Accuracy of Visual Assessment of Dopamine Transporter Imaging in Early Parkinsonism

Dopamine transporter (DaT) imaging may be supportive in the initial clinical diagnostic workup in patients with suspected parkinsonian diseases, given that the method has the potential to detect dopaminergic degeneration. We investigated the diagnostic accuracy of visual assessment of the initial DaT single-photon emission CT (DaT-SPECT) with ¹²³I-FP-CIT in a large group of early-stage parkinsonian patients. After inclusion in a long-term multidisciplinary population-based prospective study, a baseline DaT-SPECT was done in 171 incidental, L-dopa-naïve, parkinsonian patients (102 men and 69 women) and 37 healthy controls (19 men and 18 women). The results of the DaT-SPECTs were linked to criteria-based clinical diagnoses, which were set after a mean follow-up of 4.6 (±1.7) years. The outcome of the visual assessment was also compared with that of a semiquantitative evaluation method using regions of interest to measure uptake ratios in the caudate and putamen. We found that visual assessment of DaT-SPECT in clinically diagnosed incidental Parkinson's disease patients had a sensitivity of 94% and a specificity of 92%, rendering a positive likelihood ratio of 11.75 and a negative likelihood ratio of 0.07. The proportion of false positives was 1.4% and false negatives 4.8% at baseline. These figures were comparable to those of the semiquantitative method. This study demonstrates that visual interpretation of presynaptic dopamine imaging with ¹²³I-FP-CIT offers reliable support in the diagnostic procedure of early parkinsonian diseases.

Alterations in gene expression during radiation-induced mitotic catastrophe in HeLa Hep2 cells

AIM

To explore kinetic changes in the gene expression profile during radiation-induced mitotic catastrophes.

MATERIALS AND METHODS

Gene expression changes were measured in HPV-infected HeLa Hep2 tumor cells following exposure to 5 Gy of ionizing radiation ((60)Co). Signaling pathways were explored and correlated to the biological responses linked to mitotic catastrophe.

RESULTS

Following irradiation a transient G2-arrest was induced. Anaphase bridge formation and centrosome hyperamplification was observed. These phenotypical changes correlated well with the observed gene expression changes. Genes with altered expression were found to be involved in mitotic processes as well as G2- and spindle assembly checkpoints. Also centrosome-associated genes displayed an increased expression.

CONCLUSION

This study elucidates specific characteristics in the altered gene expression pattern induced by irradiation, which can be correlated to the events of mitotic catastrophe in HeLa Hep2 cells. Therapeutic strategies modulating these alterations might potentiate future therapy and enhance tumor cell killing.

Dopamine release in nucleus accumbens during rewarded task switching measured by [¹¹C]raclopride

Reward and motivation have positive influences on cognitive-control processes in numerous settings. Models of reward implicate corticostriatal loops and the dopamine (DA) system, with special emphasis on D2 receptors in nucleus accumbens (NAcc). In this study, 11 right-handed males (35-40 years) were scanned with positron emission tomography (PET) in a single [(11)C]raclopride dynamic scan during rewarded and non-rewarded task switching. Rewarded task switching (relative to baseline task switching) decreased [(11)C]raclopride binding in NAcc. Decreasing NAcc [(11)C]raclopride binding was strongly associated with task reaction time measures that reflect individual differences in effort and control strategies. Voxelwise analyses additionally revealed reward-related DA release in anterodorsal caudate, a region previously associated with task-switching. These PET findings provide evidence for striatal DA release during motivated cognitive control, and further suggest that NAcc DA release predicts the task reaction time benefits of reward incentives.

Cross-camera comparison of ROI-based semi-quantitative ¹²³I-IBZM SPECT data in healthy volunteers using an anthropomorphic phantom for calibration

BACKGROUND

In (123)I-Iolopride (IBZM) SPECT reference values may diverge between camera systems. If multicenter pooling of normal material databases is needed, differences in measured semi-quantitative data due to equipment performance and reconstruction parameters have to be investigated in each instance to determine the comparability.

