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Biomedical subjects

R G Gould

Publications and source records attributed to R G Gould.

At least 37 records · Page 2Linked to original sources
PubMed1987

Measurement of right and left ventricular volumes in healthy individuals with cine MR imaging.

Cine magnetic resonance (MR) imaging is a new, rapid MR pulse sequence that acquires up to 32 images per cardiac cycle at up to four levels of the heart within 4 minutes. In this study, the whole heart was encompassed by contiguous 10-mm transverse sections. Ventricular volumes were calculated by adding luminal areas determined in each section at end-diastole and end-systole. The left ventricular volume index was 57 ml/m2 +/- 9 at end-diastole and 17 ml/m2 +/- 4 at end-systole. The right ventricular volume index was 63 ml/m2 +/- 9 at end-diastole and 22 ml/m2 +/- 6 at end-systole. The left to right ventricular stroke volume ratio was 0.97 +/- 0.06, which was not statistically different from the theoretically expected ratio of 1. Interobserver and intraobserver measurements were closely correlated. Volume measurements were validated with two-dimensional echocardiography in five volunteers. Cine MR imaging allows reproducible three-dimensional measurement of right and left ventricular volumes with short imaging time and good temporal resolution.

Adult↗
PubMed1987

Upper airway obstruction in infants and children: evaluation with ultrafast CT.

The diagnostic accuracy of ultrafast computed tomography (CT) was evaluated prospectively in 25 infants and children with suspected airway obstruction. All examinations were conducted in spontaneously breathing, nonsedated children. Scan acquisition times were 0.05 or 0.1 second. CT examinations, completed in an average of 10 minutes, routinely included localizing, contiguous sections through the trachea followed by serial images obtained at a rate of 17 per second through regions of interest. Imaging results were correct in 24 of 25 examinations as judged from clinical and surgical data. Ultrafast CT data permitted diagnosis of dynamic changes in airway caliber, small intraluminal polyps, focal tracheal atresia, compressive mediastinal masses, and foreign body obstructions of the major bronchi. Dose measurements showed a maximum skin exposure of 245 mR (0.06 mC/kg) per 0.05-second image. Ultrafast CT provides an accurate, minimally invasive method for dynamic imaging of the airway in nonsedated children.

Adolescent↗
PubMed1987

Cine MR imaging: potential for the evaluation of cardiovascular function.

MR imaging is valuable in defining cardiac anatomy in a variety of cardiac abnormalities. However, evaluation of cardiac function by this technique has been limited by long imaging times and low temporal resolution. New, recently described pulse sequences shorten imaging time considerably and improve temporal resolution. This paper reports our early experience with cine MR imaging of the heart, a technique of gradient-recalled acquisition in the steady state (GRASS) that uses low flip angles and gradient-recalled echoes. Images were obtained in 36 subjects (14 normal volunteers and 22 patients with coronary artery or valvular heart disease) and displayed in a cinegraphic mode for assessment of cardiac function. The acquisition of 10 to 12 levels, covering the whole heart with up to 24 time frames per level, required a maximum imaging time of only 30 min. Because systole and diastole were readily identified, and the contrast between blood and surrounding structures was excellent, systolic wall thickening, wall motion, and motion of the cardiac valves were visualized easily. Regions of myocardial infarcts were clearly visible and characterized by lack of systolic wall thickening and/or diastolic wall thinning. Turbulence caused signal loss within the flowing blood, which usually had higher signal intensity than myocardium. Therefore, turbulent blood flow in valvular regurgitation and in valvular and subvalvular stenosis could be detected. Cine MR imaging is a promising new technique for the evaluation of myocardial and valvular function.

Adult↗
PubMed1986

Radiographic quality control measurements comparing D-speed film, E-speed film, and xeroradiography.

This study evaluated quality control (QC) measurements of D-speed film, E-speed film, and xeroradiography under clinical conditions. Automatic and manual (wet-tank) film-processing techniques were assessed. The results of QC tests (speed index, contrast index, and base + fog measurements) indicated that D-speed film and E-speed film react similarly under clinical conditions with regard to speed and contrast when processed automatically. E-speed film had an elevated base + fog measurement over D-speed film in both processing methods. Manually processed D-speed film had a greater contrast than did manually processed E-speed film. Xeroradiography maintained a consistent level of image processing under clinical conditions during this 90-day trial.

Quality Control↗
PubMed1985

Feasibility, reliability, and advantage of utilizing low contrast dose digital subtraction ventriculography in a conventional catheterization laboratory.

