M Pourdehnad

University of Pennsylvania, Filadelfia, Pennsylvania, United States

Are you M Pourdehnad?

Claim your profile

Publications (19)59.34 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The main aim of this research was to demonstrate that the cortical and subcortical grey matter hypometabolism as revealed by fluorine-18 fluorodesoxyglucose-positron emission tomography ((18)F-FDG-PET) imaging in brain tumors is related to associated edema as demonstrated by magnetic resonance imaging (MRI). This in turn enhances the ability to assess disease activity in the tumor and the degree of loss of cerebral function in the adjacent and distant structures. We evaluated brain T1 and T2 weighted MRI and (18)F-FDG-PET scans of 29 patients (19 adult, 10 pediatric) with history of brain tumor. Tumor histology types included 21 gliomas, 1 melanoma, 1 primitive neuroectodermal tumor, 3 medulloblastomas and 3 ependymomas. The majority of scans were performed within the same week (94% <1 month. The extent of hypo and hypermetabolism was assessed on the (18)F-FDG-PET scans. A template of 12 regions of interest (ROI) was applied and the laterality indices of the regional counts (signal intensity) were computed. Extent of edema, enhancement, and anatomical change were assessed on the MRI scans. Extent of edema in the same ROI was evaluated by a 6-point semiquantitative scale and laterality indices were generated. Metabolic activity of the grey matter was correlated with the extent of edema using these indices. In all cases where edema was present, significant hypometabolism was observed in the adjacent structures. Overall, there was a strong correlation between the extent of edema and severity of hypometabolism (r=0.92, P=0.01). This was true regardless of the location of edema, whether there was history of radiation treatment (r=0.91, P=0.03), or not (r=0.97, P=0.17). In conclusion, edema independent of underlying variables appeared to contribute significantly to cortical and sub-cortical grey matter hypometabolism observed in patients with brain tumors. This would indicate that brain tumors can be successfully assessed by (18)F-FDG-PET and therefore the efforts for utilizing other tracers may not be justified.
    Hellenic journal of nuclear medicine 09/2011; 14(3):219-23. · 0.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to evaluate the significance of increased uptake of 18F-fluorodeoxyglucose (FDG) in patients with malignant lymphoma (ML) studied by positron emission tomography (PET). A total of 1,120 consecutive scans carried out in 848 patients were reviewed; all patients had a diagnosis of ML [574 non-Hodgkin's lymphoma (NHL) and 274 Hodgkin's disease (HD)] and were studied at completion of therapy, for suspected recurrence or during follow-up. PET was carried out after intravenous injection of 370 MBq of 18F-FDG; images were recorded after 60-90 min. Patients were selected whose reports indicated areas of increased FDG uptake. PET findings were considered positive for lymphomatous localisation when uptake occurred at sites of previous disease, in asymmetrical lymph nodes or in nodes unlikely to be affected by inflammation (mediastinal, except for hilar, and abdominal). PET findings were adjudged negative for neoplastic localisations in the following instances: physiological uptake (urinary, muscular, thymic or gastrointestinal in patients without MALT), symmetrical nodal uptake, uptake in lesions unrelated to lymphoma that had already been identified by other imaging methods at the time of PET scan, uptake at sites atypical for lymphoma, very low uptake and non-focal uptake. PET findings were compared with the results of other diagnostic procedures (including CT and ultrasound), biopsy findings and follow-up data. Overall, 354 scans (in 256 patients) showed increased FDG uptake (244 scans in NHL and 110 in HD): in 286 cases, FDG uptake was considered pathological and indicative of ML, in 41 cases the findings were described as uncertain or equivocal and in 37 cases, FDG uptake was considered unrelated to ML (in ten scans, concurrent findings of abnormal FDG uptake attributed to ML and uptake assigned to other causes were obtained) . Of the 286 patients with positive PET findings, 274 (95.8%) were found to have residual or recurrent ML (i.e. true positives). Four of the 41 patients with inconclusive findings turned out to have ML, while in 13 patients, pathological processes other than ML could be identified as the cause of FDG uptake. ML was excluded in all patients with findings reported as non-pathological (100% true-negative rate). Therefore, the false-positive rate in our series was about 5%. The main cause of increased FDG uptake mimicking ML was inflammation. Our data confirm that 18F-FDG-PET has very high but not absolute specificity for ML. As already suggested, increased FDG uptake may also be observed in patients without active disease; in most cases, however, non-pathological FDG accumulation is properly identified. Less frequently, inconclusive scans are encountered; these cases are usually caused by inflammation, which subsequently resolves.
