Motion correction of SPEC projection before reconstruction

In Single Photon Emission Computed Tomography (SPECT), the data acquisition occurs over a relatively long time, typically in the range of 5-30 minutes. During this period, the patient must lie still to guarantee the image quality. Nevertheless, patient movement has frequently been reported in clinical applications. This movement causes misalignment of the projection frames, which degrades the reconstructed image and may introduce artifacts. However, the ability to detect and correct for the motion using a computational method is valuable for quality assurance of SPECT imaging. In this work a correlation function based on Linogram and Sinogram of the projection is evaluated in order to estimate the occurred motion and correct it for the best alignment. By our implemented method the motion artifacts of our cases reduced considerably and our results showed that the misalignment (motion) between the projections could be found with a small error depending on the resolution of the images (pixel size), and the time and duration of the applied motion during the course of projection acquisition

An fMRI study of human visual cortex in response to spatiotemporal properties of visual stimuli

Background: The brain response to temporal frequencies (TF) has been already reported, but with no study reported for different TF with respect to various spatial frequencies (SF). Materials and Methods: fMRI was performed by 1.5T GE-system in 14 volunteers during checkerboard, with TFs of 4, 6, 8 and 10Hz in low and high SFs of 0.5 and 8cpd. Results: Average percentage BOLD signal change demonstrated the amplitude of the fMRI response to different TFs was maximal in 6Hz for high SF of 8cpd, while, it was maximal at TF of 8Hz for low SF of 0.5cpd. Conclusion: The results are useful for vision therapy (such as the treatment Amblyopia) and visual task selecting in fMRI studies

Spatial frequency modulates the human visual cortical response to temporal frequency variation: An fMRI study

The brain response to temporal frequencies (TF) has been already reported, but with no study for different TFs with respect to various spatial frequencies (SF). Functional Magnetic Resonance Imaging (fMRI) was performed by 1.5 Tesla General Electric-system in 14 volunteers (9 males and 5 females, range 19-26 years) during square-wave reversal checkerboard visual stimulation with different temporal frequencies of 4, 6, 8 and 10 Hz in two states of low SF of 0.5 and high SF of 8 cpd (cycles/degree). The activation map was created using the data obtained from the block designed fMRI study. Pixels whose correlation coefficient value was above a threshold of 0.33, in significant level P <0.01 were considered activated. The average percentage BOLD (blood oxygenation level dependent) signal change for all activated pixels within the occipital lobe, multiplied by the total number of activated pixels within the occipital lobe, was used as the criterion for the strength of the fMRI signal at each state of TF& SF. The results demonstrated that the strength of the fMRI signal in response to different TFs was maximum in 6Hz for high SF of 8cpd, while it was maximum at TF of 8Hz for low SF of 0.5cpd. The results of this study agree with the results of animal invasive neurophysiological studies showing spatial and temporal frequency selectivity of neurons in visual cortical areas. These results can be useful for vision therapy (such as the treatment of Amblyopia) and selecting visual task in fMRI studies. © International Federation for Medical and Biological Engineering 2007

Spatial frequency modulates visual cortical response to temporal frequency variation of visual stimuli: An fMRI study

The brain response to temporal frequency (TF) variation has already been reported, but with no study for different TF with respect to various spatial frequencies (SF). Functional magnetic resonance imaging (fMRI) was performed with a 1.5 Tesla General Electric system in 14 volunteers during square-wave reversal checkerboard visual stimulation with different temporal frequencies of 4, 6, 8 and 10 Hz in two states of low SF of 0.4 and high SF of 8 cpd (cycles/degree). The activation map was created using the data obtained from the block-designed fMRI study. Voxels whose Z value was above a threshold of 3.0, at a significance level P = 0.05, were considered activated. The results demonstrated that the percentage BOLD signal change in response to different TFs was the maximum value at 6 Hz for a high SF of 8 cpd, whereas it was the maximum at TF of 8 Hz for a low SF of 0.4 cpd. The results of this study agree with the results of animal invasive neurophysiological studies showing spatial and temporal frequency selectivity of neurons in visual cortical areas. These results can be useful for vision therapy (such as the treatment of amblyopia) and selecting a visual task in fMRI studies. © 2007 IOP Publishing Ltd

Optimization of visual tasks for detecting visual cortex activity in fMRI studies

The aim of this study was to optimize visual stimuli in various forms of visual tasks for acquiring significant and robust signals. The effects of physical parameters of visual stimuli for detecting visual cortical activity were evaluated by functional magnetic resonance imaging. These parameters were temporal frequency (TF), spatial frequency (SF), the different patterns of activation including: square wave and sine wave grating, and two different states of rest including black and white screen. Functional Magnetic Resonance Imaging (fMRI) was performed by 1.5 Tesla General Electric system in 14 volunteers (9 males and 5 females, range 19-26 years). The activation map was created using the data obtained from the block designed fMRI study. Pixels whose Z value was above a threshold of 2.3, in significant level P=0.05 were considered activated. The average percentage BOLD (blood oxygenation level dependent) signal change for all activated pixels within the occipital lobe, multiplied by the total number of activated pixels within the occipital lobe, was used as a measure for the strength of the fMRI signal at each state of TF& SF. The results demonstrated that the strength of the fMRI signal was maximum in the TF of 8 Hz with low spatial frequency of 0.50 cycle per degree (cpd) and using the black screen in the rest state. However there isn't significant difference between square-wave and sine-wave grating in producing visual activation in cortex. Physical parameters of visual tasks are effective in detecting visual cortical activity, and it is necessary to consider them for taking significant and robust signal. © International Federation for Medical and Biological Engineering 2007

Defective minor spliceosome mRNA processing results in isolated familial growth hormone deficiency

The molecular basis of a significant number of cases of isolated growth hormone deficiency remains unknown. We describe three sisters affected with severe isolated growth hormone deficiency and pituitary hypoplasia caused by biallelic mutations in the RNPC3 gene, which codes for a minor spliceosome protein required for U11/U12 small nuclear ribonucleoprotein (snRNP) formation and splicing of U12-type introns. We found anomalies in U11/U12 di-snRNP formation and in splicing of multiple U12-type introns in patient cells. Defective transcripts include preprohormone convertases SPCS2 and SPCS3 and actin-related ARPC5L genes, which are candidates for the somatotroph-restricted dysfunction. The reported novel mechanism for familial growth hormone deficiency demonstrates that general mRNA processing defects of the minor spliceosome can lead to very narrow tissue-specific consequences.Peer reviewe

Chromosomal instability by mutations in the novel minor spliceosome component CENATAC

Aneuploidy is the leading cause of miscarriage and congenital birth defects, and a hallmark of cancer. Despite this strong association with human disease, the genetic causes of aneuploidy remain largely unknown. Through exome sequencing of patients with constitutional mosaic aneuploidy, we identified biallelic truncating mutations in CENATAC (CCDC84). We show that CENATAC is a novel component of the minor (U12-dependent) spliceosome that promotes splicing of a specific, rare minor intron subtype. This subtype is characterized by AT-AN splice sites and relatively high basal levels of intron retention. CENATAC depletion or expression of disease mutants resulted in excessive retention of AT-AN minor introns in similar to 100 genes enriched for nucleocytoplasmic transport and cell cycle regulators, and caused chromosome segregation errors. Our findings reveal selectivity in minor intron splicing and suggest a link between minor spliceosome defects and constitutional aneuploidy in humans.Peer reviewe