Etoposide induced blood-brain barrier disruption in rats: duration of opening and histological sequelae.

The intracarotid infusion of the antineoplastic compound etoposide enhances blood-brain barrier (BBB) permeability. In a rat model system, the functional reversibility and anatomic sequelae of etoposide induced BBB disruption were investigated. Etoposide, in a dose range from 3.0 to 22.5 mg/kg, was infused into the left internal carotid artery of Sprague-Dawley rats. BBB disruption was evaluated by the appearance in the infused hemisphere of systemically administered Evans blue dye and quantitatively by the ratio of counts of the technetium labeled chelate of diethylenetriaminepentaacetic acid in the infused to the noninfused hemisphere. Functional reversibility of altered BBB permeability was investigated at three dose levels of etoposide (3.0, 15.0, and 22.5 mg/kg) by the administration of Evans blue dye at the time of etoposide infusion and the administration of the technetium labeled chelate of diethylenetriamine-pentaacetic acid at varying time intervals after etoposide infusion. Fourteen groups of 12 rats each were studied to define the time course of altered BBB permeability at these three doses. The anatomic sequelae of etoposide induced BBB disruption were investigated at varying time intervals (up to 3 weeks) after intracarotid etoposide infusion. Nineteen rats were examined after sacrifice by intracardiac fixation perfusion with 10% formalin. Each brain was sectioned coronally and examined under light microscopy after hematoxylin and eosin staining. Evidence of BBB disruption was seen at all dose levels of etoposide. The degree of BBB disruption increased with increasing doses of etoposide. The duration of altered BBB permeability increased from less than 1 day at 3.0 mg/kg to between 3 and 4 days at 22.5 mg/kg. Histological studies revealed no evidence of parenchymal damage, although at 4 days postdisruption, a mild perivascular lymphocytic infiltration was noted in the infused hemisphere. Etoposide infusion and subsequent BBB disruption were well tolerated by all test animals. In a rat model system the intracarotid infusion of etoposide is capable of producing prolonged reversible BBB disruption.

In vitro characterization of radiolabeled monoclonal antibodies specific for the extracellular domain of prostate-specific membrane antigen.

Prostate-specific membrane antigen (PSMA) is a well-characterized cell surface antigen expressed by virtually all prostate cancers (PCas). PSMA has been successfully targeted in vivo with (111)In-labeled 7E11 monoclonal antibody (mAb; ProstaScint; Cytogen, Princeton, NJ), which binds to an intracellular epitope of PSMA. This work reports the in vitro characterization of three recently developed mAbs that bind the extracellular domain of PSMA (PSMAext). Murine mAbs J415, J533, J591, and 7E11 were radiolabeled with 131I and evaluated in competitive and saturation binding studies with substrates derived from LNCaP cells. J415 and J591 were conjugated to 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid labeled with (111)In. The uptake and cellular processing of these antibodies were evaluated in viable LNCaP cells. All four mAbs could be labeled with 131I up to a specific activity of 350 MBq/mg with no or little apparent loss of immunoreactivity. Competition assays revealed that J415 and J591 compete for binding to PSMAext antigen. J533 bound to a region close to the J591 binding epitope, but J533 did not interfere with J415 binding to PSMA. mAb 7E11 did not inhibit the binding of J415, J533, or J591 (or vice versa), consistent with earlier work that these latter mAbs bind PSMAext whereas 7E11 binds the intracellular domain of PSMA. Saturation binding studies demonstrated that J415 and J591 bound with a similar affinity (Kds 1.76 and 1.83 nM), whereas J533 had a lower affinity (Kd, 18 nM). In parallel studies, all four mAbs bound to a similar number of PSMA sites expressed by permeabilized cells (1,000,000-1,300,000 sites/cell). In parallel studies performed with viable LNCaP cells, J415, J533, and J591 bound to a similar number of PSMA sites (i.e., 600,000-800,000 sites/cell), whereas 7E11 bound only to a subpopulation of the available PSMA sites (95,000 sites/cell). This apparent binding of 7E11 to viable cells can be accounted for by a 5-7% subpopulation of permeabilized cells produced when the cells were trypsinized and suspended. Up to five DOTA chelates could be bound to either J415 or J591 without compromising immunoreactivity. A comparison of the cellular uptake and metabolic processing of the 131I- and (111)In-labeled antibodies showed a rapid elimination of 131I from the cell and a high retention of (111)In. All four mAbs recognized and bound to similar numbers of PSMAs expressed by ruptured LNCaP cells (i.e., the exposed intracellular and extracellular domains of PSMA). By comparison to J415 and J591, J533 had a lower binding affinity. Both J415 and J591 recognized and bound to the same high number of PSMAs expressed by intact LNCaP. By contrast, 7E11 bound to fewer sites expressed by intact LNCaP cells (i.e., the exposed extracellular domain of PSMA). Both J415 and J591 are promising mAbs for the targeting of viable PSMA-expressing tissue with diagnostic and therapeutic metallic radionuclides.

