Biomedical subjects
Publications and source records attributed to J W Keyes.
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.
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.
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.
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.
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.
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.
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.
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.
Imaging of acute myocardial injury is possible with a large number of agents. All of these agents share similar patterns of uptake in acutely injured myocardial tissue. The technique appears to be a reliable way of ruling in or out the diagnosis of acute myocardial infarction.
The problem of nonuniform response, which is inherent in scintillationcamera emission computed tomography, can be minimized by proper collimator design. A specially fabricated collimator, optimized for emission computed tomography, was designed. This collimator has a calculated full width at half maximum of 1 cm at 15 cm in front of the collimator. When this collimator is used in conjunction with averaged opposed views, excellent uniformity across the reconstruction plane is achievable.
One hundred and seventy-four gallium scans of patients with biopsy-proved non-Hodgkin lymphoma were reviewed. When the lymphomas were subdivided into histologic groups, there was a significant difference in detection rates, with 62% of the histiocytic lymphomas being identified, while only 39% of the poorly differentiated lymphocytic lymphomas were detected. There was a high detection rate for lesions in the mediastinum and in extranodal locations. When analyzed with regard to therapy, the detection rate was higher in all histologic subgroups after therapy than before.
The accumulation of 99mtechnetium sulfur colloid (99mTcSC) was evaluated in 47 studies performed on 19 renal transplant patients by comparing its transplant activity to its bone marrow accumulation. There was a diagnosis of rejection of 21 of 22 studies (96.5%) in which marked transplant accumulation was noted. In 11 studies of patients with a clinical diagnosis of post-transplant acute tubular necrosis (ATN), the transplant activity varied from none to moderate. Rejection developed in 5 of 6 studies with minimal to moderate accumulation. Normally functioning renal transplant patients, or those with ATN and no superimposed rejection, do not show evidence of 99mTcSC accumulation.
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A single-photon emission tomographic system was used to study the normal anatomy of the facial bones and the usefulness of emission computed tomography in evaluating diseases of the bones of the face. The examination was performed following routine bone scintigraphy and took an additional 20-30 min. The anatomy of the facial bones was well defined, with clear separation of deep and superficial structures. Early experience with tumor, infection, bone grafts, and postirradiation osteonecrosis indicates that useful added diagnositc information can be obtained by this method.
An emission transaxial tomographic system using a scintillation camera as the detector is described. The unit allows accurate positioning of a scintillation camera's detector at any angle around a patient in order to obtain the multiple projection images needed for transaxial tomography, and it is capable of imaging any area of the body. The camera can also be used for all types of conventional imaging procedures. Image processing is performed by a small on-line computer. A convolution algorithm and a mathematical technique for approximate absorption correction are used to obtain high-resolution and high-contrast images with good quantitative accuracy. The operation of the system is described and representative phantom and patient studies are presented to illustrate the capabilities of the system.
Activity levels of 99TC-labeled compounds, 18F, and 85Sr were obtained at 1, 3, and 5 hr. postinjection in normal and healing fractured bone and in soft-tissue rat specimens. Serial diagnostic bone images and blood and urine kinetics were obtained in patients with each of the TC-labeled compounds. Computer-processed images were used to evaluate in vivo kinetics. 99mTC pyrophosphate provides the best overall characteristics for bone imaging. Improved quality and bioassay procedures are required, however, before any one agent can be designated the radiopharmaceutical of choice for diagnostic bone imaging.
Gallium citrate Ga 67 (67Ga) scans were performed in 50 consecutive lymphoma patients who underwent routine staging. The overall accuracy of 67Ga scans was greater than 80% for all nodal sites except the spleen (68%). Sensitivity was greater than 88% in the neck and mediastinum, 67% in the abdomen-pelvis, and 33% for the spleen. Specificity was greater than 85% for all nodal sites except for the mediastinum (67%). The accuracy of pedal lymphangiograms was 75%, sensitivity 87%, and specificity 68%. Gallium 67 scans complemented the lymphogram in the abdomen-pelvis but, due to limited sensitivity and high number of equivocal studies (16%), did not replace it. Infraclavicular, pectoral, and mediastinal lesions were detected by 67Ga scans when missed by other means. In 20% to 25% of patients, 67Ga scans provided information not afforded by other diagnostic studies and are therefore considered an important staging procedure for lymphoma patients.
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