Count Density Ratios Research Articles

99mTc]polyamine analogs as potential tumor imaging agent

AbstractPolyamines are essential for the growth and survival of all cells with biosynthesis and transportation of polyamines being very active in tumors. With the aim of developing a new tumor imaging agent, three artificial synthetic polyamine analogs, diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA), were labeled with 99mTc. The 99mTc‐labeled complexes were characterized by TLC and studied for stability. 99mTc‐DETA, 99mTc‐TETA, and 99mTc‐TEPA were formed in high yields and found to be stable. 99mTc‐DETA, 99mTc‐TETA, and 99mTc‐TEPA revealed high tumor uptakes of 0.65, 0.58, and 0.59% ID/g at 4 h pi, respectively, in HepA tumor‐bearing mice. The ratios of the tumor to the contralataral muscle (T/CM) were 13.68, 5.99, and 9.81, respectively. SPECT images revealed clear visualization of tumors. Excretion routes were mainly through urine and feces. The tumor‐to‐muscle count density ratios of 99mTc‐DETA, 99mTc‐TETA, and 99mTc‐TEPA were 2.47, 2.45, and 2.91, respectively. [99mTc]‐labeled polyamine analogs are promising agents for tumor imaging and warrant further evaluation. Drug Dev Res 69:520–525, 2008. © 2008 Wiley‐Liss, Inc.

Ductal carcinoma in situ: correlation between FDG-PET/CT and histopathology

The aim of this study was to determine if any correlation exists between tumor cell density and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET)/CT) for pure or predominant ductal carcinoma in situ (DCIS). Subjects in this retrospective review comprised 11 patients who underwent FDG-PET/CT for DCIS. Pathological tumor cell density and FDG-PET/CT images were compared. A tumor background count density ratio of >1.5 was defined as the detectable range for DCIS. Pathological density of disease was high in eight patients, intermediate in one, and low in two. In all eight patients with a detectable intraductal component on PET/CT, the density of disease was classified as high. In three patients undetected by PET/CT, the density of disease was classified as intermediate or low. On statistical analysis, the correlation between the density of disease and tumor background count density ratio (TBCDR) on PET/CT was significant (<0.05), whereas the nuclear grade and Van Nuys grade were not significant. In the eight patients detected by PET/CT, the discrepancy between histopathological mapping and FDG-PET/CT mapping was >20 mm in four patients and represented underestimation in four patients who showed low density of disease in the peripheral area. Tumor cell density of intraductal carcinoma appears strongly correlated to detection by FDG-PET/CT.

Diagnostic performance of PET/CT in differentiation of malignant and benign non-solid solitary pulmonary nodules

To evaluate whether [F-18] fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) can distinguish benign from malignant solitary pulmonary nodules (SPNs) with non-solid components. [F-18] FDG-PET/CT scans were performed on 53 consecutive patients (30 men, 23 women; mean age 65 years) who had SPNs with non-solid components identified by CT screening for lung cancer. All patients underwent surgical resection, and all lesions were pathologically proved. Visual score, maximal, and mean standardized uptake value (SUV), and maximal and mean lesion-to-normal tissue count density ratio (LNR) were calculated in all lesions. In addition, clinical characteristics, laboratory test results, and CT findings were assessed. Benign SPNs with non-solid components had a higher uptake on [F-18] FDG-PET/CT. Visual score, maximal and mean SUV, and maximal and mean LNR were significantly higher in the benign when compared with the malignant SPNs (P < 0.001). When the cutoff of 1.5 was assigned for maximal SUV, the diagnostic performance of [F-18] FDG-PET/CT in predicting benign SPN revealed 100.0% sensitivity, 96.4% specificity, and 100.0% accuracy. [F-18] FDG-PET/CT is useful for the differential diagnosis of SPNs with non-solid components.

Frequency of pulmonary mineralization and hypoxemia in 21 dogs with pituitary-dependent hyperadrenocorticism.

