Implementing the basic CT backprojecting algorithm in android mobile application

We have implemented the basic steps for the FDK backprojecting algorithm in computed tomography. Application works from the set of preloaded projections and uses OpenCV libraries for FFT, convolution, frequency space image filtering, image’s brightness, contrast and quality manipulation. Compared to the desktop implementation, the calculation-intensive part of the application was moved to the asynchronous background task hosted by an android fragment. This allows the task to survive the application’s configuration changes and to run in the background even if the main activity was destroyed. The minimalistic interface with the access to all main backprojecting parameters was implemented. The result of backprojection is saved as an image in the download folder of the phone. The user also has the control over the reconstructed slice location along the Z axis.

RADIATION DOSE DETERMINATION IN ABDOMINAL CT EXAMINATIONS OF CHILDREN AT SUDANESE HOSPITALS USING SIZE-SPECIFIC DOSE ESTIMATES

In this study, we thought to estimate the radiation exposure of children undergoing multi-detector CT examinations using size-specific dose estimates (SSDE). Console-displayed volume computed tomography dose index (CTDIvol) were recorded for a total of 78 paediatric abdominal CT examinations performed in six hospitals. Measurements of the patient diameters were taken from the mid-slice location on the transverse and scout CT images. Size-specific conversion coefficients were used to translate CTDIvol to the SSDE, according AAPM Report 204. For children aged 0–1 y, CTDIvol, SSDEtrans (from transverse images) and SSDEsco (from scout images) were: 12.80 ± 16.10, 14.43 ± 13.22; and 14.37 ± 13.03 mGy; respectively. For children aged 1–5 y, CTDIvol, SSDEtrans and SSDEsco were: 12.11 ± 14.47, 18.8 ± 18.61 and 16.51 ± 13.55 mGy; respectively. The obtained doses are higher than the corresponding diagnostic reference levels. SSDE increase with patient size as results of tube current modulation and is therefore a valuable tool for dose optimisation.

Influence of longitudinal position on the evolution of steady-state signal in cardiac cine balanced steady-state free precession imaging

Background Emerging quantitative cardiac magnetic resonance imaging (CMRI) techniques use cine balanced steady-state free precession (bSSFP) to measure myocardial signal intensity and probe underlying physiological parameters. This correlation assumes that steady-state is maintained uniformly throughout the heart in space and time. Purpose To determine the effects of longitudinal cardiac motion and initial slice position on signal deviation in cine bSSFP imaging by comparing two-dimensional (2D) and three-dimensional (3D) acquisitions. Material and Methods Nine healthy volunteers completed cardiac MRI on a 1.5-T scanner. Short axis images were taken at six slice locations using both 2D and 3D cine bSSFP. 3D acquisitions spanned two slices above and below selected slice locations. Changes in myocardial signal intensity were measured across the cardiac cycle and compared to longitudinal shortening. Results For 2D cine bSSFP, 46% ± 9% of all frames and 84% ± 13% of end-diastolic frames remained within 10% of initial signal intensity. For 3D cine bSSFP the proportions increased to 87% ± 8% and 97% ± 5%. There was no correlation between longitudinal shortening and peak changes in myocardial signal. The initial slice position significantly impacted peak changes in signal intensity for 2D sequences ( P < 0.001). Conclusion The initial longitudinal slice location significantly impacts the magnitude of deviation from steady-state in 2D cine bSSFP that is only restored at the center of a 3D excitation volume. During diastole, a transient steady-state is established similar to that achieved with 3D cine bSSFP regardless of slice location.

Abstract 2574: Accuracy of Apical Rotation by Two-dimensional Speckle Tracking Echocardiography is Influenced by Apical Slice Location.

Background : During the cardiac cycle, there is a systolic twist and an early diastolic untwist about LV long axis, because of opposite rotation of the basal and apical segments. Previous studies showed that speckle tracking echocardiography (STE) allows to measure the rotation of these segments and thereby to assess global LV torsion. Unfortunately, STE does not always allow visualization of the real apex, thus raising concerns about the reliability of LV torsion data using this approach. Methods : We compared LV apical rotation by tagged magnetic resonance (cMR) and STE in 30 patients with normal regional and global systolic function. With cMR, rotation was measured on serial contiguous 10 mm thick short-axis (SAX) sections, whereas with STE, it was only obtained on the most apical available SAX section. cMR and STE were compared using either the most apical cMR SAX slice or the cMR slice that best matched the end-diastolic internal dimensions of the available STE slice. Results : LV rotation measured by cMR decreased from apex to base (Fig 1 ). When using the best matched cMR SAX slice, cMR and STE were well correlated (r=0.7, Fig 2 , black dots). By contrast, when using the most apical cMR SAX slice, the correlation between cMR and STE was lost (Fig 2 , white dots). By comparing end-diastolic internal dimensions, the level of the STE slice was found to be at the real apex in 10% of pts, and at 10, 20 and 30 mm below the apex in 27%, 50% and 13% of pts, respectively. Conclusion : Although STE allows to measure LV apical rotation, it rarely does so at the level of the real apex. This results in an almost systematic and mostly unpredictable underestimation of apical rotation.

Estimating whole body intermuscular adipose tissue from single cross-sectional magnetic resonance images

Intermuscular adipose tissue (IMAT), a novel fat depot linked with metabolic abnormalities, has been measured by whole body MRI. The cross-sectional slice location with the strongest relation to total body IMAT volume has not been established. The aim was to determine the predictive value of each slice location and which slice locations provide the best estimates of whole body IMAT. MRI quantified total adipose tissue of which IMAT, defined as adipose tissue visible within the boundary of the muscle fascia, is a subcomponent. Single-slice IMAT areas were calculated for the calf, thigh, buttock, waist, shoulders, upper arm, and forearm locations in a sample of healthy adult women, African-American [ n = 39; body mass index (BMI) 28.5 ± 5.4 kg/m2; 41.8 ± 14.8 yr], Asian ( n = 21; BMI 21.6 ± 3.2 kg/m2; 40.9 ± 16.3 yr), and Caucasian ( n = 43; BMI 25.6 ± 5.3 kg/m2; 43.2 ± 15.3 yr), and Caucasian men ( n = 39; BMI 27.1 ± 3.8 kg/m2; 45.2 ± 14.6 yr) and used to estimate total IMAT groups using multiple-regression equations. Midthigh was the best, or near best, single predictor in all groups with adjusted R2 ranging from 0.49 to 0.84. Adding a second and third slice further increased R2 and reduced the error of the estimate. Menopausal status and degree of obesity did not affect the location of the best single slice. The contributions of other slice locations varied by sex and race, but additional slices improved predictions. For group studies, it may be more cost-effective to estimate IMAT based on one or more slices than to acquire and segment for each subject the numerous images necessary to quantify whole body IMAT.