MR imaging of displaced meniscal tears of the knee: Importance of a “disproportional posterior horn sign”

Purpose: Meniscal tears associated with displaced fragments are clinically significant. We propose the "disproportional posterior horn sign" as a supportive criterion to identify a posterocentrally displaced meniscal fragment on MR imaging studies. If the meniscal posterior horn in the central portion appears larger than that in the peripheral section, it is considered positive for "disproportional posterior horn sign".

Material and Methods: MR images obtained in 42 patients with 43 lesions, confirmed to have displaced meniscal tears, were included in this study. The MR images were retrospectively evaluated for the presence of the "disproportional posterior horn sign", as well as the other known signs.

Results: The "disproportional posterior horn sign" was seen in 9 (20.9%) of 43 lesions, including 1 lateral discoid meniscal tear, 5 lateral meniscal tears and 3 medial meniscal tears. Five of them also had other signs of a displaced meniscal fragment. However, the remaining 4 cases only exhibited the "disproportional posterior horn sign". For the other MR signs, the "absent bow tie sign" was detected in 40 (93%) of 43 lesions, the "flipped meniscus sign" in 27 (62.8%) of 43 lesions, the "double posterior cruciate ligament sign" in 17 (39.5%) of 43 lesions and the "notch fragment sign" in 22 (51.2%) of 43 lesions.

Conclusion: The "disproportional posterior horn sign" is helpful in demonstrating a posterocentrally displaced meniscal fragment, especially when other characteristic signs are unremarkable or absent.

Recurrent syncope due to refractory cerebral venous sinus thrombosis and transient elevations of intracranial pressure

Chronic paroxysmal intracranial hypertension leading to syncope is a phenomenon not reported previously in patients with refractory cerebral venous sinus thrombosis. We report a case of paroxysmal intracranial hypertension leading to syncopal episodes in a patient with idiopathic autoimmune hemolytic anemia and venous sinus thrombosis. This case demonstrates that intermittent elevations in intracranial pressure can lead to syncope in patients with venous sinus thrombosis and emphasizes the importance of considering this potentially treatable etiology of syncopal episodes.

Sequence influence of nonidentical InGaAsP quantum wells on broadband characteristics of semiconductor optical amplifiers--superluminescent diodes

Extremely broadband emission is obtained from semiconductor optical amplifiers-superluminescent diodes with nonidentical quantum wells made of InGaAsP/InP materials. The well sequence is experimentally shown to have a significant influence on the emission spectra. With the three In(0.67) Ga(0.33) As(0.72) P(0.28) quantum wells near the n -cladding layer and the two In(0.53) Ga(0.47) As quantum wells near the p -cladding layer, all bounded by In(0.86) Ga(0.14) As(0.3)P(0.7) barriers, the emission spectrum could cover from less than 1.3 to nearly 1.55 microm, and the FWHM could be near 300 nm.

Vertebral bone marrow perfusion evaluated with dynamic contrast-enhanced MR imaging: significance of aging and sex

PURPOSE

To investigate blood perfusion of nonfractured, normal-appearing vertebral bodies with regard to age and sex.

MATERIALS AND METHODS

Dynamic magnetic resonance imaging (160 images obtained in 80 seconds) was performed from T10 to L5 in 66 patients. Patients were assigned to three groups: group 1, those 50 years or younger without compression fracture; group 2, those older than 50 years without compression fracture; or group 3, those older than 50 years with compression fracture. Peak enhancement percentage and enhancement slope were determined from the time-intensity curve of normal (nonfractured) vertebral body. Comparisons were made between groups, and the effect of age and sex interaction was analyzed.

