Pericardial effusion swinging heart phenomenon by dynamic radionuclide ventriculography.
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Adult↗
Biomedical subjects
J W Keyes
Publications and source records attributed to J W Keyes.
Diuretic radionuclide renography and scintigraphy in the differential diagnosis of hydroureteronephrosis.
Conventional radionuclide renography has been modified to include a pharmacologic intervention by administration of intravenous furosemide. The procedure is applied in patients with hydroureteronephrosis to distinguish dilated, nonobstructed systems from those with significant mechanical obstruction. Diagnostic patterns are derived from computer-generated time-activity histograms that depict the accumulation of radiotracer prior to diuresis and in response to diuresis. In dilated, nonobstructed systems, increased urine flow following diuresis causes a decline or "washour" of activity. In significantly obstructed systems, there is a failure of tracer activity to decrease in response to diuresis. The procedure is applied most commonly in suspected ureteropelvic junction and ureterovesical junction obstruction. The significance of residual urinary tract dilatation following corrective surgery also can be readily assessed. The major current limitation to the technique is poor renal function with inadequate response of urine flow to diuresis.
Adolescent↗
Techniques for precise recording of gray-scale images from computerized scintigraphic displays.
Accurate, reproducible recording of gray-scale images from a computer requires careful calibration and control of the factors that affect photographic exposure. These include exposure time, CRT brightness and contrast, film type, and photographic processing. A method is described for calibrating the imaging system; it accounts for nonlinear CRT phosphor and film response and permits the recording of any desired gray scale. The key to this technique is a graphical method for correlating the measured film response with the desired gray scale in order to develop a translation table that will in turn produce the desired gray scale on film. The technique is applicable to any computerized nuclear medicine display system.
Data Display↗
Calculation of viable and infarcted myocardial mass from thallium-201 tomograms.
The feasibility of determining the mass of both viable and infarcted myocardium from tomographic images of thallium-201 distribution in the heart was studied in two normal dogs and ten dogs with acute infarction. Twenty-four hours after occlusion, thallium-201 was injected and 10 min later the hearts were removed and transaxial emission computed tomograms were obtained. Using the computer, an operator defined the epi- and endocardial surfaces of the left ventricle and the area of infarction in each tomogram. The computer then calculated values for total left-ventricular mass (TLVM) infarcted mass (IM) and the percentage of the left ventricle infarcted (% LVI). The calculated values were compared with measured weights, and good correlation was found between them: for TLVM, r = 0.87; for IM, r = 0.90; and for %LVI, r = 0.87. Good interobserver and intra-observer correlations were also found. Thallium-201 emission computed tomography offers a potential means to measure both myocardial mass and acute myocardial injury.
Animals↗
Oblique-angle tomography: a restructuring algorithm for transaxial tomographic data.
A set of contiguous transaxial tomographic sections obtained with a rotating-camera tomograph represents the full three-dimensional distribution of activity within a volume of the body. Tomographic sections in planes other than the origianl transverse plane can be produced from these data merely by resorting the data appropriately. The paper presents a simple and efficient algorithm for producing tomograms of the heart oriented either at right angles to the long axis of the left ventricle, or parallel to it. Tomograms in these orientations have specific advantages for imaging the heart and avoid some of the limitations seen in comparable tomograms obtained by the seven-pinhole technique.
Heart↗
Thallium-201 myocardial scintigraphy: a critical comparison of seven-pinhole tomography and conventional planar imaging.
Seven-pinhole tomographic and planar thallium-201 imaging was performed on 63 consecutive patients to assess the clinical value of these techniques. Significant coronary artery disease (stenosis greater than or equal to 70%) was present in 52 patients. Comparing the seven-pinhole results with those of the planar, the findings for sensitivity, specificity, and inter- and intraobserver agreement were, respectively, 94% against 75% (p less than 0.005), 91% against 91%, 86% against 79%, and 97% against 92%. In 25 patients in this group with a prior myocardial infarction, sensitivity was 100% for tomographic imaging and 92% for planar. In 27 patients without prior myocardial infarction, by contrast, sensitivity for tomographic imaging was 89% and for planar imaging 59% (p less than 0.01). Thus we conclude that both tomographic and planar imaging are highly sensitive for the detection of significant coronary artery disease, but tomographic imaging is significantly more sensitive in patients without prior myocardial infarction.
Coronary Disease↗
Tomographic thyroid scintigraphy: comparison with standard pinhole imaging: concise communication.