    European journal of nuclear medicine and molecular imaging 08/2005; 32(7):749-56. DOI:10.1007/s00259-004-1748-x · 5.38 Impact Factor
  • Andrew B Newberg · Janet Saffer · John Farrar · Michael Pourdehnad · Abass Alavi ·
    [Show abstract] [Hide abstract]
    ABSTRACT: To determine whether there is stability of cerebral blood flow (CBF) measures using single photon emission computed tomography (SPECT) imaging in healthy controls in a test-retest split-dose paradigm. Such a paradigm is frequently used in the clinical and research setting to assess various brain states. Five healthy volunteers underwent two brain SPECT scans after the administration of low and high doses of (99m)Tc-exametazime. The first SPECT scan was acquired approximately 30 min after the intravenous injection of approximately 259 MBq of (99m)Tc-exametazime. The second SPECT scan was acquired approximately 30 min after the intravenous injection of 925 MBq of (99m)Tc-exametazime. Both scans were acquired over approximately 30-45 min and the images were reconstructed using filtered backprojection, a low-pass filter and Chang's first-order attenuation correction. Values were obtained for regions of interest (ROIs) in major brain structures and normalized to whole brain activity. Counts on the second SPECT scan were also decay corrected for activity from the first scan. The results demonstrated a strong correlation between the low-dose and high-dose scans for all regions (r = 0.86, P<0.0001). Symmetries were preserved with a strong correlation between low-dose and high-dose scans (r = 0.70, P<0.0001). Finally, most regions demonstrated less than a 5% difference between the low-dose and high-dose scans. The results of this study demonstrate that the split-dose technique can be employed for clinical and research applications to measure CBF in different brain states using two SPECT scans on the same day.
    Nuclear Medicine Communications 05/2005; 26(5):475-8. DOI:10.1097/00006231-200505000-00013 · 1.67 Impact Factor
  • Roland Hustinx · Michael Pourdehnad · Bruno Kaschten · Abass Alavi ·
    [Show abstract] [Hide abstract]
    ABSTRACT: The exact incidence of true radiation necrosis is largely unknown. It is probably much less frequent than indicated by MR or CT findings. Differentiating radiation necrosis from recurrent tumor is a diagnostic challenge, however, and has important implications for the patient's management. Even though the first results were published 20 years ago, the total number of case studies using FDG-PET in this indication remains limited. Several reports are also hampered by methodologic limitations. The technique has been largely criticized, notably in articles that themselves were not completely free of methodological flaws. Overall however, FDG-PET seems to be a valuable clinical tool. As a general rule, suspicious lesions on MR imaging that show increased FDG uptake (ie, uptake equal to or great than that in normal cortex) are likely to represent tumor recurrence. Sensitivity is an issue, especially but not exclusively with low-grade gliomas. Although false-positive results may occur, specificity is usually high in routine clinical practice. Coregistration with MR imaging surely improves the diagnostic performances of FDG-PET because it helps delineate the suspicious area. Another important aspect is the prognostic value of FDG uptake, which is now well established. It seems clear that only the combination of FDG with a radiolabeled amino acid analogue (MET or a more recent fluorinated compound) can provide a comprehensive characterization of suspected brain tumor recurrence.