RESULTS

Higher peak enhancement percentage was demonstrated for group 1 compared with group 2 (58.21 +/- 44.65 [SD] vs 21.88 +/- 14.77, P <.005). Group 1 women revealed a higher enhancement percentage compared with group 1 men (87.17 +/- 54.13 vs 38.16 +/- 21.69, P <.05), which significantly decreased in those older than 50 years (from 87.17 +/- 54.13 to 17.98 +/- 13.80, P <.005). For men, this decrease in those older than 50 years was not as pronounced (from 38.16 +/- 21.69 to 25.38 +/- 15.43, P >.05). Presence of compression fracture at other levels of the spine (group 3) was not associated with a different enhancement percentage for normal vertebrae.

CONCLUSION

Rate of vertebral bone marrow perfusion revealed a significant decrease in subjects older than 50 years. Women demonstrated a higher marrow perfusion rate than men younger than 50 years and a more marked decrease than men older than 50 years.

Spinal fractures and pseudoarthrosis complicating ankylosing spondylitis: MRI manifestation and clinical significance

PURPOSE

To analyze magnetic resonance (MR) patterns of fractures and pseudoarthrosis of the ankylosing spondylitic spine, and related changes in the dura and adjacent soft tissue.

MATERIALS AND METHODS

Sixteen patients with radiographically evident fractures or pseudoarthrosis of the spine were included. Each underwent MR studies. Ten patients among them underwent surgical operations.

RESULTS

Both transdiscal (n = 12) and transvertebral (n = 4) fractures were identified. The levels were located from T9 to L3. Five of 16 patients had pseudoarthrosis. The fractures or pseudoarthrosis had two patterns: low signal on T1-and high signal on T2-weighted images, and low signal on both T1-and T2-weighted images. Disruption of anterior longitudinal ligament (ALL) was identified in 14 patients. Seven patients had vertebral translation, all had disruption of the ALL. Dural adhesions were noted in five patients and manifested as linear epidural enhancements with triangular blunt edges.

CONCLUSION

MR patterns of ankylosing spondylitis are important in evaluating complications of fractures or pseudoarthrosis, as well as changes in dura, soft tissue, and ligaments.

Paget's disease of the bone: a case report

Paget's disease of bone is rare in Asia. We report a case of Paget's disease in a 58-year-old Taiwanese man who was admitted with a 3-month history of bilateral numbness in the buttock region. Laboratory data disclosed an elevated serum alkaline phosphatase level (510 U/L). Plain radiographs of the lumbar spine showed generalized increased density at the third lumbar vertebra, associated with cortical thickening, loss of cortico-cancellous definition, and increased anteroposterior diameter. The T1-weighted magnetic resonance image of the lumbar spine showed diffuse, heterogeneous low signal intensity at the third lumbar vertebral body, pedicle, laminae, and spinal process; these areas showed mixed high and low signal intensity on the T2-weighted image. Technetium-99m bone scan revealed abnormal uptake in the involved vertebra. Histologic examination of the third lumbar spinal process confirmed the diagnosis of Paget's disease of bone. The patient remained well during a follow-up period of 6 months.

In vivo kinematic study of normal wrist motion: an ultrafast computed tomographic study

OBJECTIVE

To quantify in vivo carpal kinematics of a normal wrist in a dynamic continuous model.

DESIGN

The instantaneous changes in the radiocarpal and midcarpal joints during normal wrist motion were analyzed using ultrafast computed tomography (CT).

BACKGROUND

Wrist injuries account for a considerable and growing proportion of work-related disorders and disability. However, little is known about normal wrist kinematics.

METHODS

Ten uninjured subjects were studied using ultrafast CT to measure the continuous motion of the wrist from full flexion to full extension. Sagittal plane scanning was performed mediolaterally at six different locations as the wrists were moved slowly and repeatedly from full flexion to full extension. The data were printed to X-ray film and transferred to an independent work station with a video camera. The motion of the radiocarpal, midcarpal and wrist joints was determined by an image analyzing system.

