Concomitant [18F]F-FAZA and [18F]F-FDG Imaging of Gynecological Cancer Xenografts: Insight into Tumor Hypoxia.

BACKGROUND/AIM: Herein we assessed the feasibility of imaging protocols using both hypoxia-specific [18F]F-FAZA and [18F]F-FDG in bypassing the limitations derived from the non-specific findings of [18F]F-FDG PET imaging of tumor-related hypoxia. MATERIALS AND METHODS: CoCl2-generated hypoxia was induced in multidrug resistant (Pgp+) or sensitive (Pgp-) human ovarian (Pgp- A2780, Pgp+ A2780AD), and cervix carcinoma (Pgp- KB-3-1, Pgp+ KB-V-1) cell lines to establish corresponding tumor-bearing mouse models. Prior to [18F]F-FDG/[18F]F-FAZA-based MiniPET imaging, in vitro [18F]F-FDG uptake measurements and western blotting were used to verify the presence of hypoxia. RESULTS: Elevated GLUT-1, and hexokinase enzyme-II expression driven by CoCl2-induced activation of hypoxia-inducible factor-1α explains enhanced cellular [18F]F-FDG accumulation. No difference was observed in the [18F]F-FAZA accretion of Pgp+ and Pgp- tumors. Tumor-to-muscle ratios for [18F]F-FAZA measured at 110-120 min postinjection (6.2±0.1) provided the best contrasted images for the delineation of PET-oxic and PET-hypoxic intratumor regions. Although all tumors exhibited heterogenous uptake of both radiopharmaceuticals, greater differences for [18F]F-FAZA between the tracer avid and non-accumulating regions indicate its superiority over [18F]F-FDG. Spatial correlation between [18F]F-FGD and [18F]F-FAZA scans confirms that hypoxia mostly occurs in regions with highly active glucose metabolism. CONCLUSION: The addition of [18F]F-FAZA PET to [18F]F-FGD imaging may add clinical value in determining hypoxic sub-regions.

In Vivo Imaging of Ischemia/Reperfusion-mediated Aminopeptidase N Expression in Surgical Rat Model Using 68Ga-NOTA-c(NGR).

BACKGROUND/AIM: Previous studies have already shown that 68Gallium(68Ga)-labeled NGR-based radiopharmaceuticals specifically bind to the neoangiogenic molecule Aminopeptidase N (APN/CD13). The aim of this study was to evaluate the applicability of 68Ga-NOTA-c(NGR) in the in vivo detection of the temporal changes of APN/CD13 expression in the diabetic retinopathy rat model using positron emission tomography (PET). MATERIALS AND METHODS: Ischemia/reperfusion injury was initiated by surgical ligation of the left bulbus oculi of rats. In vivo PET imaging studies were performed after the surgery using 68Ga-NOTA-c(NGR). RESULTS: Significantly higher 68Ga-NOTA-c(NGR) uptake was observed in the surgically-ligated left bulbus, compared to the bulbus of the non-surgical group at each investigated time point. The western blot and histological analysis confirmed the increased expression of the neo-angiogenic marker APN/CD13. CONCLUSION: 68Ga-NOTA-c(NGR) is a suitable radiotracer for the detection of the temporal changes of the ischemia/reperfusion-mediated expression of APN/CD13 in the surgically induced diabetic retinopathy rat model.

Automated procedure assessing the accuracy of HRCT-PET registration applied in functional virtual bronchoscopy.