PURPOSE

To explore the differences in (123)I-IBZM measured uptake ratios between two different gamma cameras in healthy controls, the intra-rater reproducibility of the image evaluation method and the possibility to equalize uptake ratios by calibration through an anthropomorphic phantom.

MATERIAL AND METHODS

Differences in ROI-based semi-quantitative data from two different gamma camera systems, the three-headed brain dedicated Neurocam and the two-headed multipurpose hybrid system Infinia Hawkeye, were studied using image data from a group of healthy volunteers and an anthropomorphic brain-phantom scanned with both cameras. Several reconstruction methods and corrections were applied. To test the reliability of the ROI method, the intra-observer reproducibility was determined for the ROI method in this study.

RESULTS

The ROI method had a high reliability. Differences in mean measured uptake (123)I-IBZM ratios in healthy controls varied between 2.9% and 6.5% depending on reconstruction and correction for attenuation and scatter. After calibration, the differences decreased. There were no statistically significant differences between corrected ratios from the two camera systems in the study when images were reconstructed with attenuation correction.

CONCLUSION

The conformity of uptake ratios in attenuation corrected (123)I-IBZM images derived from the two different cameras was improved by using an anthropomorphic phantom for calibration.

Subcentimeter tumor lesion delineation for high-resolution 18F-FDG PET images: optimizing correction for partial-volume effects

In PET, partial-volume effects cause errors in estimation of size and activity for small objects with radiopharmaceutical uptake. Recent methods for image reconstruction, compared with traditional reconstruction techniques, include algorithms for resolution recovery that result in images with higher resolution and enable quantification of size and activity of smaller objects. The purpose of this study was to evaluate a combination of 2 algorithms for volume delineation and partial-volume correction on uptake volumes smaller than 0.7 mL using image reconstruction algorithms with and without resolution recovery.

METHODS

Volumes of interests (VOIs) were delineated using a threshold intensity calculated as a weighted sum of tumor and background intensities. These VOIs were used for calculating correction factors by convolving a tumor mask with the system point-spread function. The methods algorithms were evaluated using a phantom constructed from 5 small different-sized balloons filled with (18)F-FDG in background activity. Six different backgrounds were used. Data were acquired using a PET/CT scanner, and the images were reconstructed using 2 iterative algorithms, one of which used a resolution recovery algorithm.

RESULTS

For the images reconstructed using the resolution recovery algorithm, the method for volume delineation resulted in VOI sizes that were correct within 1 SD for all balloons of a volume of 0.35 mL (equivalent diameter, 8.8 mm) and larger, in all backgrounds. For the images reconstructed without resolution recovery, the VOI sizes were background-dependent and generally less accurate. Correct volume delineations generally led to accurate activity estimates.

CONCLUSION

The algorithms tested on the phantom developed for this study could, for this PET camera and these reconstruction algorithms, be used for accurate volume delineation and activity quantification of lesions 0.35 mL and larger.

Memory aging and brain maintenance

Episodic memory and working memory decline with advancing age. Nevertheless, large-scale population-based studies document well-preserved memory functioning in some older individuals. The influential ‘reserve’ notion holds that individual differences in brain characteristics or in the manner people process tasks allow some individuals to cope better than others with brain pathology and hence show preserved memory performance. Here, we discuss a complementary concept, that of brain maintenance (or relative lack of brain pathology), and argue that it constitutes the primary determinant of successful memory aging. We discuss evidence for brain maintenance at different levels: cellular, neurochemical, gray- and white-matter integrity, and systems-level activation patterns. Various genetic and lifestyle factors support brain maintenance in aging and interventions may be designed to promote maintenance of brain structure and function in late life.

Sentinel node detection in renal cell carcinoma. A feasibility study for detection of tumour-draining lymph nodes

OBJECTIVE

To evaluate the feasibility of performing sentinel node detection in patients with renal cell carcinoma (RCC).

