Interslice Gap Research Articles

Automated segmentation and source prediction of bone tumors using ConvNeXtv2 Fusion based Mask R-CNN to identify lung cancer metastasis

Lung cancer, which is a leading cause of cancer-related deaths worldwide, frequently metastasizes to the bones, significantly diminishing patients’ quality of life and complicating treatment strategies. This study aims to develop an advanced 3D Mask R-CNN model, enhanced with the ConvNeXt-V2 backbone, for the automatic segmentation of bone tumors and identification of lung cancer metastasis to support personalized treatment planning. Data were collected from two hospitals: Center A (106 patients) and Center B (265 patients). The data from Center B were used for training, while Center A’s dataset served as an independent external validation set. High-resolution CT scans with 1 mm slice thickness and no inter-slice gaps were utilized, and the regions of interest (ROIs) were manually segmented and validated by two experienced radiologists. The 3D Mask R-CNN model achieved a Dice Similarity Coefficient (DSC) of 0.856, a sensitivity of 0.921, and a specificity of 0.961 on the training set. On the test set, it achieved a DSC of 0.849, a sensitivity of 0.911, and a specificity of 0.931. For the classification task, the model attained an AUC of 0.865, an accuracy of 0.866, a sensitivity of 0.875, and a specificity of 0.835 on the training set, while achieving an AUC of 0.842, an accuracy of 0.836, a sensitivity of 0.847, and a specificity of 0.819 on the test set. These results highlight the model’s potential in improving the accuracy of bone tumor segmentation and lung cancer metastasis detection, paving the way for enhanced diagnostic workflows and personalized treatment strategies in clinical oncology.

3D isotropic MRI of ankle: review of literature with comparison to 2D MRI.

The ankle joint has complex anatomy with different tissue structures and is commonly involved in traumatic injuries. Magnetic resonance imaging (MRI) is the primary imaging modality used to assess the soft tissue structures around the ankle joint including the ligaments, tendons, and articular cartilage. Two-dimensional (2D) fast spin echo/turbo spin echo (FSE/TSE) sequences are routinely used for ankle joint imaging. While the 2D sequences provide a good signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) with high spatial resolution, there are some limitations to their use owing to the thick slices, interslice gaps leading to partial volume effects, limited fluid contrast, and the need to acquire separate images in different orthogonal planes. The 3D MR imaging can overcome these limitations and recent advances have led to technical improvements that enable its widespread clinical use in acceptable time periods. The volume imaging renders the advantage of reconstructing into thin continuous slices with isotropic voxels enabling multiplanar reconstructions that helps in visualizing complex anatomy of the structure of interest throughout their course with improved sharpness, definition of anatomic variants, and fluid conspicuity of lesions and injuries. Recent advances have also reduced the acquisition time of the 3D datasets making it more efficient than 2D sequences. This article reviews the recent technical developments in the domain 3D MRI, compares imaging with 3D versus 2D sequences, and demonstrates the use-case scenarios with interesting cases, and benefits of 3D MRI in evaluating various ankle joint components and their lesions.

Assessment of the distribution and volume of air chambers around the inner auditory canal on high-resolution computed tomography scans of the temporal bone.

Assessment of the distribution and volume of air chambers around the inner auditory canal on high-resolution computed tomography scans of the temporal bone.

Mean and Normalized Apparent Diffusion Coefficient Values and Mean Metabolic Ratios in Cerebral Metastases in Central Indian Rural Hospital Setup

