Radiodosimetry in nuclear medicine.
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Humans↗
Biomedical subjects
J T Bushberg
Publications and source records attributed to J T Bushberg.
Clinical immunoscintigraphy of recurrent ovarian cancer with indium 111-labeled B72.3 monoclonal antibody.
OBJECTIVE: To prospectively evaluate the ability for immunoscintigraphy with monoclonal antibody CYT-103 labeled with indium 111 to detect tumor presence in 15 patients with ovarian cancer undergoing second-look surgery. DESIGN: Prospective, open-label, nonrandomized trial. SETTING: Hospital-based nuclear medicine facility and operating room. STUDY PARTICIPANTS: Patients with previous ovarian cancer scheduled for second-look surgery. MAIN OUTCOME MEASURE: Correctness of prediction of immunoscintigraphy for presence or absence of ovarian cancer compared with serum CA 125 titer and computed tomography. RESULTS: Immunoscintigraphy, computed tomography, and serum CA 125 titer had respective sensitivities of 92%, 42%, and 42%; specificities of 67%, 100%, and 100%; accuracies of 87%, 53%, and 53%; and diagnostic values of 59%, 42%, and 42%. The full regional extent of recurrent tumor was correctly detected in 45% of patients by immunoscintigraphy and in none of the patients by computed tomography. Immunoscintigraphy detected miliary tumor in two of four patients and computed tomography, as expected, was unable to detect miliary disease. CONCLUSIONS: Recurrent ovarian cancer often presents as multiple small lesions throughout the abdominal cavity. In this subset of patients, immunoscintigraphy may be particularly well suited for detection of the presence of recurrent tumor.
Antibodies, Monoclonal↗
Exposure rates in high-level-control fluoroscopy for image enhancement.
High-level fluoroscopic boost options that exceed conventional exposure limits are available as a means of reducing quantum mottle during angiography. Federal law does not specify exposure limits for such high-level controls but requires specific means of activation to safeguard against inadvertent use. The American Association of Physicists in Medicine recently recommended that high-level exposure rates not exceed 2.58 mC/kg/min (10R/min). At six institution surveyed, maximum exposure rates ranged from 5.42 to 24 mC/kg/min (21-93 R/min). Activation of high-level capability varied from a simple foot switch to a keyed interlock requiring a second operator to engage. There appears to be no industry coherence in high-level control exposure limits as yet, although the Center for Devices and Radiological Health recently initiated an investigatory program.
Environmental Exposure↗
Comparative uptake of 67Ga and 99mTc MDP in rabbits with a benign noninfected bone lesion (fracture).
Mid-shaft fractures of the radius and ulna were produced in 3 to 4 kg New Zealand white rabbits and quantitative uptake of 99mTc MDP and 67Ga determined at 11, 18, 25, 32, 51, and 78 days following fracture. Two hundred microCi of 67Ga was administered 24 hours prior to sacrifice and 1.5 mCi 99mTc MDP 2 hours prior to sacrifice. Specific activity ratios (SARs) were determined between fracture and control sides for bone, muscle and skin. SARs for bone were surprisingly similar for 99mTc MDP and 67Ga, reaching peak values of 6.07 +/- 0.64 (99mTc 18 days); 6.58 +/- 0.90 (67Ga 32 days), subsequently decreasing to minimum values at 78 days postfracture (99mTc MDP 2.25 +/- 0.14; 67Ga 2.18 +/- 0.08). There was no statistically significant difference in SAR for 99mTc MDP vs. 67Ga in bone at any time after fracture. Whole sections of limb were resected on selected animals and activity ratios determined for these sections as a function of the contribution of activity from the various tissues in the volume of interest. Total activity ratios of 67Ga were lower than bone SARs as a result of the contribution of activity from muscle and skin. Thus the apparent lower activity ratios noted on 67Ga images compared with 99mTc MDP images in this fracture model were not due to differences in bone SARs but rather due to the higher soft tissue background activity contribution in the 67Ga images.
Animals↗
Compounds which mediate gallium-67 transfer from lactoferrin to ferritin.
