David L. Herbert

Bone stress: a radionuclide imaging perspective.

Thirty-five college athletes with lower leg pain underwent radiography and radionuclide studies to rule out a stress fracture. Their asymptomatic extremities and 13 pain-free athletes served as controls. Four main patterns were observed: (a) sharply marginated scintigraphic abnormalities and positive radiographs; (b) sharply marginated scintigraphic abnormalities and negative radiographs; (c) ill-defined scintigraphic abnormalities and negative radiographs; and (d) negative radionuclide images and negative radiographs. Since the patients with the first two patterns were otherwise identical medically, the authors feel that this scintigraphic appearance is characteristic of bone stress in the appropriate clinical setting, regardless of the radiographic findings. A schema is proposed to explain the occurrence of positive radionuclide images and negative radiographs in the same patient, using a broad conceptual approach to the problem of bone stress.

The function of the parotid gland following radiation therapy for head and neck cancer

Abstract The parotid gland was selected for study of its salivary output before and after radiation therapy for head and neck cancer. Before radiation therapy, a sialogram of the parotid gland was performed with the patients head positioned for radiation therapy; a lateral radiographic view of the parotid gland was used to compare with the radiation treatment portal to determine the portion of the parotid gland to he irradiated. Samples of stimulated saliva were collected from the parotid gland before and at 1 and 6 months post-radiation. Eighteen patients with head and neck cancer who received radiation therapy were studied. The data showed that in the irradiation of nasopharyageal, advanced oropbaryngeal and Waldeyers ring lesions, 100% of the parotid gland was irradiated; for the early oropharyageal and hypopbaryugeal lesions, from 30 to 90% of the parotid gland was irradiated and for the supragiottic and oral cavity lesions, 25–30% of the parotid gland was irradiated. When 100% of the parotid gland was irradiated, no saliva was produced at 1 month post-radiation; this remained the same when re-tested at 4–8 months, however, when any portion of the parotid gland was not irradiated, there was residual salivary function.

Regional pulmonary ventilation measurements by xenon enhanced dynamic computed tomography: an update.

New developments in computed tomographic technology permit rapid, serial images that may yield information concerning tracer kinetics through a large tissue volume. One possible application of these developments is the derivation of local lung ventilation by observing the temporal changes of stable xenon concentrations. Preliminary results from six multilevel ventilation studies in dogs demonstrate that the lung may be repeatedly imaged during reproducible phases of respiration even when interscan table incrementation is employed to survey a number of tissue segments and breathing is permitted between scans. In addition, subanesthetic xenon concentrations provide adequate enhancement for possible quantification.

Mapping of human local pulmonary ventilation by xenon enhanced computed tomography.

Functional maps of local pulmonary ventilation are derived from serial computed tomographic images acquired prior to and during a short period of inhalation of subanesthetic xenon/oxygen gas mixtures. Preliminary results from human studies yield quantitative maps of local ventilation rates with excellent anatomic specificity demonstrating nonuniformities in the distribution of ventilation in normal and abnormal human lungs.

Xenon enhanced dynamic computed tomography: multilevel cerebral blood flow studies.

Xenon enhanced computed tomography with a fast scanning mode and interscan table incrementation was used to derive local cerebral blood flow in a nonhuman primate 19 days following infarction. The in vivo autoradiographic methodology was used to derive blood flow in normal and diseased tissue at four different brain levels (slices) during a single inhalation study.

Local lung ventilation in critically ill patients using nonradioactive xenon-enhanced transmission computed tomography

Nonradioactive xenon is sufficiently radiodense to increase the density of gas-containing lung as seen in a computed tomography (CT) scan. Subtraction of a baseline CT scan from the xenon-enhanced CT scan can accentuate gas space differences by subtracting fixed tissue densities. The baseline scan and the scan obtained during wash-in of xenon (before equilibration) allow circulation of local ventilation. The xenon CT scan, thus, provides more precise information about distribution of ventilation than planar radiogas techniques. The technical aspects of application to a critically ill patient and the mathematical basis of the technique are presented.

