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Biomedical subjects

M D Schnall

Publications and source records attributed to M D Schnall.

At least 37 records · Page 2Linked to original sources
PubMed2000

MR imaging: its current and potential utility in the diagnosis and management of breast cancer.

The rapid evolution of the treatment of breast cancer has been paralleled by a similar rapid improvement in the imaging of breast cancer. High-resolution contrast-enhanced MR imaging of the breast has recently emerged as a sensitive instrument for the detection of breast cancer. The sensitivity of MR imaging makes it an excellent tool in specific clinical situations, such as the detection of local recurrence in patients who have received breast-conservation therapy. Furthermore, MR imaging of the breast has the potential to be a powerful aid in presurgical planning and to be a useful adjunct to mammography in selected patients. MR imaging, however, has a significant false-positive rate, is not readily available in all areas, and is more expensive than mammography and sonography. It also remains unclear if alterations of management plans based on MR imaging findings actually benefit affected patients. Therefore rigorous clinical trials are needed to define precisely the exact role that MR imaging should play in the diagnosis and management of breast cancer patients.

Breast↗
PubMed1999

Curvilinear areas in the perinephric fat seen on MR images.

AIM: On magnetic resonance (MR) images, strands correspond to curvilinear areas running in the perinephric fat, and haloes to those lying on the renal surface. Our aim was to examine the diagnostic significance and histopathological basis of these areas. PATIENTS AND METHODS: MR images obtained in 46 patients without renal disease and 96 patients with renal disease were assessed for the signal intensity and extent of strands and haloes, and their degree of right-left asymmetry. RESULTS: Strands usually revealed low signal intensity on T1-weighted MR images and high signal intensity on fat-suppressed T2-weighted images and contrast-enhanced fat-suppressed T1-weighted images. Haloes revealed high signal intensity on fat-suppressed T2-weighted images, but most of haloes were not clearly depicted on T1-weighted images or contrast-enhanced fat-suppressed T1-weighted images. Strands and haloes were common and usually symmetrical or only mildly asymmetrical in both patient groups. However, in 11 of the 96 patients with renal disease, prominent strands and/or haloes appeared with remarkable asymmetry and likely represented definite changes in the perinephric fat. At histopathology, vascular loose fibrous tissue was found at the sites of strands and haloes. CONCLUSION: Strands and haloes usually represent normal anatomical variations. However, the presence of prominent strands or haloes with remarkable right-left asymmetry implies abnormality and may provide additional information in the evaluation of renal disease.

Adipose Tissue↗
PubMed1999

Discrimination of MR images of breast masses with fractal-interpolation function models.

RATIONALE AND OBJECTIVES: The authors evaluated the feasibility of using statistical fractal-dimension features to improve discrimination between benign and malignant breast masses at magnetic resonance (MR) imaging. MATERIALS AND METHODS: The study evaluated MR images of 32 malignant and 20 benign breast masses from archived data at the University of Pennsylvania Medical Center. The test set included four cases that were difficult to evaluate on the basis of border characteristics. All diagnoses had been confirmed at excisional biopsy. The fractal-dimension feature was computed as the mean of a sample space of fractal-dimension estimates derived from fractal interpolation function models. To evaluate the performance of the fractal-dimension feature, the classification effectiveness of five expert-observer architectural features was compared with that of the fractal dimension combined with four expert-observer features. Feature sets were evaluated with receiver operating characteristic analysis. Discrimination analysis used artificial neural networks and logistic regression. Robustness of the fractal-dimension feature was evaluated by determining changes in discrimination when the algorithm parameters were perturbed. RESULTS: The combination of fractal-dimension and expert-observer features provided a statistically significant improvement in discrimination over that achieved with expert-observer features alone. Perturbing selected parameters in the fractal-dimension algorithm had little effect on discrimination. CONCLUSION: A statistical fractal-dimension feature appears to be useful in distinguishing MR images of benign and malignant breast masses in cases where expert radiologists may have difficulty. The statistical approach to estimating the fractal dimension appears to be more robust than other fractal measurements on data-limited medical images.

Algorithms↗
PubMed1999

Role of magnetic resonance imaging and magnetic resonance imaging--guided surgery in the evaluation of patients with early-stage breast cancer for breast conservation treatment.