Gated blood pool scintigraphic monitoring of doxorubicin cardiomyopathy: comparison of camera and computerized probe results in 101 patients.

Serial gated blood pool scintigraphic monitoring of cardiac function with both a nonimaging scintillation probe and a conventional gamma camera-computer imaging system was performed in 101 patients receiving doxorubicin hydrochloride (Adriamycin) chemotherapy. Comparison of probe- and camera-derived ejection fractions (n = 287) correlated significantly (r = 0.70, p less than 0.005) as did the interstudy (n = 183) change in ejection fraction (r = 0.76, p greater than 0.005). Significant discordance in probe- and camera-derived ejection fraction change occurred in 3 (1.6%) of 183 interstudy intervals. Average intrastudy variability of absolute probe-derived ejection fraction was 2.9%. This variability was unrelated to the level of cardiac function. Thirteen patients (13%) developed clinical cardiotoxicity, including four at cumulative Adriamycin levels less than 450 mg/m2. Mean absolute camera ejection fraction decline for these patients was 21% from baseline evaluation, and mean absolute probe ejection fraction decline was 22%. The minimal absolute ejection fraction decline was 11% for patients with clinical congestive heart failure. Eight asymptomatic patients had therapy terminated before the development of clinical cardiotoxicity after a mean decline in absolute camera ejection fraction of 19 +/- 4% (SD) and in probe ejection fraction of 19 +/- 9% into abnormal ranges (a decline in magnitude equivalent to that in patients developing congestive failure). None of these five asymptomatic patients available for clinical follow-up at 6 months after termination of Adriamycin therapy subsequently developed signs of ventricular dysfunction. The majority of patients (83%) studied at 450 mg/m2 cumulative dose levels did not have a 15% or greater decline from baseline into the abnormal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of cardiac conduction abnormalities using segmental vector Fourier analysis of radionuclide gated blood pool scans.

Timing abnormalities of myocardial contractility may occur as inter- or intraventricular asynchrony. Gated blood pool scintigraphy was performed on 21 patients with a normal ejection fraction and the following electrocardiograms: six normal, six with left bundle branch block, four with right bundle branch block and five with right ventricular pacemaker rhythm. A phase and amplitude of the first harmonic of the Fourier transform was obtained for each pixel, and left and right ventricles were trisected. A mean vector phase for each region was obtained by vector summation. Regional and global values were analyzed within each group and compared with normal values. The phase differences between the entire left and right ventricles (mean +/- standard deviation) were: 9 +/- 3 in the normal patients, 38 +/- 8 (p less than 0.01) in patients with left bundle branch block, -6 +/- 7 (p less than 0.05) in patients with right bundle branch block and 15 +/- 9 (difference not significant) in patients with pacemaker rhythm. The phase differences between left ventricular posterolateral and septal regions were -4 +/- 2 in the normal patients, 10 +/- 5 (p less than 0.01) in patients with left bundle branch block, -7 +/- 10 (p less than 0.05) in patients with right bundle branch block and 10 +/- 5 (p less than 0.01) in patients with pacemaker rhythm. Within the right ventricle, phase differences between the apical and septal segments were 14 +/- 9 in the normal patients, 14 +/- 10 (NS) in patients with left bundle branch block, -2 +/- 3 (p less than 0.01) in patients with right bundle branch block and -22 +/- 18 (p less than 0.01) in patients with pacemaker rhythm. Interventricular phase differences were greatest in patients with left bundle branch block and absent or reversed in right bundle branch block.(ABSTRACT TRUNCATED AT 250 WORDS)