BACKGROUND: Bronchoscopy serves as direct visualisation of the airway. Virtual bronchoscopy provides similar visual information using a non-invasive imaging procedure(s). Early and accurate image-guided diagnosis requires the possible highest performance, which might be approximated by combining anatomical and functional imaging. This communication describes an advanced functional virtual bronchoscopic (fVB) method based on the registration of PET images to high-resolution diagnostic CT images instead of low-dose CT images of lower resolution obtained from PET/CT scans. PET/CT and diagnostic CT data were collected from 22 oncological patients to develop a computer-aided high-precision fVB. Registration of segmented images was performed using elastix. RESULTS: For virtual bronchoscopy, we used an in-house developed segmentation method. The quality of low- and high-dose CT image registrations was characterised by expert's scoring the spatial distance of manually paired corresponding points and by eight voxel intensity-based (dis)similarity parameters. The distribution of (dis)similarity parameter correlating best with anatomic scoring was bootstrapped, and 95% confidence intervals were calculated separately for acceptable and insufficient registrations. We showed that mutual information (MI) of the eight investigated (dis)similarity parameters displayed the closest correlation with the anatomy-based distance metrics used to characterise the quality of image registrations. The 95% confidence intervals of the bootstrapped MI distribution were [0.15, 0.22] and [0.28, 0.37] for insufficient and acceptable registrations, respectively. In case of any new patient, a calculated MI value of registered low- and high-dose CT image pair within the [0.28, 0.37] or the [0.15, 0.22] interval would suggest acceptance or rejection, respectively, serving as an aid for the radiologist. CONCLUSION: A computer-aided solution was proposed in order to reduce reliance on radiologist's contribution for the approval of acceptable image registrations.

Effect of grey-level discretization on texture feature on different weighted MRI images of diverse disease groups.

PURPOSE: Many studies of MRI radiomics do not include the discretization method used for the analyses, which might indicate that the discretization methods used are considered irrelevant. Our goals were to compare three frequently used discretization methods (lesion relative resampling (LRR), lesion absolute resampling (LAR) and absolute resampling (AR)) applied to the same data set, along with two different lesion segmentation approaches. METHODS: We analyzed the effects of altering bin widths or bin numbers for the three different sampling methods using 40 texture indices (TIs). The impact was evaluated on brain MRI studies obtained for 71 patients divided into three different disease groups: multiple sclerosis (MS, N = 22), ischemic stroke (IS, N = 22), cancer patients (N = 27). Two different MRI acquisition protocols were considered for all patients, a T2- and a post-contrast 3D T1-weighted MRI sequence. Elliptical and manually drawn VOIs were employed for both imaging series. Three different types of gray-level discretization methods were used: LRR, LAR and AR. Hypothesis tests were done among all diseased and control areas to compare the TI values in these areas. We also did correlation analyses between TI values and lesion volumes. RESULTS: In general, no significant differences were reported in the results when employing the AR and LAR discretization methods. It was found that employing 38 TIs introduced variation in the results when the number of bin parameters was altered, suggesting that both the degree and direction of monotonicity between each TI value and binning parameters were characteristic for each TI. Furthermore, while TIs were changing with altering binning values, no changes correlated to neither disease nor the MRI sequence. We found that most indices correlated weakly with the volume, while the correlation coefficients were independent of both diseases analyzed and MR contrast. Several cooccurrence-matrix based texture parameters show a definite higher correlation when employing the LRR discretization method However, with the best correlations obtained for the manually drawn VOI. Hypothesis tests among all disease and control areas (co-lateral hemisphere) revealed that the AR or LAR discretization techniques provide more suitable texture features than LRR. In addition, the manually drawn segmentation gave fewer significantly different TIs than the ellipsoid segmentations. In addition, the amount of TIs with significant differences was increasing with increasing the number of bins, or decreasing bin widths. CONCLUSION: Our findings indicate that the AR discretization method may offer the best texture analysis in MR image assessments. Employing too many bins or too large bin widths might reduce the selection of TIs that can be used for differential diagnosis. In general, more statistically different TIs were observed for elliptical segmentations when compared to the manually drawn VOIs. In the texture analysis of MR studies, studies and publications should report on all important parameters and methods related to data collection, corrections, normalization, discretization, and segmentation.

[Methods and feasibilities of texture analysis in PET diagnostics]. / A textúraanalízis módszere és lehetoségei a PET-diagnosztikában.

One of the current research objectives of medical imaging is to determine the prognostic value of tumor textures and related numerical values. In PET/CT studies the diagnostic and prognostic values of specific texture parameters were confirmed at several tumor types (lung, prostate, cervix, colon, head and neck). However, the results are often contradictory, various publications find different texture parameters useful for the same tumor type. The reason for the contradictions is partly methodological, since the definition and the calculation of texture data is a multi-step process. Such steps include scan protocol, image reconstruction, tumor segmentation, re-sampling the voxel values and the form of texture algorithms. Recent publications show that by harmonizing these steps, the prognostic power and reliability of the texture features can be improved. The most optimal way of harmonization would be a special phantom application that could simulate inhomogeneous distributions typical for tumor tissues, with high reproducibility.