Magnetic resonance imaging (MRI) may be more sensitive than mammography for detecting breast cancer and may have an adjunctive role in assessing patients with early-stage disease for breast conservation treatment. This study was performed to analyze the impact of breast MRI on the clinical management of 83 patients being considered for breast conservation treatment. Eighty-three consecutive cases of patients undergoing breast MRI during standard workup and evaluation for breast conservation treatment from 1993 to 1996 were retrospectively reviewed. Records were reviewed for patient and tumor characteristics, mammographic findings, MRI findings, timing of MRI study, findings from MRI-guided surgery (when done), and whether the patient underwent breast conservation treatment. MRI definitely altered management in 15 patients (18%), may have affected management in 4 patients (5%), and did not change management in 64 patients (77%). Thirteen patients underwent additional surgery because of MRI findings; the positive predictive value for MRI-guided surgery was 38% (5 of 13). Ultimately, 82% of the patients received breast conservation treatment. No predictive factor was identified to characterize the patients most likely to have management affected by MRI findings. These findings suggest that breast MRI may be useful in the evaluation of patients with early-stage breast cancer for breast conservation treatment. A larger study population and outcome data will be required to confirm these findings and to define those patients most likely to benefit from breast MRI.

Adult↗
PubMed1999

Renal artery stenosis: evaluation with conventional angiography versus gadolinium-enhanced MR angiography.

PURPOSE: To evaluate the interobserver and intermodality variability of conventional angiography and gadolinium-enhanced magnetic resonance (MR) angiography in the assessment of renal artery stenosis. MATERIALS AND METHODS: Fifty-four patients underwent conventional angiography and gadolinium-enhanced three-dimensional gradient-echo MR angiography. Three angiographers blinded to each other's interpretations and the MR angiographic findings assessed the conventional angiograms for renal artery stenosis. Similarly, three blinded MR imagers evaluated the MR angiograms. RESULTS: Interobserver variability for the degree of renal artery stenosis in the 107 kidneys evaluated was not significantly different between the two modalities. The mean SD of the degree of stenosis was 6.9% at MR angiography versus 7.5% at conventional angiography (alpha < or = .05, P > .05). In 70 kidneys (65%), the average degree of stenosis reported by the readers for the two modalities differed by 10% or less. In 22 cases (21%), the degree of stenosis was overestimated with MR angiography by more than 10% relative to the results of conventional angiography. In 15 cases (14%), the degree of stenosis was underestimated with MR angiography by more than 10%. CONCLUSION: Gadolinium-enhanced MR angiography permits evaluation of renal artery stenosis with an interobserver variability comparable with that of conventional angiography.

Angiography↗
PubMed1999

Breast MR imaging in patients with axillary node metastases and unknown primary malignancy.

PURPOSE: To assess the usefulness of magnetic resonance (MR) imaging of the breast in patients with malignant axillary adenopathy and unknown primary malignancy. MATERIALS AND METHODS: Between October 1993 and December 1997, 38 women with malignant axillary adenopathy and negative mammographic and physical examination findings underwent contrast material-enhanced MR imaging. Sixteen patients were excluded due to axillary tail cancer (n = 7), lack of follow-up (n = 4), second primary malignancy (n = 3), or chemotherapy before MR imaging (n = 2). The study population comprised the remaining 22 patients. Histopathologic findings were available in 20 patients; follow-up MR imaging findings were available in two patients. RESULTS: MR imaging depicted a primary breast cancer in 19 patients (86%; identified at excisional biopsy or mastectomy in 17, resolved on follow-up MR images during treatment in two). MR imaging depicted 4-30-mm cancers (mean, 17 mm), which correlated closely with histopathologic size. Two patients (9%) had false-negative findings: (a) One had a 2-mm invasive ductal carcinoma, and (b) one had 17- and 20-mm invasive ductal carcinomas. Of the 19 patients, 11 underwent mastectomy, seven underwent breast-conservation therapy, and one did not undergo a surgical procedure. CONCLUSION: MR imaging is very sensitive for the detection of mammographically and clinically occult breast cancer in patients with malignant axillary adenopathy. In these patients, MR imaging offers potential not only for cancer detection but also for staging the cancer within the breast, which may be useful for treatment planning.

Axilla↗
PubMed1999

Pulmonary perfusion: respiratory-triggered three-dimensional MR imaging with arterial spin tagging--preliminary results in healthy volunteers.

The authors used a spin-tagging method of magnetic resonance perfusion imaging to measure pulmonary perfusion in eight healthy volunteers with use of a respiratory-triggered three-dimensional pulse sequence. The average signal intensity (SI) decrease upon arterial labeling was 24%. The perfusion SI increased by 21% after exercise (P = .02). Focal blood flow abnormalities were observed in a patient with chronic obstructive pulmonary disease.

Adult↗
PubMed1999

Cost-effectiveness of MR imaging and core-needle biopsy in the preoperative work-up of suspicious breast lesions.

