Patellar motion analyzed by magnetic resonance imaging

We have analyzed the normal patellar motion during the first 30 degrees of knee flexion by magnetic resonance imaging (MRI). Ten males and 10 females without knee symptoms were examined. The patellar articulation was imaged both sagittaly and axially with the knee flexed 0, 10, 20, and 30 degrees. The axial images were produced through the middle of the patellar articular cartilage. When the knee was in extension compared to 30 degrees flexion, the sulcus angle was greater, the lateral patellofemoral angle was smaller, there was more lateral patellar displacement, the patella tilted more laterally, and the congruence angle was directed more laterally. Differences between males and females were found.     

Patellar motion analyzed by kinematic and dynamic axial magnetic resonance imaging in patients with anterior knee pain syndrome

Ten consecutive patients (12 knees), all women, with anterior knee pain syndrome participated in the study. The patellofemoral joints were examined with the knee in 0°, 10°, 20°, and 30° of flexion. At each knee position, kinematic and dynamic, an axial magnetic resonance (MR) image was used to focus on the sagittal plane, followed by an axial image focused through the middle of the patella. Ten healthy volunteers (20 knees) with no history of previous or current knee problems or anterior knee pain also underwent MRI scanning following the same procedure. Three angles were measured: patellar tilt angle (PTA), sulcus angle (SA), and congruence angle (CA). For statistical analyses, we used the Mann-Whitney U-test. Compared with the control knees, five patterns of malalignment were identified. The most frequently observed was tilt and lateralisation, with elevated CA and decreased PTA. In extension, the average CA for this group was 22° and PTA –4.8° vs –8.1° and 14.3° for control knees respectively. Contraction of the muscles caused tilt of the patella in symptomatic knees. This decrease of the PTA was statistically significant in extension (P < 0.05) and in 10° of flexion (P < 0.05). Contraction of the thigh muscle increased CA in 30° of flexion. This lateral pull was statistically significant (P < 0.05). There were no statistically significant differences of SA between the groups, regardless of muscle contraction or flexion angle. At 30° of flexion, muscle contraction increased CA and decreased PTA. In our opinion, imaging in the first 30° of flexion with thigh muscle contraction is necessary for a correct diagnosis. Received: 17 February 1998     

Assessment of relative brain-skull motion in quasistatic circumstances by magnetic resonance imaging

Abstract Brain-skull relative motion plays a pivotal role in the etiology of traumatic brain injury (TBI). The present study aims to assess brain-skull relative motion in quasistatic circumstances, and to correlate cortical regions with high motion amplitudes with sites prone to cerebral contusions. The study includes 30 healthy volunteers scanned using a clinical 3-T MR scanner in four different head positions. Through image processing and 3D model registration, pairwise comparisons were performed to calculate the brain shift between sagittal and coronal head positional change. Next, local brain deformation was evaluated by comparison between cortical and ventricular amplitudes. Finally, the influence of age, sex, and skull geometry on the cortical and ventricular motion was investigated. The results describe complex brain shift patterns, with high regional and inter-individual variations, outweighing age and sex patterns. Regions with maximum motion amplitudes were identified at the inferolateral aspects of the frontal and temporal lobes, congruent with predilection sites for contusions. No significant influences of age and sex on the cortical shift amplitudes were detected. The 3D cortical deviations varied from -7.86?mm to +5.71?mm for the sagittal head movement, and from -11.46?mm to +7.30?mm for head movement in the coronal plane, for a 95% confidence interval. The present study contributes to a better understanding of the mechanopathogenesis of frontotemporal contusions, and is useful for the optimization of finite-element head models and neurosurgical navigation procedures. Moreover, our results prove that in vivo MRI allows for accurate assessment of brain-skull relative motion in quasistatic conditions.     

Characterizing osteochondral lesions by magnetic resonance imaging

In a double-blind prospective study, 12 patients with osteochondral lesions of either the knee or talus were studied using magnetic resonance imaging (MRI) prior to arthroscopic treatment. MRI correctly staged 11 of the 12 lesions. We developed a new staging system for osteochondral lesions, which accurately correlates MRI with arthroscopic findings.     

Mandibular chloroma demonstrated by magnetic resonance imaging

A case of chloroma or granulocytic sarcoma in the mandible of a young child is presented with magnetic resonance imaging (MRI) features.     

Renal magnetic resonance imaging

PURPOSE OF REVIEW: Current magnetic resonance imaging systems allow the visualization of normal and diseased kidney, with exquisite resolution of renal structures. Dynamic contrast magnetic resonance imaging has the potential, unique among all noninvasive modalities, to differentiate diseases that affect different portions of the vascular-nephron system. This article reviews the most important recently published studies in selected topics chosen because of their clinical relevance or potential for technical developments. RECENT FINDINGS: Magnetic resonance imaging is used increasingly to evaluate renal masses, the prenatal genitourinary system, urinary obstruction and infection, renal vasculature, and the kidneys of transplant donors and recipients. Dynamic contrast magnetic resonance renography based on gadolinium chelated to diethylenetriamine pentaacetic acid, a safe (non-nephrotoxic) paramagnetic agent, emerges as the functional renal imaging modality of choice. Both perfusion and filtration rates can be assessed in individual kidney. SUMMARY: Magnetic resonance imaging has the potential to provide a complete anatomic, physiologic, kidney-specific evaluation. With future advances in automated image analysis methods we can expect functional renal magnetic resonance imaging to play an influential role in management of renal disease.     