Background: To evaluate mean metabolite ratios and Apparent diffusion co-efficient value with normalization in cerebral metastases using MRS in rural hospital setup in Central India. Method: A cross sectional hospital based observational study conducted over a time period of 2 years. All the cases registered with Acharya Vinoba Bhave Rural Hospital, Sawangi, Wardha, diagnosed on histopathological findings as cerebral metastases were included in this present study. All patients were examined on GE Brivo MRI machine with 1.5 Tesla magnetic field strength in the Department of Radiodiagnosis using b value of 1000 s/sq. mm, slice thickness 5mm, interslice gap 2mm applied in the x, y and z axes, central as well as peripheral portions of the tumor were manually sampled, preferably getting rid of cystic or necrotic areas. Histopathological diagnostic acumen was augmented with ADC values with normalization. Result: Range of ADC values observed was from 0.683 10-3 mm2/s to 0.873 10-3 mm2/s. Normalized ADC values were calculated on basis of observed ADC values and were in range of 0.8537510-3 mm2/s to 1.09125 10-3 mm2/s. Mean ADC value was calculated as 0.749 x 10-3 mm2/s. Mean normalised ADC value was calculated to be 0.9372 x 10-3 mm2/s. Observed metabolite ratios were derived from metabolic values obtained on MRS for Choline, Creatinine, Lipid lactate, myoinositol and n-acetyl aspartate. Range for Choline:Creatinine, Choline:n-acetyl aspartate, choline : myoinositol and choline : lipid lactate was 3.97 to 5.73, 3.24 to 5.76, 4.35 to 5.49 and 0.32 to 0.997 respectively. Mean values for Choline:Creatinine, Choline:n-acetyl aspartate, choline : myoinositol and choline : lipid lactate were 4.1289, 3.7838, 4.1256 and 0.9095 respectively. Conclusion: Research gap analysis towards which research question was framed stands filled up by the generated new knowledge in terms of 'Mean metabolite ratios','Apparent Diffusion Coefficient' and 'Normalised Apparent Diffusion Coefficient' values for cerebral metastases in the present study.

Ferumoxytol-enhanced 4D multiphase, steady-state imaging with magnetic resonance in congenital heart disease: ventricular volume and function across 2D and 3D software platforms.

BackgroundQuantitative ventricular volumetry and function are important in the management of congenital heart disease (CHD). Ferumoxytol-enhanced (FE) 4D multiphase, steady state imaging with contrast enhancement (MUSIC) enables high-resolution, 3D cardiac phase-resolved magnetic resonance imaging (MRI) of the beating heart and extracardiac vessels in a single acquisition and without concerns about renal impairment. We aim to evaluate the semi-automatic quantification of ventricular volumetry and function of 4D MUSIC MRI using 2D and 3D software platforms.MethodsThis HIPAA-compliant and IRB-approved study prospectively recruited 50 children with CHD (3 days to 18 years) who underwent 4D MUSIC MRI at 3.0T between 2013–2017 for clinical indications. Each patient was either intubated in the neonatal intensive care unit (NICU) or underwent general anesthesia at MRI suite. For 2D analysis, we reformatted MUSIC images in Digital Imaging and Communications in Medicine (DICOM) format into ventricular short-axis slices with zero interslice gap. For 3D analysis, we imported DICOMs into a commercially available 3D software platform. Using semi-automatic thresholding, we quantified biventricular volume and ejection fraction (EF). We assessed the bias between MUSIC-derived 2D vs. 3D measurements and correlation between MUSIC vs. conventional 2D balanced steady-state free precession (bSSFP) cine images. We evaluated intra- and inter-observer agreement.ResultsThere was a high degree of correlation between MUSIC-derived volumetric and functional measurements using 2D vs. 3D software (r=0.99, P<0.001). Volumes derived using 3D software platforms were larger than 2D by 0.2 to 2.0 mL/m2 whereas EF measurements were higher by 1.2–3.0%. MUSIC volumetric and functional measures derived from 2D and 3D software platforms corresponded highly with those derived from multi-slice SSFP cine images (r=0.99, P<0.001). The mean difference in volume for reformatted 4D MUSIC relative to bSSFP cine was 1.5 to 3.9 mL/m2. Intra- and inter-observer reliability was excellent.ConclusionsAccurate and reliable ventricular volumetry and function can be derived from FE 4D MUSIC MRI studies using commercially available 2D and 3D software platforms. If fully validated in multicenter studies, the FE 4D-MUSIC pulse sequence may supercede conventional multislice 2D cine cardiovascular MRI acquisition protocols for functional evaluation of children with complex CHD.

