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J W Keyes

Publications and source records attributed to J W Keyes.

At least 37 records · Page 2Linked to original sources
PubMed1994

Distinguishing tumor recurrence from irradiation sequelae with positron emission tomography in patients treated for larynx cancer.

PURPOSE: Distinguishing persistent or recurrent tumor from postradiation edema, or soft tissue/cartilage necrosis in patients treated for carcinoma of the larynx can be difficult. Because recurrent tumor is often submucosal, multiple deep biopsies may be necessary before a diagnosis can be established. Positron emission tomography with 18F-2fluoro-2deoxyglucose (FDG) was studied for its ability to aid in this problem. METHODS AND MATERIALS: Positron emission tomography (18FDG) scans were performed on 11 patients who were suspected of having persistent or recurrent tumor after radiation treatment for carcinoma of the larynx. Patients underwent thorough history and physical examinations, scans with computerized tomography, and pathologic evaluation when indicated. Standard uptake values were used to quantitate the FDG uptake in the larynx. RESULTS: The time between completion of radiation treatment and positron emission tomography examination ranged from 2 to 26 months with a median of 6 months. Ten patients underwent computed tomography (CT) of the larynx, which revealed edema of the larynx (six patients), glottic mass (four patients), and cervical nodes (one patient). Positron emission tomography scans revealed increased FDG uptake in the larynx in five patients and laryngectomy confirmed the presence of carcinoma in these patients. Five patients had positron emission tomography results consistent with normal tissue changes in the larynx, and one patient had increased FDG uptake in neck nodes. This patient underwent laryngectomy, and no cancer was found in the primary site, but nodes were pathologically positive. One patient had slightly elevated FDG uptake and negative biopsy results. The remaining patients have been followed for 11 to 14 months since their positron emission studies and their examinations have remained stable. In patients without tumor, average standard uptake values of the larynx ranged from 2.4 to 4.7, and in patients with tumor, the range was 4.9 to 10.7. CONCLUSION: Positron emission tomography with labeled FDG appears to be useful in distinguishing benign from malignant changes in the larynx after radiation treatment. This noninvasive technique may be preferable to biopsy, which could traumatize radiation-damaged tissues and precipitate necrosis.

Deoxyglucose↗
PubMed1994

Salivary gland tumors: pretherapy evaluation with PET.

PURPOSE: To determine whether positron emission tomography (PET) can help differentiate benign from malignant lesions of the salivary glands before surgery. MATERIALS AND METHODS: Masses of the salivary glands were examined in 26 patients by means of computed tomography, magnetic resonance imaging, PET, biopsy (n = 18), and surgery. Contiguous PET scans were obtained from the midcranium to the lower chest 45 minutes after administration of 370 MBq (10 mCi) of fluorine-18 fluorodeoxyglucose (FDG). Standard uptake values (SUVs) were determined for all suspect lesions and for normal parotid glands and cerebellum. RESULTS: All lesions were visualized, and all but two showed some increase in FDG uptake. PET findings helped correctly differentiate benign from malignant masses in 18 (69%) but were false-positive for malignancy in eight (31%). SUV analysis, lesion-to-normal SUV ratios, and lesion-to-cerebellar SUV ratios also failed to differentiate the lesions. CONCLUSION: FDG PET is not useful in classifying salivary gland tumors as benign or malignant.

Adult↗
PubMed1994

Evaluation of emission-transmission registration in thoracic PET.

UNLABELLED: The intent of this investigation was to quantitate the amount of misregistration between PET emission and transmission scans of the thorax that occurs in a normal clinical environment. METHODS: The data from 17 FDG myocardial studies were evaluated. Prior to injection, a transmission study was acquired for 15 min using a 68Ge/68Ga ring source. The location of the cross-hairs from a laser alignment system was marked on the patient who was then removed from the scanner and injected with 10 mCi of FDG. After 45 min, the patient was placed back on the table and repositioned with the previously placed marks and a 15-min emission scan was acquired. The outline of the lungs on both the transmission and emission images was manually segmented. Both attenuation-corrected and noncorrected emission images were evaluated and the one that provided clearer visualization of the outline of the lungs was chosen for segmentation. The segmented contours of the transmission and emission scans were then registered with the method described by Pelizzari et al. using the transmission image as the "head" and the emission image as the "hat." The allowable transformations were x and y shifts and rotation in the transverse plane. RESULTS: Shifts in the x-axis averaged 2.4 mm (range: 0.2-7.3 mm, 80% less than 3.3 mm) with shifts in the y-axis averaging 2.6 mm (range: 0.1-8.7 mm, 80% less than 2.4 mm) and rotations in the transverse plane averaging 1.6 degrees (range: 0.2 to 5.1 degrees, 80% less than 2.4 degrees). A phantom study indicated that the accuracy of this method of evaluating misregistration was 2.35 mm and 1.81 mm in the x and y directions, respectively. CONCLUSION: Our preliminary evaluation indicates that careful application of laser alignment is an adequate method of registration in most cases.

