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J W Monroe

Publications and source records attributed to J W Monroe.

4 recordsLinked to original sources
PubMed1995

Phased array coils for upper extremity MRA.

A phased array coil was constructed for imaging the upper extremity vasculature for patients undergoing dialysis treatment. The phased array coil exhibits improved signal-to-noise ratio (SNR) over the body coil and allows imaging of the entire upper extremity. SNR as a function of depth was measured on a homogeneous phantom with the arm coil and compared with the body coil. Near the coil there is an improvement of a factor of 7 and at a depth of approximately 6-7 cm, there is an improvement of factor 2. In vivo SNR measurements resulted in similar improvements. Images of the upper extremity vasculature of healthy volunteers were generated using 2D-time-of-flight (2DTOF) angiography. Blood flow velocity was assessed in a CINE-phase contrast study.

Arm↗
PubMedDate not supplied

Phased array RF coils for high-resolution MRI of the inner ear and brain stem.

OBJECTIVE: The spatial resolution in MRI is predominantly limited by the available signal-to-noise ratio (S/N). To increase the S/N, a four coil phased array consisting of bilateral pairs of semioval coils was constructed for high resolution imaging of the temporal bone and brainstem. MATERIALS AND METHODS: Coil sizes of 10 x 6 and 6 x 4.5 cm were tested. The S/N values were measured in vivo and with homogeneous phantoms and compared to commercial 3 in receive and quadrature head coils. RESULTS: At a depth of 4-5 cm, phantom studies yielded S/N improvements of a factor of 1.26-1.37 with the large array compared to the 3 in coil and 2.33-1.74 compared to the head coil. Similar improvements (1.16 and 2.37) were obtained in inner ear images. No further improvement was achieved at this depth with the small array. At a depth of 8 cm, phantom studies yielded similar S/N for the quadrature head coil and two bilaterally placed large array coils, while a factor of 1.27 was obtained in brainstem images. CONCLUSION: The use of phased array coils yields significantly increased S/N and is thus valuable for high resolution MRI.

Brain Stem↗