Ventriculography was performed with conventional biplane fluoroscopic equipment; a 1:4 dilution of contrast medium in a standard injectate volume was delivered by a power injector. The biplane images were acquired with two video tape recorders and enhanced by means of a portable digital image processor. By a simple modification and calibration of our standard light pen-computer system, volumes could be calculated and global and segmental wall motion analysis performed. Fifteen patients underwent conventional and low-dose left ventriculography. Good correlation was found in end-diastolic volume (EDV), in end-systolic volume (ESV), and in ejection fraction (EF) (r = 0.90, r = 0.93, and r = 0.92, respectively). The quality of the images enabled a frame-by-frame analysis of a cardiac cycle to be performed (r = 0.99 when compared in one patient) and regional wall motion abnormalities identified (21 out of 23 abnormal segments). Although conventional ventriculography caused a rise in left ventricular end-diastolic pressure (17 +/- 8 vs 23 +/- 11, p less than 0.002) and no change in systolic blood pressure (132 +/- 23 vs 135 +/- 23, p greater than 0.5), low-dose ventriculography had no effect on left ventricular end-diastolic pressure (18 +/- 7 vs 21 +/- 10, p greater than 0.05) and produced a rise in systolic blood pressure (144 +/- 20 vs 149 +/- 22, p less than 0.05). A system of digital enhancement that is capable of producing high-quality ventriculograms with lessened contrast morbidity can be assembled with minimal expense and adapted to any conventional catheterization laboratory.

Cardiac Catheterization↗
PubMed1985

Intraarterial digital subtraction imaging cost considerations.

In an attempt to quantitate the cost-effectiveness of digital arterial imaging, we compared our real costs for angiographic procedures during a 6-month period with the costs for digital arteriographic imaging after the procedure was well established and accepted by both radiologists and clinicians. This study based on 400 angiograms per year, revealed that use of a digital angiographic unit resulted in an 82% reduction in film costs, a 25% reduction in staffing costs, a 19% reduction in the time required per examination, and a 30% reduction in the time required per run. Thirteen percent more runs were performed with the digital unit because it was more convenient and had a limited field of view. Overall operating cost savings were 43%. If amortized additional capital costs are included, there is a 12% reduction in overall costs. The digital imaging unit provides an immediate cost savings, with no appreciable loss of diagnostic quality. In addition, patient comfort, and perhaps safety, are improved.

Angiography↗
PubMed1982

Improved radiation protection for physicians performing cardiac catheterization.

Physicians and their assistants performing diagnostic angiography must be concerned with the radiation exposure they receive. The introduction of hemiaxial projections for imaging has increased diagnostic accuracy but has also greatly increased the physicians' exposure to scattered radiation. This increase is especially critical for the eyes and thyroid of the physician who routinely performs these procedures. To reduce such exposure a ceiling-suspended shield (60 x 45 cm), made of 6.4 mm glass with a 19.5 kg/m2 (4 lb/ft2) lead equivalency, was developed. During procedures the shield is interposed between the physician and the region of the patient acting as the source of scattered radiation. The degree of radiation protection to the operator was assessed by measuring the distribution of scattered radiation in the vicinity of the operator with and without the shield. The effectiveness of the shield was determined in the 30 degrees right anterior oblique (RAO), 5 degrees left anterior oblique (LAO), 35 degrees LAO, and 50 degrees LAO-15 degrees cranial angulations. At critical heights such as the level of the eyes and thyroid, scattered radiation levels were reduced by 85% or greater in all angulations. Without interfering with the physician's ability to observe the patient or manipulate the catheter, this shield can significantly reduce the physician's exposure to radiation.

Angiocardiography↗
PubMed1982

Direct magnification radiography of the newborn infant.

Recent advances in technology have made direct radiographic magnification of the newborn infant clinically feasible. A microfocus radiographic tube and a rare-earth, high-speed recording system were combined to obtain more than 2,000 radiographs at magnifications of 2-2.5. Special positioning devices permitted imaging of even those infants confined to incubators and connected to life-supporting systems. When quantitatively compared with three conventional contact radiographic systems with respect to resolution, contrast, and noise, magnification radiography showed overall superiority of image characteristics. Definition of subtle abnormalities and anatomically small structures permitted diagnoses which could not be made from conventional images. Furthermore, infant radiation exposure was markedly less (15 mR [3.9 mC/kg] maximum skin exposure) as compared with conventional contact radiographic systems (24 mR [6.1 mC/kg] to 45 mR [11.6 mC/kg]).

Humans↗
PubMed1981

Quantitative and qualitative comparison of two microfocus-tube imaging systems.

Two microfocus-tube magnification systems were compared: one used an RSI tube (stationary anode, Pierce-gun cathode) and the other used a GE tube (rotating anode, biased cathode). Imaging parameters for body parts of three thicknesses, the hand (low), knee (medium), and hip (high), were considered at a magnification of 2. The focal-spot MTF was measured on and off the central ray of the beam, as well as beam quality and the intensity of scatter in the image plane. Patient exposures were also determined. While both systems gave high-quality images at acceptable exposure levels, the RSI unit was judged superior for body parts up to 15 cm thick. For thicker parts, scatter degraded contrast with the RSI unit, making the GE unit superior.