Brain tumor visualization for magnetic resonance images using modified shape-based interpolation method

&lt;span&gt;3D visualization plays an essential role in medical diagnosis and setting treatment plans especially for brain cancer. There have been many attempts for brain tumor reconstruction and visualization using various techniques. However, this problem is still considered unsolved as more accurate results are needed in this critical field. In this paper, a sequence of 2D slices of brain magnetic resonance Images was used to reconstruct a 3D model for the brain tumor. The images were automatically segmented using a wavelet multi-resolution expectation maximization algorithm. Then, the inter-slice gaps were interpolated using the proposed modified shape-based interpolation method. The method involves three main steps; transferring the binary tumor images to distance images using a suitable distance function, interpolating the distance images using cubic spline interpolation and thresholding the interpolated values to get the reconstructed slices. The final tumor is then visualized as a 3D isosurface. We evaluated the proposed method by removing an original slice from the input images and interpolating it, the results outperform the original shape-based interpolation method by an average of 3% reaching 99% of accuracy for some slice images.&lt;/span&gt;

Real-world analysis of manual editing of deep learning contouring in the thorax region.

User-adjustments after deep-learning (DL) contouring in radiotherapy were evaluated to get insight in real-world editing during clinical practice. This study assessed the amount, type and spatial regions of editing of auto-contouring for organs-at-risk (OARs) in routine clinical workflow for patients in the thorax region. A total of 350 lung cancer and 362 breast cancer patients, contoured between March 2020 and March 2021 using a commercial DL-contouring method followed by manual adjustments were retrospectively analyzed. Subsampling was performed for some OARs, using an inter-slice gap of 1-3 slices. Commonly-used whole-organ contouring assessment measures were calculated, and all cases were registered to a common reference shape per OAR to identify regions of manual adjustment. Results were expressed as the median, 10th-90th percentile of adjustment and visualized using 3D renderings. Per OAR, the median amount of editing was below 1mm. However, large adjustments were found in some locations for most OARs. In general, enlarging of the auto-contours was needed. Subsampling DL-contours showed less adjustments were made in the interpolated slices compared to simulated no-subsampling for these OARs. The real-world performance of automatic DL-contouring software was evaluated and proven useful in clinical practice. Specific regions-of-adjustment were identified per OAR in the thorax region, and separate models were found to be necessary for specific clinical indications different from training data. This analysis showed the need to perform routine clinical analysis especially when procedures or acquisition protocols change to have the best configuration of the workflow.

MRI sequences and interslice gap influence leptomeningeal metastasis detection in children with brain tumors

Accurate detection of leptomeningeal metastasis (LM) is critical for risk stratification and treatment of pediatric brain tumors. Poor-quality staging MRI has been associated with decreased survival in this population, but technical factors differentiating good from poor quality screening MRIs remain undefined. To test the hypothesis that key technical factors are associated with accurate MRI diagnosis of leptomeningeal metastasis in children with leptomeningeal seeding brain tumors. MRIs acquired at outside facilities and repeated in our institution within 35days for 75 children with leptomeningeal seeding tumors were assessed for slice thickness and gap; use of T2 FLAIR + Contrast, acquisition plane of 3DT1WI + Contrast (brain); axial T1 + Contrast sequence, and use of pre-contrast T1 images (spine). Reported findings were recorded as positive, negative, or equivocal for LM and classified as true positive (TP; unequivocal metastasis), false negative (FN; not reported), false positive (FP; resolved without treatment), or true negative. Wilcoxon signed-rank and Fisher's exact test were used to assess technical differences between TP and FN MRIs. Rate of LM detection was greater with smaller interslice gap in brain (P = 0.003) and spine (P = 0.002); use of T2 FLAIR + Contrast (P = 0.005) and sagittal plane for 3DT1WI + Contrast (P = 0.028) in brain; and use of alternatives to axial TSE/FSE in spine (P = 0.048). Slice thickness was not significant. Pre-contrast T1WI did not contribute to LM diagnosis in spine. Using post-contrast T2 FLAIR and sagittal 3DT1 in brain, small/no interslice gap, and avoiding TSE/FSE axials in spine may facilitate leptomeningeal metastasis detection in children with brain tumors.