Rhenium-186-labeled hydroxyethylidene diphosphonate dosimetry and dosing guidelines for the palliation of skeletal metastases from androgen-independent prostate cancer.

Rhenium-186 (tin)-labeled hydroxyethylidene diphosphonate (186Re-labeled HEDP) was evaluated in 27 men with progressive androgen-independent prostate cancer and bone metastases. Administered activities ranged from 1251 to 4336 MBq (33.8-117.2 mCi). The primary objectives were to assess tumor targeting, normal organ dosimetry, and safety. Antitumor effects were assessed by posttherapy changes in prostate-specific antigen and, when present, palliation of pain. Whole-body kinetics, blood and kidney clearance, skeletal dose, marrow dose, and urinary excretion of the isotope were assessed. Targeting of skeletal disease was observed over the period of quantification (4-168 h). Radiation doses to whole body, bladder, and kidney were well tolerated. The dose-limiting toxicity was myelosuppression (grade III) at 4107 MBq (111 mCi) and grade II at 296 MBq (80 mCi). Probe clearance (whole body) and urinary excretion measurements were highly correlated. Of the six patients treated at the highest dosage schedules (three at 1510 MBq/m2 and three at 1665 MBq/m2), three showed a posttherapy decline in prostate-specific antigen of 50% or more. The declines were not sustained. The determination of total activity retained at 24 h, as well as an estimate of marrow dose, correlated with the amount of myelosuppression observed. These results suggest that a single 24-h measurement of retained activity would allow individualized dosing and an improved therapeutic index relative to fixed dosing schema. Repetitive dosing is required to increase palliation.

Physiological influences on perfusion imaging in transient myocardial ischaemia: importance of early distribution of thallium-201.

We tested the hypothesis that visualisation of defects on thallium-201 (201Tl) myocardial perfusion images (MPI) depends on the duration of the ischaemic state between 201Tl injection and the time of reperfusion of an occluded coronary artery. Praecordial imaging with a gamma camera was performed in 24 anaesthetised, open-chest dogs with transient coronary occlusion. Results indicated that if the duration of the ischaemic state after 201Tl injection was less than 3 min before reperfusion, then the MPI 5 to 15 min after 201Tl injection was falsely negative (201Tl activity in zone (IZ)/normal zone (NZ)greater than 0.85). Dogs which were ischaemic more than 5 min always had MPI defects 5 to 15 min after 201Tl injection (IZ/NZ201Tl ratio less than 0.85). MPI results (201Tl IZ/NZ) 15 min after 201Tl injection were determined by the duration of the ischaemic state after 201Tl injection (r = -0.86) because prolonged ischaemia allowed 201Tl to distribute from blood to myocardium before reperfusion: 201Tl (IZ/NZ( = 0.356 +/- 1.00 (fraction of total 201Tl remaining in blood at the end of the ischaemic state), r = 0.94.

Radial and vertebral bone density in white and black women: evidence for racial differences in premenopausal bone homeostasis.