    Radiologic Clinics of North America 02/2005; 43(1):35-47. DOI:10.1016/j.rcl.2004.09.009 · 1.98 Impact Factor
  • Source
    Andrew B. Newberg · Michael Pourdehnad · Abass Alavi · Eugene G d'Aquili ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Meditative practices typically require several coordinated cognitive activities. This study measured changes in cerebral blood flow during "verbal" based meditation by Franciscan nuns involving the internal repetition of a particular phrase. These results are compared with those we previously described in eight Buddhist meditators who use a type of "visualization" technique. Three experienced practitioners of verbal meditation were injected via i.v. at rest with 260 MBq of Tc-99m HMPAO and scanned 30 min. later on a triple head SPECT camera for 45 min. Following the baseline scan, subjects meditated for approximately 40 min. at which time they were injected with 925 MBq of HMPAO while they continued to meditate for 10 min. more (total of 50 min. of meditation). The injection during meditation was designed not to disturb practice. Subjects were scanned 20 min. later for 30 min. Counts were obtained for regions of interest for major brain structures and normalized to whole-brain blood flow. Compared to baseline, mean verbal meditation scans showed increased blood flow in the prefrontal cortex (7.1%), inferior parietal lobes (6.8%), and inferior frontal lobes (9.0%). There was a strong inverse correlation between the blood flow, change in the prefrontal cortex and in the ipsilateral superior parietal lobe (p<.01). This study on a limited number of subjects demonstrated the feasibility of studying different types of meditation with neuroimaging techniques, suggested that several coordinated cognitive processes occur during meditation, and also raised important methodological issues.
    Perceptual and Motor Skills 11/2003; 97(2):625-30. DOI:10.2466/PMS.97.5.625-630 · 0.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The association of hyperglycaemia with reduced fluorodeoxyglucose (FDG) uptake by tumour cells is well established. Therefore, it is standard practice that all patients must fast for at least several hours prior to FDG positron emission tomography (PET) imaging. However, the effect of hyperglycaemia on FDG uptake by inflammatory and infectious lesions is unknown. The aim of this study was to investigate this important issue. For in vitro studies human mononuclear cells were isolated from 12 normal volunteers and FDG uptake was determined in medium containing differing concentrations of glucose. FDG uptake by human mesothelioma cells was also measured for comparison. For studies involving patients, 416 FDG PET scans of patients with confirmed malignancy (n=321) or benign lesions (n=95) were reviewed retrospectively. The relationship between serum glucose level and FDG uptake by the lesions was assessed utilizing the standardized uptake value (SUV) technique. In the in vitro studies, while FDG uptake by mesothelioma cells decreased as glucose concentration increased, there was no differential uptake of FDG uptake by mononuclear cells at glucose concentrations less than 250 mg x dl(-1). In clinical patients, FDG uptake by malignant lesions was slightly, but negatively affected by serum glucose level (r= -0.21, P<0.01) (glucose range 49-187 mg x dl(-1)). In contrast, FDG uptake by inflammatory lesions was positively associated with serum glucose level (r=0.43, P<0.01) (glucose range 54-215 mg x dl(-1)). While the degree of FDG uptake is primarily influenced by the nature of the underlying lesion, serum glucose concentration appears to have a small effect on FDG uptake, which differs between malignant disorders and inflammatory processes. Our data suggest that below a certain level, elevated glucose concentration might not have a negative effect on FDG uptake in inflammatory cells, contrary to that observed in malignant disorders.
