Short TE proton MRS and neurofibromatosis type 1 intracranial lesions.

PURPOSE: The intracranial lesions of neurofibromatosis type 1(NF-1) have variable pathology and growth based on molecular genetics. Because of this variable pathology and growth, the lesions are followed by sequential MRI. Our hypothesis was that MR spectroscopy (MRS) could provide a noninvasive neurochemical biopsy of NF-1 lesions, thereby distinguishing the different lesions, monitoring their variable growth, and having added value when compared with MRI. METHOD: Nineteen patients fulfilling the National Institutes of Health criteria for NF-1 were followed with sequential MRI and short TE proton MRS. MRI monitored the lesions by observing the area of prolonged T2, mass effect, and degree of enhancement. MRS monitored the lesions by following the level of neurons, cellularity, and a by-product of the inositol signaling pathway. A comparison was made between the MRI and MRS findings to determine if MRS provided added value. Sixty-nine spectra were obtained in 24 resions. RESULTS: MRI was able to identify hamartomas, gliomas, and indeterminate lesions. MRS was able to distinguish three distinct spectra when compared with the cellularity of normal deep white matter (DWM): a hamartoma spectrum with a choline/creatine (CHO/CRE) ratio below 1.5, a transitional spectrum with a CHO/CRE ratio above 1.5 and below 2.0, and a glioma spectrum with a CHO/CRE ratio above 2.0. On comparing MRS and MRI, MRS provided added value by identifying changes in cellularity while MR images were stable, identifying spectra that could distinguish hamartomas from gliomas, and identifying a transitional spectrum that could progress or regress into glioma or hamartoma spectrum. CONCLUSION: MRS was able to identify three distinct spectra in NF-1 lesions when compared with the cellularity of normal DWM, thereby providing a neurochemical means to characterize lesions.

Clinical impact of MR spectroscopy when MR imaging is indeterminate for pediatric brain tumors.

OBJECTIVE: We undertook this study to determine if single-voxel proton (hydrogen) MR spectroscopy could have clinical impact on the management of pediatric brain tumors when MR findings were indeterminate. SUBJECTS AND METHODS: Eleven children (mean age, 9 years) being examined for brain tumors underwent MR imaging that revealed indeterminate criteria of enhancement, mass effect, and prolonged T1 and T2 signal. MR spectroscopy was then used to distinguish radiation necrosis from tumor in one patient, differentiate residual tumor from scarring in two patients, document early treatment response in three patients, and discriminate benign from malignant masses in five patients. RESULTS: In 10 of the 11 patients, spectra were successfully acquired. Based on the chemical analysis of the indeterminate area shown on MR imaging, clinical impact was achieved in these 10 patients. Clinical impact included treatment modification in five patients, follow-up studies replacing further treatment in three patients, and tumor characterization in the remaining two patients. Confirmation was by histology in four patients and by follow-up MR imaging and MR spectroscopy for up to 30 months in the remaining six patients. CONCLUSION: When MR imaging is indeterminate in evaluating pediatric brain tumors, MR spectroscopy can provide objective neurochemical information, thereby altering treatment.

Kinematic MRI of the shoulder.

OBJECTIVE: Clinical evaluation of shoulder pain can be difficult. Pain in the shoulder is often dynamic/positional, and it can often be elicited only during specific activity or function. Soft tissue deforms or changes in shape through motion. These complex interrelationships at the glenoid humeral joint require dynamic studies to accurately evaluate normal anatomy and abnormal pathology. The objective of our study was to evaluate the use of a dynamic cyclic cine imaging to evaluate the glenoid humeral joint. MATERIALS AND METHODS: Kinematic MRI was performed using axial 5 mm sections of the gradient echo and dedicated shoulder surface coil. The patient's arm was placed in the Bonutti cine shoulder system and allowed fixed incremental rotational movement of the shoulder at 10 degrees intervals. Images were reformatted onto a dynamic cine motion by oscillating from internal to external rotation then back to internal rotation. A total of 24 asymptomatic shoulders and 35 symptomatic painful shoulders were studied. RESULTS: Normal variations in the glenoid labrum were readily identified. The glenoid labrum in external rotation is taunt and triangular with well-identified capsular attachments. In neutral rotation the labrum often has increased signal and the middle glenoid humeral ligament occasionally blends with the labrum, making identification difficult. In maximum internal rotation the labrum is rounded and occasionally infolded. Variations in signal through the labrum are not indicative of tears. Capsular attachment must be followed from maximum internal to external rotation to identify stripping. The middle and inferior glenoid humeral ligaments often blend with labrum and internal rotation; however, in external rotation they can be identified as distinct and separate structures. Subcoracoid impingement can be identified in maximum internal rotation with a narrowing of the subcoracoid space to < 11 mm and buckling of the subscapularis and lesser tuberosity against the coracoid process. CONCLUSION: Accurate evaluation of the capsular/labral complex requires cine studies for accurate diagnosis. Signal changes alone or labral morphology alone varies through rotation, and static MRI does not accurately assess these morphologic changes, which vary with extremity position. Capsular attachments can be identified with cine studies accurately and reproducibly. Subcoracoid impingement can be identified with a narrowing of the coracohumeral distance to < 11 mm in internal rotation, which is suggestive of pathology.

