PubMed Health⌕ Search

Biomedical subjects

Mitchell D Schnall

Publications and source records attributed to Mitchell D Schnall.

29 records · Page 2Linked to original sources
PubMed2003

Breast MR imaging.

Contrast-enhanced breast MR imaging has made significant progress since its introduction into the radiological literature in 1989. The techniques and technology continue to be refined, and understanding of the interpretation strategies has improved dramatically. Clinical applications in difficult diagnostic cases and the evaluation of the extent of breast cancer are now being practiced in many centers worldwide. There is great excitement over the potential for breast MR imaging to address the problem of screening high-risk women. Despite all of the progress made over the past years, however, there is still a significant amount of work ahead before a clear understanding of how this technique will affect the health care of women is obtained.

Breast Neoplasms↗
PubMed2003

A direct comparison of signal behavior between 4.0 and 1.5 T: a phantom study.

INTRODUCTION: Higher magnetic fields (>or=3 T) afford higher spatial and/or temporal resolution in MR imaging with contrast agents, however, studies containing direct comparisons of signal intensity among different magnetic fields are substantially sparse. Our aim was to quantify the differences in terms of signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) between higher and lower (<or=1.5 T) magnetic fields and to clarify the benefit of higher magnetic fields. METHODS: The same sets of phantom experiments were conducted at both 4 and 1.5 T on whole-body MR scanners with head coils. Phantoms included different concentrations of Gd chelate water solution. A standard contrast-enhanced MR angiographic sequence with the same imaging parameters was utilized to confirm changes in signal intensities. Furthermore, the results were compared with a computer simulation. RESULTS: Peak SNRs at 4 T increased at least 2.21 times higher compared with those at 1.5 T. Moreover, peak CNRs at 4 T increased at least 1.59 times higher compared with those at 1.5 T in the range of Gd concentration expected during clinical use. CONCLUSION: Higher magnetic fields benefit CNRs as well as SNRs. These advantages may lead to a high resolution imaging and reduction of scan time.

Computer Simulation↗
PubMed2003

Abdominal imaging at 4 T MR system: a preliminary result.

In this study, the potential for abdominal MR images at 4 T using a tailored coil was demonstrated using healthy volunteers. These images were compared with those obtained in the same subject at 1.5 T to discuss whether 4 T would be superior to 1.5 T in abdominal imaging. MR images at 4 T were characterized by high contrast and signal-to-noise ratios, more than 2.95 times higher than those at 1.5 T. In conclusion, abdominal MR imaging at 4 T was feasible. Furthermore, abdominal MR imaging at 4 T was superior to that at 1.5 T in qualitative and quantitative analyses.

Abdomen↗
PubMed2002

Effect of breast magnetic resonance imaging on the clinical management of women with early-stage breast carcinoma.

PURPOSE: To determine the impact of breast magnetic resonance imaging (MRI) on the clinical management of patients with early-stage breast cancer. PATIENTS AND METHODS: A review was performed of the records of 207 women with early-stage breast cancer (including five women with bilateral disease) who underwent breast MRI during work-up for breast conservation treatment. All patients presented with clinical stage 0, I, or II disease. For each patient, a determination was made whether the breast MRI affected the clinical management, and if so, whether the patient was well served by the change in management. RESULTS: The MRI findings affected the clinical management in 43 cases (20% of 212 breast cancers). Based on the pathology findings and the overall clinical course for each case, the breast MRI was judged to have had a strongly favorable effect on management in 18 cases (8%), a somewhat favorable effect in six cases (3%), an uncertain effect in five cases (2%), a somewhat unfavorable effect in 11 cases (5%), and a strongly unfavorable effect in three cases (1%). The effect of MRI was not significantly different for invasive carcinoma compared with ductal carcinoma-in-situ (all P > or =.27). However, the effect of MRI was significantly greater when the MRI was performed before an excisional biopsy (P =.0011) or for larger tumors (P =.0089). CONCLUSIONS: Breast MRI alters the clinical management for a sizable fraction of women with early-stage breast cancer and appears to offer clinically useful information for determining optimal local treatment.

Adult↗
PubMed2002

Optimal post-contrast timing of breast MR image acquisition for architectural feature analysis.

PURPOSE: To define a post-contrast imaging time span during which diagnostic accuracy of breast magnetic resonance (MR) architectural feature analysis is maintained. MATERIALS AND METHODS: Seventy-five patients with mammographically-visible or palpable findings underwent MR examination. Three sequential post-contrast, fat-saturated, three-dimensional gradient-echo imaging runs were acquired spanning 0-90, 90-180, and 180-270 seconds after contrast injection. Five readers independently predicted the malignant potential of the MR abnormalities. RESULTS: Receiver-operator characteristics (ROC) curves were our primary measure of diagnostic accuracy. The accuracy of four readers was unchanged over the three post-contrast runs. One reader was slightly more accurate using the second and third runs than using the first. CONCLUSION: For most readers, a single post-contrast run performed at any point during the first four minutes and 30 seconds following injection should yield an equivalent diagnostic accuracy. If any time period is less optimal, it is that of our first run, performed between 0-90 seconds after contrast injection.

Adult↗
PubMed2002

Comparison of quantitative perfusion imaging using arterial spin labeling at 1.5 and 4.0 Tesla.