Impact of intensity discretization on textural indices of [18F]FDG-PET tumour heterogeneity in lung cancer patients.

Quantifying tumour heterogeneity from [18F]FDG-PET images promises benefits for treatment selection of cancer patients. Here, the calculation of texture parameters mandates an initial discretization step (binning) to reduce the number of intensity levels. Typically, three types of discrimination methods are used: lesion relative resampling (LRR) with fixed bin number, lesion absolute resampling (LAR) and absolute resampling (AR) with fixed bin widths. We investigated the effects of varying bin widths or bin number using 27 commonly cited local and regional texture indices (TIs) applied on lung tumour volumes. The data set were extracted from 58 lung cancer patients, with three different and robust tumour segmentation methods. In our cohort, the variations of the mean value as the function of the bin widths were similar for TIs calculated with LAR and AR quantification. The TI histograms calculated by LRR method showed distinct behaviour and its numerical values substantially effected by the selected bin number. The correlations of the AR and LAR based TIs demonstrated no principal differences between these methods. However, no correlation was found for the interrelationship between the TIs calculated by LRR and LAR (or AR) discretization method. Visual classification of the texture was also performed for each lesion. This classification analysis revealed that the parameters show statistically significant correlation with the visual score, if LAR or AR discretization method is considered, in contrast to LRR. Moreover, all the resulted tendencies were similar regardless the segmentation methods and the type of textural features involved in this work.

2D and 3D texture analysis to differentiate brain metastases on MR images: proceed with caution.

OBJECTIVE: To find structural differences between brain metastases of lung and breast cancer, computing their heterogeneity parameters by means of both 2D and 3D texture analysis (TA). MATERIALS AND METHODS: Patients with 58 brain metastases from breast (26) and lung cancer (32) were examined by MR imaging. Brain lesions were manually delineated by 2D ROIs on the slices of contrast-enhanced T1-weighted (CET1) images, and local binary patterns (LBP) maps were created from each region. Histogram-based (minimum, maximum, mean, standard deviation, and variance), and co-occurrence matrix-based (contrast, correlation, energy, entropy, and homogeneity) 2D, weighted average of the 2D slices, and true 3D TA were obtained on the CET1 images and LBP maps. RESULTS: For LBP maps and 2D TA contrast, correlation, energy, and homogeneity were identified as statistically different heterogeneity parameters (SDHPs) between lung and breast metastasis. The weighted 3D TA identified entropy as an additional SDHP. Only two texture indexes (TI) were significantly different with true 3D TA: entropy and energy. All these TIs discriminated between the two tumor types significantly by ROC analysis. For the CET1 images there was no SDHP at all by 3D TA. CONCLUSION: Our results indicate that the used textural analysis methods may help with discriminating between brain metastases of different primary tumors.

A Study on the Basic Criteria for Selecting Heterogeneity Parameters of F18-FDG PET Images.

Textural analysis might give new insights into the quantitative characterization of metabolically active tumors. More than thirty textural parameters have been investigated in former F18-FDG studies already. The purpose of the paper is to declare basic requirements as a selection strategy to identify the most appropriate heterogeneity parameters to measure textural features. Our predefined requirements were: a reliable heterogeneity parameter has to be volume independent, reproducible, and suitable for expressing quantitatively the degree of heterogeneity. Based on this criteria, we compared various suggested measures of homogeneity. A homogeneous cylindrical phantom was measured on three different PET/CT scanners using the commonly used protocol. In addition, a custom-made inhomogeneous tumor insert placed into the NEMA image quality phantom was imaged with a set of acquisition times and several different reconstruction protocols. PET data of 65 patients with proven lung lesions were retrospectively analyzed as well. Four heterogeneity parameters out of 27 were found as the most attractive ones to characterize the textural properties of metabolically active tumors in FDG PET images. These four parameters included Entropy, Contrast, Correlation, and Coefficient of Variation. These parameters were independent of delineated tumor volume (bigger than 25-30 ml), provided reproducible values (relative standard deviation< 10%), and showed high sensitivity to changes in heterogeneity. Phantom measurements are a viable way to test the reliability of heterogeneity parameters that would be of interest to nuclear imaging clinicians.