    Nuclear Medicine Communications 10/2001; 22(10):1123-8. DOI:10.1097/00006231-200110000-00011 · 1.67 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Anterior temporal lobectomy offers a high chance of seizure-free outcome in patients suffering from drug-refractory complex partial seizure (CPS) originating from the temporal lobe. Other than EEG, several functional and morphologic imaging methods are used to define the spatial seizure origin. The present study was undertaken to compare the merits of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET), magnetic resonance imaging (MRI) and single-voxel proton MR spectroscopy (MRS) for the lateralization of temporal lobe seizure foci. The clinical charts and imaging data of 43 consecutive CPS patients were reviewed. Based on surface EEG, 31 patients were classified with temporal lobe epilepsy (TLE; 25 lateralized, 6 not lateralized) and 12 with non-temporal lobe epilepsy. All were examined by FDG-PET, MRS and MRI within 6 weeks. FDG-PET and MRI were interpreted visually, while the N-acetyl-aspartate to creatine ratio was used for MRS interpretation. One FDG-PET scan was invalid due to seizure activity post injection. The MR spectra could not be evaluated in five cases bilaterally and three cases unilaterally for technical reasons. A total of 15 patients underwent anterior temporal lobectomy. All showed a beneficial postoperative outcome. When the proportions of agreement between FDG-PET (0.77), MRI (0.58) and MRS (0.56) and surface EEG in TLE cases were compared, there were no significant differences (P>0.10). However, FDG-PET showed a significantly higher agreement (0.93) than MRI (0.60; P=0.03) with the side of successful temporal lobectomy. The concordance of MRS with the side of successful temporal lobectomy was intermediate (0.75). When the results of functional and morphologic imaging were combined, no significant differences were found between the rates of agreement of FDG-PET/MRI and MRS/MRI with EEG (0.80 vs 0.68; P=0.50) and with the side of successful temporal lobectomy (0.87 vs 0.92; P=0.50) in TLE cases. However, MRS/MRI showed significantly more lateralized temporal lobe abnormalities in non-temporal lobe epilepsy cases than FDG-PET/MRI (0.90 vs. 0.17; P<0.01). Although FDG-PET seems to be the most reliable and stable method for this purpose, we conclude that in TLE cases it may be justified to perform MRS, which is less expensive, faster and has no radiation exposure, in combination with MRI before FDG-PET, since FDG-PET offers little additional diagnostic information if MRS and MRI indicate the same seizure focus lateralization.
    European Journal of Nuclear Medicine 10/2001; 28(10):1529-40. DOI:10.1007/s002590100602 · 5.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The aim of this study was to investigate the difference in the rates of FDG uptake between malignant and inflammatory cells and processes. In vitro studies: (18)F-FDG uptake by different tumor cell lines (human mesothelioma [REN]; rat mesothelioma [II45]; mice melanoma [B18F10]; mice mesothelioma [AB12]; human myeloma [GM1500]; and human ovarian cancer [SKOV3]) and peripheral blood mononuclear cells isolated from 8 healthy human volunteers was measured 20 and 60 min after FDG was added into growth medium. Animal studies: II45 cells were implanted into the left flank of rats (n = 5) and a focal inflammatory reaction (mechanical irritation) was generated in the right flank. PET images at 45 and 90 min after injection of FDG were obtained and standardized uptake values (SUVs) were determined. Patient studies: Seventy-six patients who had dual time FDG PET scans were retrospectively analyzed. All results were expressed as the percentage change in SUV of the later time image from that of the earlier time (mean +/- SD). In vitro studies: Except for the SKOV3 cell line, which had only minimally increased FDG uptake (+10% +/- 26%; P > 0.3), all other tumor cell lines tested showed significantly increased FDG uptake over time (GM1500, +59% +/- 19%; B18F10, +81% +/- 15%; AB12, 93% +/- 21%; II45, +161% +/- 21%; REN, +198% +/- 48%; P < 0.01 for all). By contrast, FDG uptake in mononuclear cells was decreased in 7 of 8 donors. Animal studies: SUVs of tumors from 90-min images were significantly higher than those from 45-min images (+18% +/- 8%; P < 0.01), whereas the SUVs of inflammatory lesions decreased over time (-17% +/- 13% of the early images; P < 0.05). Clinical studies: The SUVs of delayed images from the known malignant lesions compared with those of earlier scans increased over time (+19.18% +/- 9.58%; n = 31; P < 0.001; 95% confidence interval, 15.8%-22.6%). By contrast, the SUVs of benign lung nodules decreased slightly over time (-6.3% +/- 8.1%; n = 12; P < 0.05; 95% confidence interval, -10.9% to -1.7%). The SUV of inflammatory lesions caused by radiation therapy (+1.16% +/- 7.23%; n = 8; P > 0.05; 95% confidence interval, -3.9%-6.2%) and the lesions of painful lower limb prostheses (+4.03% +/- 11.32%; n = 25; P > 0.05; 95% confidence interval, -0.4%-8.5%) remained stable over time. These preliminary data show that dual time imaging appears to be useful in distinguishing malignant from benign lesions. Further research is necessary to confirm these results.