PURPOSE: To assess the clinical and economic consequences of the use of preoperative breast magnetic resonance (MR) imaging and core-needle biopsy (CNB) to avert excisional biopsy (EXB). MATERIALS AND METHODS: A decision-analytic Markov model was constructed to compare MR imaging, CNB, and EXB without preoperative testing in a woman with a suspicious breast lesion. Stage-specific cancer prevalence, tumor recurrence, progression rates, and MR imaging and CNB sensitivity and specificity were obtained from the literature. Cost estimates were obtained from the literature and from the Medicare fee schedule. RESULTS: EXB without preoperative testing was associated with the greatest quality-adjusted life expectancy, followed by MR imaging and CNB; life expectancies were 17.409, 17.405, and 17.398 years, respectively. EXB resulted in the greatest lifetime treatment cost ($31,438), followed by MR imaging ($29,072) and CNB ($28,573). Results were robust over a wide range of cancer prevalence, stage distribution, tumor progression rates, and procedure and treatment costs. Incremental cost-effectiveness ratios showed that preoperative testing was cost-effective, but the choice between MR imaging and CNB was highly dependent on the accuracy of each test and to patient preferences. CONCLUSION: Preoperative testing of most suspicious breast lesions was cost-effective. More precise estimates of MR imaging and CNB test performance characteristics are needed. Until those are available, patient preferences should inform individual decisions regarding preoperative testing.

Biopsy, Needle↗
PubMed1999

Solitary intraductal papilloma: findings at MR imaging and MR galactography.

OBJECTIVE: The purpose of this article is to describe MR findings in surgically proven solitary intraductal papillomas of the breast, including findings on MR galactography. CONCLUSION: Women with spontaneous nipple discharge and solitary intraductal papilloma show, on MR imaging, dilated ducts with an associated enhancing, well-circumscribed mass.

Adult↗
PubMed1998

Bilateral imaging using separate interleaved 3D volumes and dynamically switched multiple receive coil arrays.

Multiple receive coil arrays are often designed for unilateral imaging of anatomy having bilateral symmetry. A technique is described for extending the utility of such arrays to simultaneously image both bilaterally symmetric anatomical features. A separate, complete multiple receive coil array is placed at each location. Two separate, noncontiguous 3D volumes are then acquired, one at each location, in an interleaved fashion. High-impedance blocking networks are alternately activated and deactivated to minimize coupling between the arrays. It is demonstrated that there is no degradation in image quality when compared to a unilateral exam. A general method for analyzing the interactions between separate multiple coil arrays is presented.

Breast↗
PubMed1998

Fast imaging of phosphocreatine using a RARE pulse sequence.

A technique is described for acquiring phosphocreatine (PCr) images of skeletal muscle using a rapid acquisition with relaxation enhancement (RARE) pulse sequence. All of the phosphorus metabolites other than PCr are forced to dephase within the first few echoes, whereas the Carr-Purcell Meiboom-Gill (CPMG) pulse sequence maintains a high PCr signal long enough to acquire 64 echoes in a single shot. Axial PCr images of a human forearm with a signal-to-noise ratio of 9 were acquired in 2 min. The effect of the refocusing pulse section profile on the ratio of desired to undesired metabolite signal is demonstrated.

Forearm↗
PubMed1998

MRI of hyperpolarized 3He gas in human paranasal sinuses.

In this study, MRI of hyperpolarized 3He gas in human paranasal sinuses is presented. Helium images were obtained at 1.5 T, using a surface coil and a 2D, fast gradient-echo sequence with a nominal constant flip angle of 12 degrees. Coronal images of 20-mm thick slices were generated and compared with proton images of the corresponding sections. The images enable visualization of the paranasal sinuses and the nasal cavity, suggesting a potential use of this method not only in identifying the anatomical configuration of these pneumatic spaces, but also in assessing sinus ventilation.

Adult↗
PubMed1998

Future directions in imaging of breast diseases.

In the near future, investigation and refinement of emerging anatomic and functional breast imaging techniques will enable clinical trials that will evaluate their utility and potential for improving the survival and quality of life for patients with breast cancer. In the longer term, strategic research collaborations among investigators in the fields of functional imaging, molecular biology, and pathology are needed to merge existing science and advance the development of biomarker and genetic techniques focused on detecting and characterizing disease at the cellular and molecular levels. This research could create clinical tools for (a) detecting breast cancer earlier, (b) more accurately quantifying the extent of disease, (c) noninvasively evaluating lymph node involvement, (d) identifying micrometastases and residual microscopic disease, and (e) enhancing therapy by means of imaging-guided biomarker or tumor-specific delivery of pharmacologic, chemosensitizing, or radiosensitizing agents to tumors.

Breast↗
PubMed1998

Human breast lesions: characterization with proton MR spectroscopy.