RESULTS

Wrist motion was expressed as a ratio of capitate-lunate (C-L) (midcarpal) motion and radio-lunate (R-L) (radiocarpal) motion. In the volar flexion of normal wrists, the contribution of the radiocarpal joint and midcarpal joint were approximately equal; while dorsal flexion of the normal wrist occurred mainly at the midcarpal joint.

CONCLUSIONS

In normal wrists, the radiocarpal joint and midcarpal joint contribute equally to volar flexion, while the midcarpal joint is more important in dorsal flexion.

RELEVANCE

In this study, we demonstrated the suitability of using two-dimensional computed tomographic images in a quantitative study of flexion/extension kinematics of the normal wrist.

The evaluation of false negative mammography from malignant and benign breast lesions

Preoperative mammograms from 395 breast cancers and 132 benign breast lesions were enrolled for this study. The false-negative (FN) rate for breast cancers from preoperative reading was 9.6% with 38 breast cancers missed on mammograms. The statistically significant differences occurred between true-positive (TP) and FN cancers for younger age (P<.025), smaller lesion size (P<.001), denser breast (P<.05), deep retroglandular location (P<.001). None of the FN cancers exhibited calcifications. The FN rate for mammography for benign breast lesions from preoperative reading was 18.9% with 25 lesions misdiagnosed. The statistically significant difference between benign TP and FN lesions occurred for central and subareolar location (P<.025). Exploration of possible factors and imaging features in FN mammograms can help reduce the FN rate for mammography.

Solitary vertebral collapse: distinction between benign and malignant causes using MR patterns

Differentiation of benign from malignant causes of vertebral compression fracture can be difficult at a single location. We studied 37 patients with solitary vertebral collapse (SVC) in the spine using magnetic resonance imaging (MRI). Sixteen of them were found to have a benign cause of SVC, while the remaining 21 were found to have malignancy. The following four MRI characteristics were investigated: ill- or well-defined margin of the intravertebral lesion (P < 0.005); pedicle involvement (P < 0.05); MR enhancement pattern (P < 0.005); and paravertebral soft tissue lesion (PSL) (P < 0.025). It was found that cases of malignant SVC tended to have an ill-defined margin, abnormal signal involvement of the pedicle, a marked and heterogenous MR enhancement pattern, and irregular nodular-type PSL. Pedicle change with expansile lesion totally excluded a benign cause. By using these criteria, we were able to differentiate benign or malignant causes of SVC accurately.

Early diagnosis of single segment vertebral osteomyelitis--MR pattern and its characteristics

Nine cases of single segment vertebral osteomyelitis were included based on the single level of vertebral body involvement according to the MR findings. They were 3 cases with tuberculous infection and 6 cases with pyogenic infection. The vertebral body involvement was presented as abnormal signal changes (100%) and heterogenous enhancement (77.7%). They usually caused the cortical disruption in its anterior aspect (100%). It goes along the upward subligamentous spread (100%) most often, then the upper disc involvement (66.6%) and downward subligamentous spread (55.5%). The lower disc involvement is least common (11.1%). By using these criteria, the single segment vertebral osteomyelitis could be earlier diagnosed.

Bilateral elastofibroma dorsi. Two case reports

Elastofibroma dorsi is a benign fibroproliferative lesion of unknown pathogenesis. It is most commonly found in the periscapular region in elderly women. The majority of patients are asymptomatic. The lesions have a characteristic location and a specific magnetic resonance imaging (MRI) appearance allowing accurate prospective diagnosis. The importance of recognizing the benign nature of this lesion to avoid an unnecessary operation is apparent. We describe two cases of bilateral elastofibroma dorsi with characteristic findings on MRI and typical histological appearances.

Pyogenic liver abscess complicating a ventriculoperitoneal shunt

Pyogenic liver abscess is a rare complication of ventriculoperitoneal (VP) shunting. We report a 4-month-old female with this complication who was successfully treat ed by computed tomography-guided percutaneous transhepatic catheter drainage, shunt externalization, and parenteral antibiotics. Liver abscess is a possible intra-abdominal complication of VP shunting, and imaging studies are good adjuncts in making the clinical diagnosis.

