Kenneth A. Buckwalter

Precision of Hyaline Cartilage Thickness Measurements

Measurement of cartilage thickness in vivo is an important indicator of the status of a joint as the various degenerative and inflammatory arthritides directly affect the condition of the cartilage. In order to assess the precision of thickness measurements of hyaline articular cartilage, we undertook a pilot study using MR imaging, plain radiography, and ultrasonography (US). We measured the cartilage of the hip and knee joints in 10 persons (4 healthy volunteers and 6 patients). The joints in each patient were examined on two separate occasions using each modality. In the hips as well as the knee joints, the most precise measuring method was plain film radiography. For radiographs of the knees obtained in the standing position, the coefficient of variation was 6.5%; in the hips this figure was 6.34%. US of the knees and MR imaging of the hips were the second best modalities in the measurement of cartilage thickness. In addition, MR imaging enabled the most complete visualization of the joint cartilage.

Magnetic resonance imaging of knee hyaline cartilage and intraarticular pathology.

Injuries to the hyaline cartilage of the knee joint are difficult to diagnose without invasive techniques. Even though these defects may be the most important prog nostic factors in assessing knee joint injury, they are usually not diagnosed until arthrotomy or arthroscopy. Once injuries to hyaline cartilage are found and/or treated, no technique exists to follow these over time. Plain radiographs, arthrograms, and even computed tomography fail to detail most hyaline cartilage defects. We used magnetic resonance imaging (MRI) to eval uate five fresh frozen cadaver limbs and 10 patients whose pathology was known from arthrotomy or ar throscopic examination. Using a 0.35 Tesla supercon ducting magnet and spin-echo imaging technique with a head coil, we found that intraarticular fluid or air helped to delineate hyaline cartilage pathology. The multiplane capability of MRI proved to be excellent in detailing small (3 mm or more) defects on the femoral condyles and patellar surface. Cruciate ligaments were best visualized on sagittal oblique projections while meniscal pathology was best seen on true sagittal and coronal projections. MRI shows great promise in providing a noninvasive technique of evaluating hyaline cartilage defects, their response to treatment, and detailed anatomical infor mation about cruciate ligaments and menisci.

Magnetic resonance imaging of the collateral ligaments of the thumb

Injury to the ulnar collateral ligament of the metacarpal phalangeal joint of the thumb can usually be diagnosed on the basis of a combination of history, radiographic examination, and clinical stress testing of the joint when appropriate. Occasionally, when the patient is seen late and the diagnosis is doubtful, stress evaluation may be ill-advised because a nondisplaced ligament may be displaced in the process. We had recent experience with three patients in whom the use of magnetic resonance imaging was helpful in diagnosing a displaced ulnar collateral ligament in two cases, and an intraligamentous injury in the other. These studies were conducted at no charge to the patient as part of institutional investigational research. The current cost of this technology is prohibitive for routine use; however, when it becomes less expensive, it may be helpful as a diagnostic tool.

MRI in osteoarthritis of the hip: Gradations of severity

In a prospective study, 10 patients with well-documented osteoarthritis (O.A.) of the hips were imaged using spin-echo pulse sequences (TR = 0.5 to 1.5 s and TE = 28 to 60 ms). After analyzing the changes observed, an MR grading system for assessing severity of O.A. in the hips was developed. Using this grading system and an established grading system for osteoarthritis using roentgenograms (both systems use grades 0-4), two radiologists independently graded the MR studies and plain films separately, twice. The roentgenogram grading system was more accurate in predicting symptoms in the more severe cases, whereas the MR grading system was slightly more useful in the less severe cases. Our results show that MR can demonstrate a spectrum of changes of O.A. in the hips. Its ability to directly image articular cartilage makes it a powerful research and clinical tool.

Visualization of myocardial infarction and subsequent coronary reperfusion with MRI using a dog model

Twelve anesthetized mongrel dogs underwent left thoracotomy with placement of a removable ligature around the left circumflex coronary artery. Following a 3 to 6 hour delay, ECG-gated spin-echo MRI was performed. The ligature was then removed reperfusing the heart, and after a 10-15 min period, MRI repeated. Finally, post-sacrifice images were obtained, and the hearts chemically stained for infarct evaluation. The MR images were subjectively and quantitatively evaluated for visibility of the endocardial border and of the injured myocardium, and for changes after reperfusion. The injured tissue was variably visible in vivo, the major limitation a result of motion blurring and artifact. The abnormal tissue was easily visible on MRI in 11 animals, and not clearly visible in one. The endocardial border was easily seen in 10 animals. The variation of calculated relaxation times was high for both normal and ischemic/infarcted myocardium in the beating hearts (normal: T1 = 566 +/- 288, T2 = 38 +/- 6; injured myocardium: T1 = 637 +/- 250, T2 = 41 +/- 12) in contrast, relatively stationary skeletal muscle measured in the same images had narrower ranges (T1 = 532 +/- 199, T2 = 28 +/- 2). Changes with reperfusion were seen, but not reliably. The infarcted or ischemic zones were easily visible on post-sacrifice images in all animals imaged. Post-sacrifice relaxation times were T1 = 564 +/- 69 msec, T2 = 39 +/- 3 msec for normal heart muscle, and 725 +/- 114, T2 = 47 +/- 5 for ischemic/infarcted tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Case report 427

This 42-year-old man with a 10 year history of psychiatric disorders presented with acute changes in his mental status. Physical examination demonstrated masses over the Achilles tendons, the left knee and on the eyelids. Laboratory data demonstrated a normal serum cholesterol, normal serum uric acid, elevated serum triglycerides, and elevated cholestanol levels in the serum und urine. EEG findings were consistent with a metabolic encephalopathy. CT and M R studies were performed after a plain film study of the right ankle (Figs. 1-5). A biopsy of a tendon was performed.

Case report 483

Fig. 1. A A 5-mm thick, coronal spin-echo image, midportion of the left knee, TR 2000, TE 40 ms. The medially displaced discoid lateral meniscus (white arrowheads) has a teardrop shape. Note the focal concavity in the adjacent medial portion of the lateral femoral condyle (black arrows). The medial meniscus (white arrows) has the expected triangular shape. M medial, L lateral, t tibia, f femur. B Near midline sagittal image, TR 2000, TE 40 ms. The central portion of the medially displaced lateral meniscus is again demonstrated (white arrowheads). e epiphysis, p patella

BOLUS DYNAMIC COMPUTED TOMOGRAPHY IN THE EVALUATION OF PULMONARY SEQUESTRATION

Three cases of pulmonary sequestration evaluated by bolus dynamic computed tomography are described. The computed tomography appearance and the differential diagnosis are discussed. It is important to recognize the advantages of the bolus dynamic technique in the evaluation of pulmonary sequestration as it may eliminate the need for further studies.