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.

The Effect of Passive Movement for Paretic Ankle-Foot and Brain Activity in Post-Stroke Patients.

BACKGROUND: This study aims at investigating the short-term efficacy of the continuous passive motion (CPM) device developed for the therapy of ankle-foot paresis and to investigate by fMRI the blood oxygen level-dependent responses (BOLD) during ankle passive movement (PM). METHODS: Sixty-four stroke patients were investigated. Patients were assigned into 2 groups: 49 patients received both 15 min manual and 30 min device therapy (M + D), while the other group (n = 15) received only 15 min manual therapy (M). A third group of stroke patients (n = 12) was investigated by fMRI before and immediately after 30 min CPM device therapy. There was no direct relation between the fMRI group and the other 2 groups. All subjects were assessed using the Modified Ashworth Scale (MAS) and a goniometer. RESULTS: Mean MAS decreased, the ankle's mean plantar flexion and dorsiflexion passive range of motion (PROM) increased and the equinovalgus improved significantly in the M + D group. In the fMRI group, the PM of the paretic ankle increased BOLD responses; this was observed in the contralateral pre- and postcentral gyrus, superior temporal gyrus, central opercular cortex, and in the ipsilateral postcentral gyrus, frontal operculum cortex and cerebellum. CONCLUSION: Manual therapy with CPM device therapy improved the ankle PROM, equinovalgus and severity of spasticity. The ankle PM increased ipsi- and contralateral cortical activation.

[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.

Body fat distribution and metabolic consequences - Examination opportunities in dogs.

The relationship between metabolic disorders and the distribution of fat in different body regions is not clearly understood in humans. The aim of this study was to develop a suitable method for assessing the regional distribution of fat deposits and their metabolic effects in dogs. Twenty-five dogs were subjected to computed tomographic (CT) imaging and blood sampling in order to characterise their metabolic status. The different fat areas were measured on a cross-sectional scan, and the animals' metabolic status was evaluated by measuring fasting glucose, insulin and leptin levels. The volume of visceral adipose tissue is the main determinant of leptin levels. The correlation of visceral fat volume and leptin concentration was found to be independent of insulin levels or the degree of insulin resistance. There was a positive correlation between the visceral to subcutaneous fat volume ratio and serum insulin concentration, and a similar trend was observed in the relationship of fat ratio and insulin resistance. The distribution of body fat essentially influences the metabolic parameters in dogs, but the effects of adiposity differ between humans and dogs. The findings can facilitate a possible extrapolation of results from animal studies to humans with regard to the metabolic consequences of different obesity types.

[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.

Multicentric study on the reproducibility and robustness of PET-based radiomics features with a realistic activity painting phantom.

Previously, we developed an "activity painting" tool for PET image simulation; however, it could simulate heterogeneous patterns only in the air. We aimed to improve this phantom technique to simulate arbitrary lesions in a radioactive background to perform relevant multi-center radiomic analysis. We conducted measurements moving a 22Na point source in a 20-liter background volume filled with 5 kBq/mL activity with an adequately controlled robotic system to prevent the surge of the water. Three different lesion patterns were "activity-painted" in five PET/CT cameras, resulting in 8 different reconstructions. We calculated 46 radiomic indeces (RI) for each lesion and imaging setting, applying absolute and relative discretization. Reproducibility and reliability were determined by the inter-setting coefficient of variation (CV) and the intraclass correlation coefficient (ICC). Hypothesis tests were used to compare RI between lesions. By simulating precisely the same lesions, we confirmed that the reconstructed voxel size and the spatial resolution of different PET cameras were critical for higher order RI. Considering conventional RIs, the SUVpeak and SUVmean proved the most reliable (CV<10%). CVs above 25% are more common for higher order RIs, but we also found that low CVs do not necessarily imply robust parameters but often rather insensitive RIs. Based on the hypothesis test, most RIs could clearly distinguish between the various lesions using absolute resampling. ICC analysis also revealed that most RIs were more reproducible with absolute discretization. The activity painting method in a real radioactive environment proved suitable for precisely detecting the radiomic differences derived from the different camera settings and texture characteristics. We also found that inter-setting CV is not an appropriate metric for analyzing RI parameters' reliability and robustness. Although multicentric cohorts are increasingly common in radiomics analysis, realistic texture phantoms can provide indispensable information on the sensitivity of an RI and how an individual RI parameter measures the texture.

