MRI of anterior cruciate ligament repair with patellar and hamstring tendon autografts.

OBJECTIVE: Several MRI sequences were used to evaluate the 2-year postoperative appearance of asymptomatic knee with a torn anterior cruciate ligament (ACL) reconstructed with bone-patellar tendon-bone (BTB) and semitendinosus and gracilis (STG) tendon autografts. DESIGN AND PATIENTS: Two groups with successful repair of ACL tear with BTB (n = 10) or STG (n = 10) autografts were imaged at 1.5 T with sagittal and oblique coronal proton density-, T2-weighted and sagittal STIR sequences and plain and contrast-enhanced oblique coronal T1-weighted sequences. The appearance of the graft and periligamentous tissues was evaluated. RESULTS: In all 20 cases, the ACL graft showed homogeneous, low signal intensity with periligamentous streaks of intermediate signal intensity on T2-weighted images. In 10 cases, localised areas of intermediate signal intensity were seen in the intra-articular segment of the graft on proton density- and T1-weighted images. The graft itself did not show enhancement in either of the two groups, but mild to moderate periligamentous enhancement was detected in 10 cases. CONCLUSION: The MRI appearance of ACL autograft is variable on proton density- and T -weighted images. Periligamentous tissue showing contrast enhancement is a typical MRI finding after clinically successful ACL reconstruction.

MR imaging of overuse injuries of the Achilles tendon.

OBJECTIVE: This study was conducted to illustrate and classify the abnormalities found on high-resolution MR imaging of symptomatic Achilles tendons in athletic adult patients. SUBJECTS AND METHODS: One hundred patients with 118 painful Achilles tendons were imaged with a 1.5-T magnet. The tendon, peritendinous tissues, tendon insertion, and musculotendinous junction were examined on MR imaging. Twenty-eight patients underwent surgery, and histopathologic samples were taken in 13. Long-term follow-up was performed, on average, 3.4 years after MR imaging. RESULTS: Of 118 painful Achilles tendons, abnormalities were detected in 111. These were in the tendon (n = 90), surrounding structures, or both. Fifty-four tendons had a focal area of increased intratendinous signal, best detected on axial high-resolution T1-weighted gradient-echo MR imaging. Histopathology confirmed abnormal tendon structure. Of the 21 surgically proven foci of tendinosis, 20 were revealed on MR imaging. At the level of the insertion, changes were found in the tendon in 15%, in the retrocalcaneal bursa in 19%, and in the calcaneal bone marrow in 8% of the studies. Abnormalities in peritendinous soft tissues were detected in 67%. More than one type of abnormality was found in 64% of the studies. CONCLUSION: Lesions in the Achilles tendon and in the peritendinous structures can have similar clinical presentation. MR imaging detects and characterizes these changes. A more specific diagnosis and prognosis can be made with the use of MR imaging than with clinical examination alone.

High-resolution MR imaging of the asymptomatic Achilles tendon: new observations.

OBJECTIVE: Our aim was to describe the normal appearance of the Achilles tendon and peritendinous tissues in asymptomatic active volunteers using high-resolution MR imaging. MATERIALS AND METHODS: One hundred clinically asymptomatic Achilles tendons were imaged at 1.5 T with axial high-resolution T1-weighted gradient-echo (fast low-angle shot [FLASH]) and short inversion time inversion recovery (STIR) sequences. The tendons, peritendinous tissues, tendon insertions, and musculotendinous junctions were separately evaluated by two observers. RESULTS: The average anteroposterior diameter (+/-SD) of the asymptomatic Achilles tendons was 5.2+/-0.73 mm. The anterior margin was flat or concave in all, except for 10 tendons that showed mild convexity. A wave-like bulge, which shifted from lateral to medial in the craniocaudal direction, was detected in the anterior margin of 56 tendons. The signal intensity was heterogeneous in 45 tendons. In these tendons, distal stripes or punctate foci were seen. A small (3 mm) intermediate intensity intratendinous region thought to represent tendon degeneration was detected in four cases on FLASH images. The retrocalcaneal bursae contained a prominent fluid collection in 15 cases. The paratenon was visualized in all cases on both FLASH and STIR images. CONCLUSION: High-resolution MR imaging depicts the Achilles tendon and peritendinous soft tissues in great detail. The normal anatomy of the asymptomatic Achilles tendon is variable. We postulate that the variability may be a potential source of diagnostic misinterpretation.

Magnetic resonance imaging during healing of surgically repaired Achilles tendon ruptures.

Twenty consecutive patients with 21 surgically repaired Achilles tendon ruptures were imaged with a 0.1-T magnet at 3 and 6 weeks, and at 3 and 6 months after surgery. Clinical follow-up examinations and functional tests were performed at the time of scanning. An intratendinous area of high-intensity signal was observed in 19 of the 21 surgically repaired Achilles tendons at 3 months after surgery on proton density- and T2-weighted images. The three patients with the largest lesions had clinically poor outcomes at 3 months, whereas those with smaller intratendinous lesions had normal recoveries. Furthermore, patients with an abnormal walk at 3 months (N = 5) had statistically larger intratendinous lesions than patients who could walk normally. In all patients the cross-sectional area of the rejoined Achilles tendon showed the largest increase after cast removal (between 6 weeks and 3 months after surgery). In all cases the largest tendon area was measured at 3 months after surgery. Magnetic resonance imaging provides a precise valuable tool to evaluate the postsurgical internal structure of the surgically repaired Achilles tendon.