Magnetic resonance imaging in patients with hemodialysis-related arthropathy

From April 1993 to December 1993, we prospectively studied the knees of 15 patients (mean age, 48 +/- 11 yr) receiving long-term hemodialysis (mean duration, 9 +/- 4 yr) using magnetic resonance imaging (MRI) techniques including, T1 weighted spin-echo, multiplanar gradient recalled, and postcontrast T1 with chemical shift-selective, fat-saturation pulse sequences. Analysis of these images revealed that the three findings most indicative of hemodialysis-related arthropathy were intramedullary, cortical and soft tissue lesions. Knee pain was significantly correlated with the presence of soft tissue lesions. Cortical lesions were usually associated with soft tissue lesions. Inflammatory changes adjacent to soft tissue lesions were demonstrated in postcontrast studies in all patients with soft tissue lesions. Increases in water content in those lesions appeared to increase the signal intensity. Our results indicate that MRI is useful in demonstrating the extent of hemodialysis-related arthropathy involvement, especially in hemodialysis patients suffering from knee pain.

Malignant chondroid syringoma

A case of malignant chondroid syringoma on a foot with multiple bone metastases is presented. An 18-year-old male patient first noticed a protruding mass on the plantar surface of his right foot at 9 years of age. A sweat gland tumor of a benign nature was diagnosed and excised at that time. The tumor recurred three times during the 10 years after surgery and was finally diagnosed as malignant chondroid syringoma. Multiple bone metastases involving the calcaneus, talus and fibula of the lesion side were found after extensive radiologic survey. The patient underwent below-knee amputation with total removal of the fibula. However, pelvic bone metastasis developed 1 year after the amputation. He died of this disease due to brain and diffuse bony metastasis 36 months after the amputation. This is a rare case of malignant chondroid syringoma with a long history but ominous outcome. We recommend that sweat gland tumors be carefully examined and treated more radically when there is a suspicion of malignancy.

Infectious spondylitis: MRI characteristics

Magnetic resonance imaging (MRI) scans of 24 patients with clinically proven infectious spondylitis were retrospectively evaluated. Evaluation was made of abnormal signal and enhancement patterns within vertebral bodies, intervening disks, and epidural and paraspinal abscesses. The causative organisms included Mycobacterium tuberculosis, fungi and pyogenic bacteria. Staphylococcus aureus was the predominant causative organism among pyogentic bacteria. Decreased signal intensity of vertebral marrow on T1-weighted images was more extensive in pyogenic infections. Multilevel involvement (more than two) was observed in six of the 24 patients. Contiguous multilevel involvement was observed only in patients with tuberculous spondylitis. Noninvolvement of the intervertebral disk space was observed in two patients with pyogenic spondylitis. Epidural abscess was found in 15 patients, most of whom had dense, homogeneous enhancement. Paraspinal abscess was found in 18 patients. Diffuse patchy enhancement without obvious abscess formation in the paraspinal compartment was found in those patients with pyogenic infections. "Rice bodies" were found in paraspinal abscesses in only three patients with tuberculous spondylitis. It was difficult to differentiate candidal from tuberculous spondylitis on MRI. Compared with pyogenic infection, tuberculous spondylitis had a predilection for spinal deformity, subligamentous spread, contiguous multilevel involvement, presence of signal voids in paraspinal abscesses on T2WT and a lesser extent of marrow edema.

