degrees immediately after pitching. ILSE had greater recovery from Post-P values at Post-TM or Post-24 h than the other methods in all 5 shoulder strengths. On the other hand, the soreness in shoulder internal rotation was increased significantly from Post-P and continued by Post-24 h. Both IT and ILSE had beneficial effects on reducing the shoulder muscle soreness at Post-TM or Post-24 h. CONCLUSION: The findings of this study suggested that ILSE was the optimal therapeutic measure against decreased shoulder strength or increased shoulder muscle soreness resulting from the repetitive baseball pitching.

Magnetic resonance imaging of the rotator cuff muscles after baseball pitching.

AIM: The purposes of present study were to investigate quantitatively using functional MR imaging the effect of a series of throwing activities on rotator cuff muscles and to compare the effect of pitching with that of all-out shoulder external rotator exercise as the targeted external rotator muscle group (the infraspinatus and the teres minor). EXPERIMENTAL DESIGN: MRI measurements after 135 baseball pitches or all-out shoulder external rotator exercise (concentric mode) in each subject's nondominant shoulder. PARTICIPANTS: 6 amateur baseball pitchers. MEASURES: serial T2-weighted images of rotator cuff muscles were obtained before pitching (or shoulder exercise) and immediately, 30, 60 min, 24, 48, 96 hrs after pitching (or shoulder exercise). T2 relaxation times (T2) at each measurement time were calculated for the rotator cuff muscles. RESULTS: Both the supraspinatus and the external rotator muscle group showed significant T2 elevations until 96 hrs after pitching. The subscapularis also showed significantly increased T2 until postpitching 48 hrs. On the other hand, a significant T2 elevation continued until 60 min after shoulder exercise, but thereafter returned towards the value at rest over the next 24 hrs. CONCLUSION: Long lasting T2 elevations in rotator cuff muscles would be associated with an increase in each intramuscular water content, and may be attributed to the muscle damage that resulted from eccentric contraction during pitching. This information should serve as a useful complement to shoulder injury prevention for baseball pitchers.

[Preliminary trial of three-dimensional water-excitation magnetization transfer contrast MR imaging of articular cartilage].

MR images of articular cartilage were evaluated with a three-dimensional (3D) water-excitation sequence (repetition time/echo time/flip angle = 28 msec/14 msec/20 degrees) with and without on-resonance magnetization transfer contrast (MTC) pulse in-vitro and in-vivo. 3D water-excitation images with MTC pulse showed a significantly higher contrast-to-noise ratio between normal saline or joint effusion and articular cartilage than images without MTC pulse. In 2 patients with osteoarthritis of the knee, joint effusion showed higher signal intensity than cartilage (arthrogram-like effect) on 3D water-excitation MTC images. The contrast between joint effusion and articular cartilage on 3D water-excitation MTC images was similar to that on fat-suppressed 2D protondensity-weighted fast spin echo images. In conclusion, 3D water-excitation MTC imaging is a promising method by which to evaluate articular cartilage in osteoarthritis and cartilage defect with thin sections and a reasonable scan time.

High temporal resolution dynamic contrast MRI in a high risk group for placenta accreta.