PURPOSE: To assess the clinical usefulness of spatially localized hydrogen-1 magnetic resonance (MR) spectroscopy in distinguishing benign from malignant lesions on the basis of total choline levels. MATERIALS AND METHODS: These studies were performed at 1.5 T with a four-channel multicoil that compresses the breast sagittally. Contrast material-enhanced MR imaging and single-voxel H-1 MR spectroscopy were performed in 17 patients (age range, 25-68 years) who had nonspecific mammographic findings. Histopathologic correlations were made from biopsy or surgical specimens. Ten patients had various malignant breast lesions 1-4 cm in diameter, and seven patients had benign processes. RESULTS: Most studies were performed with nominal voxel sizes (< 2 cm3). Spectra obtained with an echo time of 31 msec showed resonances from water and mobile fatty acids and, in some cases, the N-trimethyl resonance of choline-containing compounds (Cho) at 3.2 ppm. The absolute concentration of Cho in each lesion was determined with a phantom containing 1 mmol/L Cho as an external reference. On the basis of reference measurements, the least detectable level of Cho was 0.2 mmol/L. With this threshold, seven of 10 malignant lesions showed detectable levels of Cho. In contrast, Cho was seen in only one patient with an extremely rare benign process, a tubular adenoma. The remaining six patients with benign processes demonstrated no detectable Cho levels. CONCLUSION: Spatially localized H-1 MR spectroscopy can provide sufficient sensitivity and spectral resolution at 1.5 T to demonstrate Cho in human breast lesions with a spectroscopic protocol that provides up to 1-cm3 resolution. Determining the presence of Cho may provide a useful test for malignancy.

Adult↗
PubMed1998

Use of endorectal MR imaging to predict prostate carcinoma recurrence after radical prostatectomy.

PURPOSE: To determine the ability of endorectal magnetic resonance (MR) imaging to help predict postprostatectomy disease recurrence and, thereby, patient outcome. MATERIALS AND METHODS: The authors evaluated 116 patients referred for prostate MR imaging during 1991 and 1992 who subsequently underwent radical prostatectomy and for whom follow-up data through 1996 could be obtained. The MR reports, clinic charts, and pathology reports were reviewed. Disease recurrence was established by means of detectable levels of serum prostate-specific antigen (PSA) after surgery. RESULTS: Thirty-four patients (29%) had postoperative disease recurrence. Patients with recurrence had higher preoperative PSA values (P < .0001). These patients also more frequently had positive surgical margins (P = .0005), transcapsular tumor spread (P < .0001), seminal vesicle involvement (P = .0012), and tumors of advanced stage (P < .0001) and high grade (P = .0058). Of 13 patients whose MR examinations showed definite extracapsular disease, eight (62%) had disease recurrence. The recurrence rate when MR imaging indicated limited disease (24%) was similar to that when MR imaging showed possible microscopic extension (27%). An MR finding of definite extracapsular disease was 24% sensitive and 94% specific for the prediction of disease recurrence. CONCLUSION: MR imaging findings of definite extracapsular spread of disease helped predict prostate tumor recurrence with high specificity, although with low sensitivity.

Case-Control Studies↗
PubMed1998

Extracranial atherosclerotic carotid artery disease: evaluation of non-breath-hold three-dimensional gadolinium-enhanced MR angiography.

OBJECTIVE: The purpose of this study was to compare the diagnostic information provided by a combination of two-dimensional and three-dimensional (3D) time-of-flight (TOF) techniques with that provided by non-breath-hold 3D spoiled gradient-echo gadolinium-enhanced MR angiography. MATERIALS AND METHODS: Fifty patients suspected of having extracranial atherosclerotic carotid artery disease were examined with all three imaging techniques using a 1.5-T MR imaging system. Three observers independently and retrospectively measured the degree of stenosis according to the North American Symptomatic Carotid Endarterectomy trial criteria. The observers were unaware of the results of other MR imaging pulse sequences and digital subtraction angiography. The standard of reference was established by digital subtraction angiography. Results were evaluated with receiver operating characteristic curve analysis. The degree of interobserver agreement was determined using pairwise kappa statistics. RESULTS: The grading of carotid artery stenosis as measured by the area under the receiver operating characteristic curve was less accurate with non-breath-hold 3D gadolinium-enhanced MR angiography than with TOF imaging. Interobserver variability was greater for non-breath-hold 3D gadolinium-enhanced MR angiography than for TOF techniques. CONCLUSION: Routine evaluation of carotid artery stenosis at the level of the bifurcation using non-breath-hold 3D gadolinium-enhanced MR angiography is less accurate than is TOF imaging and is therefore not recommended. The weakness of this technique may be due to problems in timing the injection of gadolinium and the masking of the carotid bifurcation by the venous jugular system.

Aged↗