Magnetic resonance imaging of vertebral compression fractures

In this study, magnetic resonance imaging (MRI) was used to analyze the signal intensity and vascularity of compression fractures of vertebrae in 74 patients. The possibility of nonunion was assessed according to the specific image findings and clinical presentation. All patients had chronic back pain for more than 3 months and compression fractures of the vertebrae initially demonstrated by plain radiography. Pre-enhanced T1 and T2*-weighted images (*multiplaner gradient recall sequence) and postenhanced MRI were obtained. Images were divided into three categories according to the signal intensity of the fractured vertebrae such as hyperintensity (n = 35), hypointensity (n = 24) on T1-weighted image and necrotic type compression fractures of the vertebrae (n = 15). Of the 15 necrotic-type cases, 13 disclosed "fluid"-containing space at the collapsed vertebrae and two showed "air"-containing space at the vertebral body. We believe that these findings are pathognomonic signs of nonunion of the collapsed vertebrae. Surgical specimens were obtained from the four patients whose vertebrae showed necrosis and granulation tissue. After posterior spinal instrumentation, the collapsed vertebral body regained the height and presence of the open end-plate of the vertebra on postoperative lateral radiography. The superior capabilities of MRI offers useful criteria that make the diagnosis of nonunion in compression fractures of the spine possible. Thus, a space with "fluid" or "air" collection at the anterior aspect of a collapsed vertebra as well as strong enhancement with Gd-DTPA at the posterior aspect of the collapsed vertebra may be considered to be pathognomonic signs of nonunion of the fractured vertebra.

Magnetic resonance imaging of glomus tumour in the hand

Glomus tumours of the hand are benign tumours that arise from the neuromyoarterial apparatus. The most common site for a glomus tumour is in the distal phalanx. They frequently display a classic triad of symptoms-pain, tenderness and temperature sensitivity. Ten treated cases examined with magnetic resonance imaging (MRI) preoperatively are described. All were female with a mean age of 43 years. All except 2 suffered the classic triad of symptoms. The mean duration from onset of symptoms to therapeutic intervention was 7.4 years. MRI depicted the tumours in excellent detail and aided diagnosis in the 4 patients without subungual blue discolouration. The lesions showed a low signal on the T1-weighted image and a high signal on the T2-weighted image. All except 3 were located in the subungual region. All patients underwent surgical excision with pathological confirmation. The postoperative course was smooth and there were no sequelae. High resolution MRI, providing a clear contrast between tumorous and normal tissues, has proved to be a useful non-invasive method for imaging glomus tumours in the hand.

MRI of meniscus and cruciate ligament tears correlated with arthroscopy

Findings from magnetic resonance imaging (MRI) studies of 50 knees were retrospectively interpreted. The results were correlated with arthroscopic findings. Multiple pulse sequences were performed including sagittal double-echo, coronal T1-weighted and gradient echo, axial gradient echo or fat suppression imaging. Three-dimensional MRI was performed if there was a high suspicion of a tear of the anterior cruciate ligament. The individual positive predictive value, sensitivity, specificity and accuracy were calculated from the comparison between MRI and arthroscopic findings of the menisci, anterior cruciate ligament and posterior cruciate ligament. The following results were obtained: 1) Tears of the medial meniscus-positive predictive value, 72%; sensitivity, 87%; specificity, 86%; and accuracy, 86%. 2) Tears of the lateral meniscus-positive predictive value, 85%; sensitivity, 85%; specificity, 90%; and accuracy, 88%. 3) Tears of the anterior cruciate ligament-positive predictive value, 88%; sensitivity, 95%; specificity, 89%; and accuracy, 92%. 4) Tears of the posterior cruciate ligament-positive predictive value, 100%; sensitivity, 100%; specificity, 100%; and accuracy, 100%. It is concluded that MRI is a noninvasive and accurate method for detecting the internal derangement of the knee.

Epiphyseal scar of the femoral head: risk factor of osteonecrosis

PURPOSE

To find out whether a correlation exists between the presence of epiphyseal scar within the femoral head and osteonecrosis at examination with magnetic resonance (MR) imaging.

MATERIALS AND METHODS

A total of 117 femoral heads in 60 patients were examined. Lipogenic factors (defined as either the use of steroid or alcohol abuse) were positive in 46 patients (average age, 37 years) and absent in 14 (average age, 47 years). Both hip joints were examined simultaneously at 1.5 T; three pulse sequences were used in each imaging study. All images were interpreted for type of epiphyseal scar and presence or absence of osteonecrosis.