The reasons for a different incidence of osteoporotic fractures in white and black women are unknown. Previous racial comparisons of bone mass have been limited by racial differences in body weight and socioeconomic, health, and nutritional status. This cross-sectional study examined bone density in 105 black and 114 white healthy nonobese women, 24-65 yr old, using dual photon absorptiometry of the lumbar spine and single photon absorptiometry of the distal radius. Bone density at both sites was higher in blacks at all ages than in whites. When adjusted for age and body mass index, mean bone density was 6.5% higher in blacks at both spine and radius (P less than 0.0001). The cross-sectional rate of decline of vertebral bone density was similar between races; however, radial density increased 3.8%/decade (P = 0.03) in premenopausal blacks under age 46 yr, while it declined 3.2%/decade (P = 0.09) in premenopausal whites. The racial difference in slopes in these premenopausal women is significant (P = 0.002). These findings suggest that attainment of higher peak bone mass and delayed onset of bone loss contribute to the lower incidence of osteoporotic fractures in black women.

Differential skeletal uptake of Tc-99m-tagged pyrophosphate and methylene diphosphonate in leukemia.

Three leukemic patients showing minimal bone uptake of Tc-99m pyrophosphate but with good uptake of methylene diphosphonate are described.

The use of technetium-99m sulfur colloid as a marker for experimental venous thrombosis: concise communication.

The binding of technetium-99m sulfur colloid to in vivo thrombi was studied in a rat model of deep vein thrombosis. After thrombosis was induced by mechanical traumatization of a right femoral vein segment, technetium-99m sulfur colloid was injected into the peripheral veins of different experimental groups at intervals of 30 min and 1-7 days. Ratios of mean activity in traumatized right femoral vein segment to activity in control segments of left femoral vein (R/L ratios) ranged form 2.97-11.0 for all in situ venous thrombi studied. There was no relation between clot size and R/L ratios. The significant uptake ratios observed by us for venous thrombi up to 1 wk in age suggest that in vivo thrombus detection may be feasible by imaging with a gamma camera after technetium-99m sulfur colloid injection in a peripheral vein.

Acute effects of radiation therapy on indium-111-labeled leukocyte uptake in bone marrow.

We recently performed [99mTc]MDP bone and 111In-labeled leukocyte scintigraphy on a patient receiving radiation therapy to the lower cervical and upper thoracic spine. While the bone images revealed only minimally increased activity in the radiation port, leukocyte images revealed diffuse, intensely increased uptake in this same region. Radiation therapy should be included in the differential diagnosis of increased bone marrow activity on 111In leukocyte images.

Bone SPECT in patients with persistent back pain after lumbar spine surgery.

Twenty-five patients with persistent pain after lumbar spine surgery for pain were evaluated by single photon emission computed tomography (SPECT) bone scanning. The patients were divided into three groups, depending on the type of surgery performed. The data obtained indicates that lumbar spine SPECT is most useful in conditions where there is the greatest likelihood of instability. The study shows that the improved contrast and better three-dimensional patient information gained through lumbar spine SPECT permits more accurate delineation of the level of maximum instability and stress on the vertebra.

Bremsstrahlung radiation exposure from pure beta-ray emitters.

UNLABELLED: With increasing therapeutic use of radionuclides that emit relatively high-energy (>1 MeV) beta-rays and the production in vivo of bremsstrahlung sufficient for external imaging, the potential external radiation hazard warrants evaluation. METHODS: The exposure from a patient administered beta-ray-emitting radionuclides has been calculated by extending the National Council on Radiation Protection and Measurement model of a point source in air to account for biologic elimination of activity, the probability of bremsstrahlung production in vivo and its mean energy and the absorption by the patient's body of the bremsstrahlung thus produced. To facilitate such calculations, a quantity called the "specific bremsstrahlung constant" (in C/kg-cm2/MBq-h), betaBr, was devised and calculated for several radionuclides. The specific bremsstrahlung constant is the bremsstrahlung exposure rate (in C/kg/h) in air at 1 cm from a 1 MBq beta-ray emitter of a specified maximum beta-ray energy and frequency of emission in a medium of a specified effective atomic number. RESULTS: For pure beta-ray emitters, the retained activities at which patients can be released from medical confinement (i.e., below which the effective dose equivalent at 1 m will not exceed the maximum recommended value of 0.5 cSv for infrequently exposed members of the general public) are extremely large: on the order of hundreds of thousands to millions of megabecquerels. CONCLUSION: Radionuclide therapy with pure beta-ray emitters, even high-energy beta-ray emitters emitted in bone, does not require medical confinement of patients for radiation protection.