Postoperative MR imaging and ultrasonography of surgically repaired Achilles tendon ruptures.

PURPOSE: To evaluate and compare MR and US findings in an unselected group of patients with 1-3-year-old surgically repaired complete ruptures of the Achilles tendon. MATERIAL AND METHODS: Thirteen patients with complete Achilles tendon rupture underwent clinical, MR and US examinations. The average time interval from rupture to postoperative imaging was 18 months. RESULTS: The cross-sectional area of a postoperative tendon was 4.2 times that of the unaffected side. The shape of the operated tendon was more rounded than the unaffected side and it had irregular margins both in MR imaging and in US examination. In 4 of 13 cases an intratendinous area of intermediate to high signal intensity on proton density- and T2-weighted images was seen on MR. The size of this area varied from 4 to 18% of the cross-sectional tendon area. Two patients with the largest intratendinous area had poor clinical outcome. On US the tendon had mixed echogenicity in all cases and the tendon bands were thinner and shorter than normal. Comparison of dimension between MR and US revealed that in a.p. dimension the correlation was good (r = 0.87, p = 0.001), but in transversal width there was no significant correlation (r = 0.58, p = 0.06). CONCLUSION: The increased size and round irregular area of the operated Achilles tendon rupture was well detected by both MR and US, but intratendinous lesions were seen only by MR.

MR imaging of the developing human brain. Part 2. Postnatal development.

In vivo magnetic resonance (MR) images of the brain in neonates and infants up to 24 months of age were retrospectively studied to evaluate normal maturation patterns in the brain. Sequential changes in myelination of various brain structures and development of the corpus callosum were noted. At birth and for the first 4-6 months of life, signal intensities of gray and white matter are the reverse of those seen in an adult brain, with the signal intensity of white matter being lower than that of gray matter on T1-weighted images and higher than that of gray matter on T2-weighted images. With advancing age, white matter shows a progressive increase in signal intensity on T1-weighted images. On T2-weighted images, high-signal-intensity unmyelinated white matter progressively changes to myelinated white matter of a signal intensity lower than that of gray matter. At birth, the corpus callosum is isointense relative to white matter and progressively increases in signal intensity, so that at age 8 months the corpus callosum has an appearance identical to that of an adult. Familiarity with the temporal sequence of normal myelination as seen with MR imaging is helpful in the diagnosis of pathologic processes involving white matter.

MR imaging of the developing human brain. Part 1. Prenatal development.

To establish a baseline of the magnetic resonance (MR) imaging appearance of the fetal brain in early stages of development, the authors undertook a study of fixed and fresh specimens of embryos and fetuses of 6-28 weeks gestational age. Images of formalin-preserved and fresh specimens were comparable in their depiction of anatomic structures. On MR images of embryos of 6 weeks gestational age, the rhombic and cervical flexures, aqueduct of Sylvius, diencephalon, cerebellum, cerebral hemisphere, and fourth ventricle could be differentiated. The optic recess and chiasm, pituitary gland, pineal recess, third ventricle, pons, olfactory lobe, corpus striatum, insula, and parietal and temporal lobes could be distinguished as early as 11 weeks gestation. Although MR imaging is impractical as a screening tool for intrauterine abnormalities, it can demonstrate the fetus in great detail and allows a more specific evaluation of fetal anatomy. With the information provided by MR imaging, it may be possible to establish guidelines for assessment of the stage of development during intrauterine life.

MRI assisted treatment planning for radiation therapy of the head and neck.

Improved visualization of head and neck tumors has been demonstrated with the use of magnetic resonance imaging (MRI). Using standard plastic radiation therapy immobilization casts and an MR positive surface marker system developed in this institution, we have utilized MRI as an adjunct to the simulation of complex radiation treatments for tumors of the head and neck. This technique includes an indirect display of field margins and/or isodose curves over selected MR images. The lack of induced artifact from the immobilization cast, improved delineation of tumor extension from normal anatomy and the ability to image in arbitrary planes without changing patient positioning favor the use of MR over CT for radiation therapy planning in the head and neck, while ensuring reproducibility of the treatment plan at subsequent therapy sessions.

MR of visual pathways in patients with neurofibromatosis.

MR was performed on six patients clinically diagnosed as having neurofibromatosis. Owing to its multiplanar capability, MR greatly helped determine the extent of visual pathway disease. We attempted to find specific optimal pulse sequences for evaluating the prechiasmatic, chiasmatic, and retrochiasmatic visual system at 0.35 T. Using spin-echo techniques, we evaluated a T1-weighted sequence (TR 300 msec/TE 35 msec), an intermediate T2-weighted sequence (TR 1500 msec/TE 35 msec), and a T2-weighted sequence (TR 1500 msec/TR 70 msec). We found that the orbital and intracanalicular optic nerves were most accurately and easily seen with the T1-weighted sequence axially and coronally; the chiasm was best seen with the intermediate T2-weighted coronal sequence; and the retrochiasmatic visual pathway was optimally evaluated with T2-weighted spin-echo technique.