[New trends and novel possibilities in functional medical imaging: imaging methods]. / Újdonságok és új lehetoségek a funkcionális képalkotásban: Leképezéstechnikai újdonságok.

The aim of the study is to review the new tomographic imaging technologies which enable to investigate the metabolic activity of the human body. Accordingly, we overview the current promising methodology in the field of PET and SPECT, but we will also mention interesting applications at the area of MRI and CT.

[New trends in functional medical imaging: quantitative methods]. / Újdonságok és új lehetoségek a funkcionális képalkotásban: kvantitatív módszerek.

Deriving quantitative measures from the medical imaging methods is a key issue for the optimal oncologic therapy, when the anatomical abnormalities and changes of the metabolic state of the tissues need to be characterized. In order to improve the effectiveness of the therapy, the results of medical imaging procedures should be comparable after two or more consecutive scans. There are several tomographic imaging applications (CT, MRI, SPECT and PET), but in this work we will focus on the quantitative capability of PET, because this method provides the most versatile possibilities for quantifying the resulting images.

18FDG, [18F]FLT, [18F]FAZA, and 11C-methionine are suitable tracers for the diagnosis and in vivo follow-up of the efficacy of chemotherapy by miniPET in both multidrug resistant and sensitive human gynecologic tumor xenografts.

Expression of multidrug pumps including P-glycoprotein (MDR1, ABCB1) in the plasma membrane of tumor cells often results in decreased intracellular accumulation of anticancer drugs causing serious impediment to successful chemotherapy. It has been shown earlier that combined treatment with UIC2 anti-Pgp monoclonal antibody (mAb) and cyclosporine A (CSA) is an effective way of blocking Pgp function. In the present work we investigated the suitability of four PET tumor diagnostic radiotracers including 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)FDG), (11)C-methionine, 3'-deoxy-3'-[(18)F]fluorothymidine ((18)F-FLT), and [(18)F]fluoroazomycin-arabinofuranoside ((18)FAZA) for in vivo follow-up of the efficacy of chemotherapy in both Pgp positive (Pgp(+)) and negative (Pgp(-)) human tumor xenograft pairs raised in CB-17 SCID mice. Pgp(+) and Pgp(-) A2780AD/A2780 human ovarian carcinoma and KB-V1/KB-3-1 human epidermoid adenocarcinoma tumor xenografts were used to study the effect of the treatment with an anticancer drug doxorubicin combined with UIC2 and CSA. The combined treatment resulted in a significant decrease of both the tumor size and the accumulation of the tumor diagnostic tracers in the Pgp(+) tumors. Our results demonstrate that (18)FDG, (18)F-FLT, (18)FAZA, and (11)C-methionine are suitable PET tracers for the diagnosis and in vivo follow-up of the efficacy of tumor chemotherapy in both Pgp(+) and Pgp(-) human tumor xenografts by miniPET.

¹8FDG a PET tumor diagnostic tracer is not a substrate of the ABC transporter P-glycoprotein.

2-[(18)F]fluoro-2-deoxy-d-glucose ((18)FDG) is a tumor diagnostic radiotracer of great importance in both diagnosing primary and metastatic tumors and in monitoring the efficacy of the treatment. P-glycoprotein (Pgp) is an active transporter that is often expressed in various malignancies either intrinsically or appears later upon disease progression or in response to chemotherapy. Several authors reported that the accumulation of (18)FDG in P-glycoprotein (Pgp) expressing cancer cells (Pgp(+)) and tumors is different from the accumulation of the tracer in Pgp nonexpressing (Pgp(-)) ones, therefore we investigated whether (18)FDG is a substrate or modulator of Pgp pump. Rhodamine 123 (R123) accumulation experiments and ATPase assay were used to detect whether (18)FDG is substrate for Pgp. The accumulation and efflux kinetics of (18)FDG were examined in two different human gynecologic (A2780/A2780AD and KB-3-1/KB-V1) and a mouse fibroblast (3T3 and 3T3MDR1) Pgp(+) and Pgp(-) cancer cell line pairs both in cell suspension and monolayer cultures. We found that (18)FDG and its derivatives did not affect either the R123 accumulation in Pgp(+) cells or the basal and the substrate stimulated ATPase activity of Pgp supporting that they are not substrates or modulators of the pump. Measuring the accumulation and efflux kinetics of (18)FDG in different Pgp(+) and Pgp(-) cell line pairs, we have found that the Pgp(+) cells exhibited significantly higher (p⩽0.01) (18)FDG accumulation and slightly faster (18)FDG efflux kinetics compared to their Pgp(-) counterparts. The above data support the idea that expression of Pgp may increase the energy demand of cells resulting in higher (18)FDG accumulation and faster efflux. We concluded that (18)FDG and its metabolites are not substrates of Pgp.

