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Biomedical subjects

G Santyr

Publications and source records attributed to G Santyr.

4 recordsLinked to original sources
PubMed2000

Chemical shift imaging with continuously flowing hyperpolarized xenon for the characterization of materials.

In this contribution we report new approaches to the MRI of materials using continuously produced laser-polarized (129)Xe gas. This leads to vastly improved sensitivity and makes new kinds of information available. The hyperpolarized xenon is produced in a continuous flow system that conveniently delivers the xenon at low partial pressure to probes for NMR and MRI experiments. We illustrate applications to the study of micropore and other kinds of void space and show for the first time that with flowing hyperpolarized xenon it is possible to obtain chemical-shift-resolved images in a relatively short time.

Calcium↗
PubMed1999

Accurate and rapid quantitative dynamic contrast-enhanced breast MR imaging using spoiled gradient-recalled echoes and bookend T(1) measurements.

A method is presented that converts dynamic T(1)-weighted spoiled gradient-recalled echo (SGRE) image intensities into estimates of T(1) without the errors associated with imperfections in the slice profile and transmitter coil magnetic field (B(1)). The method involves T(1) measurements performed before and after a series of dynamic SGRE images. These measurements serve to calibrate and correct the SGRE signal strength equation used to estimate T(1). Simulations and phantom experiments were performed to test the method for slice-selective (two-dimensional) and slab-selective (three-dimensional) imaging, as well as for imaging performed with optimized and un-optimized B(1). For nearly all test conditions, T(1) was estimated accurately (within 10%) over a range of T(1) values expected in vivo ( approximately 1200 --> 300 msec). This method should be useful for quantifying dynamic SGRE imaging for many different applications including breast MR imaging. Magn Reson Med 42:746-753, 1999.

Breast↗
PubMed1995

Gadolinium-enhanced breast MRI.

The inherent overlap in the T1 and T2 relaxation of benign and malignant breast lesions has hindered progress in the application of MRI to evaluate this organ. Indeed, lesions in a glandular breast may completely blend in with normal breast tissues, a problem unenhanced MRI shares with mammography. However, infusion of intravenous Gd-DPTA accompanied by rapid MR imaging results in successful detection of most invasive breast malignancies. Inspection of the lesion morphology and enhancement profile shows that most malignancies have an irregular border, enhance very rapidly, and display a distinct early washout phase. On the other hand, fibroadenomas have a smooth or gently lobulated border and enhance in a continuous monotonic fashion. Some pitfalls exist such as the variable enhancement associated with DCIS and premenopausal breast tissue. This publication reviews the literature with respect to Gd-enhanced breast MRI, focusing on strengths and weaknesses, and suggests appropriate indications for employing this new approach to breast imaging. Patient preparation and discussion of technical parameters and tradeoffs is also addressed. The exact place of MRI in the work-up of the breast-problem patient has yet to be settled, but already MRI can help radiologists offer a more conclusive diagnosis in mammographically perplexing situations, particularly in patients with radiographically dense breasts.

Breast↗