MATERIALS AND METHODS

An open series of 13 arbitrarily selected patients with T1b-T3b RCC scheduled for radical nephrectomy at a single Tertiary Academic Centre were examined with different modalities of sentinel node detection. Preoperative ultrasonography-guided injection of radioactive isotope, lymphoscintigram and single photon emission computed tomography/computed tomography, followed by intraoperative gamma-probe detection and Patent Blue detection, as well as postoperative scintigram of the main specimen were the planned interventions. These investigations were performed in conjunction with intended open radical nephrectomy.

RESULTS

In 10 of the 13 patients sentinel node detection was achieved with 32 sentinel nodes displayed. Radio-guided surgery using an intraoperative gamma-probe resulted in the highest realtive detection rate with detection of sentinel nodes in nine patients. In total, nine metastatic sentinel nodes were detected in three patients. One patient, preoperatively staged as N+, was restaged after sentinel node detection and histopathology as pN0.

CONCLUSIONS

Sentinel node detection in renal tumours is feasible although evaluation of different modes of detection needs further refinement and standardization. All nodes preoperatively detected by routine computed tomography as suspicious metastatic lesions were confirmed as sentinel nodes, including two nodes considered as metastatic by preoperative routine imaging but ultimately staged as non-metastatic sentinel nodes.

Association of adipose tissue blood flow with fat depot sizes and adipokines in women

OBJECTIVE

To explore possible associations between adipose tissue (AT) blood flow (ATBF), AT depot sizes and adipocyte-derived hormones (adipokines) in women.

SUBJECTS

In all, 43 healthy women were divided into four groups: normal-weight (n=11) and obese (n=11) pre-menopausal women and normal-weight (n=10) and obese (n=11) post-menopausal women.

METHODS

Fasting levels of adipokines were obtained, and a single-slice computed tomography scan at the level of L4-L5 was used to estimate fat depot sizes. ATBF was assessed by xenon washout while in a fasting state and after oral glucose load. We also measured glucose, insulin and non-esterified fatty acids.

RESULTS

Total, subcutaneous and visceral AT areas strongly correlated with ATBF (all P<0.001). Circulating leptin levels strongly and inversely correlated with ATBF (P=0.001), but this association did not remain after adjustment for body mass index. Adiponectin was not associated with blood flow.

CONCLUSION

ATBF is closely linked to subcutaneous and visceral AT size. Further analyses are needed to determine possible mediators of this association, including mechanistic studies to assess a putative role for leptin as a significant modulator of blood flow.

H HRMAS NMR Derived Bio-markers Related to Tumor Grade, Tumor Cell Fraction, and Cell Proliferation in Prostate Tissue Samples

A high-resolution magic angle spinning NMR spectroscopic approach is presented for evaluating the occurrence, amount and aggressiveness of cancer in human prostate tissue samples. Using this technique, key metabolites in malignant and non-malignant samples (n = 149) were identified, and patterns of their relative abundance were analyzed by multivariate statistical methods. Ratios of various metabolites – including (glycerophophorylcholine + phosphorylcholine)/creatine, myo-inositol/scyllo-inositol, scyllo-inositol/creatine, choline/creatine, and citrate/creatine – correlated with: i) for non-malignant tissue samples, the distance to the nearest tumor and its Gleason score and; ii) the fraction of tumor cells present in the sample; and iii) tumor cell proliferation (Ki67 labelling index). This NMR-based approach allows the extraction of information that could be useful for developing novel diagnostic methods for prostate cancer.