[The status of domestic PET/CT attendance in the light of the waiting list data]. / A hazai PET/CT-ellátás helyzete a várólista adatai alapján.

The aim of the study is to demonstrate the diagnostic and geographical distribution of the domestic PET/CT examinations financed by the OEP based on the data from the waiting list of the past 4 years. The analysis of the demonstrated data can support the rational usage of PET/CT examination contingents in the domestic oncological attendance, which has growing importance. PET examinations with oncological aims have started in Debrecen more than 10 years ago. In 2005 already 1500 PET examinations have been carried out. According to the governmental regulation accepted in 2006, OEP ensures the financing of the three PET/CT centers until 2012, which means 12,000 examinations in 2012. However, the number of domestic oncological patients requiring PET/CT examinations can reach the number of 20,000-30,000 patients. The study summarizes the number of patients who applied for PET/CT examinations for the first time and later again between 2006 and 2010, based on the data of the waiting list, and the change of the patient assigning diagnosis and the number of examinations carried out with 18F-FDG and with 11C-methionine. The study demonstrates the number of examinations by counties which characterize the population's access to PET/CT. The assigning diagnosis in 2007 was already widespread and focused on problems. After the regulation came in to force in 2008 the possibilities significantly decreased. Clinical cases which were efficiently examined with PET/CT earlier were left out from the indication list. The distribution by county is uneven, although the number of examinations increases year by year. The number of repeated examinations increases as well. As a conclusion, the annual PET/CT examination contingents are constantly exploited. This might seem sufficient, because the method has not become a part of the oncological routine in all counties. Although the current indication list includes the most frequent oncological cases requiring PET/CT, the abandoning of the less frequent ones narrowed the professional latitude, which is disadvantageous for the patients suffering from such diseases. The radiopharmacon supply of PET/CT centers is inadequate thus they cannot provide modern oncological diagnostic attendance in case of frequent types of cancer (such as prostate). In the long run the growing number of repeated PET/CT examinations built in the oncological professional protocol has to be taken into account.

Serial noninvasive in vivo positron emission tomographic tracking of percutaneously intramyocardially injected autologous porcine mesenchymal stem cells modified for transgene reporter gene expression.

BACKGROUND: Porcine bone marrow-derived mesenchymal stem cells (MSCs) were stably transfected with a lentiviral vector for transgene expression of the trifusion protein renilla luciferase, red fluorescent protein and herpes simplex truncated thymidine kinase (LV-RL-RFP-tTK; positron emission tomography [PET] reporter gene) for in vivo noninvasive tracking of the intramyocardially delivered MSC fate. METHODS AND RESULTS: A closed-chest, reperfused myocardial infarction was created in farm pigs. Sixteen days after myocardial infarction, LV-RL-RFP-tTK-MSCs were injected intramyocardially using electromechanical mapping guidance in the infarct border zone (n=7). PET-computed tomographic metabolic and perfusion imaging was performed after an intravenous injection of 10 mCi [18F]-FHBG and 13N-ammonia PET at 30+/-2 hours and 7 days after LV-RL-RFP-tTK-MSC treatment. Fusion imaging of the [18F]-FHBG PET-computed tomography with MRI was used to determine the myocardial location of the injected LV-RL-RFP-tTK-MSCs. Seven days after injections, [18F]-FHBG PET showed a decreased cardiac uptake with a mild increased pericardial and pleura uptake in the treated animals, which was confirmed by the measurement of luciferase activity. At 10 days, infarct size by MRI in the LV-RL-RFP-tTK-MSC-treated animals was smaller than controls (n=7) (23.3+/-1.5% versus 30.2+/-3.5%, P<0.005). The presence of the LV-RL-RFP-tTK-MSCs (5.8+/-1.1% of the injected cells) in the myocardium 10 days after intramyocardial delivery was confirmed histologically. CONCLUSIONS: Reporter gene imaging enables the tracking of the persistence of viable LV-RL-RFP-tTK-MSC in the peri-infarcted porcine myocardium at 10 days after delivery using clinical PET scanners.