High-field arterial spin labeling (ASL) perfusion MRI is appealing because it provides not only increased signal-to-noise ratio (SNR), but also advantages in terms of labeling due to the increased relaxation time T(1) of labeled blood. In the present study, we provide a theoretical framework for the dependence of the ASL signal on the static field strength, followed by experimental validation in which a multislice pulsed ASL (PASL) technique was carried out at 4T and compared with PASL and continuous ASL (CASL) techniques at 1.5T, both in the resting state and during motor activation. The resting-state data showed an SNR ratio of 2.3:1.4:1 in the gray matter and a contrast-to-noise ratio (CNR) of 2.7:1.1:1 between the gray and white matter for the difference perfusion images acquired using 4T PASL, 1.5T CASL, and 1.5T PASL, respectively. However, the functional data acquired using 4T PASL did not show significantly improved sensitivity to motor cortex activation compared with the 1.5T functional data, with reduced fractional perfusion signal change and increased intersubject variability. Possible reasons for these experimental results, including susceptibility effects and physiological noise, are discussed.

Adult↗
PubMed2002

Methods for modeling and predicting mechanical deformations of the breast under external perturbations.

Currently, high field (1.5 T) superconducting MR imaging does not allow live guidance during needle breast procedures. The current procedure allows the physician only to calculate approximately the location and extent of a cancerous tumor in the compressed patient breast before inserting the needle. It can then become relatively uncertain that the tissue specimen removed during the biopsy actually belongs to the lesion of interest. A new method for guiding clinical breast biopsy is presented, based on a deformable finite element model of the breast. The geometry of the model is constructed from MR data, and its mechanical properties are modeled using a non-linear material model. This method allows imaging the breast without or with mild compression before the procedure, then compressing the breast and using the finite element model to predict the tumor's position during the procedure. A silicon phantom containing a stiff inclusion was imaged uncompressed then compressed. A model of the phantom was constructed and compressed using custom-written software, and also using a commercial FEM simulation package. The displacement of the inclusion's corners was recorded both in the real phantom and in the two compressed models. A patient's breast was imaged uncompressed then compressed. A deformable model of the uncompressed breast was constructed, then compressed. The displacement of a cyst and of two vitamin E pills taped to the surface of the breast were recorded both in the real and in the modeled breast. The entire procedure lasted less than a half-hour, making it clinically useful. The results show that it is possible to create a deformable model of the breast based on finite elements with non-linear material properties, capable of modeling and predicting breast deformations in a clinically useful amount of time.

Artifacts↗
PubMed2002

Conditional activation of Neu in the mammary epithelium of transgenic mice results in reversible pulmonary metastasis.

To determine the impact of tumor progression on the reversibility of Neu-induced tumorigenesis, we have used the tetracycline regulatory system to conditionally express activated Neu in the mammary epithelium of transgenic mice. When induced with doxycycline, bitransgenic MMTV-rtTA/TetO-NeuNT mice develop multiple invasive mammary carcinomas, essentially all of which regress to a clinically undetectable state following transgene deinduction. This demonstrates that Neu-initiated tumorigenesis is reversible. Strikingly, extensive lung metastases arising from Neu-induced mammary tumors also rapidly and fully regress following the abrogation of Neu expression. However, despite the near universal dependence of both primary tumors and metastases on Neu transgene expression, most animals bearing fully regressed Neu-induced tumors ultimately develop recurrent tumors that have progressed to a Neu-independent state.

Adenocarcinoma↗
PubMed2002

Breast conservation treatment for patients presenting with axillary lymphadenopathy from presumed primary breast cancer: the role of breast magnetic resonance imaging for staging.

Three female patients presented with malignant axillary lymphadenopathy presumed to be from primary breast cancer. No evidence of primary cancer was found in the breast on either mammography or breast magnetic resonance imaging (MRI). All 3 patients underwent axillary lymph node dissection and systemic chemotherapy followed by radiation therapy to the breast and regional lymph nodes. Two patients remain relapse free with a follow-up of 3.7 years each. The third patient achieved locoregional control in the ipsilateral breast and regional lymph nodes but relapsed in the contralateral axilla. These 3 cases illustrate the potential for breast conservation treatment for patients presenting with axillary adenopathy from a presumed primary breast cancer but without either mammographic or breast MRI findings.

Axilla↗
PubMedDate not supplied

MRI-guided diffuse optical spectroscopy of malignant and benign breast lesions.

We present the clinical implementation of a novel hybrid system that combines magnetic resonance imaging (MRI) and near-infrared (NIR) optical measurements for the noninvasive study of breast cancer in vivo. Fourteen patients were studied with a MR-NIR prototype imager and spectrometer. A diffuse optical tomographic scheme employed the MR images as a priori information to implement an image-guided NIR localized spectroscopic scheme. All patients who entered the study also underwent gadolinium-enhanced MRI and biopsy so that the optical findings were cross-validated with MR readings and histopathology. The technique quantified the oxy- and deoxyhemoglobin of five malignant and nine benign breast lesions in vivo. Breast cancers were found with decreased oxygen saturation and higher blood concentration than most benign lesions. The average hemoglobin concentration ([H]) of cancers was 0.130+/-0.100 mM, and the average hemoglobin saturation (Y) was 60+/-9% compared to [H]=0.018+/-0.005 mM and Y=69+/-6% of background tissue. Fibroadenomas exhibited high hemoglobin concentration [H]=0.060+/-0.010 mM and mild decrease in oxygen saturation Y=67+/-2%. Cysts and other normal lesions were easily differentiated based on intrinsic contrast information. This novel optical technology can be a significant add-on in MR examinations and can be used to characterize functional parameters of cancers with diagnostic and treatment prognosis potential. It is foreseen that the technique can play a major role in functional activation studies of brain and muscle as well.

Biopsy↗