Assessment of Brain Deep White Matter Hyperintensities in Smokers in Azerbaijan

Bacground: T2 hyperintense foci (white matter hyperintensities) are seen in the white matter of the brain on magnetic resonance imaging (MRI) in smokers. The aim of the study is to reveal the relationship, number and size of these white matter hyperintensities with smoking in Azerbaijani smoking men and to compare them with the control group. Materials and Methods: Total of 120 patients between 37 and 70 years were included in this study. The mean age was 50,2±0,8. Eighty(80) of the patients were smokers and 40 of them was healthy individuals. In our study we exam the location(according to the brain lobes), size and frequency of T2 hyperintense foci on MRI. We used 1.5-Tesla Magnetom Aera MRI equipment and images obtained with T2 turbo inversion recovery magnitude (TIRM) sequences. MRI images were obtained using TR-9200, TI 2450, TE 84 and 3.5 mm slice thickness, and 10% interslice gap. Results: The mean age of the smokers was 50,7±1,0 (37-70) years. The mean age of the healthy individuals was 49±1,1(39-62) (Pu=0,556). WMH was not found in 21(52,5%) patient from 40 healthy individuals. The average number of WMH detected in 47.5%(19) of patients was 3.2±0,8 (min0-max20) and the average size was 1.9±0,1 mm (min1.5-max 2.5). According to the measurements and numbers performed on 80 smokers included in the study, the average number of WMHs was 8.8±1,5(min0-max70) and the average size was 2.3±1,0 mm(min1.5-max6). At the same time, WMHs were not observed in 28 (35,0%) smokers. It was found that the number of WMH in smokers was higher than in control group-healthy individuals(Pu=0,025). But the size of WMH in smokers was not differ so much than in healthy individuals(Pu=0,459). Conclusion: An increase in the number of white matter hyperintensities in the brain was found in smoking men in Azerbaijan compared to the healthy individuals. There was no significant difference in the statistically correct correlation (in the number and size of the WMH) between those who had smoked for longer years-50 years and those who had smoked the least-15 years. The number of WMH increases with age, regardless of whether the patient smokes or not.

Inter-rater and inter-session reliability of lumbar paraspinal muscle composition in a mobile MRI device.

Objective:To assess the reliability of measurements of paraspinal muscle transverse relaxation times (T2 times) between two observers and within one observer on different time points.Methods:14 participants (9f/5m, 33 ± 5 years, 176 ± 10 cm, 73 ± 12 kg) underwent 2 consecutive MRI scans (M1,M2) on the same day, followed by 1 MRI scan 13–14 days later (M3) in a mobile 1.5 Tesla MRI. T2 times were calculated in T2 weighted turbo spin-echo-sequences at the spinal level of the third lumbar vertebrae (11 slices, 2 mm slice thickness, 1 mm interslice gap, echo times: 20, 40, 60, 80, 100 ms) for M. erector spinae (ES) and M. multifidius (MF). The following reliability parameter were calculated for the agreement of T2 times between two different investigators (OBS1 & OBS2) on the same MRI (inter-rater reliability, IR) and by one investigator between different MRI of the same participant (intersession variability, IS): Test–Retest Variability (TRV, Differences/Mean*100); Coefficient of Variation (CV, Standard deviation/Mean*100); Bland–Altman Analysis (systematic bias = Mean of the Differences; Upper/Lower Limits of Agreement = Bias+/−1.96*SD); Intraclass Correlation Coefficient 3.1 (ICC) with absolute agreement, as well as its 95% confidence interval.Results:Mean TRV for IR was 2.6% for ES and 4.2% for MF. Mean TRV for IS was 3.5% (ES) and 5.1% (MF). Mean CV for IR was 1.9 (ES) and 3.0 (MF). Mean CV for IS was 2.5% (ES) and 3.6% (MF). A systematic bias of 1.3 ms (ES) and 2.1 ms (MF) were detected for IR and a systematic bias of 0.4 ms (ES) and 0.07 ms (MF) for IS. ICC for IR was 0.94 (ES) and 0.87 (MF). ICC for IS was 0.88 (ES) and 0.82 (MF).Conclusion:Reliable assessment of paraspinal muscle T2 time justifies its use for scientific purposes. The applied technique could be recommended to use for future studies that aim to assess changes of T2 times, e.g. after an intense bout of eccentric exercises.