Coded-aperture imaging (CAI) and multiple-view pinhole imaging (PI) of the thyroid were compared in a prospective study in 136 consecutive patients. Following 10 mCi of pertechnetate, 200K-count pinhole images were obtained in the anterior, RAO, and LAO projections, and CAI data were obtained in the anterior position. Four coronal tomographic sections were reconstructed by computer. Five observers read the studies separately, and ROC curves were constructed. Based on 109 pairs of studies, the ROC curves revealed similar performance for all observers for both techniques. When four observers compared the studies subjectively they rated the CAI more useful in 36% of cases, the PI in 6%, and the two equal in 58%. The advantages offered by the tomograms included improved contrast, accurate size representation of the gland at all depths, freedom frm pinhole-type distortion, and faster data acquisition. The major disadvantage to tomography was the 2-hr computer-processing time required. It this can be reduced, CAI offers sufficient advantages over conventional pinhole imaging to warrant its routine use.
Adult↗
Assessment of hydroureteronephrosis in children using diuretic radionuclide urography.
Diuretic radionuclide urography was developed as a safe, accurate and non-invasive method of assessing nephroureteral dilatation to distinguish between obstructive and non-obstructive hydronephrosis. The nuclear medicine gamma camera/computer system is used to monitor the washout pattern of an isotope from any locus of suspected obstruction in the upper urinary tract. This technique was used to study 62 children with hydroureteronephrosis of diverse causes. Our experience suggests that it is accurate in determining whether true obstruction exists in dilated systems and effective in predicting which patients will benefit from corrective operation.
Adolescent↗
Coded-aperture imaging of the heart.
Coded-aperture imaging of the heart combines the advantages of tomography with good sensitivity, high resolution, and accurate size scaling. Since the images are multiplexed, the method may be adapted to small, portable cameras for bed-side use without sacrificing image resolution. A new coded aperture designed especially for cardiac imaging has been constructed and tested. This aperture incorporates significant improvements over previous designs. Longitudinal tomograms are calculated at 1-cm intervals using a modified ART algorithm. Experimental lateral resulution at 140 keV with a portable scintillation camera is 3.8 mm FWHM at 4 cm, and 7.8 mm FWHM at 12 cm. Dpth resolution determined from a sloping line source is 1.1 cm FWHM at 4 cm, and 2.9 cm at 12 cm. The calculated point-source sensitivities in air at 4 cm and 12 cm, respectively, are 20 and 8 cps/microCi. Images of good diagnostic quality have been obtained in phantoms and in a dog model of acute myocardial infarction, using thallium-201, technetium-99m pyrophosphate, and gated ventricular blood-pool imaging with Tc-labeled red blood cells. Preliminary studies in humans confirm the good results in animals.
Animals↗
Segmental wall-motion analysis in the right anterior oblique projection: comparison of exercise equilibrium radionuclide ventriculography and exercise contrast ventriculography.
Thirty-nine patients with known or suspected coronary artery disease were studied at rest and during supine bicycle exercise with radionuclide and contrast left ventriculography. Analysis of regional wall motion was made by visual evaluation of the five standard 30 degrees right anterior oblique (RAO) wall segments in the contrast images and the corresponding 10 degrees RAO radionuclide segments. The radionuclide studies were evaluated independently by three observers using a five-point grading system. The interobserver wall-motion grading agreed completely in more than 80% of segments at rest and exercise, and agreed within one wall-motion grade in more than 95% of segments. The comparison of wall-motion grades between radionuclide and contrast ventriculograms showed complete agreement in 86% of segments at rest and in 78% during exercise, and agreement within one wall-motion grade in 97% of rest and 96% of exercise segments. Visual evaluation of 10 degrees RAO rest and exercise radionuclide ventriculograms compares favorably with rest and exercise 30 degrees RAO contrast ventriculograms and demonstrates satisfactory interobserver agreement.
Coronary Disease↗
Diuretic radionuclide urography: a non-invasive method for evaluating nephroureteral dilatation.
The diuretic radionuclide urogram is a simple, rapid and non-invasive technique to determine whether true obstruction exists in dilated nephroureteral systems. The methodology, results and interpretation of 102 studies in 41 patients are presented and compared to the conventional methods of assessing hydroureteronephrosis.
Adolescent↗
Skeletal scintigraphy following incidental trauma.
The significance of antecedent trauma in skeletal scintigraphy was assessed in 503 patients, of whom 241 (46%) had prior fracture or tooth extraction. In patients with sufficiently accurate histories for site-by-site analysis, 33 of 131 fracture sites and 16 of 83 dental-procedure sites were positive scintigraphically. In general, the frequency of scan positivity diminished as the interval between trauma and scanning increased, but a significant number of patients showed prolonged uptake at fracture sites. Several patterns of uptake suggested trauma rather than metastatic disease. Knowledge of a history of trauma is often critical in bone scan interpretation.
