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Biomedical subjects

M L Rhodes

Publications and source records attributed to M L Rhodes.

At least 19 recordsLinked to original sources
PubMed1988

CT in the preoperative assessment of the mandible and maxilla for endosseous implant surgery. Work in progress.

A new computer software program that generates panoramic and oblique computed tomography scans was used to examine 205 patients who were being considered for endosseous dental implants in the mandibular or maxillary arches. This technique allowed recognition of the course of the inferior alveolar nerve canal and measurement of the alveolar ridge, which facilitated the design and placement of an optimal dental prosthesis.

Alveolar Process↗
PubMed1984

Computed tomography of the spine: curved coronal reformations from serial images.

A new imaging format described here uses nonplanar reformations that follow the contour of curved structures intersected by a series of regularly spaced CT scans. The CT scanning procedure is described, and algorithmic details of this new format are presented. A standard set of reformatted images is suggested, and clinical examples are given to illustrate the diagnostic value of this new format.

Adult↗
PubMed1983

Data compression techniques for CT image archiving.

Large digital files are inherent to computed tomography (CT) image data. The CT installations that routinely archive patient data are penalized computer time, technologist's time, tape, purchase, and file space. This paper introduces compression techniques that reduce the amount of tape needed to store image data and the amount of computer time to do so. The benefits delivered by this technique have also been applied to CT disk systems in which limited on-line memory requires compact file storage. Typical reductions of 40 to 50% of original file space are reported.

Computers↗
PubMed1982

Stereotactic neurosurgery using 3-D image data from computed tomography.

During the last decade computer tomography (CT) scanners have provided images that show internal anatomy of unsurpassed resolution and that, since they are inherently digital, a format computer graphics software can easily process. By combining CT images, a specially designed head-mounted instrument, and the software to coordinate them, improved surgical accuracy can result for stereotactic surgery. Using the head-mounted frame and the interactive computer software described here, the entire stereotactic approach is transportable to computer systems of three major CT manufacturers. Neurosurgeons now have a tool that allows trajectory selection and probe placement entirely within the CT suite. Compared with conventional stereotaxis, the CT-aided approach offers increased accuracy, with a significant fluid contrast injection for finding reference points and the avoidance of important brain structures due to the direct visualization afforded with CT. Key interactive features are shown here that allow unrestricted views of anatomy in the area of surgical interest. For example, oblique views that are normal to the trajectory of neurosurgical instruments are extracted in real time during the surgical procedure. Standard sagittal (lateral) and coronal (frontal) image planes are also shown integrated with the interactive technique. The surgical procedure is outlined and details of the pattern recognition technique for image-to-frame registration are presented. Test, phantom, and patient results are given.

Brain↗
PubMed1982

Pulmonary superoxide dismutase activity in the euthyroid and hypothyroid ovine fetus.

Pulmonary superoxide dismutase (SOD) activity was measured in 11 euthyroid and 15 hypothyroid ovine fetuses at 130 days gestation. In the euthyroid fetus, the mean pulmonary SOD activity was similar in saline- and thyroxine-infused groups. Compared to the euthyroid fetus, the mean pulmonary SOD activity was significantly lower in the noninfused or saline-infused athyrotic fetus. Administration of thyroxine to the hypothyroid fetus results in a normalization of pulmonary SOD activity to control values. Thus, thyroxine appears to influence the maturation of pulmonary SOD activity in the ovine fetus during the third trimester.

Animals↗
PubMed1982

Theophylline elimination in the pregnant and fetal rabbit.

Aminophylline and theophylline are commonly used to treat asthma. We studied theophylline pharmacokinetics in the pregnant and nonpregnant rabbit as well as in the intrauterine and extrauterine fetus. The t1/2 was increased (p less than 0.05) and the clearance was decreased (p less than 0.05) in the pregnant compared to the nonpregnant rabbit. The t1/2 of theophylline in the newborn rabbit was 43.5 +/- 12.0 hr, approximately 15 times longer than in the nonpregnant rabbit. Twenty-four hours after a 20 min maternal aminophylline infusion, both the intrauterine fetus and maternal serum theophylline concentrations were very similar. The transplacental transfer from the maternal to fetal circulation occurred in less than 1 hr. The maternal to fetal serum ratios for theophylline were similar after a 5-day maternal aminophylline infusion (ratio 1.22 +/- 0.20) or after a 20 min infusion (ratio 1.24 +/- 0.20). Our findings indicate that the newborn rabbit eliminates theophylline very slowly, and maternal aminophylline or theophylline therapy that would result in high peak serum concentrations in the fetus, particularly just before birth, should be avoided.