Na+/Ca2+ exchanger inhibitors modify the accumulation of tumor-diagnostic PET tracers in cancer cells.

AIM: To establish the effects of Na(+)/Ca(2+) exchanger (NCX) blockers on 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)FDG) and (11)C-choline accumulation in different cancer cells. METHODS: The tumor cells were incubated with NCX inhibitors, and the uptakes of (18)FDG and (11)C-choline were measured. Flow cytometric measurements of intracellular Ca(2+) and Na(+) concentrations were carried out. The presence of the NCX antigen in the cancer cells was proved by Western blotting, flow cytometry and confocal laser scanning microscopy. RESULTS: The NCX is expressed at a noteworthy level in the cytosol and on the cytoplasmic membrane of the examined cells. Incubation of the cells with three chemically unrelated NCX blockers (bepridil, KB-R7943 or 3',4'-dichlorobenzamil hydrochloride) resulted in an increase in the intracellular Ca(2+) concentration, with a simultaneous decrease in the intracellular Na(+) concentration. The treatment with the NCX inhibitors increased the energy consumption of the tumor cells by 50-100%. Thapsigargin abolished the NCX-induced (18)FDG accumulation in the cells. The NCX blockers applied decreased the (11)C-choline accumulation of all the investigated cancer cells by 60-80% relative to the control. CONCLUSION: A possible masking effect of NCX medication must be taken into consideration during the diagnostic interpretation of PET scans.

Paclitaxel modifies the accumulation of tumor-diagnostic tracers in different ways in P-glycoprotein-positive and negative cancer cells.

AIM: To study how paclitaxel treatment modifies the accumulation of tumor-diagnostic radiotracers in P-glycoprotein (P-gp) positive and negative cancer cells. METHODS: The accumulations of different P-gp substrates, including rhodamine 123, daunorubicin and [(99m)Tc]hexakis-2-methoxybutyl isonitrile ((99m)Tc-MIBI), were measured in P-gp-positive (A2780AD) and P-gp-negative human ovarian carcinoma cells (A2780) and JY human lymphoid B cells. The uptakes of the tumor-diagnostic tracers (11)C-choline and 2-[(18)F]fluoro-2-deoxy-d-glucose ((18)FDG) were measured in the same cell lines. The P-gp expression and function were demonstrated by flow-cytometry. RESULTS: The (18)FDG measurements revealed that the glucose metabolic rate was significantly higher (p<0.01) in the P-gp-positive A2780AD cells than in the P-gp-negative cells. Paclitaxel (1-70microM) increased the (18)FDG uptake (up to 200%) of both P-gp-positive and P-gp-negative cells, whereas it did not modulate their (11)C-choline uptake. Paclitaxel reinstated the (99m)Tc-MIBI accumulation of the A2780AD cells (to 1500% of the control) in a concentration-dependent manner, while it increased the uptake of the P-gp-negative cells to a lesser extent (to a maximum of 200% of the control). CONCLUSION: Paclitaxel modifies the uptake of tumor-diagnostic tracers in both P-gp-dependent and independent manners. Interpretation of the multifactorial effects of paclitaxel may promote a correct in vivo diagnosis of P-gp-positive and P-gp-negative tumors.

Regional cerebral (18)FDG uptake during subarachnoid hemorrhage induced vasospasm.