The purpose of this study was to determine the frequency of hypoxemia and pulmonary mineralization using 99mTc-methylene diphosphonate (99mTc-MDP) in dogs with pituitary-dependent hyperadrenocorticism (PDH). Twenty-one dogs with PDH were prospectively evaluated using thoracic radiography, arterial blood gas analysis, and bone phase and pulmonary perfusion scintigraphy (using 99mTc-macro-aggregated albumin [99mTc-MAA]). The radiographs and bone and perfusion studies were evaluated subjectively. An averaged quantitative count density ratio was calculated between the thorax and cranial thoraco-lumbar vertebrae from lateral thoracic 99mTc-MDP images. Thoracic:vertebral ratios were calculated using 99mTc-MDP studies from 21 control dogs. The thoracic:vertebral ratios were compared between the 2 groups (PDH and control). The mean age (+/-SD) of the 21 PDH dogs was 10.2 (+/-3) years, whereas the mean age of the control group was 9.8 (+/-3) years. Seven of the 21 dogs with PDH were hypoxemic (defined as an arterial partial pressure of oxygen [PaO2] < 80 mm Hg) with an average PaO2 (+/-SD) of 62 (+/-15) mm Hg. Of the 7 hypoxemic dogs, 2 were found to have pulmonary mineralization based on bone scintigraphic images. Pulmonary perfusion abnormalities were not identified using 99mTc-MAA in any of the 21 PDH dogs. Six PDH dogs had an abnormal interstitial pulmonary pattern and 5 of these dogs were hypoxemic. The average quantitative thoracic:vertebral ratio was not significantly different between the PDH and control dogs (0.5 +/- 0.4 versus 0.4 +/- 0.1, P = .16). Causes of hypoxemia other than pulmonary thromboembolism should be considered in dogs with PDH. Pulmonary mineralization may contribute to hypoxemia in dogs with PDH.

Radiolabeled l-Lysine for Tumor Imaging

The aims of this study were to label the versatile amino acid l-lysine with (99m)Tc using 2,3-dimercapto-succinic acid (DMSA) as a chelator, and to assess its tumor imaging feasibility under in vivo and in vitro conditions, and finally to determine the subcellular biodistribution of this radiopharmaceutical. DMSA-l-lysine was chemically synthesized and labeled with sodium pertechnetate. Nuclear magnetic resonance (NMR) and mass spectral analysis of DMSA-l-lysine were conducted. Radiochemical purity was determined by thin-layer chromatography (TLC) and paper chromatography. Cellular uptake, competition and subcellular localization studies were performed in rat breast cancer cells (13762). In vivo studies of planar imaging and biodistribution studies were performed on female Fischer 344 rats. Medical Internal Radiation Dose (MIRD) dosimetry estimates were calculated. Radiochemical purity (determined by radio-TLC and high-performance liquid chromatography) of these compounds was >95%. (99m)Tc-DMSA-l-lysine showed good uptake in in vitro cell culture assays and uptake was reduced in competition studies. (99m)Tc-DMSA-l-lysine accumulates in the nucleus as much as in the cytoplasm and it was also shown that accumulation of the (99m)Tc-DMSA-l-lysine in the nucleus increases as a function of a time. There was an increase in tumor-to-blood and tumor-to-muscle count density ratios. Tumor/background ratios were 5.75 at 1 hour and 6.87 at 2 hours. In vivo tissue distribution studies revealed that radiation dosimetry of blood-forming organs were within radiation dose limits. DMSA-l-lysine kits can be labeled with (99m)Tc easily and efficiently, with high radiochemical purity and cost-effectiveness. In vitro cellular uptake and scintigraphic imaging studies demonstrated the pharmacokinetic distribution and feasibility of using (99m)Tc-DMSA-l-lysine for tumor imaging.