RESULTS

Six types of epiphyseal scar (A-F), each with a different shape, were seen. A total of 72 femoral heads had type A or B sealed-off scars; 32 of these 72 had osteonecrosis. Of the 45 femoral heads with type C, D, E, or F perforated scars, only one had osteonecrosis. The difference between these two groups was statistically significant (P < .001).

CONCLUSION

The presence of a sealed-off epiphyseal scar was associated with a very high risk of osteonecrosis of the femoral head.

Magnetic resonance imaging of rotator cuff lesions

The purpose of this study was to evaluate the diagnostic performance of magnetic resonance imaging (MRI) in rotator cuff diseases. Forty consecutive patients studied by MRI from September 1990 to September 1992 were included in the study. MRI was performed on a 1.5 tesla MR scanner. Each MRI study was reviewed by two radiologists experienced in rotator cuff tendons. The MRI finding was compared with the surgical result. MRI sensitivity for all tears (partial and complete) was 1.0 (22/22), specificity 0.89 (16/18), accuracy rate 0.95 (38/40), and the predictive value 0.92 (22/24). Signal changes of the rotator cuff tendon (primary signs) were the most reliable criteria in diagnosis of the tear. Changes of subacromial and subdeltoid fat planes and bursa (secondary signs) were complimentary when primary signs were indeterminant. The direction of the long axis of abnormal signal intensity in the rotator cuff tendon may be a good indicator when differentiating tears from tendinitis. We conclude that MRI shows excellent performance in the determination of the presence or absence of a rotator cuff tear.

Correlation between MRI and operative findings of the rotator cuff tear

Rotator cuff disease is one of the most common causes of shoulder pain. Various methods have been used to evaluate this problem. In this study, we determine the accuracy of magnetic resonance imaging (MRI) of the shoulder in diagnosing the rotator cuff tear based on operative findings. Ten patients with a painful shoulder requiring operation received an MRI of the shoulder before surgery. A GE 1.5 Tesla MR scanner with a five-inch planar surface coil was applied and the diagnosis was confirmed by an experienced radiologist in the field of musculoskeletal MRI. All patients underwent surgery within two weeks of MRI examination. Nine of the 10 patients were shown to have rotator cuff tear by MRI. Among the nine MRI positive patients, eight were proven to have such lesions on operation (two massive tears, four moderate complete tears, and two bursal side tears). One false-positive result was found to be an adhesive capsulitis and supraspinatus tendinitis at operation. The remaining case, diagnosed as tendinitis by MRI, turned out to be a small incomplete tear on operation. Therefore, the sensitivity of MRI for rotator cuff tear in this study was 0.89. The overall accuracy was 80%. We concluded that MRI has a high accuracy in detecting the rotator cuff tear. False-positive and false-negative diagnoses were attributed to a severe tendinitis and an incomplete tear, respectively.

Magnetic resonance imaging of an obscure glomus tumour in the fingertip

Magnetic resonance imaging was performed on a patient with chronic obscure pain in her little finger. MRI findings helped to establish the diagnosis and guide the surgeon to the glomus tumour.

Evaluation of hip disorders by radiography, radionuclide scanning and magnetic resonance imaging

Thirty-six hips were studied because of significant hip pain. Radiography of the hip and bone scintigraphy showed subtle changes. Magnetic resonance imaging (MRI) was performed using a 1.5 Tesla superconductive unit. All MRI findings were confirmed by surgical or pathologic results. Twenty-nine hips had a single lesion, including: infection (one), fracture (eight), avascular necrosis of the femur(two), or contralateral hip (four), transient osteoporosis (six), osteoporosis (one), post-irradiation myositis (one), metastasis (four), and synovitis (two). Twenty-six lesions (89.6%) appeared normal on the radiographs of the hip, while three lesions (10.4%) showed only osteoporotic change. Another seven hips had more than one lesion, including: avascular necrosis and fracture (four), fracture foci (two), and metastasis and fracture (two). Radiography of the hip showed either a negative finding or detected only a single lesion, missing other important pathologic foci. MRI is extremely sensitive to alterations in the bone marrow that may represent pathology occult to plain radiography and bone scintigraphy of the hips. For diagnosis and treatment planning, MRI of the hips should be performed early in patients with persistent pain and negative radiography findings.