Impact of Fat Distribution and Metabolic Diseases on Cerebral Microcirculation: A Multimodal Study on Type 2 Diabetic and Obese Patients.

Background: Since metabolic diseases and atherosclerotic vascular events are firmly associated, herein we investigate changes in central microcirculation and atherosclerosis-related body fat distribution in patients with type 2 diabetes mellitus and obesity. Methods: Resting brain perfusion single-photon emission computed tomography (SPECT) imaging with Technetium-99m hexamethylpropylene amine oxime ([99mTc]Tc-HMPAO SPECT) was performed, and the breath-holding index (BHI) and carotid intima-media thickness (cIMT) were measured to characterise central microcirculation. Besides CT-based abdominal fat tissue segmentation, C-peptide level, glycaemic and anthropometric parameters were registered to search for correlations with cerebral blood flow and vasoreactivity. Results: Although no significant difference was found between the resting cerebral perfusion of the two patient cohorts, a greater blood flow increase was experienced in the obese after the breath-holding test than in the diabetics (p < 0.05). A significant positive correlation was encountered between resting and provocation-triggered brain perfusion and C-peptide levels (p < 0.005). BMI and cIMT were negatively correlated (rho = -0.27 and -0.23 for maximum and mean cIMT, respectively), while BMI and BHI showed a positive association (rho = 0.31 and rho = 0.29 for maximum and mean BHI, respectively), which could be explained by BMI-dependent changes in fat tissue distribution. cIMT demonstrated a disproportional relationship with increasing age, and higher cIMT values were observed for the men. Conclusions: Overall, C-peptide levels and circulatory parameters seem to be strong applicants to predict brain microvascular alterations and related cognitive decline in such patient populations.

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.

3D printed anthropomorphic left ventricular myocardial phantom for nuclear medicine imaging applications.

BACKGROUND: Anthropomorphic torso phantoms, including a cardiac insert, are frequently used to investigate the imaging performance of SPECT and PET systems. These phantom solutions are generally featuring a simple anatomical representation of the heart. 3D printing technology paves the way to create cardiac phantoms with more complex volume definition. This study aimed to describe how a fillable left ventricular myocardium (LVm) phantom can be manufactured using geometry extracted from a patient image. METHODS: The LVm of a healthy subject was segmented from 18F-FDG attenuation corrected PET image set. Two types of phantoms were created and 3D printed using polyethylene terephthalate glycol (PETG) material: one representing the original healthy LVm, and the other mimicking myocardium with a perfusion defect. The accuracy of the LVm phantom production was investigated by high-resolution CT scanning of 3 identical replicas. 99mTc SPECT acquisitions using local cardiac protocol were performed, without additional scattering media ("in air" measurements) for both phantom types. Furthermore, the healthy LVm phantom was inserted in the commercially available DataSpectrum Anthropomorphic Torso Phantom ("in torso" measurement) and measured with hot background and hot liver insert. RESULTS: Phantoms were easy to fill without any air-bubbles or leakage, were found to be reproducible and fully compatible with the torso phantom. Seventeen segments polar map analysis of the "in air" measurements revealed that a significant deficit in the distribution appeared where it was expected. 59% of polar map segments had less than 5% deviation for the "in torso" and "in air" measurement comparison. Excluding the deficit area, neither comparison had more than a 12.4% deviation. All the three polar maps showed similar apex and apical region values for all configurations. CONCLUSIONS: Fillable anthropomorphic 3D printed phantom of LVm can be produced with high precision and reproducibility. The 3D printed LVm phantoms were found to be suitable for SPECT image quality tests during different imaging scenarios. The flexibility of the 3D printing process presented in this study provides scalable and anthropomorphic image quality phantoms in nuclear cardiology imaging.

Phantom Study on the Robustness of MR Radiomics Features: Comparing the Applicability of 3D Printed and Biological Phantoms.