Targeted functional imaging of estrogen receptors with 99mTc-GAP-EDL

To evaluate the feasibility of using (99m)Tc-glutamate peptide-estradiol in functional imaging of estrogen receptor-positive [ER(+)] diseases. 3-Aminoethyl estradiol (EDL) was conjugated to glutamate peptide (GAP) to yield GAP-EDL. Cellular uptake studies of (99m)Tc-GAP-EDL were conducted in ER(+) cell lines (MCF-7, 13762 and T47D). To demonstrate whether GAP-EDL increases MAP kinase activation, Western blot analysis of GAP-EDL was performed in 13762 cells. Biodistribution was conducted in nine rats with 13762 breast tumors at 0.5-4 h. Each rat was administered (99m)Tc-GAP-EDL. Two animal models (rats and rabbits) were created to ascertain whether tumor uptake of (99m)Tc-GAP-EDL was via an ER-mediated process. In the tumor model, breast tumor-bearing rats were pretreated with diethylstilbestrol (DES) 1 h prior to receiving (99m)Tc-GAP-EDL. In the endometriosis model, part of the rabbit uterine tissue was dissected and grafted to the peritoneal wall. The rabbit was administered with (99m)Tc-GAP-EDL. There was a 10-40% reduction in uptake of (99m)Tc-GAP-EDL in cells treated with DES or tamoxifen compared with untreated cells. Western blot analysis showed an ERK1/2 phosphorylation process with GAP-EDL. Biodistribution studies showed that tumor uptake and tumor-to-muscle count density ratio in (99m)Tc-GAP-EDL groups were significantly higher than those in (99m)Tc-GAP groups at 4 h. Among (99m)Tc-GAP-EDL groups, region of interest analysis of images showed that tumor-to muscle ratios were decreased in blocking groups. In the endometriosis model, the grafted uterine tissue could be visualized by (99m)Tc-GAP-EDL. Cellular or tumor uptake of (99m)Tc-GAP-EDL occurs via an ER-mediated process. (99m)Tc-GAP-EDL is a useful agent for imaging functional ER(+) disease.

PET and Planar Imaging of Tumor Hypoxia With Labeled Metronidazole

This study was aimed to develop 99mTc- and 68Ga-labeled metronidazole (MN) using ethylenedicysteine (EC) as a chelator and evaluate their potential use to assess tumor hypoxia. EC-MN was labeled with 99mTc in the presence of tin (II) chloride. Labeling EC-MN with 68Ga was achieved by adding 68GaCl3 (2 mCi with 3.4 microg cold GaCl3). In vitro cellular uptakes of 99mTc- and 68Ga-EC-MN were obtained in various types of tumor cells at 0.5-4 hours. Tissue distribution and PET imaging of 99mTc and 68Ga-EC-MN were evaluated in breast tumor-bearing rats at 0.5-4 hours. Tumor oxygen tension was measured using an oxygen probe. There were similar cellular uptakes (2-10%) between 99mTc- and 68Ga-EC-MN at 0.5-4 hours. In vivo biodistribution of 99mTc- and 68Ga-EC-MN in breast tumor-bearing rats showed increased tumor-to-blood and tumor-to-muscle count density ratios as a function of time. Positron emission tomography images confirmed that the tumors could be visualized clearly with 68Ga-EC-MN. Oxygen tension in tumor tissue was determined to be 6-10 mm Hg compared with 40-50 mm Hg in normal muscle tissue. The results indicated that it is feasible to use 99mTc- and 68Ga-EC-MN for assessment of tumor hypoxia. These agents may be useful in selecting and evaluating cancer therapy.

99mTc-EC-Guanine: Synthesis, Biodistribution, and Tumor Imaging in Animals

DNA markers are useful in assessing cell proliferation. The purpose of this study was to synthesize (99m)Tc-ethylenedicysteine-guanine (EC-Guan) for evaluation of cell proliferation. Tumor cells were incubated with (99m)Tc-EC-Guan for cell cycle analysis. Prostate tumor cells that were overexpressing the HSV thymidine kinase gene, or various tumor cells were incubated with (99m)Tc-EC-Guan at 0.5-2 h. Thymidine incorporation assays were performed in lung cancer cells incubated with EC-Guan at 0.1-1 mg/well. Tissue distribution, autoradiography, and planar scintigraphy of (99m)Tc-EC-Guan and (99m)Tc-EC (control) were determined in tumor-bearing rodents at 0.5-4 h. Cell culture assays indicated that EC-Guan was incorporated in DNA, and there was no significant uptake difference between HSVTK overexpressed and normal groups. Biodistribution and scintigraphic imaging studies of (99m)Tc-EC-Guan showed increased tumor/tissue count density ratios as a function of time. Our results indicate that (99m)Tc-EC-Guan may be useful as a tumor proliferation imaging agent.