    Journal of Nuclear Medicine 09/2001; 42(9):1412-7. · 6.16 Impact Factor
  • F Ponzo · HM Zhuang · FM Liu · M Pourdehnad · NV Ghesani · A Alavi ·

    Congress of the european association of nuclear medicine, Napoli, Italy; 08/2001
    [Show abstract] [Hide abstract]
    ABSTRACT: Fluorodeoxyglucose positron emission tomography (FDG PET) has been used extensively to detect and stage various cancers. However, normal variation and inflammatory lesions may lead to false-positive interpretations of PET findings. The authors report three cases of increased pelvic FDG uptake with differing origins. Although the findings are similar, a postpartum uterus, lymphoma, and a bleeding uterus caused pelvic FDG uptake in these patients. Interestingly, of these three patients, the patient with lymphoma had the lowest level of FDG uptake. Clinical correlation is needed for the accurate interpretation of FDG-PET findings.
    Clinical Nuclear Medicine 07/2001; 26(6):515-7. DOI:10.1097/00003072-200106000-00007 · 3.93 Impact Factor
  • H Zhuang · M Pourdehnad · A J Yamamoto · M D Rossman · A Alavi ·

    Clinical Nuclear Medicine 06/2001; 26(5):458. DOI:10.1097/00003072-200105000-00020 · 3.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study measured changes in regional cerebral blood flow (rCBF) during the complex cognitive task of meditation using single photon emission computed tomography. Eight experienced Tibetan Buddhist meditators were injected at baseline with 7 mCi HMPAO and scanned 20 min later for 45 min. The subjects then meditated for 1 h at which time they were injected with 25 mCi HMPAO and scanned 20 min later for 30 min. Values were obtained for regions of interest in major brain structures and normalized to whole brain activity. The percentage change between meditation and baseline was compared. Correlations between structures were also determined. Significantly increased rCBF (P<0.05) was observed in the cingulate gyrus, inferior and orbital frontal cortex, dorsolateral prefrontal cortex (DLPFC), and thalamus. The change in rCBF in the left DLPFC correlated negatively (P<0.05) with that in the left superior parietal lobe. Increased frontal rCBF may reflect focused concentration and thalamic increases overall increased cortical activity during meditation. The correlation between the DLPFC and the superior parietal lobe may reflect an altered sense of space experienced during meditation. These results suggest a complex rCBF pattern during the task of meditation.
    Psychiatry Research 04/2001; 106(2). DOI:10.1016/S0925-4927(01)00074-9 · 2.47 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to evaluate the feasibility of using 18F-FDG and PET for the detection of infection associated with lower limb arthroplasty. Seventy-four prostheses in 62 patients in whom infection was suspected after artificial hip or knee placement were studied with this technique. Images were obtained 60 min after an intravenous injection of FDG. The images were interpreted as positive for infection if tracer uptake was increased at the bone-prosthesis interface. A final diagnosis was made by surgical exploration or clinical follow-up for 1 y. PET results were compared with the follow-up outcome in all patients. The sensitivity, specificity, and accuracy of PET for detecting infection associated with knee prostheses were 90.9%, 72.0%, and 77.8%, respectively. The sensitivity, specificity, and accuracy of PET for detecting infection associated with hip prostheses were 90%, 89.3%, and 89.5%, respectively. Overall, the sensitivity was 90.5% and the specificity was 81.1% for detection of lower limb infections. FDG PET is a useful imaging modality for detecting infections associated with lower limb arthroplasty and is more accurate for detecting infections associated with hip prostheses than for detecting infections associated with knee prostheses.