Abstract P770: An Mri-Based Method for Assessing the Extent and Location of Bleeding in a Rat Model of Subarachnoid Hemorrhage

Objective: Studies in subarachnoid hemorrhage (SAH) animal models are limited to early timepoints, after which the brain is extracted to confirm hemorrhage. For long-term studies, blood is resorbed by the time of euthanasia and thus alternative methods of confirming SAH are necessary. Here, we used in vivo MRI to determine the presence, extent, and location of blood in the endovascular perforation rat model of SAH. Methods: Animals were divided into two groups - SAH and sham controls (no perforation). Rats were imaged at 24 hours in a 9.4T MRI scanner. T2-weighted imaging (T2WI) was used to quantify and localize the volume and extension of blood. T2WI was performed with a fast spin echo sequence with TR/TE = 5000/60 ms, FOV = 40x40 mm 2 , 0.75 mm slice thickness, and no interslice gap. SAH was identified as hypointense signal at the skull base, a normally hyperintense region due to cerebrospinal fluid in the basal cisterns. Regions of interest were identified and segmented manually. Pixels were converted to areas, and the total hypointense volume (V hypo ) was computed by summing all areas. V hypo was normalized to total brain volume (TBV) for each animal. Ability to detect blood via MRI was compared to the gold standard of direct visualization of blood after brain extraction using receiver operating characteristic (ROC) curves. The location of blood was plotted along a standardized antero-posterior axis. 3D reconstructions were developed in 3D Slicer to visualize the spatial distribution of hemorrhage. Results: V hypo values were 1.6±1.4 mm 3 sham (n = 8) and 7.5±3.9 mm 3 for SAH (n = 10) [p=0.0003]. This difference persisted when V hypo was normalized to TBV (p=0.0005). There was no difference in the TBV between groups (p=0.1493). V hypo distinguished between SAH and sham animals (p=0.001, area under curve = 0.963). A cutoff of V hypo = 4.63 mm 3 corresponded to 100% specificity and 80% sensitivity for confirming SAH. The spatial distribution of bleeding varied along the antero-posterior axis within the subarachnoid space. Conclusions: We developed an in vivo MRI method for the quantification of SAH blood volume and location in rats. This will be used for future long-term studies to confirm and grade severity of SAH.

2D multislice MP2RAGE sequence for fast T1 mapping at 7 T: Application to mouse imaging and MR thermometry.

To develop a 2D radial multislice MP2RAGE sequence for fast and reliable T1 mapping at 7 T in mice and for MR thermometry. The 2D-MP2RAGE sequence was performed with the following parameters: TI1 -TI2 -MP2RAGETR = 1000-3000-9000 ms. The multiple dead times within the sequence were used for interleaved multislice acquisition, enabling one to acquire six slices in 9 seconds. The excitation pulse shape, inversion selectivity, and interslice gap were optimized. In vitro comparison with the inversion-recovery sequence was performed. The T1 variations with temperature were measured on tubes with T1 ranging from 800 ms to 2000 ms. The sequence was used to acquire T1 maps continuously during 30 minutes on the brain and abdomen of healthy mice. A three-lobe cardinal sine excitation pulse, combined with an inversion slice thickness and an interslice gap of respectively 150% and 50% of the imaging slice thickness, led to a SD and bias of the T1 measurements below 1% and 2%, respectively. A linear dependence of T1 with temperature was measured between 10°C and 60°C. In vivo, less than 1% variation was measured between successive T1 maps in the mouse brain. In the abdomen, no obvious in-plane motion artifacts were observed but respiratory motion in the slice dimension led to 6% T1 underestimation. The multislice MP2RAGE sequence could be used for fast whole-body T1 mapping and MR thermometry. Its reconstruction method would enable on-the-fly reconstruction.

Rapid framework for quantitative magnetization transfer imaging with interslice magnetization transfer and dictionary-driven fitting approaches.

To develop a rapid framework for quantitative magnetization transfer (qMT) imaging based on the 2D interslice MT and dictionary-driven fitting approaches. Sequential balanced steady-state free precession (bSSFP) scanning was performed on a whole human brain in a total of 12 conditions from six different interslice gaps and two different flip angles. To obtain qMT maps, the acquired 12 datasets were fitted to a dictionary predefined by using Bloch equation simulations based on the two-pool MT model. The proposed qMT method was compared to the conventional qMT methods, in terms of qMT parameter maps and processing time. The proposed method yielded qMT maps similar to those of the conventional method, indicating feasibility of modulating MT saturation frequency and power with the interslice gap and flip angle. The whole-brain qMT imaging could be completed in 8min because of the absence of separate MT pulses. The time for processing qMT parameters was significantly reduced through the dictionary-driven approach; it is 1000 times shorter than that without the dictionary-driven approach and 3 times shorter than that with the spoiled gradient recalled echo-qMT method that uses an analytical solution. The proposed dictionary-driven interslice qMT imaging provides qMT maps close to those from the conventional method with significantly reduced scan time and postprocessing time, which can make qMT imaging more clinically acceptable.