Iodine toxicity in a plant-solution system with and without humic acid

Aqueous iodine (I2(aq)) is a potent disinfectant that is being evaluated as a soil sanitizer for agricultural fields and a water purification treatment for the International Space Station. Rice (Oryza sativa L.) plants were grown in solution culture containing different I compounds at approximately 0, 18, or 30 μM total I [I2(aq) + iodide (I−)] consisting of 0, 6, and 20 μM I as I2(aq), respectively. In addition, humic acid (HA) was added to half the treatments. Most I2(aq) was electrochemically reduced to the endpoint metabolite I− within 24 h with HA promoting the response. Plants receiving the highest dose of I2(aq), particularly those in treatments without HA, had the least growth and the greatest biomass I concentrations. Roots from both I2(aq) treatments without HA were periodically sampled for bacteria. Viable and direct caints of bacterial cell density declined with increasing I2(aq) concentrations within the first hour after treatment application. However, cell densities recovered within 96 hours and eventually surpassed the control treatment cell density. Additionally, the resulting high viable: direct count density ratio suggests that opportunistic species likely dominated the post I2(aq) environment.

The effect of imaging time, radiopharmaceutical, full fat milk and water on interfering extra-cardiac activity in myocardial perfusion single photon emission computed tomography

Extra-cardiac activity can interfere with observer interpretation of myocardial perfusion single photon emission computed tomography (SPECT) images. Fatty meals and drinks to reduce interference have been tested; however, a simple study of delayed imaging with (99m)Tc-tetrofosmin and (99m)Tc-sestamibi has not been specifically addressed. The aim was to quantify the effects of imaging time, radiopharmaceutical and oral administration of full fat milk and water on interfering activity. Myocardial perfusion SPECT images were acquired using either tetrofosmin or sestamibi. Patients were imaged at 0.5, 1 or 2 h post-injection (tetrofosmin, 59; sestamibi, 72). Additional groups of patients were imaged either with or without milk (tetrofosmin, 54; sestamibi, 45) and with milk and water (sestamibi, 30). A myocardial region was drawn on the anterior projection and a thin adjacent extra-cardiac region was generated automatically. The count density ratio was calculated and validated with a trial of five observers. A decreasing ratio correlated significantly with observer rank of increasing interference with SPECT image interpretation (r=0.95, P=0.001). The ratio improved significantly as the imaging time increased for both tetrofosmin and sestamibi groups (P<0.05). The groups given milk or milk plus water showed no significant improvement against control groups (P > or = 0.2). There was no significant difference between tetrofosmin and sestamibi at any time point (P > or = 0.4). Image interpretation may be improved by delayed imaging for tetrofosmin and sestamibi. However, in contrast with common practice, the administration of milk or water appears to be of no clinical value compared with delayed imaging, and there is no significant difference between interfering activity from tetrofosmin and sestamibi.

The effect of imaging time, radiopharmaceutical and milk on extra-cardiac activity in myocardial perfusion SPECT

Background and aim: Extra-cardiac activity can interfere with the interpretation of myocardial perfusion SPECT images. Fatty meals to clear hepatobiliary uptake have been attempted. However, the simple solution of delayed imaging has not been studied. The aim was to quantify the effects of imaging time, oral administration of full fat milk and radiopharmaceutical on interfering activity. Method: Myocardial perfusion SPECT images were acquired using either 99mTc tetrofosmin or sestamibi. Patients were imaged at 30 min, 1 h or 2 h post-injection (tetrofosmin=72, sestamibi=59). A further set of patients was imaged either with or without milk (tetrofosmin=54, sestamibi=45). A myocardial region was drawn on the anterior projection and an extra-cardiac region automatically generated. The count density ratio was calculated and validated with a trial of 5 observers. A decreasing ratio correlated significantly with observer rank of increasing interference with SPECT image interpretation (r=0.95, P=0.001). Results: Results are shown in Table 1. The ratio improved significantly as the imaging time increased for both tetrofosmin and sestamibi groups (P<0.05). Milk made no significant improvement (P=0.2). There was no significant difference between tetrofosmin and sestamibi (P=0.4).Table 1: Results for myocardial perfusion SPECT images acquired by using either 99mTc tetrofosmin or sestamibiConclusion: Image interpretation may be improved by delayed imaging for tetrofosmin and sestamibi. However, in contrast to common practice administration of milk is of no clinical value.