The objectives of our study were to (a) evaluate the feasibility of using 3D printed phantoms in magnetic resonance imaging (MR) in assessing the robustness and repeatability of radiomic parameters and (b) to compare the results obtained from the 3D printed phantoms to metrics obtained in biological phantoms. To this end, three different 3D phantoms were printed: a Hilbert cube (5 × 5 × 5 cm3) and two cubic quick response (QR) code phantoms (a large phantom (large QR) (5 × 5 × 4 cm3) and a small phantom (small QR) (4 × 4 × 3 cm3)). All 3D printed and biological phantoms (kiwis, tomatoes, and onions) were scanned thrice on clinical 1.5 T and 3 T MR with 1 mm and 2 mm isotropic resolution. Subsequent analyses included analyses of several radiomics indices (RI), their repeatability and reliability were calculated using the coefficient of variation (CV), the relative percentage difference (RPD), and the interclass coefficient (ICC) parameters. Additionally, the readability of QR codes obtained from the MR images was examined with several mobile phones and algorithms. The best repeatability (CV ≤ 10%) is reported for the acquisition protocols with the highest spatial resolution. In general, the repeatability and reliability of RI were better in data obtained at 1.5 T (CV = 1.9) than at 3 T (CV = 2.11). Furthermore, we report good agreements between results obtained for the 3D phantoms and biological phantoms. Finally, analyses of the read-out rate of the QR code revealed better texture analyses for images with a spatial resolution of 1 mm than 2 mm. In conclusion, 3D printing techniques offer a unique solution to create textures for analyzing the reliability of radiomic data from MR scans.

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.

Q-Bot: automatic DICOM metadata monitoring for the next level of quality management in nuclear medicine.

BACKGROUND: Regular and precise inspection of the realization of the local nuclear medicine standard operation procedures (SOPs) is very complex and time-consuming, especially when large amount of patient data is obtained from a wide scale of different scan procedures on a daily basis. DICOM metadata comprise a complete set of data related to the patient and the imaging procedure, and consequently all information necessary to evaluate the compliance with the actual SOP. METHODS: Q-Bot, an automatic DICOM metadata monitoring tool which is capable to verify SOP conformities, was tested for 11 months at two nuclear medicine departments. Relevant parameters, such as patient ID, patient mass and height, injected activity, and uptake time, were investigated in the case of adult 18F-FDG whole-body PET/CT and 99mTc-MDP gamma camera bone scans on a daily basis. Q-Bot automatically inspected the actual SOP compliance of these relevant DICOM parameters. Q-Bot graphical user interface (GUI) provided a summary of the outliers in a table format to be investigated by a dedicated technologist. In addition, information related to the error handling was also collected for retrospective analysis of long-term tendencies. RESULTS: In total, 6702 PET/CT and 2502 gamma camera scans were inspected, from which 8581 were confirmed as valid patient study without errors. Discrepancies related to the lack of a parameter, not appropriate format, or improper scan procedures were found in 623 cases, and 156 out of these were corrected before the medical reading and reporting. SOP non-conformities explored with Q-Bot were found to be non-correctable in 467 cases. Systematic errors to our practice turned out to be the manual radiopharmaceutical injection, the allowance to use both SI and non-SI units, and the clear definition of decimal point symbol to use. CONCLUSION: The daily evaluation of Q-Bot results provided early detection of errors and consequently ensured the minimization of error propagation. Integration of a QM software that inspects protocol compliance at a nuclear medicine department provides significant support to detect non-conformities for technologists, and much higher confidence in image quality for physicians.

[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.

[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.

Activity painting: PET images of freely defined activity distributions applying a novel phantom technique.