Bone Neoplasms↗
A simple model for anatomic bone scanning studies.
A simple anatomic model for studying the scintigraphic appearance of various skeletal structures is described. The technique makes use of the fact that technitium pyrophosphate uptake in bone occurs by chemisorption to the surface of crystals in the bone matrix. By soaking clean bones in solutions of technetium pyrophosphate they can be rendered radioactive and subsequently studied by various imaging techniques.
Bone and Bones↗
Thyroid scintigraphy with time-coded aperture.
Coded aperture imaging (CAI) and multiple-view pinhole imaging (MVPI) of the thyroid were compared in 19 patients to determine whether CAI's theoretical advantages of high resolution, high efficiency, freedom from distortion, accurate size representation, and tomographic presentation could be realized in the clinical setting, and to determine whether CAI offers any advantage over conventional MVPI. The coded aperture images were judged better than the pinhole images in five cases, equal in 13 cases, and worse in one case. The major problem with CAI was the long reconstruction time. Further development and an extended clinical trial appear warranted.
Humans↗
Technical considerations in in vivo thyroid studies.
Radionuclide thyroid studies, although among the oldest of clinical nuclear medicine procedures, continue to show growth and change. In the 7 years since thyroid studies were last reviewed in the Seminars, there have been marked changes in the preferred ways of doing these studies. In the areas of radiopharmaceuticals, 131I remains a useful agent in selected circumstances, but 99mTc-pertechnetate has become the agent of choice for imaging applications. Iodine-123 represents an exciting possibility for the future if problems in cost and radiopurity can be solved. New data on the dosimetry of the various agents allow for more rational choices among them, and useful guidelines can now be given for the use of these radiopharmaceuticals in problem areas such as pregnancy, nursing, and the pediatric age group. The scintillation camera with a pinhole collimator has become the instrument of choice for thyroid imaging, and the use of computers and the availability of systems for fluorescent scanning have added new possibilities for thyroid evaluation. Ancillary techniques such as ultrasound scanning also offer the possibility of improved diagnostic accuracy. These developments are reviewed in the context of clinical studies, together with a discussion of specific clinical applications and a brief look to the future.
Female↗
Myocardial imaging using emission computed tomography.
Single-photon emission computed tomography (ECT) was evaluated during myocardial studies in dogs. Acute anterior and posterior infarcts were imaged following injection of 99mTc-pyrophosphate or 201Tl. In most cases, tomographic delineation of infarct location and extent correlated with tissue section. The 99mTc images were far superior to the 201Tl images. ECT improves delineation of tracer within the myocardium.
Animals↗
Myocardial infarct quantification in the dog by single photon emission computed tomography.
Radionuclide techniques for sizing acute myocardial infarction have been hampered by the intrinsic limitations of the scintillation camera. Emission computed tomography can overcome these limitations. Single photon emission computed tomograms of the distribution of technetium-99m pyrophosphate in acute anterior and posterior infarcts were obtained in 16 dogs after death. Tomograms were also obtained in 10 dogs during life without gating. The size of the infarcts was determined by staining gross sections of the heart with nitro blue tetrazolium, dissecting out the infarcted tissue and weighing it. Infarct sizes were determined from the tomographic images and compared with the measured infarct sizes. Good images showing the location and three-dimensional extent of the infarcts were obtained in all dogs. The measured and calculated infarct sizes correlated well (r = 0.85). Comparison of the calculated sizes in the living (non-gated) and dead ("physiologically" gated) animals showed reasonable agreement (r = 0.87). Single photon emission computed tomography is a feasible and useful technique for localizing and sizing acute myocardial infarctions.
Animals↗
False negative bone scans in neuroblastoma metastatic to the ends of long bones.
Studies of 12 children with neuroblastoma were performed to assess the comparative sensitivity of skeletal radiography and 99mTc pyrophosphate bone scintigraphy in the detection of metastases to the ends of long bones. A total of 18 lesions were detected in six patients. Fourteen were demonstrated only by radiography, whereas four were positive by both methods. In no case was a lesion detected by scintigraphy alone. Small lesion size, lytic radiographic appearance, metaphyseal location, and technical difficulties in imaging the knee all contribute to the high incidenmce of false negative scans. Lesions in two of the nine patients with metastatic disease to bone would have been missed on the basis of bone scans alone. Accordingly, the radiographic skeletal survey seems to remain a necessary part of the neuroblastoma workup.
Bone Neoplasms↗