Biomedical subjects

Scott A Mirowitz

Publications and source records attributed to Scott A Mirowitz.

7 recordsLinked to original sources

PubMed2004

Fast multi-planar gradient echo MR imaging: impact of variation in pulse sequence parameters on image quality and artifacts.

The purpose of this investigation was to quantitatively evaluate the practical impact of alteration of key imaging parameters on image quality and artifacts in fast multi-planar gradient echo (GRE) pulse sequences. These include multi-planar GRASS (MPGR) and fast multi-planar spoiled GRASS (FMPSPGR). We developed a composite phantom with different T(1) and T(2) values comprising the range of common biological tissues, which was also subjected to periodic motion in order to evaluate motion effects. Magnetic resonance imaging was performed on a GE Signa 1.5-T system. Experimental variations in key parameters included excitation flip angle (FL), echo time (TE), repetition time (TR), and receive bandwidth (BW). Quantitative analysis consisted of signal-to-noise-ratio (SNR) and contrast (CN), image nonuniformity (NU), full-width-at-half-maximum (FWHM) (i.e., blurring or geometric distortion), and ghosting ratio (GR). We found that flip angle, TE, and TR play particularly critical roles in determining image signal, homogeneity, and ghosting artifact with these sequences. Optimum clinical application of these pulse sequences requires careful attention to these imaging parameters and to their complex interactions.

Artifacts↗

PubMed2004

How to plan and perform a cardiac MR imaging examination.

Because of the enormous economic and social impact of cardiovascular disease in the United States there is a need for improved noninvasive diagnosis. Cardiac MR imaging isa versatile, comprehensive technique for assessing cardiac morphology and function. With an understanding of cardiac anatomy and physiology and MR imaging physical principles,cardiac MR imaging can be performed and can play an important role in patient management. This article provides the reader with a basic understanding of cardiac MR imaging and the practical applications required to perform cardiac MR imaging.

Cardiovascular Diseases↗

PubMed2003

Fast T2-weighted MR imaging: impact of variation in pulse sequence parameters on image quality and artifacts.

The purpose of this study was to quantitatively evaluate in a phantom model the practical impact of alteration of key imaging parameters on image quality and artifacts for the most commonly used fast T(2)-weighted MR sequences. These include fast spin-echo (FSE), single shot fast spin-echo (SSFSE), and spin-echo echo-planar imaging (EPI) pulse sequences. We developed a composite phantom with different T1 and T2 values, which was evaluated while stationary as well as during periodic motion. Experiments involved controlled variations in key parameters including effective TE, TR, echo spacing (ESP), receive bandwidth (BW), echo train length (ETL), and shot number (SN). Quantitative analysis consisted of signal-to-noise ratio (SNR), image nonuniformity, full-width-at-half-maximum (i.e., blurring or geometric distortion) and ghosting ratio. Among the fast T(2)-weighted sequences, EPI was most sensitive to alterations in imaging parameters. Among imaging parameters that we tested, effective TE, ETL, and shot number most prominently affected image quality and artifacts. Short T(2) objects were more sensitive to alterations in imaging parameters in terms of image quality and artifacts. Optimal clinical application of these fast T(2)-weighted imaging pulse sequences requires careful attention to selection of imaging parameters.

Artifacts↗

PubMed2003

Manifestation of magic angle phenomenon: comparative study on effects of varying echo time and tendon orientation among various MR sequences.

The purpose of this study was to systematically investigate the effect of varying the echo time (TE) values and angle of the tendon to the main magnetic field (B(o)) upon the signal intensity observed with the magic angle phenomenon in tendons among most commonly used MR pulse sequences, including conventional spin echo (CSE), fast spin echo (FSE) and gradient echo (GRE) sequences. The intact bovine Achilles tendon was imaged using a clinical 1.5-T MR scanner. Magic angle phenomenon occurs in CSE, FSE and GRE sequences with different grade, appearing most severe in CSE, middle in FSE, and weakest in GRE sequence. In addition, the tendon signal changes produced by the magic angle phenomenon could be greatly reduced by increasing the TE to above a certain critical value in all three sequences. These critical TE values were different among CSE (40 msec), FSE (70 msec), and GRE (30 msec) sequences.

Achilles Tendon↗

PubMed2003

Performing cardiac MR imaging: an overview.

Because of the enormous economic and social impact of cardiovascular disease in the United States, there is a need for improved noninvasive diagnosis. Cardiac MR imaging is a versatile, comprehensive technique for assessing cardiac morphology and function. With an understanding of cardiac anatomy and physiology as well as MR physical principles, cardiac MR imaging can be performed and play an important role in patient management.

Cardiovascular Diseases↗

PubMed2002

Comparative study of fast MR imaging: quantitative analysis on image quality and efficiency among various time frames and contrast behaviors.

The purpose of this study is to quantitatively compare the image quality and efficiency provided by widely available fast MR imaging pulse sequences. A composite phantom with various T1 and T2 values and subjected to periodic motion was imaged at 1.5 T. The fast MRI sequences evaluated included fast spin-echo (FSE), single shot fast spin-echo (SSFSE), echo-planar imaging (EPI), multi-slice gradient recalled (MPGR), fast MPGR (FMPGR), and fast multi-slice spoiled gradient echo (FMPSPGR). T1-weighted (T1WI), T2-weighted (T2WI), proton-density-weighted (PDWI), and T2*-weighted (T2*WI) images were evaluated in breath-hold and non-breath-hold time frames. Analysis included measurement of image signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), nonuniformity, ghosting ratio, SNR per unit time and CNR per unit time. Among fast T2WI sequences, FSE with breath-hold time frame resulted in the highest image quality and in superior SNR and CNR efficiency by a factor of 5 or 6 as compared with conventional spin echo sequence. Among fast T1WI sequences, FMPGR and FMPSPGR both with non-breath-hold time frame produced the highest image quality and SNR and CNR efficiency by a factor of greater than 5 as compared with conventional spin echo. Among fast PDWI and T2*WI sequences, FSE produced the highest SNR and CNR, and was maximally efficient with a factors of greater than 6 as compared with conventional spin echo.

Echo-Planar Imaging↗

PubMedDate not supplied

T2-weighted echo planar MR imaging of the abdomen: optimization of imaging parameters.

Echo planar imaging (EPI) is an ultra-fast magnetic resonance (MR) imaging method that provides strong T2-weighted contrast, which is important for the detection and characterization of various abdominal abnormalities. However, EPI may be associated with significant artifacts. The prominence of these artifacts, as well as overall image quality, is dramatically impacted by selection of imaging parameters. The purpose of this study is to demonstrate the effects of controlled alterations in operator-defined imaging parameters on image quality in breath-hold abdominal T2-weighted EPI. An understanding of these effects facilitates optimizing parameter selection for acquisition of abdominal EPI images.

Abdomen↗