MR patterns of rotator cuff and labral lesions: comparison between low-field and high-field images

Eighteen people (10 men, 8 women) were examined on a 0.3-T (low-field) imager with T1-weighted axial and coronal images and either axial or coronal T2-weighted images. Thirty-two people (22 men, 10 women) were examined on a 1.5-T (high-field) imager with axial T1-weighted images and coronal, sagittal dual-echo images. Rotator cuff lesions were diagnosed by the following findings: abnormal signal in the tendon, irregularity or discontinuity at the musculo-tendinous junction, or muscle abnormality. Glenoid labrum tears were considered if one or more of the following criteria were present: labral deformity of unusual size, focal defect, amputation or displacement with fluid, or capsular stripping. Comparison between the high-field and low-field MR images in the evaluation of rotator cuff lesions suggests that the high-field imager is better than the low-field imager in the differentiation of tendinitis from tears, in the confirmation of bursitis and in detection of subscapularis lesions. A higher contrast-to-noise ratio (CNR), less time consumption, and more section planes (especially, sagittal sections) appear to be the main reasons for this. As far as labral lesions are concerned, the performances of the high-field imagers and low-field imagers were almost equal. The artifact of greater chemical shift with a high-field imager would more or less, we assume, degrade the better CNR achievable in the diagnosis of labral lesions.

Multiplanar gradient recalled images of the knee: comparison of different flip angles and echo times

To determine the most appropriate combination of echo time (TE) and flip angle in gradient echo images of the knee, the authors used different TEs (10, 20 and 30 msec) and flip angles (10, 30, 50, 70, 90, 120 and 150 degrees) to perform a systematic study of MRI on 10 volunteer knees. Contrast-to-noise ratios of cartilage-fat, fluid-cartilage, fluid-fat and fluid-ligament were calculated and compared. Images with a 30-degree flip angle combined with 20 msec of TE were found to have the best contrast-to-noise ratios in both objective data analysis and subjective observation. Hyaline cartilage of the knee was hyperintense and was well delineated on this pulse sequence, appearing distinct in contrast to the intra-articular fluid. It is concluded that this T2-weighted gradient echo pulse sequence is an alternative to conventional spin echo T2-weighted imaging of the knee.

Acute stroke: detection of changes in cerebral perfusion with dynamic CT scanning

Fifteen patients with acute cerebral infarct in the territory of the middle cerebral artery were examined with dynamic computed tomography (CT) to evaluate cerebral perfusion changes. Perfusion changes could be detected in 93% of the patients within a short period after the attack (the earliest instance was within 2 hours) and before any detectable morphologic change. The attenuation coefficient of the area of infarction showed a statistically significant difference in peak amplitude compared with that in the contralateral unaffected brain or with that in the control group (P less than .05). A delay in the time to peak in the affected side versus in the contralateral side was observed in six patients with stroke and ranged from 4.2 to 49.2 seconds with or without a change in peak amplitude. The clinical outcome in the patients correlated well with the initial perfusion change measured with dynamic CT scanning. The greater the difference in peak amplitude, the worse the residual neurologic defect. Patients with a prolonged time to peak (greater than 8 seconds) usually had poor clinical outcome. The whole dynamic study took 10-15 minutes more than a conventional CT study but provided more complete information as a basis for clinical treatment and an indication of clinical outcome.