Algorithms↗
PubMed1992

Sensitivity, resolution and image quality with a multi-head SPECT camera.

This investigation sought to determine which collimation factors were most important in providing superior image quality with a three-headed SPECT device. The relationship between sensitivity, resolution and SPECT image quality was studied. Two different sets of parallel-hole collimators were used. The ultrahigh-resolution collimators have higher spatial resolution (8.9 versus 11.0 mm), but only 55% of the sensitivity of the high-resolution collimators. A phantom with hot rods was imaged with both collimator sets. Observers compared images with the ultrahigh-resolution collimators to images of varying counts with the high-resolution collimators and determined which high-resolution images matched the ultrahigh-resolution images in image quality. Eleven patient studies were acquired with both collimator sets for equal time, and observers chose which image set they preferred. Transverse images of brain and liver studies were simulated with varying resolution and counts and subjectively compared. The phantom study indicated that the improvement in resolution led to image quality comparable to increasing the number of counts by a factor of 2.5 to 3.4. The clinical studies showed that the ultrahigh-resolution collimators were preferred in a large majority of the cases. These trends were also seen in the simulation study. These results confirm that higher resolution collimators should be used with multihead SPECT devices. The improvement in resolution more than compensates for the loss in sensitivity, leading to an overall improvement in image quality.

Brain↗
PubMed1991

Improved detection of small cavernous hemangiomas of the liver with high-resolution three-headed SPECT.

The purpose of this study was to review our experience with 99mTc-red blood cell scintigraphy for diagnosis of cavernous hemangiomas of the liver using a new three-headed, high-resolution dedicated SPECT system. Of 19 patients referred with a total of 38 lesions seen on CT, US, or MRI, 14 patients had 24 lesions that were hemangioma-positive with SPECT (all true-positives). Six of these 14 patients also had 9 hemangioma-negative lesions; all were less than or equal to 1.3 cm in size and false-negative. The remaining five patients had hemangioma-negative lesions only (1 false-negative, 4 true-negatives). Two hemangiomas were seen by SPECT that were not detected by CT, US, or MR. The sensitivity for hemangiomas greater than or equal to 1.4 cm. was 100% (20/20). The sensitivity was 33% for lesions 0.9-1.3 cm, and 20% for lesions less than or equal to 0.8 cm. The smallest hemangioma detected was 0.5 cm. These results show a definite improvement in sensitivity with high-resolution triple-headed SPECT over previously reported results using single-headed SPECT. High-resolution SPECT has improved our ability to detect small cavernous hemangiomas of the liver.

Erythrocytes↗
PubMed1990

In vivo SPECT imaging of CNS D-2 dopamine receptors: initial studies with iodine-123-IBZM in humans.

Iodobenzamide (IBZM) is a D-2 dopamine receptor antagonist. In this paper the results of Phase I clinical studies of iodine-123-(123I)IBZM in humans are reported. Preliminary imaging studies, both planar and single-photon emission tomography (SPECT), of no-carrier added [123I]IBZM in humans show specific localization in the basal ganglia of the brain. At 2 hr after an i.v. injection, the brain uptake was 3.72% of the dose, and at 20 hr later the uptake diminished to 0.7%. Radiation dosimetry calculation indicated that the radiation dose to the brain was minimum, 0.039 rad/mCi, while the large intestine wall received the highest dose, 0.28 mrad/mCi. The radiation dosimetry and pharmacology data suggest that this agent is safe for human use.

Adult↗
PubMed1989

Clinical applications of SPECT.

The clinical use of single photon emission computed tomography (SPECT) has grown steadily over the last decade. SPECT is now an essential technique for certain studies such as cerebral blood flow imaging. Many other common nuclear medicine studies give better results when they are performed with SPECT. These include myocardial perfusion imaging with thallium-201 or the new technetium-99m perfusion agents, myocardial infarct imaging with infarct-avid agents, imaging of tumors or infections with agents such as gallium-67 or indium-111 WBC's, and certain cases of bone imaging. Still other studies such as liver/spleen imaging, most brain studies, and perhaps renal imaging may benefit from SPECT even though planar imaging gives satisfactory results. Future developments in 3D display techniques and faster computers may extend the clinical usefulness of SPECT to other areas such as pulmonary perfusion imaging and gated cardiac blood pool imaging.