Salivary gland involvement in chronic pancreatitis of various etiologies

Objective Both the pancreas and salivary glands show many histological and functional similarities. Recently, autoimmune pathogenesis has been postulated in some chronic pancreatitis cases. To examine whether a cell-mediated phenomenon involving the pancreas has a secondary effect on the salivary glands, we assessed the frequency of salivary gland dysfunction in patients with chronic pancreatitis of various etiologies. Methods Function of the salivary glands was examined by sialochemistry and salivary gland scintigraphy in patients with chronic pancreatitis (n = 33), Sjogren’s syndrome (n = 45), and controls (n = 28). Etiologies of chronic pancreatitis were alcoholic (19 cases), idiopathic (seven cases), and autoimmune (seven cases). Concentrations of Na+, amylase, and β2-microglobulin in saliva were investigated. In submandibular and parotid gland scintigraphy, time-activity curves were generated, and the ratios of peak count density and washout were calculated. Results Concentrations of Na+ in saliva of patients with idiopathic chronic pancreatitis and of β2-microglobulin in saliva of patients with idiopathic and autoimmune chronic pancreatitis were significantly elevated than those of the control group. In submandibular and parotid gland scintigraphy, the peak count density ratio of patients with all chronic pancreatitis and washout ratio of patients with alcoholic and idiopathic chronic pancreatitis were significantly lower than those of the control group. Conclusions Salivary gland function was frequently impaired in the course of chronic pancreatitis of various etiologies. Salivary gland dysfunction might be the result of a common pathophysiological effect of alcohol in patients with alcoholic chronic pancreatitis and the aggressive immune mechanism against the pancreatic and the salivary ducts in patients with autoimmune and idiopathic chronic pancreatitis.

Salivary gland involvement in chronic pancreatitis of various etiologies

Both the pancreas and salivary glands show many histological and functional similarities. Recently, autoimmune pathogenesis has been postulated in some chronic pancreatitis cases. To examine whether a cell-mediated phenomenon involving the pancreas has a secondary effect on the salivary glands, we assessed the frequency of salivary gland dysfunction in patients with chronic pancreatitis of various etiologies. Function of the salivary glands was examined by sialochemistry and salivary gland scintigraphy in patients with chronic pancreatitis (n = 33), Sjogren's syndrome (n = 45), and controls (n = 28). Etiologies of chronic pancreatitis were alcoholic (19 cases), idiopathic (seven cases), and autoimmune (seven cases). Concentrations of Na+, amylase, and beta2-microglobulin in saliva were investigated. In submandibular and parotid gland scintigraphy, time-activity curves were generated, and the ratios of peak count density and washout were calculated. Concentrations of Na+ in saliva of patients with idiopathic chronic pancreatitis and of beta2-microglobulin in saliva of patients with idiopathic and autoimmune chronic pancreatitis were significantly elevated than those of the control group. In submandibular and parotid gland scintigraphy, the peak count density ratio of patients with all chronic pancreatitis and washout ratio of patients with alcoholic and idiopathic chronic pancreatitis were significantly lower than those of the control group. Salivary gland function was frequently impaired in the course of chronic pancreatitis of various etiologies. Salivary gland dysfunction might be the result of a common pathophysiological effect of alcohol in patients with alcoholic chronic pancreatitis and the aggressive immune mechanism against the pancreatic and the salivary ducts in patients with autoimmune and idiopathic chronic pancreatitis.

Detection of acute postoperative mediastinitis in mice using (99m)Tc-liposomes.

To evaluate the usefulness of size-modified (99m)Tc-labeled liposomes for the detection of acute postoperative mediastinitis in a mouse model. Fourteen mice underwent low-neck collar incision and had sterile abscesses induced in mediastinum with turpentine. Ten of these animals were injected intravenously with anionic liposomes of 516 +/- 20 nm containing poly(ethylene)glycol labeled with (99m)Tc; the remaining four mice were injected with (67)Ga citrate and used as positive controls. In addition, eight mice either underwent the same surgical procedure but without turpentine (n = 4) or were not operated (n = 4). These were used as negative controls. Therefore, scintigraphy using (99m)Tc-liposomes was performed in eighteen and (67)Ga citrate in four mice. Target area of interest was outlined, and target to background count density ratio and percentage-injected dose were measured. Significant accumulation of radiolabeled liposomes was observed at sites of inflammation within 1 hour in abscess-bearing animals. This correlated well with the findings of the lower quality (contrast) of (67)Ga images at 24 and 48 hours. The radiopharmaceutical did not significantly accumulate in the mediastinum of negative control animals. (99m)Tc-liposomes (size modified) may prove useful nonspecific agent for the early diagnosis of postoperative mediastinitis.