Humans↗
PubMed1981

Follow-up of Wilms tumor: comparison of CT with other imaging procedures.

In a retrospective review, computed tomography (CT) was compared to a "routine" combination of other diagnostic imaging procedures used for follow-up evaluations of 13 children being treated for Wilms tumor. The examined variables were diagnostic accuracy, expense, and duration of examination. Results from 13 patients indicated that CT most accurately answers diagnostic queries pertinent to follow-up evaluation of Wilms tumor: the presence and extent of bilateral renal tumors, local recurrence, contralateral renal hypertrophy, and metastasis to liver or lungs, For diagnosing pulmonary metastases, CT was superior to conventional chest radiography both in sensitivity (4/4 vs. 2/4) and specificity (9/9 vs. 6/9). In depiction of liver metastases, CT (3/3) was superior to liver scintigraphy (2/3). The extent of bilateral Wilms tumors was better defined by CT than by urography. In no instances were the alternative diagnostic imaging studies found to be more accurate than CT for detection of recurrent tumor. Average cost for a CT examination ($344) is considerably less than the cost for a routine combination of the other imaging studies ($594). Examination time and diagnostic radiation does are also reduced using CT. Pending larger comparison studies, CT is recommended as the primary diagnostic method for follow-up evaluation of patients with Wilms tumor.

Child↗
PubMed1980

Studies on the mechanisms of the rapid modulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase in intact liver by mevalonolactone and 25-hydroxycholesterol.

A rapid, biphasic inhibition of rat hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase (mevalonate:NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34) was induced by intragastric administration of R,S-mevalonolactone. The initial phase had a t1/2 of 5.3 min. 30 min after drug administration the inhibition could be reversed in vitro by cytosol or a partially purified cytosolic activator. The reactivation was prevented by 50mM NaF. Thus the initial inhibition appeared to be the result of reversible inactivation possibly by phosphorylation of the enzyme. Consistent with this was the finding that the net reductase activator (phosphatase) activity present in cytosol was decreased 64% in these animals. The rapid reversible inhibition could not be reproduced in vitro by incubating microsomes or postmitochondrial supernatants with mevalonate suggesting the intact cell was necessary for expression of the effect. The second phase of inhibition due to mevalonate administration had a t1/2 of 1.3 h and was not reversible. It was attributed to inhibition of synthesis of reductase probably as the result of sterol accumulation in the cell. Perfusion of 25-hydroxycholesterol through livers isolated from animals at the circadian peak of cholesterol biosynthesis resulted in a rapid, 75-80% inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase. This inhibition was not reversed by incubation with cytosol or partially purified activator. Further, there was no apparent change in net activator levels in cytosol from the livers perfused with 25-hydroxycholesterol. This suggests the effect of this sterol on reductase does not involve reversible phosphorylation-dephosphorylation. On the basis of this study it is postulated that there are at least two mechanisms by which 3-hydroxy-3-methylglutaryl coenzyme A reductase activity can be rapidly suppressed in the intact liver. One is reversible and appears to be the result of alteration in the reductase kinase-phosphatase system. The second is irreversible and may be due to acceleration of the normal degradation system.

Animals↗
PubMed1980

Xeroradiography of dental structures. IV. Image properties of a dedicated intraoral system.

Dental xeroradiography, a new imaging system designed specifically for intraoral use, provides a convenient, rapid, low-dose alternative to conventional film radiography. In this study the new imaging system was compared to conventional direct-exposure dental film technique for basic imaging characteristics of contrast, resolution, and noise. Dental xeroradiography proved to be a superior imaging system for demonstrating dental structures and did so at radiation doses one-third of those required for conventional dental (film) radiography.

Humans↗
PubMed1980

Objective performance measurements versus perceived image quality in intensified fluoroscopic or photospot images.

The relationship between perceived image quality and measurable performance parameters of an intensified fluoroscopic image, viewed via a TV monitor or recorded on 105mm film, was investigated. Four specially manufactured image tubes, differing significantly in x-ray absorption efficiency, spatial resolution, and/or contrast resolution, were studied. Quantitative measurements of tube performance included the conversion factor, the quantum detection efficiency, the limiting resolution, the contrast ratio, and the contrast-detail characteristics. An assessment of the quality of clinical images was made by two radiologist-observers, working independently and without knowledge of any quantitative results. The observers were asked to rate the noise, lag, resolution, and contrast of the images during a variety of fluoroscopic procedures on each tube. While general agreement was found between the quantitative measurements and the radiologists' perceptions of image quality, the noise and contrast performance of an intensifier had greater influence on the radiologists' judgment of image quality than did resolution.

Fluoroscopy↗