Forecasting↗
PubMed1989

Delayed redistribution in thallium 201 SPECT myocardial perfusion studies.

Stress 201Tl myocardial perfusion studies are useful in differentiating viable, reversibly ischemic from infarcted myocardium. A perfusion defect that shows redistribution 2 to 4 h after 201Tl injection is diagnostic of ischemia, while a fixed defect suggests infarction. However, occasional patients with a fixed defect at 4 h have redistribution at 24 h. This study evaluates the frequency and significance of this delayed redistribution with SPECT 201Tl. Patients with either no or incomplete redistribution at 4 h had repeat imaging 18 to 48 h later. Delayed redistribution was seen in 8/26 (31 percent). Four had incomplete and four had no redistribution at 4 h. Delayed redistribution with SPECT 201Tl is more common than generally appreciated, and we recommend delayed images in patients with fixed perfusion defects or incomplete redistribution at 4-h imaging, particularly in patients with previous infarctions for whom a revascularization procedure is being considered.

Adult↗
PubMed1988

Characterization of the rotating display.

The rotating display is a useful method for reviewing single photon emission computed tomography (SPECT) data. This study evaluated the requirements for a subjectively pleasing and useful implementation of this technique. Twelve SPECT data sets were modified and viewed by several observers who recorded the minimum framing rates for apparent smooth rotation, 3D effect, effects of image size, and other parameters. The results showed that a minimum of 16 frames was needed for a useful display. Smaller image sizes and more frames were preferred. The recommended minimal framing rate for a 64-frame study is 16-17 frames per second and for a 32-frame study, 12-13 frames per second. Other enhancements also were useful.

Data Display↗
PubMed1987

Cholescintigraphic detection of intraperitoneal bile leakage from a perforated duodenal ulcer.

A 66-year-old woman with known gallstones and peptic ulcer disease presented with acute epigastric pain. Cholescintigraphy revealed nonvisualization of the gallbladder with subhepatic and perihepatic accumulation of tracer. An upper gastrointestinal examination with water-soluble contrast revealed a perforated duodenal ulcer, with leakage confirmed at laparotomy. The gallbladder was intact.

Aged↗
PubMed1987

Quantitative organ visualization using SPECT.

Quantitative organ visualization (QOV) was performed using single photon emission computed tomography (SPECT). Organ size was calculated from serial, contiguous ECT images taken through the organ of interest with image boundaries determined using a maximum directional gradient edge finding technique. Organ activity was calculated using ECT counts bounded by the directional gradient, imaging system efficiency, and imaging time. The technique used to perform QOV was evaluated using phantom studies, in vivo canine liver, spleen, bladder, and kidney studies, and in vivo human bladder studies. It was demonstrated that absolute organ activity and organ size could be determined with this system and total imaging time restricted to less than 45 min to an accuracy of about +/- 10% providing the minimum dimensions of the organ are greater than the FWHM of the imaging system and the total radioactivity within the organ of interest exceeds 15 nCi/cc for dog-sized torsos. In addition, effective half-lives of approximately 1.5 hr or greater could be determined.

Animals↗
PubMed1986

Tumor blood flow and systemic shunting in patients receiving intraarterial chemotherapy for head and neck cancer.

Radionuclide techniques have been used to estimate the systemic shunt and to quantitate blood flow to the tumor and a reference normal tissue in nine patients undergoing intraarterial chemotherapy for head and neck cancer. The systemic shunt was calculated as the percentage of pulmonary trapping of intraarterially injected 99mTc-labeled macroaggregated albumin. The mean systemic shunt in the 12 separate arteries studied was 23 +/- 13% (SE) (range 8-43%). Quantitative blood flow was determined from the slope of the washout curve of intraarterially injected 133Xe. The mean tumor blood flow was 13.6 +/- 6.7 ml/100 g/min, while the mean blood flow to the scalp was 4.2 +/- 2.1 ml/100 g/min providing a mean tumor/normal tissue ratio of 3.9 +/- 2.7. An estimate of blood flow distribution was obtained by calculating the ratio of counts/pixel in the tumor mass versus the remainder of the head as determined by single photon emission computed tomography following an intraarterial injection of 99mTc-labeled macroaggregated albumin. The mean ratio of tumor to normal tissue perfusion by this technique was 5.6 +/- 3.7. These techniques have allowed noninvasive determination of the blood flow parameters associated with intraarterial chemotherapy. At least part of the therapeutic advantage of regional chemotherapy in patients with head and neck cancer is due to a tumor/normal tissue blood flow ratio that favors drug delivery to the tumor contained within the infused volume.

Adult↗