Antenatal diagnosis of placenta accreta with MR is not easy even now because T2-weighted images (T2WI) cannot differentiate chorionic villi from decidua basalis. We performed dynamic contrast MRI to study whether trophoblastic villi could be separately demonstrated from the decidua basalis, and whether the contrast resolution between the placenta and myometrium could improve compared to T2WI. Six pregnant women with prior cesarean section were examined at 34-38 gestational weeks. Sagittal T2-weighted images with fast spin echo sequences and dynamic contrast studies with fast field echo sequence every 10-14 s after contrast injection were performed. We analyzed the enhancing pattern of the placenta and compared the contrast between placenta and myometrium. We reviewed medical records to identify complications during the placental delivery and the complications of their newborns. In the early phase after contrast enhancement, multiple foci of the strong lobular enhancement were observed in all cases. Other parts of placenta were slowly but strongly enhanced following them. We speculated that the former corresponded to intervillous space and the latter decidua basalis. The contrast between placenta and myometrium tended to be distinct near the inner cervical os on both T2WI and dynamic contrast study. On the other hand, it was indistinct in the upper part of the uterine body on T2WI despite it was clearly demonstrated on dynamic contrast study. The placentae were delivered without any complication in all cases. Although two neonates showed fetal distress, none of the infant remained any sequelae at the time of the discharge. The other four were well although one of them complicated with meconium staining. As dynamic contrast MRI can differentiate chorionic villi and decidua basalis, and can provide excellent contrast between placenta and myometrium at anywhere within the uterus, it may be a promising technique for antepartum diagnosis of the placenta accreta.

Kinematic MR imaging of the knee.

This is an overview of the "cine magnetic resonance (MR) imaging" system and rapid (ultra-fast) MR imaging of the knee for evaluation of injury of the cruciate ligament including its function during flexion and extension. Cine MR imaging using a gating system and a cine acquisition delineates alterations of the signal and shape of the cruciate ligaments and menisci. Rapid (ultra-fast) MR images with a single acquisition time of half second or less using a mobile knee brace and a flexible surface coil has enabled rapid acquisition of moving knee motion in multi-image frames. Visualization of the moving normal and torn anterior cruciate ligaments indicates that kinematic MR imaging of the moving knee is advantageous in evaluating the continuity and tension in the cruciate ligaments.

[MR imaging of posterior cruciate ligament injuries].

Posterior cruciate ligament(PCL) injuries are less frequent than anterior cruciate ligament(ACL) injuries, but are presumably more common than once thought. Thirty-nine patients with PCL injuries identified on MR images were studied. The criteria for PCL injury were complete tear, partial tear, and avulsion fracture. The approximate site of a partial tear was categorized as proximal, midsubstance, distal, or combination. Fourteen patients(35.9%) had complete tears of the PCL, 21 patients(53.8%) had partial tears, and four patients(10.3%) had avulsion fractures. A total of 12 patients (30.7%) had isolated PCL injuries, while the remaining 27 patients demonstrated evidence of other coexistent knee injuries, such as meniscal tears and ligamentous injuries. Of coexistent knee injuries, meniscal tears(18 patients, 46.2%) were most often seen.

Current practice of knee MR imaging in Japan (radiologist's view).

The knee is probably the most frequent site for MR imaging of the extremities in most institutions, and it has significantly changed the practice of knee surgery, including arthroscopy. The following commentary by a radiologist discusses the growing number of MR units, which facilitates increases in the number of MR examinations of the knee in Japan. This easy access to MRI includes elderly patients with degenerative knee disorders, as well as younger patients with traumatic injuries. With prolonged life expectancy, indication for MRI of the knee will be expanded, despite its high cost. Precise evaluation of articular cartilage in the early stages of regeneration is still a challenge; proper use of MR imaging for this disorder must be considered.

Polyamines of the thermophilic eubacteria belonging to the genera Thermosipho, Thermaerobacter and Caldicellulosiruptor.

Cellular polyamines of four new thermophiles located in three early branched eubacterial clades, were investigated for the chemotaxonomic significance of polyamine distribution profiles. The thermophilic anaerobic Thermosipho japonicus, belonging to the order Thermotogales, contained norspermidine, norspermine and thermospermine in addition to spermidine and spermine. The polyamine profile was identical to the polyamine composition of Thermotoga, Fervidobacterium and Petrotoga species of the order. Spermidine, norspermidine, spermine, N4-bis(aminopropyl)spermidine and agmatine were found in thermophilic aerobic Thermaerobacter marianensis. Some differences were observed in the polyamine compositions of the phylogenetically related thermophilic anaerobes, Moorella, Dictyoglomus, Thermoanaerobacterium and Thermoanaerobacter species. Thermophilic anaerobic Caldicellulosiruptor kristianssonii and Caldicellulosiruptor owensensis contained a linear penta-amine, thermopentamine, and two quaternary branched penta-amines, N4-bis(aminopropyl)spermidine and N4-bis(aminopropyl)norspermidine, as the major polyamines. A novel tertiary branched penta-amine, N4-aminopropylspermine, was found in the two Caldicellulosiruptor species.