PENGARUH VARIASI INTERSLICE GAP TERHADAP KUALITAS CITRA DAN INFORMASI CITRA ANATOMI PADA MRI BRAIN POTONGAN AXIAL T1WI SPIN ECHO

Background : Interslice gap is the distance between slices, usually its value is based on the percentage of slice thickness, interslice gap is one of the parameters that can affect the quality of MRI image. Rarely are radiographers willing and able to manipulate the value of the interslice gap, so it can produce a good image. The purpose of this study is, to determine the effect of interslice gap variation on quality on MRI brain pieces axial T1WI spin echo, to know the difference of interslice gap variation to anatomical image information on MRI brain T1WI spin echo axial, to know the value of interslice gap which has an optimal anatomical image information on MRI brain T1WI spin echo axial.&#x0D; Methods : This type of research is quantitative and qualitative with an experimental approach. The research was conducted at the General Hospital of dr. Sardjito Yogyakarta. The data were 32 images of MRI brain T1WI spin echo from the variation of interslice gap used 0%, 10%, 20%, and 30% from slice thickness 5 mm. The test was performed on image quality that was statistically analyzed by linear regression test. While for information of anatomical image analyzed with Friedman test, from friedman test can be known information of best anatomical image, seen from mean rank.&#x0D; Results : The results of this study indicate that there is an effect of interslice gap variation on quality on MRI brain of T1WI spin echo axial pieces, seen from p value of SNR (0.010) and CNR (0.001) &lt;0.05. In addition there is influence, there is also differences in anatomical image information on MRI brain pieces axial T1WI spin echo, seen from p value that is 0.001 &lt;0.05. seen from the mean rank interslice gap 10% has the best anatomical image information.&#x0D; Conclusion : There is an effect of interslice gap on image quality on MRI brain axial of T1WI spin echo, there is difference of MRI brain anatomical image information of T1WI spin echo axial with interslice gap variation, interslice gap 10% value has the most optimal information.&#x0D;

Analysis of magnetization transfer (MT) influence on quantitative mapping of T2 relaxation time.

Multi-echo spin-echo (MESE) protocol is the most effective tool for mapping T2 relaxation in vivo. Still, MESE extensive use of radiofrequency pulses causes magnetization transfer (MT)-related bias of the water signal, instigated by the presence of macromolecules (MMP). Here, we analyze the effects of MT on MESE signal, alongside their impact on quantitative T2 measurements. Study used 3 models: in vitro urea phantom, ex vivo horse brain, and in vivo human brain. MT ratio (MTR) was measured between single-SE and MESE protocols under different scan settings including varying echo train lengths, number of slices, and inter-slice gap. MTR and T2 values were extracted for each model and protocol. MT interactions biased MESE signals, and in certain settings, the corresponding T2 values. T2 underestimation of up to 4.3% was found versus single-SE values in vitro and up to 13.8% ex vivo, correlating with the MMP content. T2 bias originated from intra-slice saturation of the MMP, rather than from indirect saturation in multi-slice acquisitions. MT-related signal attenuation was caused by slice crosstalk and/or partial T1 recovery, whereas smaller contribution was caused by MMP interactions. Inter-slice gap had a similar effect on in vivo MTR (21.2%), in comparison to increasing the number of slices (18.9%). MT influences MESE protocols either by uniformly attenuating the entire echo train or by cumulatively attenuating the signal along the train. Although both processes depend on scan settings and MMP content, only the latter will cause underestimation of T2 .

