Biomedical subjects

S A Mirowitz

Publications and source records attributed to S A Mirowitz.

63 records · Page 4Linked to original sources

PubMedDate not supplied

CT depiction of prostatic zonal anatomy.

The objective of this study was to investigate the frequency of recognition of prostatic zonal anatomy on CT. Computed tomography in 71 patients without known prostate disease was reviewed. Differential attenuation allowed for distinction of the peripheral zone and central gland of the prostate in 24% patients. The peripheral zone was of lower attenuation than the central gland, attributable to relatively increased water content in the peripheral zone. Patients in whom zonal anatomy was evident were significantly older and had prostate glands significantly larger than those in whom the prostate appeared as a homogeneous structure. All patients in whom prostatic zonal anatomy was visualized had received intravenous contrast material injection. Development of benign prostatic hyperplasia nodules within the central gland may contribute to relative increased attenuation or increased contrast enhancement within this region of the prostate gland.

Adult↗

PubMedDate not supplied

Use of nutritional support formula as a gastrointestinal contrast agent for MRI.

The objective of this study was to evaluate the potential utility of a nutritional support formula to serve as a practical means of enhancing the gastrointestinal tract on abdominal MR images. Nutritional support formula (Ensure Plus) was administered to 29 patients prior to abdominal MRI. Standard T1-weighted and T2-weighted pulse sequences were performed, in addition to fat suppression and inversion recovery sequences in selected patients. Images in these patients were evaluated for degree and uniformity of gastrointestinal tract enhancement and delineation of the bowel wall and pancreas. Results were compared with those obtained in 10 control patients. Marked enhancement of gastric contents was present in nearly all patients who received nutritional support formula on both T1-weighted and T2-weighted sequences, with mild to moderate enhancement of small bowel and colon in most patients. Although gastrointestinal and respiratory motion artifacts often limited bowel wall delineation, excellent delineation of the gastric wall and pancreas was provided. Phantom experiments demonstrated that gastrointestinal tract enhancement with nutritional support formula is due to the paramagnetic trace elements, corn syrup, and lipid material it contains. Such a formula requires no preparation, is safe, inexpensive, palatable, readily available, and represents a practical means of enhancing the gastrointestinal tract on MRI.

Adipose Tissue↗

PubMedDate not supplied

Apparent vascular occlusion on cranial TOF MRA with peripheral presaturation technique.

OBJECTIVE: Improvement in the visibility and accurate representation of intracranial vessels may be achieved on cranial time-of-flight (TOF) MR angiography (MRA) when the signal intensity of orbital and superficial fat is suppressed. This may be accomplished by placement of spatial radiofrequency presaturation bands along the periphery of the head. The objective of this study was to evaluate the potential for this peripheral presaturation technique to result in a spurious appearance of vascular occlusion. MATERIALS AND METHODS: Three-dimensional TOF MRA of the head was performed in three patients. Flow-compensated spoiled gradient echo images were acquired in the transaxial plane, using the peripheral presaturation technique. The MRA acquisitions were then subsequently repeated in each patient following retraction of the peripheral presaturation bands. A phantom study was also performed to assess the slice profile of the presaturation bands. RESULTS: There was absence of flow-related enhancement, indicating apparent vascular occlusion, involving one carotid siphon in each patient on initial MRA images. Following lateral retraction and/or removal of presaturation bands, the carotid siphons were documented to be patent, with normal caliber and flow-related enhancement demonstrated. Image analysis and phantom experiments indicate this vascular pseudoocclusion is due to proximity of the lateral presaturation band to the lateral aspect of the petrous segment of the internal carotid artery. In this location, there is inadvertent saturation of flowing spins due to imperfections in the presaturation band slice profile. CONCLUSION: The use of peripheral presaturation bands for cranial TOF MRA is useful for improving vascular depiction. However, patent vessels may occasionally demonstrate an absent signal intensity, suggesting occlusion when this technique is used. Awareness of this diagnostic pitfall is important so that serious misdiagnosis does not occur.

Aged↗

PubMedDate not supplied

Motion artifact as a pitfall in diagnosis of meniscal tear on gradient reoriented MRI of the knee.

OBJECTIVE: Reorientation of the phase and frequency encoding gradients is frequently performed for knee MRI to improve visualization of the cruciate ligaments. This technique allows pulsation artifacts arising from the popliteal vessels to be redirected away from the intercondylar notch. The objective of this study was to evaluate the potential for this method to result in false-positive depictions of meniscal tears based on subtle patient motion. MATERIALS AND METHODS: Magnetic resonance imaging of the knee was performed in five patients using gradient reorientation. Repeat examinations were then performed following deliberate instruction to the patients regarding the importance of refraining from moving the extremity. RESULTS: The MRI performed with gradient reorientation demonstrated apparent meniscal tears using standard criteria. However, the repeat examinations following deliberate patient instructions to refrain from moving demonstrated the affected menisci to be normal in all patients. CONCLUSION: Knee motion during image acquisition may result in ghosting artifacts of relatively high signal intensity structures such as marrow within the femoral condyles and hyaline cartilage along the articular surfaces. These artifacts may traverse the menisci on gradient-reoriented images and result in confusion with meniscal tear. Whereas gradient reorientation is a valuable tool for improving depiction of the cruciate ligaments, one must be aware of the potential for this technique to result in simulation of meniscal tears.

Adult↗

PubMedDate not supplied

Principles and applications of echo-planar imaging: a review for the general radiologist.