Accuracy and precision of regional multiharmonic Fourier analysis of gated blood-pool images.

In order to estimate the precision and accuracy of parameters derived from segmental multiharmonic Fourier analysis of gated blood-pool images, a Monte Carlo computer noise simulation was tested on five sample regional time-activity curves. The first three Fourier harmonics were retained and the precision and accuracy of parameters of ventricular function were calculated, varying the ejection fraction, segment size, and framing rate. Precision improved with higher ejection fraction, higher counts per frame, or higher framing rate. There was no change in precision as the framing rate changed at fixed total counts. Accuracy changed little with changing framing rate. Thus, for segmental analysis there is no advantage to using a higher framing rate. Regions five or more pixels in size are recommended for reliable results. This study provides useful information for the optimization of acquisition and processing conditions for regional gated blood-pool analysis.

Planar imaging of positron-emitting radionuclides with a multicrystal camera.

A multicrystal gamma camera has been evaluated for the imaging of 511-keV photons resulting from positron emission. With minor instrument modifications, images of a phantom demonstrating good resolution are obtained. Satisfactory planar images are obtained in animals using fluorine-18 or rubidium-82. These findings establish the feasibility of planar imaging of positron emitters in a clinical setting, and may make possible the more rapid development assessment, and dissemination of positron-emitting radionuclides, thus promoting utilization of tomographic positron imaging techniques.

Radiochemical analysis of Tc-99m human serum albumin with high-pressure liquid chromatography: concise communication.

High-pressure liquid chromatography (HPLC) can be performed with an aqueous size-exclusion column to separate proteins or other macromolecules on the basis of molecular size. An HPLC system with a Spherogel-TSK SW column was modified to detect simultaneously uv absorption and radioactivity. Characteristic retention times (RT) were determined for pure human serum albumin (HSA) (RT = 17 min) and pertechnetate (RT = 28.5 min). When analysis was performed on Tc-99m HSA preparations, Tc-99m radioactivity was resolved into five different peaks, with RT ranging from 10.2 to 28.5 min. Less than 2% radioactivity was associated with the pertechnetate peak, whereas the remaining Tc-99m was protein bound. Most of the activity (90%) corresponded to the albumin peak, and 7% was bound to contaminants of high molecular weight with RTs of 10.2 and 14 min. Rapid separation of various radiochemical components differing in molecular size provides an improved basis for understanding the biodistribution of a Tc-99m HSA preparation. This technique would be useful for the preparation and analysis of various radiolabeled macromolecules such as enzymes, immunoglobulins, and other proteins.

SPECT imaging in the diagnosis of Budd-Chiari syndrome.

We recently performed planar and single photon emission computed tomographic (SPECT) liver/spleen scintigraphy in a patient with Budd-Chiari syndrome. While planar imaging revealed only nonspecific hepatocellular dysfunction, tomographic images demonstrated increased radiotracer accumulation in the caudate lobe of the liver, the classical scintigraphic finding in this entity. This case suggests that SPECT may enhance the sensitivity of the scintigraphic diagnosis of this uncommon condition, especially when the occlusion of the hepatic veins is incomplete.

Radionuclide diagnosis of vertebral osteomyelitis: indium-111-leukocyte and technetium-99m-methylene diphosphonate bone scintigraphy.

