Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
Background: The imaging assessment of paraspinal muscle morphology and fatty\ninfiltration has gained considerable attention in the past decades, with reports suggesting\nan association between muscle degenerative changes and low back pain (LBP).\nTo date, qualitative and quantitative approaches have been used to assess paraspinal\nmuscle composition. Though highly reliable, manual thresholding techniques are time\nconsuming and not always feasible in a clinical setting. The tedious and rater-dependent\nnature of such manual thresholding techniques provides the impetus for the\ndevelopment of automated or semi-automated segmentation methods. The purpose\nof the present study was to develop and evaluate an automated thresholding algorithm\nfor the assessment of paraspinal muscle composition. The reliability and validity\nof the muscle measurements using the new automated thresholding algorithm were\ninvestigated through repeated measurements and comparison with measurements\nfrom an established, highly reliable manual thresholding technique.\nMethods: Magnetic resonance images of 30 patients with LBP were randomly\nselected cohort of patients participating in a project on commonly diagnosed lumbar\npathologies in patients attending spine surgeon clinics. A series of T2-weighted MR\nimages were used to train the algorithm; preprocessing techniques including adaptive\nhistogram equalization method image adjustment scheme were used to enhance\nthe quality and contrast of the images. All muscle measurements were repeated\ntwice using a manual thresholding technique and the novel automated thresholding\nalgorithm, from axial T2-weigthed images, at least 5 days apart. The rater was blinded\nto all earlier measurements. Inter-method agreement and intra-rater reliability for each\nmeasurement method were assessed. The study did not received external funding and\nthe authors have no disclosures.\nResults: There was excellent agreement between the two methods with intermethod\nreliability coefficients (intraclass correlation coefficients) varying from 0.79\nto 0.99. Bland and Altman plots further confirmed the agreement between the two\nmethods. Intra-rater reliability and standard error of measurements were comparable\nbetween methods, with reliability coefficient varying between 0.95 and 0.99 for the\nmanual thresholding and 0.97ââ?¬â??0.99 for the automated algorithm.\nConclusion: The proposed automated thresholding algorithm to assess paraspinal\nmuscle size and composition measurements was highly reliable, with excellent agreement\nwith the reference manual thresholding method....
Background: It was the primary purpose of our study to evaluate the inter- and intra-observer reliability of a\nstandardized SPECT/CT algorithm for evaluating patients with painful primary total hip arthroplasty (THA).\nThe secondary purpose was a comparison of semi-quantitative and 3D volumetric quantification method for\nassessment of bone tracer uptake (BTU) in those patients.\nMethods: A novel SPECT/CT localization scheme consisting of 14 femoral and 4 acetabular regions on standardized\naxial and coronal slices was introduced and evaluated in terms of inter- and intra-observer reliability in 37 consecutive\npatients with hip pain after THA. BTU for each anatomical region was assessed semi-quantitatively using a color-coded\nLikert type scale (0-10) and volumetrically quantified using a validated software. Two observers interpreted the SPECT/\nCT findings in all patients two times with six weeks interval between interpretations in random order. Semi-quantitative\nand quantitative measurements were compared in terms of reliability. In addition, the values were correlated using\nPearsons correlation. A factorial cluster analysis of BTU was performed to identify clinically relevant regions, which\nshould be grouped and analysed together.\nResults: The localization scheme showed high inter- and intra-observer reliabilities for all femoral and acetabular\nregions independent of the measurement method used (semiquantitative versus 3D volumetric quantitative\nmeasurements). A high to moderate correlation between both measurement methods was shown for the distal\nfemur, the proximal femur and the acetabular cup. The factorial cluster analysis showed that the anatomical\nregions might be summarized into three distinct anatomical regions. These were the proximal femur, the distal\nfemur and the acetabular cup region.\nConclusions: The SPECT/CT algorithm for assessment of patients with pain after THA is highly reliable independent\nfrom the measurement method used. Three clinically relevant anatomical regions (proximal femoral, distal femoral,\nacetabular) were identified....
Compressed sensing (CS) has been applied to accelerate magnetic resonance imaging (MRI) for many years. Due to the lack of\ntranslation invariance of the wavelet basis, undersampled MRI reconstruction based on discrete wavelet transform may result in\nserious artifacts. In this paper, we propose a CS-based reconstruction scheme, which combines complex double-density dual-tree\ndiscrete wavelet transform (CDDDT-DWT) with fast iterative shrinkage/soft thresholding algorithm (FISTA) to efficiently reduce\nsuch visual artifacts. The CDDDT-DWT has the characteristics of shift invariance, high degree, and a good directional selectivity.\nIn addition, FISTA has an excellent convergence rate, and the design of FISTA is simple. Compared with conventional CS-based\nreconstruction methods, the experimental results demonstrate that this novel approach achieves higher peak signal-to-noise ratio\n(PSNR), larger signal-to-noise ratio (SNR), better structural similarity index (SSIM), and lower relative error....
X-ray fluorescence computed tomography (XFCT) based on sheet beam can save a huge amount of time to obtain a whole\nset of projections using synchrotron. However, it is clearly unpractical for most biomedical research laboratories. In this paper,\npolychromatic X-ray fluorescence computed tomography with sheet-beam geometry is tested by Monte Carlo simulation. First,\ntwo phantoms (...
Background: Safe robot-assisted intervention using magnetic resonance imaging\n(MRI) guidance requires the precise control of assistive devices, and most currently\navailable tools are rarely MRI-compatible. To obtain high precision, it is necessary to\ncharacterize and develop existing MRI-safe actuators for use in a high magnetic field\n(ââ?°Â¥3 T). Although an ultrasonic motor (USM) is considered to be an MRI-safe actuator,\nand can be used in the vicinity of a high field scanner, its presence interferes with MR\nimages. Although an MR image provides valuable information regarding the pathology\nof a patientââ?¬â?¢s body, noise, generally of a granular type, decreases the quality of the\nimage and jeopardizes the true evaluation of any existing pathological issues. An eddy\ncurrent induced in the conductor material of the motor structure can be a source of\nnoise when the motor is close to the isocenter of the image. We aimed to assess the\neffects of a USM on the signal-to-noise ratio (SNR) of MR images in a 3-T scanner. The\nSNR was compared for four image sequences in transverse directions for three orientations\nof the motor (x, y, and z) when the motor was in the ââ?¬Å?offââ?¬Â state. The SNR was evaluated\nto assess three artifact reduction methods used to minimize the motor-induced\nartifacts.\nResults: The SNR had a range of 5ââ?¬â??10 dB for slices close to the motor in the x and y\norientations, and increased to 15ââ?¬â??20 dB for slices far from the motor. Averaging the\nSNR for slices in all cases gave an SNR loss of about 10 dB. The maximum SNR was\nmeasured in the z orientation. In this case, the SNR loss was almost the same as that of\nother motor orientations, approximately 10 dB, but with a higher range, approximately\n20ââ?¬â??40 dB.\nConclusions: The selection of certain scanning parameters is necessary for reducing\nmotor-generated artifacts. These parameters include slice selection and bandwidth. In\ndeveloping any MRI-compatible assisted device actuated by a USM, this study recommends\nthe use of an approximately 3-mm slice thickness with minimum bandwidth to\nachieve optimized SNR values when a USM is operating close to (within approximately\n40 mm) the region being imaged. The SNR can be further enhanced by increasing\nthe number of signal averages, but this is achieved only at the cost of increased scan\nduration....
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