Characterization of the pigment from homogentisic acid and urine and tissue from an alkaptonuria patient.

When urine samples from alkaptonuria patients are allowed to stand, they turn black, presumably owing to the oxidation of homogentisic acid to a melanin-like substance. We report the characterization of the pigments formed by polymerization of (a) the components in the urine from a patient with alkaptonuria and (b) homogentisic acid. The absorption spectra and electron spin resonance signals of these pigments are similar to those of eumelanins. Irradiation of the pigments with nitroblue tetrazolium caused reduction of the tetrazolium; this was partially inhibited by superoxide dismutase. Irradiation of Ehrlich ascites carcinoma cells with the pigments from homogentisic acid or urine caused cell lysis. Since this lysis was inhibited by catalase, we have concluded that it was mediated by H2O2. A similar pigment was also extracted from the tissue from an alkaptonuria patient. It is suggested that the degeneration of tissue in vivo may be due to the deposition of melanin-like pigments in the tissues, probably in combination with metal ions.

Ferromagnetism and MR imaging: safety of carotid vascular clamps.

Metallic extracranial carotid vascular clamps of the Selverstone, Crutchfield, Poppen-Blaylock, Salibi, Kindt, and tantalum varieties have been placed for treatment of large, giant, or inoperable intracranial aneurysms. To ascertain what adverse effect, if any, MR imaging would have on these clamps, magnetic deflection at 1.5 T was measured for various carotid clamps. Marked magnetic deflection (and torque) was displayed by stainless steel Poppen-Blaylock clamps. Relatively mild magnetic deflection was displayed by the stainless steel Selverstone, Salibi, Crutchfield, and Kindt clamps. Three patients with previously placed carotid clamps (two Selverstone, one Salibi) and one patient with a nonferromagnetic tantalum carotid clip had cranial or cervical MR studies at field strengths ranging from 0.35 to 0.60 T. No patient experienced any discomfort or neurologic sequelae as a result of MR imaging. Although the ferromagnetic clamps created severe "black-hole" artifacts and image distortion within the cervical and facial regions, no significant image degradation was apparent during spin-echo imaging of the brain. The tantalum clip created a far smaller MR artifact than did ferromagnetic clamps and allowed effective spin-echo and gradient-echo imaging in the cervical region. Our findings indicate that most patients with carotid vascular clamps (and nonferromagnetic clips) can probably be imaged safely with MR.

MR imaging in patients with intracranial aneurysm clips.

Four patients with intracranial aneurysm clips made from a variety of alloys were studied without incidence by MR imaging at field strengths ranging from 0.35 to 0.6 T. Knowledge of the type of alloy used in the manufacturing of an aneurysm clip is important in determining whether the clip will or will not deflect in a magnetic field. Ferromagnetic clips show deflection and torque in a magnetic field and have the potential to dislodge from the aneurysm. Nonferromagnetic or weakly ferromagnetic aneurysm clips such as the Sugita (Elgiloy), Yasargil (316 LVM stainless steel), Heifetz (Elgiloy), Yasargil (Phynox), and Vari-Angle McFadden (MP35N) do not deflect or deflect weakly in the magnetic field and therefore would not be expected to dislodge during MR. The option of imaging many patients with intracranial aneurysm clips with MR extends the usefulness of the technique to a previously excluded population.

A paramagnetic agent causing ochronotic arthropathy.

Magnetic resonance imaging (MRI) identified a paramagnetic substance in the hyaline cartilage of the hips and knees in a patient with ochronosis. Chemical studies characterized the paramagnetic agent as melanin. The free radicals contained in melanin were shown to initiate cytotoxicity. The loss of cartilage in ochronotic arthropathy now can be explained at the electron level using the superoxide theory of oxygen toxicity. Inappropriate metabolism of oxygen also may explain early cartilage degeneration in hemochromatosis, hemosiderosis, and Wilson's disease.