Assessment of antiangiogenic effect using 99mTc-EC-endostatin.

Tumor vascular density may provide a prognostic indicator of metastatic potential or survival. The purpose of this study was to develop 99mTc-ethylenedicysteine-endostatin (99mTc-EC-endostatin) for the evaluation of anti-angiogenesis therapy. 99mTc-EC-endostatin was prepared by conjugating ethylenedicysteine (EC) to endostatin, followed by adding pertechnetate and tin chloride. Radiochemical purity was > 95%. In vitro cell viability, affinity and TUNEL assays were performed. Tissue distribution and planar imaging of radiolabeled endostatin were determined in tumor-bearing rats. To assess anti-angiogenic treatment response, rats were treated with endostatin, paclitaxel and saline, followed by imaging with 99mTc-EC-endostatin. Tumor response to endostatin therapy in tumor-bearing animal models was assessed by correlating tumor uptake dose with microvessel density, VEGF, bFGF and IL-8 expression during endostatin therapy. In vitro cell viability and TUNEL assays indicated no marked difference between EC-endostatin and endostatin. Cellular uptake assay suggests that endostatin binds to endostatin receptor. Biodistribution of 99mTc-EC-endostatin in tumor-bearing rats showed increased tumor-to-tissue count density ratios as a function of time. Tumor uptake (%ID/g) of 99mTc-EC-endostatin was 0.2-0.5. Planar images confirmed that the tumors could be visualized clearly with 99mTc-EC-endostatin. The optimal time for imaging using radiolabeled endostatin was 2 hrs. 99mTc-EC-endostatin could assess treatment response. There was a correlation between tumor uptake and cellular targets expression. The results indicate that it is feasible to use 99mTc-EC-endostatin to assess efficiency of anti-angiogenesis therapy.

Technetium-99m tetrofosmin chest imaging related to p-glycoprotein expression for predicting the response with paclitaxel-based chemotherapy for non-small cell lung cancer.

Our aim was to use technetium-99m tetrofosmin (Tc-TF) uptake in non-small cell lung cancer (NSCLC) for predicting the chemotherapeutic response of NSCLC to paclitaxel and to compare the results with the expression of multidrug resistance (MDR) - P-glycoprotein (Pgp). Twenty patients with advanced NSCLC were enrolled in this study before chemotherapy with paclitaxel. Tc-TF chest imaging was performed to calculate early and delayed tumor-to-normal lung (T/NL) count-density ratios, as well as washout indexes (WIs). Immunohistochemical analyses were performed on multiple nonconsecutive sections of the biopsy specimens to detect Pgp expression. The response to chemotherapy was evaluated by clinical and radiological methods in the third month after completion of treatment. The early and delayed T/NL count-density ratios of patients with good response were significantly higher than those of patients with poor response (p <0.05). However, no significant difference in WI between the two groups of patients was found (p > 0.05). A significantly higher incidence of good response was found in patients with negative Pgp expression (100%) than in patients with positive Pgp expression (40%) (p <0.05). Significantly higher early and delayed T/NL count-density ratios as well as decreased WIs were found in patients with negative Pgp expression than in patients with positive Pgp expression. However, other prognostic factors (age, sex, body weight loss, performance status, tumor stage, and tumor cell type) were not significantly different between the patients with good response and those with poor response. Because Tc-TF chest images can correctly represent the expression of Pgp in NSCLC, it can accurately predict the chemotherapeutic response to paclitaxel.