OBJECTIVES: The aim was to elucidate whether aneurysmal subarachnoid hemorrhage (SAH)-induced vasospasm induces changes of regional glucose uptake in surgically treated, asymptomatic cases. METHODS: (18)FDG uptake (standardized uptake value, SUV) was analysed with PET in eight surgically treated aneurismal patients with a mean middle cerebral artery flow velocity >120 cm/seconds measured with transcranial Doppler ultrasound. Data were compared with a healthy control group using Statistical Parametric Mapping (SPM99b). RESULTS: Six of the eight patients had no focal neurological signs. The inhomogeneous bilateral increase in SUV (p<0.0001) was asymmetrical, with an almost 70% larger volume on the operated side. Reduced glucose uptake was found in the frontal and temporobasal regions of the two patients with neurological deficits (p<0.0001); the affected volume was 40% larger on the operated side. DISCUSSION: SAH-induced vasospasm results in widespread increase of glucose uptake-probably reflecting increased glycolysis. This was earlier than neurological focal signs appear. Decreased glucose uptake can be detected in severe cases of vasospasm reflected by neurological deficit. Although the changes are more prominent where surgery had taken place our results suggest that not only the surgery, but also subarachnoid blood might have resulted in our findings.

Biphasic accumulation kinetics of [99mTc]-hexakis-2-methoxyisobutyl isonitrile in tumour cells and its modulation by lipophilic P-glycoprotein ligands.

AIM: To study the accumulation and washout kinetics of [99mTc]-hexakis-2-methoxyisobutyl isonitrile (99mTc-MIBI) in MDR positive and MDR negative tumour cells and how this is modified by lipophilic P-glycoprotein ligands. METHODS: The tumour cells were incubated in the presence and absence of the ligands and the uptakes of 99mTc-MIBI, rhodamine 123 and 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) were measured. RESULTS: The accumulation of 99mTc-MIBI in the tumour cells followed biphasic kinetics. Verapamil and cyclosporin A increased the membrane fluidity and significantly enhanced the 99mTc-MIBI uptake of the MDR negative cells, while the rhodamine 123 uptake was not affected. Verapamil significantly increased the uptake of rhodamine 123 and 18FDG but did not modify that of 99mTc-MIBI in the MDR positive cells. Cyclosporin A significantly increased the 18FDG uptake of the MDR positive and negative tumour cells; these effects were ouabain-sensitive. Depolarization of the cytoplasmic membrane, acidification of the extracellular medium and the administration of CCCP decreased the accumulation of 99mTc-MIBI and rhodamine 123 uptake in the tumour cells. CONCLUSIONS: Lipophilic P-glycoprotein ligands modified the biphasic accumulation kinetics of the 99mTc-MIBI uptakes of MDR negative and positive tumour cells in different and complex ways and could therefore mask the P-glycoprotein pump-dependent changes in tracer accumulation.

Effects of miltefosine on membrane permeability and accumulation of [99mTc]-hexakis-2-methoxyisobutyl isonitrile, 2-[18F]fluoro-2-deoxy-D-glucose, daunorubucin and rhodamine123 in multidrug-resistant and sensitive cells.

Miltefosine is a phospholipid analog that exhibits antineoplastic activity against breast cancer metastases, but its mechanism of action remains uncertain. The aim of this study was to investigate the transport mechanism for the removal of miltefosine and [99mTc]-hexakis-2-methoxyisobutyl isonitrile (99mTc-MIBI) from multidrug-resistant cells. The P-glycoprotein pump function, cell viability, and 99mTc-MIBI and 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) uptakes were measured in NIH 3T3 (3T3) and NIH 3T3MDR1 G185 (3T3MDR1) mouse fibroblasts and human lymphoid B JY cells. Miltefosine treatment increased the permeability and fluidity of these tumor cells in a concentration-dependent manner. The multidrug-sensitive cells were 3-4 times more sensitive to miltefosine than the multidrug-resistant ones. The extent of 99mTc-MIBI accumulation in the P-glycoprotein-expressing cells increased in the presence of miltefosine, whereas the rhodamine123 and daunorubicin uptakes of the cells did not change significantly. In the 3T3MDR1 cells verapamil reinstated the rhodamine123 and daunorubicin accumulation, but not the 99mTc-MIBI uptake. Cyclosporin A reinstated the uptakes of 99mTc-MIBI, daunorubicin and rhodamine123 by the 3T3MDR1 cells. In a concentration-dependent manner miltefosine decreased the extents of 99mTc-MIBI, rhodamine123, daunorubicin and 18FDG accumulation in the JY and 3T3 cells. Our findings indicate a common transport mechanism for 99mTc-MIBI and miltefosine, which is distinct from that for rhodamine123 and daunorubicin in MDR cells.