Biomedical subjects

R F Busse

Publications and source records attributed to R F Busse.

9 recordsLinked to original sources

PubMed2001

Steady-state preparation for spoiled gradient echo imaging.

While spoiled gradient echo sequences provide a rapid means of acquiring T(1)-weighted images, it is often desirable that the magnetization be in the steady state to avoid artifacts. For some applications, this requires many "dummy" repetitions of the pulse sequence prior to data collection, delaying image acquisition. A method is presented in which a saturation pulse, followed by a prescribed recovery period, places longitudinal magnetization levels of all materials near steady state, ready for data acquisition much sooner than when employing only dummy repetitions to achieve steady state. Effects of transverse coherences are studied using configuration theory. The method is shown to be effective in both phantom studies and in vivo applications, including real-time imaging, multiphase cardiac imaging, and triggered contrast-enhanced angiography. Magn Reson Med 45:653-661, 2001.

Humans↗

PubMed2000

Interactive fast spin-echo imaging.

It is shown that a spin-echo sequence may be used to acquire T(2)-weighted, high-resolution, high-SNR sections at quasi-real-time frame rates for interactive, diagnostic imaging. A single-shot fast spin-echo sequence was designed which employs driven equilibrium to realign transverse magnetization remaining at the final spin echo. Driven equilibrium is shown to improve T(2) contrast at a given TR, or conversely to reduce TR by approximately 1000 msec and thus increase temporal resolution while maintaining a given level of contrast. Wiener demodulation of k-space data prior to reconstruction is shown to reduce blurring caused by T(2)-decay while constraining noise often associated with other inverse filters. Images are continuously acquired, reconstructed, and displayed at rates of one image every one to two seconds, while section position and contrast may be altered interactively. The clinical utility of this method is demonstrated with applications to dynamic pelvic floor imaging and interactive obstetric imaging.

Computer Systems↗

PubMed2000

Three-dimensional contrast-enhanced MR angiography with real-time fluoroscopic triggering: design specifications and technical reliability in 330 patient studies.

Technical reliability was determined for triggering three-dimensional (3D) contrast material-enhanced magnetic resonance (MR) angiography with MR fluoroscopy. Technical requirements for high reliability were also identified. Reliability was evaluated in 330 consecutive patient studies of the neck, thorax, abdomen, and pelvis. Contrast material arrival was detected fluoroscopically in 325 of the 330 studies (98.5%), and the 3D sequence was successfully triggered in 321 of 330 studies (97.3%). Fluoroscopic triggering of centrically encoded 3D MR angiographic acquisitions is a highly reliable means of obtaining 3D MR angiograms with high spatial resolution.

Abdomen↗

PubMed1999

Interactive three-point localization of double-oblique sections using MR fluoroscopy.

Magnetic resonance imaging allows significant freedom in selecting the orientation and position of a tomographic section. However, it can nonetheless be challenging to determine quickly and efficiently the correct parameters required to image a targeted anatomic structure that may lie at an oblique angle in the imaging volume. We describe a three-point tool in which a) the user interactively selects three points from an anatomic structure of interest during live MR fluoroscopy; b) adjustments to pulse sequence are calculated to image the tomographic section defined by the three points; and c) the section is then immediately imaged fluoroscopically. The tool allows quick localization of, for example, longitudinal images of specific arterial structures.

Algorithms↗

PubMed1999

A flexible view ordering technique for high-quality real-time 2DFT MR fluoroscopy.

A method to tailor the view order to the reconstruction cycle is introduced for real-time MRI. It is well known that view sharing and oversampling central k-space views can improve the temporal resolution of gradient-echo pulse sequences. By ordering phase-encodes to synchronize k-space acquisition with the reconstruction cycle, apparent temporal resolution can match the frame rate with as few as one-fourth of the phase-encodes sampled per reconstruction. Spatial resolution is maintained by periodically updating high spatial frequencies. In addition to apparent temporal resolution, three other criteria for real-time imaging are identified and evaluated: display latency, dispersion, and frame-to-frame consistency. Latency is minimized by ordering views in a reverse-centric manner within each reconstruction interval, sampling high-energy views immediately prior to beginning reconstruction. Dispersion is kept low and consistent by synchronizing acquisition and reconstruction, thus avoiding poorly timed reconstruction instances. Real-time implementation demonstrates pulsatile time-of-flight blood signal enhancement in humans.

