Biomedical subjects

Pratik Rohatgi

Publications and source records attributed to Pratik Rohatgi.

3 recordsLinked to original sources

PubMed2006

Characterizing radial undersampling artifacts for cardiac applications.

The undersampled radial acquisition has been widely employed for accelerated (by a factor R = N(r)/N(p)) cardiac imaging, but the resulting reduction in image quality has not been well characterized. This investigation presents a method of measuring these artifacts through synthetic undersampling of high SNR images (SNR > or = 30). After validating the method in phantoms, the method was applied to a study of short-axis, long-axis, and coronary MRI imaging in healthy subjects. For 60 projections (60 N(p)), the total artifact is approximately 10% for short and long-axis imaging (R = 2.1) and approximately 15% for coronary MRI (R = 3.7). For 60 N(p), the SD of artifact in the region of the heart is 2% for short- and long-axis imaging (R = 2.1) and 3.5% for coronary MRI (R = 3.7). The artifact content is less in the region of the heart than in the periphery. The artifact is very reproducible among subjects for standard views. A study of coronary MRI at progressively fewer projections (at constant scan time) showed that right coronary MRI images were acceptable if total artifact was <6.5% of image content (N(p) > 120, R = 2.1).

Artifacts↗

PubMed2004

3D breath-held cardiac function with projection reconstruction in steady state free precession validated using 2D cine MRI.

PURPOSE: To develop and validate a three-dimensional (3D) single breath-hold, projection reconstruction (PR), balanced steady state free precession (SSFP) method for cardiac function evaluation against a two-dimensional (2D) multislice Fourier (Cartesian) transform (FT) SSFP method. MATERIALS AND METHODS: The 3D PR SSFP sequence used projections in the x-y plane and partitions in z, providing 70-80 msec temporal resolution and 1.7 x 1.7 x 8-10 mm in a 24-heartbeat breath hold. A total of 10 volunteers were imaged with both methods, and the measurements of global cardiac function were compared. RESULTS: Mean signal-to-noise ratios (SNRs) for the blood and myocardium were 114 and 42 (2D) and 59 and 21 (3D). Bland-Altman analysis comparing the 2D and 3D ejection fraction (EF), left ventricular end diastolic volume (LVEDV) and end systolic volume (LVESV), and end diastolic myocardial mass (LVEDM) provided values of bias +/-2 SD of 0.6% +/- 7.7 % for LVEF, 5.9 mL +/- 20 mL for LVEDV, -2.8 mL +/- 12 mL for LVESV, and -0.61 g +/- 13 g for LVEDM. 3D interobserver variability was greater than 2D for LVEDM and LVESV. CONCLUSION: In a single breath hold, the 3D PR method provides comparable information to the standard 2D FT method, which employs 10-12 breath holds.

Adult↗

PubMed2003

Complementation of bacteriophage induction and recombination defects in Escherichia coli RecA(-) mutants by expression of the cloned T4 bacteriophage uvsX gene.

Previous workers reported that the T4 bacteriophage UvsX protein could promote neither RecA-LexA-mediated DNA repair nor induction of lysogenized bacteriophage, only recombination. Reexamination of these phenotypes demonstrated that, in contrast to these prior studies, when this gene was cloned into a medium but not a low-copy-number vector, it stimulated both a high frequency of spontaneous induction and mitomycin C-stimulated bacteriophage induction in a strain containing a recA13 mutation, but not a recA1 defect. The gene when cloned into a low- or medium- copy-number vector also promoted a low frequency of recombination of two duplicated genes in Escherichia coli in a strain with a complete recA gene deletion. These results suggest that a narrow concentration range of T4 UvsX protein is required to promote both high-frequency spontaneous and mitomycin C-stimulated bacteriophage induction in a recA13 gene mutant, but it facilitates recombination of duplicated genes at only a very low frequency in E. coli RecA(-) mutants with a complete recA deletion. These results also suggest that the different UvsX phenotypes are affected differentially by the concentration of UvsX protein present.

Bacteriophage T4↗