The aim of this work was to develop a novel phantom that supports the construction of highly reproducible phantoms with arbitrary activity distributions for PET imaging. It could offer a methodology for answering questions related to texture measurements in PET imaging. The basic idea is to move a point source on a 3-D trajectory in the field of view, while continuously acquiring data. The reconstruction results in a 3-D activity concentration map according to the pathway of the point source. A 22Na calibration point source was attached to a high precision robotic arm system, where the 3-D movement was software controlled. 3-D activity distributions of a homogeneous cube, a sphere, a spherical shell and a heart shape were simulated. These distributions were used to measure uniformity and to characterize reproducibility. Two potential applications using the lesion simulation method are presented: evaluation in changes of textural properties related to the position in the PET field of view; scanner comparison based on visual and quantitative evaluation of texture features. A lesion with volume of 50x50x50 mm3 can be simulated during approximately 1 hour. The reproducibility of the movement was found to be >99%. The coefficients of variation of the voxels within a simulated homogeneous cube was 2.34%. Based on 5 consecutive and independent measurements of a 36 mm diameter hot sphere, the coefficient of variation of the mean activity concentration was 0.68%. We obtained up to 18% differences within the values of investigated textural indexes, when measuring a lesion in different radial positions of the PET field of view. In comparison of two different human PET scanners the percentage differences between heterogeneity parameters were in the range of 5-55%. After harmonizing the voxel sizes this range reduced to 2-16%. The general activity distributions provided by the two different vendor show high similarity visually. For the demonstration of the flexibility of this method, the same pattern was also simulated on a small animal PET scanner giving similar results, both quantitatively and visually. 3-D motion of a point source in the PET field of view is capable to create an irregular shaped activity distribution 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.

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.

Holistic polar map for integrated evaluation of cardiac imaging results.

Polar map display (PM) is a comprehensive interpretation of the left ventricle. This is a non-rigid registration of the left ventricle originally for the visual and quantitative analysis of tomographic myocardial perfusion scintigrams. In this scheme the maximal-count circumferential profiles of well-defined short- and long-axis planes are plotted to a map showing the distribution of the perfusion tracer onto a two-dimensional polar representation. The usual coronary artery distribution is often indicated on the PMs of SPECT studies by referring to the regions of the three main coronary branches, nevertheless, the individual variations may differ extensively. We set out to develop an Access (Microsoft)-based computer program that permits an integrated evaluation of the imaging results (coronary angiography, echocardiography and SPECT) on patients with coronary artery disease. This semi-quantitative registration of the coronary tree to a PM focused on the relation between the supplying coronary branches and the myocardial regions of the 16-segment left ventricular evaluating model. All the recorded anatomical and functional data were related to these 16 left ventricular segments, which allowed the direct comparison and holistic synthesis of the results. Two projections were taken into consideration for generation of the coronary PM: from the right anterior oblique projections, the left anterior descendent (LAD)/right coronary artery (RCA) border was assessed through the comparison of the left and right coronary angiograms. The terminations of the visually detected end-arteries showed the separation of the myocardial beds supplied by the two branches. The border of the myocardial beds on the polar map was determined on the "vertical axis" of the local coordinate system. The RCA/ left circumflex (LCx) separation can be determined from the left anterior oblique view. In this projection, the left ventricular septal edge was delineated by the LAD, while the LCx indicated the lateral epicardial surface. The individual coronary artery circulation was typified from among 12 variations in the Holistic Coronary Care program. With this determination of the individual coronary circulation, the lesion-associated segments are generated automatically by the software. The lesion-associated regions are defined as the myocardial bed of a diseased artery distal to the lesion. The PMs generated from the coronary angiographic results were compared with those of 99Tc-labelled MIBI single photon emission computed tomography (SPECT) in order to test the accuracy of the localizing method. The overlap between the segments associated with the coronary lesion and the stress perfusion defects (<80% relative MIBI activity during stress tests) was analyzed in 10 patients with (sub)total coronary occlusion after myocardial infarction. The distributions of the segments with stress perfusion defects on MIBI SPECT gave positive and negative predictive values of coronary occlusion of 0.94 and 0.8, respectively. According to the 16-segment wall motion analysis by echocardiography, the positive and negative predictive values of coronary occlusion for wall motion abnormality were 0.82 and 0.76, respectively. While the distal part of the subtended region usually demonstrated a higher degree perfusion abnormality than the proximal part, the high positive predictive value proved that, during the stress condition, the perfusion defect could be detected in practically all the subtended regions. The low negative predictive value of the coronary lesion for the wall motion abnormality was associated with the remodeling of the entire left ventricle.