MR imaging of the flexed knee: comparison to the extended knee in delineation of meniscal lesions.

The aim of this study was to obtain MR images in the flexed-knee position and to compare the diagnostic value to the extended position in delineation of the menisci. With a mobile knee brace and a flexible surface coil, the knee joint was either fully extended or bent to a semi-flexed position (average 45 degrees of flexion) within a 1.5-T superconducting magnet. Sets of sagittal MR images were obtained for both the extended- and flexed-knee positions. Using the arthroscopic results as gold standards, 97 menisci were evaluated. Two observers interpreted each MR image of the extended and flexed positions independently without knowledge of the arthroscopic results. Flexed-knee MR images revealed 22 of the 27 arthroscopically proven torn menisci and 69 of the 70 intact menisci, for a sensitivity of 81.5%, a specificity of 98.6%, and an accuracy of 93.8%. Extended-knee MR images indicated a sensitivity of 81.5%, a specificity of 92.9%, and an accuracy of 89.7%. No statistically significant difference was found between the two positions. To enhance MR visualization of all the knee components, we recommend examining the knee in a flexed position within the magnet.

Measurements of macromolecule-bound and ultra-filtrable polyamines in rat liver homogenized without buffer.

Ultra-filtrable and macromolecule-bound polyamines in rat liver homogenates, made without buffer, were determined, using Potter-Elvehjem homogenizer and commercially available, pressure-aided ultrafiltration device with a membrane pore size that allows passage of particles of molecular weight no larger than 5000. About 90% of polyamines in the liver were shown to be equilibrated with externally added 15N-labeled polyamines, based on the difference in the ratio of the natural to 15N-labeled polyamine in the liver homogenate and the ultrafiltrate. The entire amount of ultrafiltrate in the homogenized liver, required for calculation of the amounts of ultra-filtrable and macromolecule-bound polyamines, was estimated to be about 0.25 g in one gram of the homogenate, using a limited dilution curve of spermine in the ultrafiltrate with phosphate buffered saline and distilled water. With this value, ultra-filtrable polyamines in normal rat liver homogenate were calculated as about 25%, 8%, and 2% of the total amount of putrescine, spermidine, and spermine, respectively. The method was then used to measure ultra-filtrable and macromolecule-bound polyamines in regenerating rat liver homogenates, to examine possible changes of polyamines during cell growth. The method was also applied to measure other ultra-filtrable compounds such as amino acids and inorganic ions in rat liver homogenate.

Changes in the liver parenchyma after proton beam radiotherapy: evaluation with MR imaging.

The objective of this study was to describe magnetic resonance (MR) findings with a 1.5T imager for hepatic parenchymal changes after proton beam radiotherapy. Thirty-two patients who received proton radiotherapy with doses of 50-87 Gy underwent MR imaging 1-75 months (mean 22 months) after the start of irradiation. Axial T(2), T(1)-weighted imaging, and a dynamic study after a gadolinium injection were performed. The irradiated areas showed hypointense in T(1)-weighted images, hyperintense in T(2)-weighted images, and intense and prolonged enhancement on the dynamic study (maximum relative enhancement 441.8%+/-263.3 vs. surrounding liver 145.6%+/-67.7, p<0.0001). T(2) values of the irradiated areas were 50.6 to 65.8 msec greater than in the surrounding liver (p<0.005). The values increased with time, being significantly greater 13 months or longer after the beginning of the therapy than after a period of less than 3 months (p<0.05). Pathologic examinations (n = 3) indicated that the irradiated areas were composed of collapsed lobules with hepatic small vein occlusions, and rich extracellular matrices which retained extracellular fluid. MR imaging can demonstrate hepatic parenchymal changes after proton beam radiotherapy, and show the changes are irreversible.