Echo-planar imaging is a very fast magnetic resonance (MR) imaging technique capable of acquiring an entire MR image in only a fraction of a second. In single-shot echo-planar imaging, all the spatial-encoding data of an image can be obtained after a single radio-frequency excitation. Multishot echo-planar imaging results in high-quality images comparable to conventional MR images. However, echo-planar imaging offers major advantages over conventional MR imaging, including reduced imaging time, decreased motion artifact, and the ability to image rapid physiologic processes of the human body. The use of echo-planar imaging has already resulted in significant advances in clinical diagnosis and scientific investigation, such as in evaluation of stroke and functional imaging of the human brain, respectively. The clinical indications for echo-planar imaging are expanding rapidly, and it can now be applied to many parts of the body, including the brain, abdomen, and heart. Today, with the availability of echo-planar imaging-capable MR imagers at many sites, the general radiologist can benefit from echo-planar imaging and its clinical applications.

Abdomen↗

PubMedDate not supplied

Characterization of musculoskeletal masses using dynamic Gd-DTPA enhanced spin-echo MRI.

Early studies evaluating the utility of Gd-diethylenetriamine pentaacetic acid (DTPA) enhanced MR imaging for characterization of musculoskeletal masses have demonstrated inconsistent and often conflicting results. In this study a new method, dynamic Gd-DTPA enhanced rapid acquisition spin echo MR imaging, was implemented in the evaluation of 18 musculoskeletal lesions and the enhancement features of these lesions were analyzed. Lesions were evaluated before, during, and sequentially following bolus Gd-DTPA injection. Analysis of intensity, volume, timing of onset, progression, uniformity, and pattern of enhancement did not demonstrate significant differences between benign (n = 8) and malignant (n = 10) masses. Significant variations in enhancement were noted in different regions within these masses, which limits the utility of previous dynamic contrast enhanced methods that provide only a single imaging slice for analysis, and are therefore subject to sampling error. This pilot study indicates no advantage for using dynamic Gd-DTPA enhanced imaging for qualitative lesion characterization.

Adolescent↗

PubMedDate not supplied

Cavernous hemangioma of the liver: assessment of MR tissue specificity with a simplified T2 index.

This is a comparison of the ability of two quantitative magnetic resonance (MR) indices: (a) the second echo signal drop (SESD) (a simplified index of T2 relaxation times that we have developed); and (b) the previously described lesion/liver signal intensity ratio (LLR) to provide histologic diagnosis in hepatic lesions greater than 2 cm in diameter. In 55 patients 108 hepatic masses [31 cavernous hemangiomas (CH), 68 metastases, and 9 hepatocellular carcinomas] were scanned at 0.5 T. Statistically significant differences between CH and malignant lesions were obtained in mean SESD (p = 0.0006) and LLR (p = 0.0008) using repetition time (TR) 2,100/echo time (TE) 35, 60 ms. Application of cutoff values derived from receiver-operator characteristic analysis led to a correct diagnosis in 100 and 94% of lesions, respectively. Using TR 2,100/TE 35, 90 ms in a different patient population, CH and malignancies again displayed significantly different mean values, using the SESD (p = 0.0090) and LLR (p = 0.0024) methods. These measurements provided a correct diagnosis in 74 and 81%, respectively. Accuracy was increased in those cases in which the diagnosis by SESD and LLR were concordant. When compared with visual analysis, these quantitative methods appear to achieve near 100% accuracy in the differentiation of hepatic CH from malignancies.

Adult↗

PubMedDate not supplied

"Pseudocoarctation" of the aorta: pitfall on cine MR imaging.

The diagnosis of coarctation of the aorta on cine magnetic resonance imaging is based upon observation of localized narrowing in the region of the aortic isthmus with jet-like signal void areas extending distally. We observed similar findings in 8 of 20 (40%) normal volunteers examined in the sagittal oblique view. These artifactual findings relate primarily to out-of-plane motion of the thoracic aorta during a portion of the cardiac cycle, leading to partial volume averaging with pulmonary air. Awareness of this pitfall will prevent misdiagnosis of aortic coarctation in normal subjects and allow for more accurate assessment of severity of true coarctation.

Aorta, Thoracic↗

PubMedDate not supplied

High-intensity basal ganglia lesions on T1-weighted MR images in neurofibromatosis.

Basal ganglia lesions, characterized on MR by increased signal intensity on T1-weighted images, were observed in seven patients with documented neurofibromatosis. These lesions most often involved the globus pallidus and internal capsules in a bilateral and symmetric fashion, and extended across the anterior commissure resulting in a "dumbbell" configuration. Smaller and less prominent foci of increased signal also were present on corresponding T2-weighted images. These lesions did not exhibit mass effect, edema, or enhancement with gadolinium-DTPA. They were not visible on CT (performed in two patients) and demonstrated no progression during a 2-year interval in three patients. Their signal characteristics and morphology suggest that they represent heterotopias containing Schwann cells and/or melanin deposits. Migrational abnormalities of these neural crest derivatives are known to occur in neurofibromatosis, and the presence of such heterotopias has been documented pathologically in patients with this disorder. While recent reports discuss foci of increased signal intensity on T2-weighted MR images in patients with neurofibromatosis, signal abnormalities on T1-weighted images have not yet been described. When lesions characterized by similar signal as well as morphologic characteristics are encountered on MR, the diagnosis of neurofibromatosis should be considered.

Adolescent↗