99MTc‐C‐Deoxyglucose: Synthesis, cellular uptake, biodistribution and scintigraphic imaging

AbstractThis study was aimed to synthesize 99mTc‐ethylenedicysteine‐deoxyglucose (EC‐DG) and determine in vitro cellular uptake and in vivo biodistribution and imaging feasibility in tumor‐bearing rodents. Experimental: Synthesis of EC‐deoxyglucose (EC‐DG) was carried out by reacting EC with glucosamine using carbodiimide as a coupling agent. After dialysis the chemical yield was 70%. By adding pertechnetate in the presence of tin chloride (0.1 mg) to EC‐DG (20–100 mg), the radiochemical yield was achieved 70–100% as determined by radio‐TLC. Hexokinase assays of EC‐DG were performed at UV wavelength 340 nm. In vitro cellular uptake assay was conducted by using a human lung cancer cell line (A549). Each well containing 80,000 cells was added d‐ and 1‐glucose (1 mg and 2.0 mg) along with 2μCi of 99mTc‐EC‐deoxyglucose and 18F‐FDG. After incubation, the cells were washed. A gamma counter counted the cells. To determine whether blood glucose level could be induced by EC‐DG and suppressed by insulin, normal Fischer 344 rats were fasting overnight prior to the experiments. The baseline of blood glucose level (mg/dl) was measured by a glucose meter. Each rat was administered 1.2 mmol/kg (i.v.) of glucosamine, FDG and EC‐deoxyglucose. In a separate experiment, rats were administered EC‐DG and FDG, and then insulin (5 units) was administered after 30 minutes. Blood samples were collected from tail vein every 30‐min up to 6 hrs post‐administration. For breast tumor‐bearing animal model, female Fischer 344 rats (150±25 g) were inoculated with tumor cells (106 cells/rat, s.c. derived from DMBA‐induced tumor cell line) into the hind legs. For lung tumor‐bearing animal model, each athymic nude mouse (20–25g) was inoculated (s.c.) with 0.1 ml of human lung tumor cells from the A549 tumor cell line suspension into the hind legs. Studies performed 17 to 21 days after implantation when tumors reached approximately 0.6–1.0 cm diameter. Each animal was injected (i.v.) with 10 μCi (per rat) or 1 μCi (per mouse) of 99mTc‐EC, 99mTc‐EC‐DG and FDG (standard) (n=3/time point). The injected mass of 99mTc‐EC‐DG was 1 mg per rodent. Following administration of the radiotracers, the rodents were sacrificed at 0.5–4 hrs and the selected tissues were excised, weighed and counted for radioactivity. Scintigraphic images were obtained 0.5–4 hours after i.v. injection of 100 μCi of the radiotracer. Results: EC‐DG showed positive hexokinase assay. By adding d‐glucose, a decreased uptake of 99mTc‐EC‐DG and 18F‐FDG was observed. Blood glucose level was induced by glucosamine, FDG and EC‐DG. This increased blood glucose level could be suppressed by co‐administration of EC‐DG or FDG and insulin. Compare to 99mTc‐EC and free 99mTc, tumor‐to tissue count density ratios increased as a function of time in 99mTc‐EC‐DG group. Brain and heart uptake was less than FDG. Tumor/brain and tumor/muscle ratios were higher than FDG. Tumor could be visualized well when compared to 99mTc‐EC (control group).

Frequency of Pulmonary Mineralization and Hypoxemia in 21 Dogs with Pituitary‐Dependent Hyperadrenocorticism

The purpose of this study was to determine the frequency of hypoxemia and pulmonary mineralization using99mTc‐methylene diphosphonate (99mTc‐MDP) in dogs with pituitary‐dependent hyperadrenocorticism (PDH). Twenty‐one dogs with PDH were pro‐spectively evaluated using thoracic radiography, arterial blood gas analysis, and bone phase and pulmonary perfusion scintigraphy (using99mTc‐macro‐aggregated albumin [99mTc‐MAA]). The radiographs and bone and perfusion studies were evaluated subjectively. An averaged quantitative count density ratio was calculated between the thorax and cranial thoraco‐lumbar vertebrae from lateral thoracic99mTc‐MDP images. Thoracic: vertebral ratios were calculated using99mTc‐MDP studies from 21 control dogs. The thoracic: vertebral ratios were compared between the 2 groups (PDH and control). The mean age (±SD) of the 21 PDH dogs was 10.2 (±3) years, whereas the mean age of the control group was 9.8 (±3) years. Seven of the 21 dogs with PDH were hypoxemic (denned as an arterial partial pressure of oxygen [PaO2] &lt;80 mm Hg) with an average PaO2(±SD) of 62 (±15) mm Hg. Of the 7 hypoxemic dogs, 2 were found to have pulmonary mineralization based on bone scintigraphic images. Pulmonary perfusion abnormalities were not identified using99mTc‐MAA in any of the 21 PDH dogs. Six PDH dogs had an abnormal interstitial pulmonary pattern and 5 of these dogs were hypoxemic. The average quantitative thoracic: vertebral ratio was not significantly different between the PDH and control dogs (0.5 ± 0.4 versus 0.4 ± 0.1,P= .16). Causes of hypoxemia other than pulmonary thromboembolism should be considered in dogs with PDH. Pulmonary mineralization may contribute to hypoxemia in dogs with PDH.