Evaluation of the vestibular aqueduct in vestibulocochlear disorders by magnetic resonance imaging.

The visibility of the vestibular aqueduct (VA) was examined using magnetic resonance imaging (MRI) in 95 patients: 15 patients with Meniere's disease, 4 with vestibular Meniere's disease, 4 with cochlear Meniere's disease and 72 patients with other vestibular and/or cochlear disorders. In order to visualize the VA, the T2-weighted image (T2WI) and the proton-density weighted image (PDWI) were obtained in the sagittal plane with a head coil. The visibility of the VA was classified into 4 grades, i.e. grade 0 (not visible), grade 1 (partially visible with PDWI), grade 2 (partially visible with T2WI) and grade 3 (clearly visible with T2WI). The visibility of the VA was significantly lower bilaterally in Meniere's disease, vestibular Meniere's disease, cochlear Meniere's disease and idiopathic bilateral sensorineural hearing loss (IBSNHL) than in the other diseases. The differences among Meniere's disease, vestibular Meniere's disease and cochlear Meniere's disease were not significant. The significance of decreased visibility in IBSNHL is unknown so far. The VA studies using MRI strongly suggest that the pathogenesis of Meniere's disease, vestibular Meniere's disease, cochlear Meniere's disease and IBSNHL is, at least in part, related to the findings of the VA.

Fibrous scar in the infrapatellar fat pad after arthroscopy: MR imaging.

PURPOSE: We describe the MR appearance of fibrous scars in the infrapatellar fat pad after arthroscopy. MATERIALS AND METHODS: The subjects were 96 patients who underwent arthroscope-assisted anterior cruciate ligament (ACL) reconstruction and were examined by oblique sagittal MR imaging at different follow-up intervals. Two observers evaluated the characteristics of the fibrous scars in the infrapatellar fat pad. RESULTS: All fibrous scars with low signal intensity were accentuated at the portal and coursed horizontally through the infrapatellar fat pad. The fibrous scar within the fat pad occurred and peaked within 6 months after arthroscopy. It then subsided gradually and had disappeared by one year later in nearly half of the patients. CONCLUSION: Identifying MR imaging characteristics of fibrous scars in the fat pad after arthroscopy may be clinically helpful to differentiate these scars from other abnormalities that involve the infrapatellar fat pad.

High-resolution MR imaging of the knee at 3 T.

PURPOSE: To examine the practical feasibility of using a 3.0-T MR unit to obtain high-quality, high-resolution images of the knee joint. MATERIAL AND METHODS: One human cadaveric and 5 porcine knees were imaged with the 3.0-T unit. Sets of T1-weighted spin echo images were obtained with in-plane resolution of 0.195x0.39 mm and an acquisition time of approximately 5 min. Two porcine knees were also imaged with the 1.0-T unit with an identical imaging protocol and the signal-to-noise (S/N) ratios were measured on images at 3 T and 1 T. RESULTS: The 3-T MR system provided detailed delineation of the knees. Deep layers of the medial collateral ligament and associated fine fibers beneath the medial and lateral collateral ligament were demarcated. We observed precise demonstration of the tibial attachment of the anterior cruciate ligament, irregularity of the meniscal free edge, and conjoint tendon formation together with the lateral collateral ligament and the biceps femoris tendon. Compared to the 1-T unit, the S/N ratio with the 3-T unit was increased by a factor of 1.39 to 1.72. CONCLUSION: Due to the potential advantage of obtaining detailed images, the 3-T MR system suggests a practical utility for fine demonstration of the knee morphology.