Brain iron in patients with Parkinson disease: MR visualization using gradient modification.

In patients with Parkinson disease, improved visualization of brain iron on a mid-field-strength magnet can be obtained with T2-weighted images and elimination of phase-encoding artifacts. A long echo delay time accentuates the loss of signal from brain iron. However, the long pulse sequence creates phase-encoding artifacts from CSF pulsations at the level of the basal ganglia. These artifacts are eliminated and resolving power increased with additional pulsing in the slice-selective and read gradients. Elimination of motion artifacts enhances visualization of brain iron in three ways: (1) extrapyramidal nuclei containing iron have better definition, (2) abnormalities are better identified, and (3) pseudolesions disappear. Our findings suggest there is significant improvement in the resolving power of brain iron on MR scans made with a mid-field-strength scanner when gradient modification is used.

Visualization of brain iron by mid-field MR.

Brain iron was visualized on a mid-field (0.5 T) scanner using a spin-echo pulse sequence. Methemoglobin was hyperintense on T1- and T2-weighted images. Deoxyhemoglobin, hemosiderin, and ferritin were seen as decreased intensity on T2-weighted images. The spin-echo pulse sequences were improved for identification of deoxyhemoglobin, hemosiderin, and ferritin by prolonging the TR to 3000 msec and the TE to 80-120 msec. Phase-encoding artifacts at the level of the sylvian fissures caused increased noise, obscuring the brain iron in the lentiform nuclei with the TE of 120 msec. This artifact was substantially reduced or eliminated by lowering the TE to 80 msec, changing the phase-encoding gradient to the Y axis, or using additional pulsing in the slice and read gradients. Use of either the improved spin-echo or gradient-echo pulse sequences on a mid-field MR scanner provides improved evaluation of brain iron.

Subtleties of Lisfranc fracture-dislocations.

Tarsometatarsal (Lisfranc) fracture-dislocations can be very difficult to recognize radiographically. The evaluation of the Lisfranc joint can be simplified by meticulously studying the alignment of the metatarsal bases with their corresponding tarsal bones. The usefulness of this observation has been confirmed by: anatomic descriptions, biomechanical analysis, and clinical foot radiographs. Subtle abnormalities identified at the Lisfranc joint using this observation included: metatarsal subluxations identified only on a single projection, associated tarsal subluxations and dislocations, irreducible metatarsal subluxations after closed manipulation, and recurrent metatarsal subluxations after reduction.

Carcinoma in a renal cyst: computed tomography diagnosis.

We report a case of carcinoma in a renal cyst diagnosed by computed tomography. Ultrasound was unavailable because of scheduling difficulties and computed tomography provided a useful alternative in identifying the cystic and solid features of the mass. There was a good correlation of the computed tomography scan with pathology except for a small tumor nodule at the base of the cyst, which was not seen on the scan.

Cecal diverticulitis in young patients.

Of the patients with cecal diverticulitis, 24 to 50% are below the age of 30, and such cases are usually misdiagnosed preoperatively as appendicitis. Two young patients with cecal diverticulitis were diagnosed preoperatively by barium enemas. The barium enemas correctly identified the extent of the disease. Treatment was tailored to the clinical and roentgenographic findings with both patients requiring elective colon resections.

Early confirmation of stress fractures in joggers.

Four joggers had early confirmation of clinically suspected stress fractures by radionuclide bone scans. The radioactive bone scan was abnormal as early as six weeks prior to the appearance of conventional roentgenographic changes. The stress fractures involved the bones of the lower extremities and included the femur, tibia, and calcaneus. Radioactive bone scanning also correctly identified stress fractures with bilateral involvement and referred pain. In joggers, when a stress fracture is clinically suspected and the conventional radiographs are negative, a radioactive bone scan is indicated for early confirmation and institution of appropriate treatment.

Common calcaneal avulsion fracture.

An avulsion fracture on the dorsolateral aspect of the calcaneus at the origin of the extensor digitorum brevis muscle was identified after inversion injuries of the ankle. The avulsion occurred in 10% of emergency room patients with clinically suspected ankle fractures. The routine dorsoplantar view of the foot and/or the routine anteroposterior view of the ankle demonstrated the fracture. The fracture is most often confused with the os peroneum, or with the fracture of the anterior process of the calcaneus. Treatment is conservative with elevation, supportive bandage, and early activity.