Biomedical subjects

B Rutt

Publications and source records attributed to B Rutt.

7 recordsLinked to original sources

PubMed1998

Bi-exponential T2 decay in dairy cream phantoms.

MRI phantoms are an important part of any experiment because they provide a reference of known parameters. There are many choices of mono-exponential T2 phantoms, but few choices for bi-exponential T2 phantoms. We have found that dairy cream provides an excellent bi-exponential T2 model with similar relaxation times to those found in white matter. Five cream phantoms of different milk fat percentages (2, 6, 10, 18 and 35 %) were imaged with an optimized Carr-Purcell-Meiboom-Gill sequence. The decay curves for each of the phantoms were fit using Non-Negative Least Squares. We found that the short T2 component fraction relative to the total energy in the distribution correlated linearly (r = 0.9973) with the milk fat percentage. The short T2 time was 38+/-4 ms and the long T2 time was 135+/-4 ms.

Brain↗

PubMed1991

Aortic valve/root interactions in porcine hearts: implications for bioprosthetic valve sizing.

The implantation of aortic allografts as well as stentless, freehand porcine xenograft valves requires proper sizing of the graft for the recipient aortic root. To visualize the aortic valve in motion and measure the cyclic expansion of the aortic root, we developed an isolated porcine heart model and a computerized three-dimensional reconstruction technique. Dynamic and static expansions of the aortic root were obtained from beating and arrested porcine hearts, and additional static expansions at varying pressures were measured from reconstructed three-dimensional models of valves obtained with high-resolution magnetic resonance imaging. Measurements of aortic root expansion have shown that it is highly dependent upon the pressures imposed on the heart. Although the aortic root expanded by only 5% between systolic pressures of 60 and 100 mmHg, the total expansion was up to 40% between rest and cyclic pressurizing to 100 mmHg. This data suggest that unstented xenograft valves should be sized 30% to 40% larger than the collapsed size of the recipient aorta. Proper sizing of valves on stents should also be attempted to reduce the large amount of leaflet redundancy that current stenting techniques produce.

Animals↗

PubMed1988

Patient anesthesia and monitoring at a 1.5-T MRI installation.

This paper describes the facilities successfully used to provide patient monitoring and anesthesia support in a 1.5-T imaging installation. The requirements for the MRI site for anesthetic gases, shielded power, and radiofrequency ports are outlined. Specific modifications in anesthesia machines, anesthesia cart, laryngoscope, mercury sphygmomanometer, oximeter, and remote blood pressure devices are described. Additional aspects of patient monitoring and support, e.g., electrocardiogram and pressure infusion, are also discussed.

Anesthesiology↗

PubMed1980

Split-filter computed tomography: a simple technique for dual energy scanning.

A simple technique for obtaining dual energy information from a single computed tomography (CT) scan is described. The method involves filtering the two halves of the X-ray fan beam differently. It is shown that during a 360 degree scan, this split-filtration geometry results in dual energy noise analysis, valid for polychromatic X-ray beams, is presented and used to determine the optimal parameters for the split-filter scans. Using the theoretically optimal split-filter design installed on a commercial CT scanner, photoelectric and Compton images of a head phantom were obtained. Recombination of the photoelectric and Compton components of attenuation at arbitrary energies demonstrates the ability to remove spectral artifacts from conventional CT images.

Calibration↗

PubMedDate not supplied

MR multispectral analysis of multiple sclerosis lesions.

Although quantification of the lesion burden from serial MR examinations of patients with multiple sclerosis (MS) is a common technique to assess disease activity in clinical trials, pathologic change may occur within a lesion without a corresponding change in volume. Therefore, measures of lesion volume and composition may improve the sensitivity of detecting disease activity. A new technique has been developed that provides information about the intensity composition of MS lesions in standard spin-echo MR examinations. The new technique is based on the multispectral "feature space" intensity distributions of the lesions and normal tissues. Analysis of MR examinations of materials with known T1 and T2 times showed that feature space position from spin-echo examinations is largely determined from proton density (rho), T2, and the interecho delay. Information about intensity composition was obtained by reducing the multidimensional intensity distribution to one dimension while minimizing the loss of information. This technique was used to analyze eight lesions in standard spin-echo MR examinations of three patients with MS. Lesion distributions were compared between examinations by first calibrating the examinations based on the intensity distributions of cerebrospinal fluid (CSF), an internal reference tissue. Many of the lesion distributions had a distinctive peak at low intensity, corresponding to normal-appearing white matter (WM). Within the lesion distributions, increases in high intensity peaks generally were accompanied by reductions in the WM peak. Serial analysis of the lesion distributions revealed some dramatic fluctuations, even when lesion volume remained constant.

Calibration↗

PubMedDate not supplied

Interactive display of volumetric data by Fast Fourier Projection.

This article describes a new algorithm for reprojection of volumetric data, called Fast Fourier Projection (FFP), which is one to two orders of magnitude faster than conventional methods such as ray casting. The theoretical basis of the new method is developed in a unified mathematical framework encompassing slice imaging and conventional volumetric reprojection methods. Software implementation is discussed in detail. The article closes with an account of experience with a prototype FFP implementation, and applications of the technique in medical visualization.

Algorithms↗

PubMedDate not supplied

The use of magnetic resonance imaging in exertional compartment syndromes.

This prospective, double-blind study was carried out to assess the usefulness of magnetic resonance imaging (MRI) as a noninvasive method in the diagnosis of chronic compartment syndrome (CCS). As well, a new radiopharmaceutical known as methoxy isobutyl isonitrile that has been shown to be taken up by muscle in direct proportion to its blood flow was used to illustrate the possible pathophysiology of this syndrome. Twenty patients with a history of chronic leg pain and possible diagnosis of CCS and five normal volunteers had preexercise and postexercise MRI, nuclear medicine imaging, and static and dynamic slit catheter pressure studies. Nine patients had classic symptoms; only five of these nine had abnormal pressure studies. The other 11 patients had an element of pain at rest and had normal pressure studies. The nuclear blood flow studies were normal in all 25 legs tested in this study. Measurement of intrinsic MRI parameters T1 and T2 in the normal legs as well as in those with an atypical history showed a marked elevation with exercise and a gradual return to baseline postexercise that was similar to the pressure curves. In the five patients with a clinical history and elevated pressures, four had abnormal MRI studies with failure of T1 to return to baseline values. Although these results demonstrate the potential of MRI as a tool for noninvasively monitoring muscle status, clinical history and examination remain important in the diagnosis of CCS. This study indicates that the pathophysiology of exertional compartment syndrome does not appear to be related to ischemia.

Adolescent↗