Aminophylline↗
PubMed1980

Extracting oblique planes from serial CT sections.

Although geometric principles describing planes oblique to an orthogonal image data set are well understood, no implementation has been offered for their practical specification, extraction, and display in a clinical environment. Fast image generation and ease of user specification-requisite credentials for successful clinical implementations-are handicapped by the large volume of data to process. Other difficulties further complicate an interactive solution. Once oblique planes are generated, their orientation is often difficult to perceive without visual cues that aid their registration with standard image formats. In addition, Moire patterns introduced by digital aliasing often currupt resultant views. In this paper, techniques are outlined for simplifying oblique plane specification, a methodology is presented for image construction, and an interactive approach is illustrated to register images for such general view planes. Finally, digital aliasing of oblique planes is discussed, and a solution is given for this application.

Computers↗
PubMed1980

Oxygen toxicity.

Explore the source record for details and available documents.

Animals↗
PubMed1979

Relationship between arterial and venous bicarbonate values.

We determined the clinical efficacy of using the venous CO2 value, as obtained with routine "electrolytes", in acid-base management. Venipuncture samples for venous CO2 content and chloride concentrations were obtained in 336 patients with arterial blood pH, PaO2, PaCO2, and oxygen saturation determinations. The linear correlation between actual calculated arterial HCO3- and the measured venous CO2 was significant (P less than .001). Using venous CO2, chloride, and arterial pH values, we present various prediction equations for estimating arterial HCO3-. We determined the effects of time delay, exposure to air, and acute changes in arterial blood pH and PaCO2 on venous CO2 levels. Venous CO2 determinations should not be substituted for the arterial HCO3 value in the Henderson-Hasselbalch equation to calculate arterial blood pH or PaCO2. Clinically, the venous CO2 value has little direct use, but when venous CO2 content is abnormal, it should alert the clinician to the need for obtaining arterial blood gas and pH values.

Acid-Base Imbalance↗
PubMed1979

Chronic intravenous infusion in the rat: a nonsurgical approach.

A rapid, simplified technique of intravenous catheterization of the unanesthetized rat was developed for continuous infusion. A 19-gauge thin-walled needle was inserted percutaneously into the dilated tail vein, and polyethylene tubing was advanced through the needle into the vein. The catheter was protected by wire mesh electrical sheathing taped securely to the tail. This approach eliminated the need for anesthesia and surgery which were traumatic to the animal and time consuming for the investigator. This method was used successfully in 32 rats given continous infusion for up to 5 days.

Animals↗
PubMed1978

An effect of paraquat on the lungs of rabbits. Its implications in smoking contaminated marihuana.

Thirty-six rabbits received the herbicide, paraquat (1,1'-dimethyl-4,4'-dipyridylium dichloride), by selective intrabronchial instillation in doses ranging from 0.1 gm to 1 pg. Sixteen additional rabbits were given paraquat dichloride (25 mg/kg of body weight) intraperitoneally, subcutaneously, intravenously, or orally. The lung of the rabbit proved to be highly sensitive to paraquat administered by intrabronchial deposition, moderately sensitive to intravenously administered paraquat, and resistant to the chemical when given intraperitoneally or subcutaneously. One picogram of paraquat dichloride delivered by bronchial catheter produced a 1.0-mm pulmonary lesion consisting of focal hemorrhage, congestion of capillaries, intra-alveolar macrophages, and moderate thickening of the alveolar septa. This finding suggests that pulmonary damage could potentially result from smoking marihuana that has been sprayed with paraquat.

Administration, Oral↗