Efficient interpolated compressed sensing reconstruction scheme for 3D MRI

3D magnetic resonance imaging (3D MRI) is one of the most preferred medical imaging modalities for the analysis of anatomical structures where acquisition of multiple slices along the slice select gradient direction is very common. In 2D multi-slice acquisition, adjacent slices are highly correlated because of very narrow inter-slice gaps. Application of compressed sensing (CS) in MRI significantly reduces traditional MRI scan time due to random undersampling. The authors first propose a fast interpolation technique to estimate missing samples in the k-space of a highly undersampled slice (H-slice) from k-space (s) of neighbouring lightly undersampled slice/s (L-slice). Subsequently, an efficient multislice CS-MRI reconstruction technique based on weighted wavelet forest sparsity, and joint total variation regularisation norms is applied simultaneously on both interpolated H and non-interpolated L-slices. Simulation results show that the proposed CS reconstruction for 3D MRI is not only computationally faster but significant improvements in terms of visual quality and quantitative performance metrics are also achieved compared to the existing methods.

The Effect of Varying Slice Thickness and Interslice Gap on T1 and T2 Measured with the Multidynamic Multiecho Sequence.

Purpose:The purpose of our study was to investigate the effect of different slice thicknesses and/or interslice gaps on longitudinal and transverse relaxation times (T1 and T2) measured by a multi-dynamic, multi-echo (MDME) sequence.Materials and Methods:This retrospective study included nine healthy subjects who underwent MDME sequence (at 3T) with four different combinations of slice thicknesses and/or interslice gaps: slice thickness of 4 mm and interslice gap of 0 mm (TH4/G0), TH4/G1, TH5/G0, and TH5/G1. T1 and T2 were measured in various brain regions by a qualified neuroradiologist with 8 years of clinical experience: the frontal white matter (WM), occipital WM, genu, splenium, frontal cortex, thalamus, putamen, caudate head, and cerebrospinal fluid (CSF). The paired samples t-test was used to investigate the effect of different slice thicknesses and interslice gaps (TH4/G0 versus TH4/G1 and TH5/G0 versus TH5/G1). P < 0.013 was considered statistically significant.Results:T2 in all brain regions and T1 in the frontal WM, putamen, and CSF did not significantly change for different slice thicknesses and/or gaps (Ps > 0.013). In addition, T1 in all brain regions of interest did not significantly change between TH4/G0, TH4/G1, TH5/G0 and TH5/G1. However, T1 in some of the brain regions was higher with TH4/G0 than with TH5/G0 (occipital WM, frontal cortex, and caudate head) and with TH4/G1 than with TH5/G1 (occipital WM, genu, splenium and thalamus, all Ps < 0.013).Conclusion:T2 estimated using the MDME sequence was stable regardless of slice thickness or gap. Although the sequence seems to provide stable relaxation values, identical slice thicknesses need to be used for follow-up to prevent potential T1 changes.

Diffusion tensor imaging and tractography of the sciatic and femoral nerves in healthy volunteers at 3T

BackgroundThe aim was to clarify the normal fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the sciatic and femoral nerves at the level of the hip joint and to visualize the neural tracts with diffusion tensor imaging (DTI).MethodsTwenty-four healthy volunteers (12 men and 12 women, age 20–29 years) underwent DTI for visualization with tractography and quantification of FA and ADC values on a 3 Tesla MRI (b value = 800 s/mm2, motion probing gradient, 11 directions, time to repeat/echo time = 9000/72.6 ms, axial slice orientation, slice thickness = 3.0 mm with no inter-slice gap, field of view = 320 × 320 mm, 96 × 192 matrix, 75 slices, number of acquisitions = 4). Regions of interest in the sciatic nerve were defined at the femoral head, the S1 root, and the midpoint levels. The femoral nerve was evaluated at 3–4 cm proximal to the femoral head level.ResultsThe tractography of the sciatic and femoral nerves were visualized in all participants. The mean FA values of the sciatic nerve were increased distally from the S1 root level, through the midpoint, and to the femoral head level (0.314, 0.446, 0.567, p = 0.001, respectively). The mean FA values of the femoral nerve were 0.565. The mean ADC values of the sciatic nerves were significantly lower in the S1 root level than in the midpoint and the femoral head level (1.481, 1.602, 1.591 × 10−3 × 10−3 mm2/s, p = 0.001, respectively). The ADC values of the femoral nerve were 1.439 × 10−3 mm2/s. FA and ADC values showed moderate to substantial inter- and intra-observer reliability without significant differences in gender or laterality.ConclusionVisualization and quantification of the sciatic and femoral nerves simultaneously around the hip joint were achieved in healthy young volunteers with DTI. Clinical application of DTI is expected to contribute to hip pain research.