Detection of Local Prostate Metabolites by Hrmas Nmr Spectroscopy: A Comparative Study of Human and Rat Prostate Tissues

The use of magnetic resonance spectroscopy (MRS) for the detection of in-vivo metabolic perturbations is increasing in popularity in Prostate Cancer (PCa) research on both humans and rodent models. However, there are distinct metabolic differences between species and prostate areas; a fact making general conclusions about PCa difficult. Here, we use High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HRMAS NMR) spectroscopy to provide tissue specific identification of metabolites and their relative ratios; information useful in providing insight into the biochemical pathways of the prostate. As our NMR-based approach reveals, human and rat prostate tissues have different metabolic signatures as reflected in numerous key metabolites, including citrate and choline compounds, but also aspartate, lysine, taurine, glutamate, glutamine, creatine and inositol. In general, distribution of these metabolites is not only highly dependent on the species (human versus rat), but also on the location (lobe/zone) in the prostate tissue and the sample pathology; an observation making HRMAS NMR of intact tissue samples a promising method for extracting differences and common features in various experimental prostate cancer models.

Pre- and postsynaptic dopamine SPECT in the early phase of idiopathic parkinsonism: a population-based study

PURPOSE

The aim of this study was to assess the diagnostic contribution of pre- and postsynaptic dopamine SPECT in drug-naïve patients with early idiopathic parkinsonism and to investigate possible differences between idiopathic Parkinson's disease (PD) and atypical parkinsonian syndromes (APS) and possible differences in motor subtypes of parkinsonism.

METHODS

A group of 128 newly diagnosed idiopathic parkinsonian patients and 48 healthy controls was studied. Presynaptic baseline SPECT with (123)I-FP-CIT was performed in all patients and in 120 patients also a baseline postsynaptic SPECT with (123)I-IBZM. Clinical diagnoses were reassessed after 12 months.

RESULTS

Presynaptic uptake in the putamen and caudate was significantly reduced in patients compared to controls. Presynaptic uptake ratios were not different between PD patients and patients with APS, and postsynaptic uptake in APS was not significantly reduced compared to PD or controls. In half of the APS patients both pre- and postsynaptic uptake ratios were reduced on the same side in the striatum. Impaired motor performance was associated with decreased presynaptic uptake in the putamen in PD. The postural instability and gait difficulty (PIGD) subtype of PD had lower presynaptic uptake ratios than patients with tremor-dominated (TD) symptoms.

CONCLUSION

Not only presynaptic putamen uptake ratios, but also caudate ratios were reduced in a majority of the patients in our study. At baseline scan, i.e. in an early stage of the disease, the accuracy of excluding APS in the whole study population was 85% using a combination of pre- and postsynaptic SPECT. Already at baseline, lower presynaptic SPECT ratios were seen in PD with PIGD at onset compared to those with TD subtype.

Dopamine D2 receptor SPECT with (123)I-IBZM: evaluation of collimator and post-filtering when using model-based compensation-a Monte Carlo study

In (123)I-IBZM brain SPECT, the main interest is the activity uptake in the striatum relative to the background, and semi-quantitative techniques using regions of interest are typically used for this purpose. Uncertainties in the measured uptakes can however be a problem due to low contrasts and high noise levels. Like SPECT in general, IBZM SPECT should benefit from reconstruction methods that include model-based compensation, but it is important that image acquisition is optimized for this technique. An important factor is the choice of collimator. In this study we compare four different parallel-hole collimators for IBZM SPECT regarding overall quantitative accuracy and measured uptake ratio as a function of image noise and uncertainty. The collimators are low-energy high-resolution (LEHR), low-energy general-purpose (LEGP), extended LEGP (ELEGP) and medium-energy general-purpose (MEGP). The effect of three Butterworth post-filters with cut-off frequencies of 0.3, 0.45 and 0.6 cm(-1) (power factor 8) is also studied. All raw-data projections are produced using Monte Carlo simulations. Of the investigated collimators, the one that is most sensitive to the primary photons, ELEGP, proved to be the most optimal for realistic noise levels. Butterworth post-filtering is advantageous, and the cut-off frequency 0.45 cm(-1) was the best compromise in this study.

Apoptotic signalling in HeLa Hep2 cells following 5 Gy of cobalt-60 gamma radiation

BACKGROUND

The apoptotic signalling pathways involved in the delayed type of apoptosis occurring in HeLa Hep2 cells following radiation were investigated.

