Biomedical subjects

James S Whiting

Publications and source records attributed to James S Whiting.

4 recordsLinked to original sources

PubMed2006

Noninvasive calibration of cardiac pressure transducers in patients with heart failure: an aid to implantable hemodynamic monitoring and therapeutic guidance.

BACKGROUND: Implantable cardiac pressure monitors require assurance of calibration. This study evaluated if airway pressure responses during Valsalva maneuver (VM) can be used for calibrating intracardiac pressure transducers. METHODS AND RESULTS: Thirty-eight heart failure patients performed VMs while cardiac and airway pressures were recorded. Patients were designated as Lower (L) if baseline PCW was <20 mm Hg (n = 17); otherwise, they were categorized as Higher (H) (n = 21). VMs were repeated in 9 H patients after nitroglycerin. Procedural success was 92% and there were no complications. Differences between filling pressure and airway pressure (effective pressure) were eliminated during VM (RA(eff) = -0.9 +/- 1.3, RVED(eff) = 1.2 +/- 1.1, PCW(eff) = 2.1 +/- 2.8, and LVED(eff) = 0.9 +/- 1.6 mm Hg), and filling pressures were highly correlated with airway pressure r = 0.94. On average, group H had higher PCW(eff) and LVED(eff) than L patients by 1.8 and 2.5 mm Hg (P < or = .002), respectively, but after nitrates their responses were identical. CONCLUSION: The relationships between cardiac filling pressure and airway pressure during the Valsalva maneuver are sufficiently reliable to be considered as a new, noninvasive method for establishing the calibration of cardiac pressure sensors in patients with heart failure.

Aged↗

PubMed2002

Improved localization of coronary stents using layer decomposition.

Accurate placement and expansion of coronary stents is hindered by the fact that most stents are only slightly radiopaque and hence difficult to see in typical coronary X-ray images. We propose a new technique for improved image guidance of multiple coronary stent deployment using layer decomposition of coronary X-ray image sequences. We hypothesize that layer decomposition can improve the accuracy of localization of the end of a deployed stent. Layer decomposition is used to obtain good quality images of a stent in vitro. The resultant background-subtracted stent images are embedded into other cine X-ray image sequences to form a database of simulated image sequences. For each simulated sequence, the position of the stent edge is estimated from raw and layer-decomposed images using a small region of the original layer image as a template. Layer decomposition reduced median position errors in 33 of 47 image sequences (70%), including 16 of 18 sequences in which the position errors for raw and layer images differed by 5.0 pixels (0.5 mm) or more. Layer decomposition significantly reduces errors in determination of stent edge location in simulated cine X-ray image sequences.

Cineangiography↗

PubMed2002

Validation of the localization of the target tissue for intracoronary brachytherapy.

In a previous meta-analysis of intracoronary brachytherapy (ICBT) studies, we identified the target tissue at 0.6 to 0.7 mm tissue depth and we developed two models, describing the relationship between dose and ICBT effectiveness. The purpose of the present study was to validate the identified target tissue depth and the developed dose models, using the results of 1) two prospective animal studies with ICBT, 2) a retrospective analysis of animal studies with external beam irradiation and 3) results of recent clinical ICBT trials. ICBT effectiveness in the porcine restenosis studies was quantified as inhibition of neointima proliferation. The results of these studies were correlated with the developed dose-effectiveness model. Finally, the agreement of the restenosis rates of the recent clinical trials with the developed dose-restenosis model was tested. The porcine restenosis studies demonstrated a dose-related inhibition of neointima proliferation. The radiation effectiveness of both prospective studies and the effectiveness of the studies with external beam irradiation demonstrated the best agreement with the developed dose model at a tissue depth of 0.6 mm. Furthermore, the restenosis rates of the recent clinical ICBT studies were in concordance with the developed dose-restenosis model. In conclusion, the current study validated the localization of the target tissue for ICBT at a tissue depth of 0.6 to 0.7 mm as well as the relationship between dose and ICBT effectiveness at this depth. The data provide a rationale for setting a common dose prescription point at 0.6 to 0.7 mm tissue depth.

Angioplasty, Balloon, Coronary↗

PubMed2002

Evaluation of layer decomposition for multiframe quantitative coronary angiography.

Multiframe quantitative coronary angiography is typically performed by averaging measurements of artery diameter over multiple frames. This approach reduces errors attributable to random noise but may not reduce systematic errors caused by background structures, nonlinear system response, and motion blur. We attempt to reduce these sources of error by decomposing the image sequence into moving layers, one of which includes the artery. We embed simulated arteries into clinical angiographic sequences so that the true vessel dimensions are known accurately. The measurement tasks are minimum diameter, geometric percent stenosis, and densitometric percent stenosis. We compare measurements for single and multiple raw images, single images with fixed mask subtraction, single and multiple images with layered background subtraction, and time-averaged layer images. We find that both multiframe averaging and layer decomposition significantly improve geometric and densitometric accuracy compared with single-frame measurements. The best results were obtained by averaging measurements from multiple frames of layered background-subtracted images.

Algorithms↗