Complementary roles of antibody affinity and specificity for in vivo diagnostic cardiovascular targeting: How specific is antimyosin for irreversible myocardial damage?

Background. Identification of irreversible myocyte injury with antimyosin antibody imaging depends on both antibody specificity and affinity. To characterize the role of antibody affinity, we performed studies in dogs with acute coronary occlusion followed by reperfusion using 3 monoclonal antimyosin antibodies with different affinities. Methods and Results. Dogs with experimental reperfused acute myocardial infarction were injected with 2 high-affinity radiolabeled monoclonal antimyosin Fab fragments (R11D10 and 2G42D7), 1 low-affinity antimyosin Fab (3H31E6), and a nonspecific Fab. The left lateral gamma images at 5 H were used to assess the infarct (I) to blood (B) region of interest (ROI) count density ratios by computer planimetry. All infarcts were confirmed by in vivo imaging with 201TI for perfusion defects as well as by postmortem histochemical staining. The mean I/B ROI (± standard deviation [SD]) for R11D10 (1.701 ± 0.376) was not significantly different from that of 2G42D7 (1.501 ± 0.267, P = NS), but both were significantly greater than that of 3H31E6 Fab (0.85 ± 0.12, P = .0001 and .0012, respectively). The I/B ROI of 3H31E6 Fab was similar to that of nonspecific Fab (0.75 to 0.77 range). Radiolabeled R11D10 and 2G42D7 were unequivocally positive by gamma imaging in all infarcts by 5 H. No infarcts were visualized with 3H31E6 or nonspecific Fab. Conclusions. The low-affinity antibody, despite its specificity for cardiac myosin, cannot be used to image the infarct zone. Therefore immunoscintigraphic diagnosis of irreversible myocardial injury with radiolabeled antimyosin Fab is doubly specific because in vivo visualization required both specificity and high enough affinity of the antibody.

99mTc-ethylenedicysteine-folate: a new tumor imaging agent. Synthesis, labeling and evaluation in animals.

It is known that membrane folic acid receptors are responsible for cellular accumulation of folate and folate analogs such as methotrexate and overexpressed on various tumor cells. However, these receptors are highly restricted in normal differentiated tissues. Results of limited in vitro and in vivo animal studies suggest that folate receptors could be a potential target for tumor imaging. This study aimed to develop a 99mTc-labeled folic acid using ethylenedicysteine (EC) as a chelator and evaluate its labeling efficiency and potential use as a tumor seeking agent. Tissue distribution of 99mTc-EC-folate was determined in breast tumor-bearing rats at 20 min, 1, 2, and 4 h (n = 3/time interval, 370 KBq/rat, i.v.). Blocking study was employed to determine receptor-mediated process; 99mTc-EC-folate was co-administrated with 50 and 150 mumol/kg of cold folic acid to tumor-bearing rats. Planar imaging and whole-body autoradiograms were performed. The data was compared to that using 99mTc-EC (control). In animal studies, tumor/blood count density ratios at 20 min-4 h increased from 0.81 +/- 0.09 to 1.23 +/- 0.13 with 99mTc-EC-folate. Conversely, these values showed time-dependent decrease from 0.77 +/- 0.32 to 0.65 +/- 0.01 with 99mTc-EC in the same time period. Tumor/muscle and tumor/blood count density ratios significantly decreased with folic acid co-administrations. Planar images and autoradiograms confirmed that the tumors could be visualized clearly with 99mTc-EC-folate.