Imaging Facilities' Adherence to PI-RADS v2 Minimum Technical Standards for the Performance of Prostate MRI

This study aimed to assess variability in imaging facilities' adherence to the minimum technical standards for prostate magnetic resonance imaging acquisition established by Prostate Imaging-Reporting and Data System (PI-RADS) version 2 (v2). A total of 107 prostate magnetic resonance imaging examinations performed at 107 unique imaging facilities after the release of PI-RADS v2 and that were referred to a tertiary care center for secondary interpretation were included. Image sets, DICOM headers, and outside reports were reviewed to assess adherence to 21 selected PI-RADS v2 minimum technical standards. Hardware arrangements were 23.1%, 1.5T without endorectal coil; 7.7%, 1.5T with endorectal coil; 63.5%, 3T without endorectal coil; and 5.8%, 3T with endorectal coil. Adherence to minimum standards was lowest on T2 weighted imaging (T2WI) for frequency resolution ≤0.4 mm (16.8%) and phase resolution ≤0.7 mm (48.6%), lowest on diffusion-weighted imaging (DWI) for field of view (FOV) 120-220 mm (30.0%), and lowest on dynamic contrast-enhanced (DCE) imaging for slice thickness 3 mm (33.3%) and temporal resolution <10 s (31.5%). High b-value (≥1400 s/mm2) images were included in 58.0% (calculated in 25.9%). Adherence to T2WI phase resolution and DWI inter-slice gap were greater (P < .05) at 3T than at 1.5T. Adherence did not differ (P > .05) for any parameter between examinations performed with and without an endorectal coil. Adherence was greater for examinations performed at teaching facilities for T2WI slice thickness and DCE temporal resolution (P < .05). Adherence was not better for examinations performed in 2016 than in 2015 for any parameter (P > .05). Facilities' adherence to PI-RADS v2 minimum technical standards was variable, being particularly poor for T2WI frequency resolution and DCE temporal resolution. The standards warrant greater community education. Certain technical standards may be too stringent, and revisions should be considered.

CT head findings in suspected cases of head injury

Background: Head injury is one of the leading causes of morbidity and mortality throughout the world. Fall injury is the main cause of head trauma followed by road traffic accidents (RTA) and physical assault. Every victim with altered level of consciousness must be evaluated for brain injury. Radiological evaluation has undergone dramatic changes with the advent of computed tomography (CT) as it can precisely define the nature and location of the culprit lesion(s).Aims and Objective: To identify the major CT scan findings in suspected cases of Head injury.Materials and Methods: Three hundred seventeen patients of age 4 years and above, with suspected cases of head injury attending emergency department of TUTH during a period of 3 months (28 June 2012 to 28 September 2012) were included in this study. Non-contrast CT scan of head was performed in a single slice Hitachi Spiral CT scanner and 10 mm axial slices of head without any interslice gap were obtained at 15-20 degrees to the canthomeatal line. Data analysis was performed in SPSS v.21.0 software.Results: From 317 patients studied 198(62.5%) were male and 119 (37.5%) were female. Head injury was more common in male. 80(25.23%) were below 15 years of age, 221(69.73%) were between 16 to 65 years and only 16(5.04%) were above 66 years of age. The mean age was 28.57 years. In 239(75.4%) of patients the CT scan was normal. The most common cause of head injury was fall which was found in 210(66.2%) patients followed by RTA 82(25.9%) and Physical Assault 25(7.9%). Fall as a cause of head injury was more common in children and old people, with the RTA being more common in adults and adolescents. The most common positive finding in CT was contusion which was found in 32(10.1%), 25(7.9%) had SDH, 11(3.5%) of the patients had EDH, 10(3.2%) had SAH. Headache was found to be nonspecific for predicting positive CT findings.Conclusion: CT was found highly sensitive in demonstrating fractures and was considered the modality of choice when imaging suspected cases of head injury and in emergency patients due to its accuracy, reliability, safety and wide availability.Asian Journal of Medical Sciences Vol.8(2) 2017 76-81