The influence of various low molecular weight compounds on the transfer of 67Ga from human lactoferrin (LF) to horse spleen ferritin (HoFE) has been examined in vitro. When LF*67Ga complex was placed in competition with HoFE using a dialysis system the initial transfer rate (TR) of 67Ga to HoFE was slow and continuous. In the presence of 1 mM pyrophosphate (PPi) ascorbate and adenosine triphosphate (ATP), the TR was dramatically enhanced. This effect was concentration sensitive since reduction of the ATP to 0.1 mM eliminated the enhancement. Other intracellular compounds did not significantly influence the TR. Although PPi and ascorbate ions yielded larger TR's, ATP was more effective in the promotion of 67Ga transfer to HoFE. When the LF/HoFE concentration ratio was decreased, in the presence of ATP, the transfer of 67Ga was significantly increased. These results suggest that ferritin present intracellularly could remove and retain 67Ga entering the cell in the form of a LF*67Ga complex. Moreover, increased synthesis of ferritin and cytosolic phosphate compounds would appear to enhance this process.
Adenosine Triphosphate↗
Desferoxamine mesylate (Desferal): a contrast-enhancing agent for gallium-37 imaging.
Desferal (desferoxamine mesylate) was investigated as a contrast-enhancing agent for tumor and abscess imaging with 67Ga-citrate. Tumor studies were performed in mice with Cloudman S-91 melanoma. Abscess studies were performed with a subcutaneous abscess model in rabbits. When Desferal is administered 16 to 18 hours after injection of 67Ga, rapid blood clearance of 67 Ga occurs with only slight (tumor) or no (abscess) loss of activity from the lesion. Retention in other organs is variable. Tumor-to-blood ratios are improved eightfold in tumor and fourfold in abscess in studies performed with single Desferal injections of 150 mg/kg. Blood and total body clearance studies in rabbits reveal that maximum Desferal effect is achieved in the 17 to 50 mg/kg dose range and that only minimal improvement occurs at higher doses.
Abscess↗
The use of indium-111-labeled leukocytes for abscess detection.
A case is reported in which a labeled white cell scan was helpful in the diagnosis of a periappendiceal abscess. The method of labeling is described and the usefulness of the technique discussed.
Abscess↗
Indium-111-labeled autologous platelets for location of vascular thrombi in humans.
Twenty-two patients suspected of having either venous or arterial thrombi were studied with In-111-labeled autologous platelets. Whole-body scans were performed 3, 24, and 48 hr following i.v. injection. Twelve patients studied with saline-washed platelets had unsatisfactory 15-min recovery and biologic half-time. When the labeling was carried out in plasma, these values compared favorably with normal values reported for Cr-51-labeled autologous platelets. Of ten patients studied using platelets labeled in plasma, three had normal scans, six had abnormal scans, and one had an equivocal scan. All six abnormal scans were confirmed with corresponding positive findings in either the venogram, arteriogram, or lung scan. J Nucl Med 19: 626-634, 1978.
Adult↗
The AAPM/RSNA physics tutorial for residents. X-ray interactions.
The diagnostic information in a radiograph or fluoroscopic image is largely the result of the quantity of x rays that are not removed from the incident x-ray beam. The information content of the image is delivered by the percentage of noninteracting photons that are successfully recorded. There are four major x-ray interactions: Rayleigh (coherent) scattering. Compton scattering, photoelectric absorption, and pair production. The degree of attenuation and the predominant mechanisms involved in the interactions are influenced by the x-ray energy and tissue composition. In the diagnostic energy range, photoelectric absorption and Compton scattering are the predominant modes of attenuation. One of the challenges in diagnostic imaging is to optimize image acquisition by controlling x-ray attenuation to obtain the appropriate contrast between the tissues while minimizing patient dose and scattered radiation in the image. Imaging techniques such as use of contrast material and dedicated mammography equipment exploit the differences in these types of x-ray interactions to improve the quality and diagnostic utility of the examination. Rayleigh scattering and pair production are presented but do not occur to any significant degree in diagnostic radiography.
Scattering, Radiation↗