MATERIALS AND METHODS

HeLa Hep2 cells were exposed to 5 Gy of cobalt-60 radiation. The activation of caspase-2, caspase-8, caspase-9 and effector caspase-3 was investigated by caspase assay plates and Western blots. Cleavage of poly (ADP-ribose) polymerase (PARP) was analysed on Western blots. HeLa Hep2 cells were irradiated with or without preincubation with inhibitors of protein synthesis (cycloheximide, CHX) and caspases, followed by TUNEL staining and caspase assay plate evaluation.

RESULTS

Initiator caspases-2, -8, -9, and effector caspase-3, were found to be activated and PARP cleaved following irradiation. CHX completely inhibited the caspase activation and the associated apoptosis. Pretreatment with caspase-2 inhibitor indicated that caspase-2 was involved in the execution of the apoptosis.

CONCLUSION

Activation of the apoptotic signalling pathways following irradiation of HeLa Hep2 cells includes components from the intrinsic as well as the extrinsic pathways and seems to require de novo protein synthesis.

Striatal dopamine D2 binding is related to frontal BOLD response during updating of long-term memory representations

Multi-modal brain imaging was used to examine the relation between individual differences in resting-state striatal dopamine D2 binding and the magnitude of prefrontal BOLD activation during updating of long-term memory (LTM) representations. Increased activity in the left prefrontal cortex was observed when LTM updating was required, and there was a positive correlation between striatal D2 activity and the magnitude of left prefrontal activity during updating. These findings support predictions from neurocomputational models of a relation of dopaminergic neurotransmission to transient cognitive operations and related brain activity.

Iodine-131 induces mitotic catastrophes and activates apoptotic pathways in HeLa Hep2 cells

Iodine-131 (131I) has been used both in unconjugated form and conjugated to antibody derivates (i.e., radioimmunotherapy; RIT) to treat malignant diseases. The mechanisms by which 131I-irradiation causes growth retardation are, however, inadequately understood. The aim of this study was to elucidate the sequential molecular and cellular events that initiate cell death in HeLa Hep2 cells exposed to 131I. In this paper, HeLa Hep2 cells were found to display a transient G2-M arrest following irradiation, but then reentered the cell cycle still containing unrepaired cellular damage. An increase of multipolar mitotic spindles, as well as a significant increase in centrosome numbers from 8.8% +/- 1.9% in controls to 54.7% +/- 2.2% in irradiated cells, was observed (p < 0.0001). A subsequent failure of cytokinesis caused the cells to progress into mitotic catastrophe. This was accompanied by the formation of giant cells with multiple nuclei, multilobulated nuclei, and an increased frequency of polyploidy cells. A fraction of the cells also displayed apoptotic features, including the activation of initiator caspases-2, -8, -9, and effector caspase-3, as well as cleavage of poly(ADP-ribose) polymerase, a cell-death substrate for active caspase-3. These findings demonstrate that mitotic catastrophes and the activation of a delayed type of apoptosis might be important mechanisms involved in cell death following the RIT of solid tumors with -emitting radionuclides, such as 131I.

Gaussian prefiltering of 123I DAT SPECT images when using depth-independent resolution recovery

Previously we have investigated a depth-independent compensation for collimator detector response (CDR) included in the OSEM reconstruction, intended for SPECT images that have been corrected for scatter and septal penetration using convolution-based methods. In this work, the aim was to study how different filtering strategies affect contrast as a function of noise when using Gaussian smoothing filters in combination with the above-described CDR compensation. The evaluation was performed for (123)I dopamine transporter (DAT) SPECT images. Prefiltering with 2D Gaussian filter kernels, where the deterioration in resolution is included in the depth-independent CDR compensation, was compared to conventional postfiltering with 3D Gaussian filter kernels. Images reconstructed without filtering are also included in the comparison. It was found that there is little benefit in noise reduction when using CDR compensation. However, this variant of prefiltering gives consistently higher contrasts as a function of noise compared with the postfiltering alternative, and that could be of interest when using other types of filters with contrast improving properties.