    Journal of Nuclear Medicine 02/2001; 42(1):44-8. · 6.16 Impact Factor
  • H Zhuang · P Sinha · M Pourdehnad · P S Duarte · A J Yamamoto · A Alavi ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Liver metastasis is a common consequence of colorectal carcinoma. Early and accurate detection of liver metastasis is crucial for a decision about partial hepatectomy, which is considered a standard and potentially curative therapy in such a setting. The presence of extrahepatic metastases will exclude surgical resection as a therapeutic option. Positron emission tomography with fluorine-18-deoxyglucose (FDG-PET) has been successful in detecting and staging a variety of malignancies. The purpose of this study was to assess the utility of FDG-PET in the accurate detection of liver and distal metastases from colorectal cancer. The results of 80 PET and computed tomography (CT) scans were compared with surgical pathology and clinical outcome. FDG-PET detected liver metastases in 28 patients, with a sensitivity of 100%. CT detected metastasis in 20 patients, giving a sensitivity of 71.4%. In addition, in one patient with negative CT findings, PET detected a focus of hypermetabolism in the region adjacent to liver, which was proven to be a second focus of primary colon carcinoma. In six patients with liver metastases, PET correctly detected extrahepatic lesions, while CT only detected hepatic lesions. In conclusion, FDG-PET is an excellent imaging modality for the detection and staging of liver metastases in patients with colorectal carcinomas.
    Nuclear Medicine Communications 10/2000; 21(9):793-8. DOI:10.1097/00006231-200009000-00002 · 1.67 Impact Factor
  • HM Zhuang · P Duarte · M Pourdehnad · AJ Yamamoto · JC Loman · P Sinha · A Alavi ·
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: In cost-effective analysis regarding to utilization of FDG-PET on lung nodules, most studies focused on lung lesions themselves (benign vs. malignant) and possible metastases if primary lesion is malignant. However, in a patient with pulmonary nodules, abnormal sites of increased FDG uptake on a whole-body PET scan may either the primary tumor or lesions unrelated to lung malignancy. The incidence of detection of the unsuspected lesions, which often changes the management of these patients, should also be included in the cost-effective analysis.Methods: We retrospectively analyzed 213 cases referred for evaluation of pulmonary nodules. 89 of them proved to have lung malignancy and were excluded in our study. None of the remaining 124 patients had prior clinical or radiographic evidence of other abnormalities before undergoing FDG-PET. All unsuspected lesions were verified either histologically or by the clinical course of the disease.Results: Among the 124 patients without lung cancer, FDG-PET revealed unsuspected abnormality in eight patients. These include other malignancy (colon cancer x 3, lymphoma x 1) and benign lesions (sarcoidosis x 3, cystic kidney x 1). None of the 124 patients studied had additional pathology found during follow-up.Conclusion: The routine uses of FDG-PET for characterizing the lung lesions significantly increases the chances detecting unexpected other pathology. The incidental FDG-PET findings of unsuspected lesions, especially those unrelated to lung cancers, no doubt have a major impact on the management of these patients and may prove to be cost-effective.
    Clinical Positron Imaging 08/2000; 3(4):180. DOI:10.1016/S1095-0397(00)00092-3
  • O Couturier · C Le Rest · J Gournay · M Pourdehnad · B Bridji · A Turzo · Y Bizais ·
    [Show abstract] [Hide abstract]
    ABSTRACT: There is no consensus regarding the best way to estimate the lag phase time (Tlag) and the constant emptying time (TRE) of the gastric emptying of solids. Furthermore, biphasic gastric emptying is usually described by the modified power exponential function of either Elashoff or Siegel. In an attempt to test the validity of the power exponential functions and to identify relevant parameters of biphasic gastric emptying, we followed an approach which consists of describing the power exponential function by two straight lines. The first line is horizontal and represents Tlag. The second line is tangential to the constant emptying [tangent at the maximum slope (MS) or at the half-emptying value]. Scintigraphic data of 132 patients and 15 controls were fitted by both power exponential functions. Each corresponding half-emptying time, Tlag and TRE estimated from the Elashof and Siegel power exponential functions were strongly correlated (0.93 < r < 1, P < 0.0001). The Bland and Altman statistical method demonstrated good agreement (<5% outliers). The half-emptying tangent method sometimes gave negative Tlag and should be abandoned. Tlag(MS) and TRE(MS) did not correlate and therefore were independent parameters. We conclude that the Elashoff and Siegel functions are equivalent and that the maximum slope tangent method allows a reliable description of the two independent phases of gastric emptying.