Algorithms↗

PubMed1999

Contrast-enhanced 3D MR breathhold imaging of porcine coronary arteries using fluoroscopic localization and bolus triggering.

The purpose of this study was to develop cardiac-gated contrast-enhanced 3D MRA for imaging the coronary arteries of pigs. Each major coronary artery was imaged individually in a single 3D slab in one breathhold. To permit acquisition within a breathhold, a limited number of partitions (12-16) were collected in a single, oblique, thin 3D slab. Typical resolution of the acquisition was 0.8 (X) x 1.6 (Y) x 1.6 (Z) mm. MR fluoroscopic localization was used to establish the 3D double-oblique orientation. Real-time MR fluoroscopy was also used to instantaneously trigger the 3D scan after detection in the aortic root of the intravenously administered contrast bolus. Six pigs were used in the study. Each pig was scanned on two separate days. Images routinely show the majority of the length of the three principal coronary arteries. Magn Reson Med 42:1159-1165, 1999.

Animals↗

PubMed1999

Real-time imaging and triggering of 3D contrast-enhanced MR angiograms using MR fluoroscopy.

Although a variety of timing techniques and data acquisition strategies have been used for three-dimensional contrast-enhanced MR angiography, many are still limited by inadequate overall reliability, limited spatial resolution, or complexity. A technique is presented in this work in which contrast arrival is detected in the targeted vasculature in real time using MR fluoroscopy. Upon detection the operator triggers a 3D MR angiographic acquisition which uses an elliptical centric view order. It is shown that the view order intrinsically provides a high degree of venous suppression which in turn allows acquisition times of 30 s or longer, permitting high spatial resolution. The reliability of fluoroscopic triggering in bolus detection is shown to be over 90%. The technique provides high quality contrast-enhanced MR angiograms for many vascular regions.

Carotid Arteries↗

PubMed1999

3D contrast-enhanced MR angiography using fluoroscopic triggering and an elliptical centric view order.

Although a variety of timing techniques and data acquisition strategies have been used for three-dimensional contrast-enhanced MR angiography, many are still limited by inadequate overall reliability, limited spatial resolution, or complexity. A technique is presented in this work in which contrast arrival is detected in the targetted vasculature in real time using MR fluoroscopy. Upon detection the operator triggers a 3D MR angiographic acquisition which uses an elliptical centric view order. It is shown that the view order intrinsically provides a high degree of venous suppression which in turn allows acquisition times of 30 seconds or longer, permitting high spatial resolution. The reliability of fluoroscopic triggering in bolus detection is shown to be over 90%. The technique provides high quality contrast-enhanced MR angiograms for many vascular regions.

Fluoroscopy↗

PubMed1999

Carotid arteries: maximizing arterial to venous contrast in fluoroscopically triggered contrast-enhanced MR angiography with elliptic centric view ordering.

PURPOSE: To obtain high-spatial-resolution, venous-suppressed, contrast material-enhanced, three-dimensional (3D) magnetic resonance (MR) angiograms of the carotid arteries and aortic arch by using an elliptic centric view ordering with MR fluoroscopic triggering. MATERIALS AND METHODS: Forty consecutive patients with cerebrovascular disease in the differential diagnosis were evaluated with fluoroscopically triggered 3D MR angiography (gadoteridol dose range, 0.1-0.3 mmol per kilogram of body weight; mean acquisition time, 40 second +/- 8 [SD]). The contrast-enhanced 3D MR angiograms were evaluated for overall quality, vascular signal intensity, venous suppression, and motion artifact. Twenty patients also underwent two-dimensional (2D) time-of-flight (TOF) MR angiography. The overall quality of the 2D TOF MR angiograms and comparative quality between the 2D TOF and contrast-enhanced 3D MR angiograms were determined. RESULTS: The contrast-enhanced 3D MR angiograms were of excellent or more than adequate quality for diagnosis in 36 of the 40 studies (90%). In 35 of the 38 contrast-enhanced 3D studies in which the contrast material bolus was detected fluoroscopically, the internal jugular vein signal intensity was either not detectable or barely visible. In 18 of the 20 patients who also underwent 2D TOF MR angiography, the quality of the contrast-enhanced 3D MR angiograms was graded as markedly superior or superior. CONCLUSION: Contrast-enhanced, elliptic centric 3D MR angiography with real-time MR fluoroscopic triggering offers high-spatial-resolution images of the carotid arteries and aortic arch with reliable venous suppression.

Aorta, Thoracic↗