Correlation of Radiographic and Histologic Findings in Arterial Calcification

Intimal calcific atherosclerosis may lead to diminished organ perfusion, whereas medial calcification (Mönckeberg type) is of no physiologic significance. Thirty-nine excised arteries were studied by correlating specimen radiographs with transverse histologic sections to determine whether intimal and medial calcification could be reliably distinguished by radiographic criteria. The calcification was correctly localized in 92% of the arteries studied. Intimal calcification was usually irregular and patchy, whereas medial calcification was regular and diffuse. In one case, extensive medial calcification obscured intimal disease. Plain radiographs may be a useful way to follow progression, regression and the effects of therapy on vaso-occlusive disease in certain high-risk patients.

Bromocriptine treatment of women with suspected pituitary prolactin-secreting microadenomas

The present study was designed to investigate the efficacy of bromocriptine in reducing serum prolactin (PRL) levels and in decreasing the size of PRL-secreting microadenomas. Bromocriptine, 5.0 mg, was administered daily for 2 years of 17 women who had galactorrhea, hyperprolactinemia, and hypocycloidal polytomographic evidence suggestive of a pituitary microadenoma. Serum PRL levels were normalized in 16 of 17 women during therapy. Associated with this was resumption of regular menses in 15 of 16 women with menstrual dysfunction and cessation of galactorrhea in 16 of the 17 women. Improvement in the roentgenographic appearance of the sella turcica occurred in two women. No progression in tumor size was found during the course of therapy. Side effects attributed to bromocriptine were minimal, transient, and usually well tolerated. These data suggest that bromocriptine is an appropriate therapeutic modality for PRL-secreting pituitary microadenomas.

Characterization of Radiologists’ Search Strategies for Lung Nodule Detection: Slice-Based Versus Volumetric Displays

The goal of this study was to assess whether radiologists’ search paths for lung nodule detection in chest computed tomography (CT) between different rendering and display schemes have reliable properties that can be exploited as an indicator of ergonomic efficiency for the purpose of comparing different display paradigms. Eight radiologists retrospectively viewed 30 lung cancer screening CT exams, containing a total of 91 nodules, in each of three display modes [i.e., slice-by-slice, orthogonal maximum intensity projection (MIP) and stereoscopic] for the purpose of detecting and classifying lung nodules. Radiologists’ search patterns in the axial direction were recorded and analyzed along with the location, size, and shape for each detected feature, and the likelihood that the feature is an actual nodule. Nodule detection performance was analyzed by employing free-response receiver operating characteristic methods. Search paths were clearly different between slice-by-slice displays and volumetric displays but, aside from training and novelty effects, not between MIP and stereographic displays. Novelty and training effects were associated with the stereographic display mode, as evidenced by differences between the beginning and end of the study. The stereo display provided higher detection and classification performance with less interpretation time compared to other display modes tested in the study; however, the differences were not statistically significant. Our preliminary results indicate a potential role for the use of radiologists’ search paths in evaluating the relative ergonomic efficiencies of different display paradigms, but systematic training and practice is necessary to eliminate training curve and novelty effects before search strategies can be meaningfully compared.

Xenon/CT blood flow mapping of the kidney and liver

A noninvasive technique for measuring blood flow by xenon-enhanced X-ray transmission CT has been developed and reported quite extensively in recent years. In this method nonradioactive xenon gas is inhaled, and the temporal changes in radiographic enhancement produced by the inhalation are measured by sequential CT. Time-dependent xenon concentration within various tissue segments is used to derive local blood flow maps. The method has been amply discussed in relation to assessment of local cerebral blood flow. Its application to other body organs is explored in this paper, in which results from six preliminary blood flow studies in the liver and kidneys of nonhuman primates are reported. Blood flow in renal cortex ranged from 150 to 280 ml/100 cc/min and hepatic tissue perfusion from 80 to 120 ml/100 cc/ min. The advantages and limitations of the method in such applications are discussed.