Teardrop bladder: demonstration by magnetic resonance imaging

Teardrop deformity of the urinary bladder and ureteral deviation may be caused by iliopsoas hypertrophy. Magnetic resonance imaging (MRI) findings in such a case are described, and the potential advantages of MRI in evaluating the pelvis are discussed.     

Diagnosis of lumbar arachnoiditis by magnetic resonance imaging

Twenty-four cases of lumbar arachnoiditis were evaluated by magnetic resonance (MR) imaging. The morphologic changes of arachnoiditis by MR were compared in 20 cases with CT myelography (CTM) and plain film myelography (PFM). An abnormal configuration of nerve roots was seen by MR. Three anatomic groups were identified. Group 1 showed conglomerations of adherent nerve roots residing centrally within the thecal sac. Group 2 demonstrated nerve roots adherent peripherally to the meninges, giving rise to an "empty sac" appearance. Group 3 showed a soft tissue mass replacing the subarachnoid space. Magnetic resonance imaging resulted in accurate diagnosis, and had excellent correlation with CT myelography and plain film myelographic findings in the diagnosis of lumbar arachnoiditis.     

Identification of aortic thrombus by magnetic resonance imaging

The unique properties of magnetic resonance imaging result in the potential to differentiate various components of the diseased arterial wall. In this article four cases are presented in which magnetic resonance imaging showed mural aortic thrombus and its anatomic relationship to the visceral and renal arteries. Once thrombus is identified and localized specific operative strategies can be undertaken to prevent recurrent embolic events and/or avoid perioperative thromboembolic complications.     

Intrasacral meningeal cyst demonstrated by magnetic resonance imaging

Intrasacral meningeal cyst, first reported by Enderle [8] in 1932, is a rare cause of low-back and leg pain [2, 3, 4, 5, 12]. Non-invasive magnetic resonance imaging appears to be very useful for initial identification of intrasacral cystic masses.     

Diagnosis of tethered cords by magnetic resonance imaging

Thirty children presented with signs and/or symptoms of tethered spinal cord, 13 in association with spina bifida occulta and 17 after myelomeningocele repair. Preoperative magnetic resonance imaging (MRI) of 27 children showed tethering (27), intradural fat (17), distal syrinxes (8), and thickened filum terminale (2). There was an excellent correlation between MRI and the surgical findings. Postoperative MRI was obtained within 1 year after operation in 14 children; spinal cord ascent was seen on only four studies and retethering was suspected on five studies. We consider MRI the procedure of choice to diagnose a tethered cord because this technique accurately defines anatomical relationships without risk to the patient. In addition, we conclude that cord ascent is seen less often than expected and that retethering may occur, especially to cadaveric dura mater.     

Diagnostic neuroimaging by magnetic resonance imaging: update

Magnetic resonance (MR) imaging remains the most versatile technique in diagnostic imaging. In addition to conventional imaging sequences such as T(1)-weighted imaging, T(2)-weighted imaging, or fluid-attenuated inversion recovery imaging, various techniques specific for certain pathological conditions are being continuously introduced. Pulse sequences for various imaging contrasts are becoming mature, and studies on high (3 T), or even ultra-high (7 T) field systems are emerging as a golden standard for neurosurgical practices. MR spectroscopic imaging capable of providing a pictorial display of the chemical properties of the brain and microscopic imaging providing images with significantly high anatomical resolution equivalent to histological preparations are now becoming essential for presurgical evaluation.     

Differentiation of adrenal masses by magnetic resonance imaging

Eighty-one adrenal masses in 68 patients were examined with magnetic resonance imaging (MRI). Masses included nonfunctioning adenomas (17), metastases (25), adrenocortical carcinomas (10), and pheochromocytomas (23). T1-weighted pulse sequences depicted the anatomy with a resolution comparable to that of computed tomography (CT). T2-weighted pulse sequences provided some histologic specificity separating nonfunctioning adenomas with low signal-intensity from metastases with intermediate signal-intensity and pheochromocytomas with high signal-intensity. Pheochromocytomas could always be distinguished from other adrenal masses. In 20% of the cases, metastases with low signal-intensity could not be distinguished from nonfunctioning adenomas.     

Occult bone trauma detected by magnetic resonance imaging

Authors deal with a case of a 23-year old women presented with a sport-related injury of the left knee joint. Initially seen in the surgical department, patient presented with pain, swelling, and decreased range of motion of the left knee. Conventional radiographs of the left knee showed no evidence of fracture or osseous abnormality, while the puncture of the joint proved haemarthros. One day later surgical examination demonstrated repeatedly pain and swelling of the left knee expanding to the proximal third of the leg. Repeated puncture exhibited haemorrhagic synovial fluid containing fat tissue, lipohaermarthos. With regard to the contradiction between the surgical examination and negative radiographs, the MRI examination was recommended. MR images revealed linear area of abnormal signal intensity in the medial condyle of the tibia indicating subchondral fracture of the posterior margin of the medial tibial condyle. This finding was associated with increased volume of the haemorrhagic intraarticular fluid. The menisci, intraarticular and capsular ligamentous apparatus was noted to be intact. The control MR examination performed six weeks later demonstrated healed fracture with surrounding bone marrow edema. The importance of non-invasive MR examination for revealing of the occult bone fractures is stressed.