Proton relaxation times in arterial wall and atheromatous lesions in man.

The proton relaxation times of autopsy samples of arterial intima-media were measured with an NMR spectrometer and results correlated to the microscopically estimated lipid content of the vascular wall. The normal arterial intima-media contained two T1 relaxation components. The short T1 component (T1s) was 90 +/- 13 ms and its relative weight was 11%. The long T1 component (T1l) was 523 +/- 89 ms and relative weight 88%, respectively. The average T2 was 99 +/- 18 ms. In diseased vessels, a positive correlation was found between the lipid content of the vessel wall and the relaxation rate of the fast component. T1s of the intima-media was significantly shorter (P less than .01) in severe atheromatosis compared with vessels without fat deposition. The results suggest that atheromatous lesions should be best highlighted in spin-echo images by using short TR and TE to suppress the influence of T1l and to avoid (noncontrast contributing) T2 decay of the signal intensity.

Demonstration of cavernomatous transformation of the portal vein by magnetic resonance imaging.

A case of cavernomatous transformation of the portal vein demonstrated by magnetic resonance (MR) imaging is reported. Correlative images on scintigraphy and ultrasound are included. As in other vascular abnormalities, MR imaging is capable of depicting the findings noninvasively.

Central nervous system disease in acquired immunodeficiency syndrome: prospective correlation using CT, MR imaging, and pathologic studies.

A prospective study compared the abilities of high-resolution computed tomography (HRCT) and magnetic resonance (MR) imaging in detection and evaluation of central nervous system disease in neurologically symptomatic patients with acquired immunodeficiency syndrome (AIDS). Eighteen CT scans and 19 MR images in 14 patients were compared. HRCT images with contrast material enhancement were superior to unenhanced 0.35-T MR images for differentiating a lesion from surrounding edema, discriminating between lesions in close proximity, locating lesions for biopsy, judging lesion activity, detecting small cortical lesions with minimal edema, and spatial resolution. MR imaging was superior to CT scanning in evaluation of white-matter lesions and detection of small lesions surrounded by edema. MR imaging exhibited higher contrast resolution and greater sensitivity. Complementary uses of MR and CT imaging are suggested.

MR imaging of multiple sclerosis: comparison with clinical and CT examinations in 74 patients.

Magnetic resonance (MR) imaging, the latest test for evaluation of patients with multiple sclerosis (MS), was assessed against clinical evidence in 74 patients with definite or probable MS. MR imaging was positive in 55 (85%) of 65 patients with definite MS but in only one (11%) of nine patients with probable MS. The examination is most likely to be positive when the patient is classified clinically as having definite MS; when the disease is active and not in remission; and if the constellation of symptoms indicates a multiplicity of regions with neurologic dysfunction. The examination was most sensitive for detecting lesions in the cerebral hemispheres, the posterior fossa, and the cervical spinal cord, in that order; it did not detect any lesions in the optic nerves. The paraclinical tests and MR imaging were of equal sensitivity in detecting MS lesions, but the latter method was more specific in localization. Cerebrospinal fluid evaluation was slightly less sensitive than the other two tests. There was no correlation between MR imaging and these examinations. The authors conclude that MR imaging is more sensitive than computed tomography (CT), which was positive in 25% of 59 patients with definite MS; it is always positive when CT is positive; and it probably can replace CT in the diagnosis and follow-up of patients with MS.

Pulse selection chart for brain MR imaging sequences.

A chart for organizing, teaching, and recording the magnetic resonance (MR) pulse sequences used for brain and cervical spine imaging is described. The chart helps document workable sequences and facilitates comparisons between different sequences. It has also been helpful in instructing residents and fellows how to approach an MR examination logically.

Carotid artery and aortic arch imaging with ECG gating in DSA.

New computer software for gated digital subtraction angiography imaging was used to study 57 patients over 3 months. Better mask registration on isolated sets of systolic and diastolic images improved image quality. Detail of vessel outline and lesion was better than that seen on non-gated images.

Sensitivity of MRI in metastatic neoplasia: a case report.

Serial magnetic resonance imaging (MRI) and computed tomography (CT) were performed on a patient with metastatic lung cancer to brain. Magnetic resonance (MR) visualized two foci of intracerebral metastasis six weeks prior to CT.

Chemical shift misregistration effect in magnetic resonance imaging.

A low intensity artifact appearing at the junction of perirenal fat and renal parenchyma on MR images was recently described. A symmetrical high intensity artifact is also observable on the opposite side of the kidneys as well as at the junction of the right lobe of the liver and adjacent adipose tissue. Both artifacts can be explained as exhibitions of pixel misregistration due to the difference in chemical shifts of fatty and non-fatty organs. Identification of the chemical shift misregistration effect is important since the existence of this artifact may cause erroneous diagnosis of calcification and/or fluid collections.