Seventy-six 111In-labeled leukocyte images performed on 71 patients with possible vertebral osteomyelitis were reviewed. Twenty-eight cases of vertebral osteomyelitis were diagnosed. Vertebral labeled leukocyte activity was normal in 2, increased in 11, and decreased in 15 cases of osteomyelitis. The median duration of symptoms was significantly longer in patients with osteomyelitis and decreased vertebral activity than in patients with osteomyelitis and increased activity (3 mo versus 2 wk; p = 0.019). No significant relationship between the duration of antibiotic therapy and the appearance of vertebral osteomyelitis on leukocyte images was identified (p = 0.62). Increased vertebral activity was highly specific (98%) for osteomyelitis but relatively insensitive (39%). Decreased activity was neither sensitive (54%) nor specific (52%). Seven patients with clinically resolved infection underwent follow-up imaging. Of four patients who initially presented with increased activity, one had normal and three had decreased vertebral activity on follow up studies. All three patients with decreased activity initially had decreased activity on follow-up. Using increased or decreased activity as criteria for infection, the accuracy of leukocyte imaging for diagnosing vertebral osteomyelitis was 66%, similar to that of 99mTc bone imaging (63%) in our population. Leukocyte imaging did however provide important information about extraosseous infection in 12 of the patients studied.

Indium-111 platelet kinetics in normal human subjects: tropolone versus oxine methods.

The effect of labeling media on the kinetics of[111In]platelets was evaluated by performing a paired crossover study in eight normal human subjects using tropolone and oxine methods. Platelets were labeled in autologous plasma with [111In]tropolone (In-tr) and in ACD-saline with [111In]oxine (In-ox) and reinjected. Starting at 1 hr, ten blood samples were obtained over an 8-day period. The in vivo platelet recovery was higher at 1 hr and throughout the 8 days of study with In-tr and the gamma camera images showed less uptake in liver and spleen than with In-ox. When platelet life-span (PLS) was estimated using all ten samples, only linear regression showed that the platelet life-span was longer with In-tr (10.7 +/- 1.5) than with In-ox (9.5 +/- 0.8). When the PLS was estimated excluding the 1-hr sample point, the life-span of platelets was significantly longer with In-tr than with In-ox based on three out of four models of curve fitting. These results demonstrate that platelets labeled with In-tr in plasma are preserved better in circulation and have equal or longer life-span than platelets labeled with In-ox in ACD-saline.

Assessing collateral cerebral perfusion with technetium-99m-HMPAO SPECT during temporary internal carotid artery occlusion.

Cerebral infarction following internal carotid artery occlusion results from either embolism or inadequate collateral blood flow. Although risk of embolism can be minimized, detecting compromised collateral circulation is more difficult. Cerebral angiography, carotid stump pressures and clinical evaluation during internal carotid artery occlusion are of limited utility. Xenon-133 radionuclide studies and stable xenon computed tomography are not readily available. We evaluated 99mTc-HMPAO SPECT, during temporary carotid artery occlusion, in 20 patients considered for internal carotid artery occlusion. Fourteen demonstrated symmetric cerebral perfusion during occlusion; eleven underwent transient and three had permanent carotid artery occlusion without complications. Five patients had ipsilateral globally decreased perfusion during temporary occlusion. One patient underwent transient occlusion of this vessel and one underwent carotid sacrifice without bypass grafting; both recovered without sequelae. The three remaining patients underwent carotid artery bypass grafting prior to sacrifice of this vessel. One patient with a small focal perfusion defect underwent carotid artery sacrifice without bypass grafting and developed acute neurologic deficits postoperatively. These initial results suggest that symmetric cerebral perfusion during temporary occlusion indicates that internal carotid artery occlusion will be tolerated. Although its implications are not yet well defined, the abnormal study identifies patients potentially at risk for postocclusion complications, thus providing a basis for neurosurgical management.

Unusual scintigraphic findings in a thyroid adenoma.

Thallium imaging is increasingly being used to evaluate the thyroid. Uptake patterns of 201Tl in benign and malignant thyroid nodules have been described. Thallium localizes all thyroid tissue with possibly different rates of washout in benign and malignant nodules. This case demonstrates a follicular adenoma presenting 123I as a clinically palpable nodule with nonvisualization of the remainder of the thyroid gland consistent with the diagnosis of an autonomously hyperfunctioning module. Subsequent thallium scanning revealed a complete reversal of tracer distribution with lack of uptake of 201Tl in the nodule while the rest of the gland showed normal thallium accumulation. Surgical excision of the nodule demonstrated follicular adenoma.