    Nuclear Medicine Communications 07/2000; 21(7):665-75. DOI:10.1097/00006231-200007000-00011 · 1.67 Impact Factor
    [Show abstract] [Hide abstract]
    ABSTRACT: Fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography has been used extensively in the diagnosis of malignant conditions with high rates of sensitivity and specificity. However, increased FDG uptake is not limited to malignant tissue. In general, lesions with a mild degree of FDG uptake as measured by standardized uptake values less than 2.0 are considered benign, whereas those with values greater than 2.5 are usually regarded as malignant. Standardized uptake values in the kidney can be as high as 22 as a result of excretion of FDG through urine. Two cases are reported in which renal abnormalities could not be distinguished from urine based on standard uptake values alone.
    Clinical Nuclear Medicine 06/2000; 25(5):358-60. DOI:10.1097/00003072-200005000-00008 · 3.93 Impact Factor
  • K L Teff · A Alavi · J Chen · M Pourdehnad · R R Townsend ·
    [Show abstract] [Hide abstract]
    ABSTRACT: We compared the vagal contribution to gastric emptying in lean and obese subjects by monitoring gastric emptying of a meal during muscarinic blockade. Lean (n = 6) and obese subjects (n = 6) underwent two treatments: 1) saline infusion and 2) atropine infusion [0.4 mg/m2 bolus, 0.4 mg. (m2)-1. h-1] for 2 h, initiated 30 min before ingestion of a 600-kcal breakfast (64% carbohydrate, 23% fat, 13% protein) composed of orange juice (labeled with Indium-111), egg sandwich (labeled with Technetium-99m), cereal, milk, and banana. Anterior and posterior images were taken every 90 s for 90 min using a dual-headed camera. Atropine significantly delayed emptying of both solid (P < 0.007) and liquid (P < 0.002). Obese subjects exhibited a greater delay in liquid emptying during muscarinic blockade compared with lean subjects (P < 0.02). Female subjects exhibited a slower rate of gastric emptying and were less sensitive to atropine. These data suggest that obese subjects exhibit altered gastric cholinergic activity compared with lean subjects and that gender differences in gastric emptying rate may be due to differences in autonomic tone.
    The American journal of physiology 03/1999; 276(3 Pt 2):R707-14. · 3.28 Impact Factor
  • A Cesano · J A Wortman · M Pourdehnad · S Visonneau · D Mozley · A Bhatnagar · A Alavi · D Santoli ·
    [Show abstract] [Hide abstract]
    ABSTRACT: The human MHC non-restricted cytotoxic T cell line TALL-104 has potent anti-tumor effects in dogs with spontaneous tumors. This study was designed to examine the effects of the development of host immune responses on the baseline organ distribution of TALL-104 cells in healthy dogs. 111In-oxine labeled TALL-104 cells (107 cells/kg) were infused systemically in three dogs, either on day 1, 3, or 5 of a 5-day injection cycle; two dogs received two more injections of the labeled cells at monthly intervals, whereas the third dog received free 111In-oxine, 3 months after the first 5-day infusion. Analysis of blood and plasma cell clearances and imaging studies indicated a progressively faster clearance of the cells from the blood and organs after multiple daily injections as well as at the time of each monthly boost when host immune responses against the xenogeneic cells had developed. These findings have important therapeutic implications for the design of effective TALL-104 cell administration schedules in clinical trials.
    International Journal of Oncology 03/1999; 14(2):233-44. DOI:10.3892/ijo.14.2.233 · 3.03 Impact Factor