ORCID Profile
0000-0003-2755-089X
Current Organisations
University of Queensland
,
University of Sydney
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Medical Physics | Other Physical Sciences | Transport Properties and Non-Equilibrium Processes | Condensed Matter Imaging
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Cancer and Related Disorders |
Publisher: Wiley
Date: 31-10-2022
DOI: 10.1002/JMRI.27409
Abstract: Rigorous validation with ground truth information such as histology is needed to reliably assess the current and potential value of MRI techniques to characterize tissue and identify disease-related tissue alterations. Commonly used methods that aim to directly correlate histology and MRI data generally fall short of this goal due to spatial errors that preclude direct matching. Errors result from tissue deformation, differences in spatial resolution and slice thickness, non-coplanar and/or nonintersecting plane orientations, and different image contrast mechanisms. Some of these problems arise from limitations in standard protocols for clinical tissue processing and histology-based pathology reporting, and to some extent can be addressed by modifications to standard protocols without compromising the clinical process. Typical modifications include ex vivo specimen MRI, block-face photography, addition of fiducial markers, and 3D printed molds to constrain tissue deformation and guide sectioning. This review summarizes the advantages and limitations of MRI validation techniques based on coregistration of MRI with whole-mount histology of tissue specimens. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY STAGE: 1.
Publisher: Wiley
Date: 11-06-2019
DOI: 10.1002/NBM.4121
Publisher: Wiley
Date: 21-03-2016
DOI: 10.1002/NBM.3510
Abstract: This study compares the theoretical information content of single- and multi-compartment models of diffusion-weighted signal attenuation in prostate tissue. Diffusion-weighted imaging (DWI) was performed at 9.4 T with multiple diffusion times and an extended range of b values in four whole formalin-fixed prostates. Ten models, including different combinations of isotropic, anisotropic and restricted components, were tested. Models were ranked using the Akaike information criterion. In all four prostates, two-component models, comprising an anisotropic Gaussian component and an isotropic restricted component, ranked highest in the majority of voxels. Single-component models, whether isotropic (apparent diffusion coefficient, ADC) or anisotropic (diffusion tensor imaging, DTI), consistently ranked lower than multi-component models. Model ranking trends were independent of voxel size and maximum b value in the range tested (1.6-16 mm(3) and 3000-10,000 s/mm(2)). This study characterizes the two major water components previously identified by biexponential models and shows that models incorporating both anisotropic and restricted components provide more information-rich descriptions of DWI signals in prostate tissue than single- or multi-component anisotropic models and models that do not account for restricted diffusion.
Publisher: Wiley
Date: 30-06-2017
DOI: 10.1002/NBM.3751
Abstract: The purpose of this study was to measure and model the diffusion time dependence of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) derived from conventional prostate diffusion-weighted imaging methods as used in recommended multiparametric MRI protocols. Diffusion tensor imaging (DTI) was performed at 9.4 T with three radical prostatectomy specimens, with diffusion times in the range 10-120 ms and b-values 0-3000 s/mm
Publisher: Elsevier BV
Date: 10-1989
DOI: 10.1016/0003-2697(89)90733-1
Abstract: A device is described which maintains homogeneous aerobic or anaerobic cell and organelle suspensions within an NMR s le tube. Line broadening due to magnetic field inhomogeneity is reduced by elimination of gas bubbles from the area of the probe receiver coils. The linewidth of the extracellular orthophosphate resonance of a yeast suspension in 31P NMR was 0.21 ppm compared with 0.4-0.7 ppm in conventionally aerated suspensions. Recirculation of the s le results in complete mixing within 90 s of addition of aliquots of acid or alkali. The maximum rate of oxygen transfer from the gaseous to the liquid phase was approximately 600 microM min-1 when aerated with 95% oxygen/5% carbon dioxide. A 60% wet weight suspension of yeast cells was recirculated for 20 h without settling of cells occurring. A method for estimating oxygen transfer rate is described.
Publisher: Elsevier BV
Date: 08-1991
DOI: 10.1016/0005-2736(91)90028-7
Abstract: Phosphate transport was studied in phosphate-starved Candida utilis using 31P-NMR and in situ pH and K(+)-specific electrodes. A transient efflux of K+ was associated with the initial net influx of orthophosphate across the plasma membrane and decrease of both the plasma membrane pH gradient and the cytosol pH. Recovery of cytosol pH, and the plasma membrane pH gradient after phosphate uptake, was slow when extracellular K+ was depleted, but rapid when K+ was added to the suspension either with orthophosphate or after phosphate uptake. Net phosphate transport into the vacuole occurs against its concentration gradient and is associated with an increase of the tonoplast pH gradient. It is proposed that transport of orthophosphate into the vacuole is mediated by an electrical uniport and driven by the tonoplast membrane potential.
Publisher: Elsevier BV
Date: 12-2002
DOI: 10.1016/S1090-7807(02)00103-9
Abstract: A device for aeration and mixing of cell or organelle suspensions in a vertical bore NMR magnet is described. Multiple external sensors (e.g., ion-selective electrodes) may be immersed in the suspension within the bore of the magnet. The sensors are positioned to avoid noise due to contact with gas bubbles and proximity to the probe head. The required s le volume is minimised. The modular design of components permits the use of the device in magnets of various internal dimensions, or with probe heads of different s le tube diameter, by modification of the simpler components of the assembly.
Publisher: Wiley
Date: 03-02-2013
DOI: 10.1002/JMRS.3
Publisher: Wiley
Date: 11-04-2014
DOI: 10.1002/JMRI.24141
Abstract: To directly compare the responsiveness of quantitative imaging measures of disease progression in knee osteoarthritis (OA). In the medial compartment of the knee comparison was made between: 1) radiographic joint space narrowing (JSN) 2) global quantitative magnetic resonance imaging (qMRI) of cartilage volume 3) regional qMRI of cartilage thickness and 4) regional analysis using an ordered value (OV) methodology. 3T MRI and weight-bearing radiography of the knees were performed at baseline and 1-year timepoints in 23 subjects (mean age 63 years) with symptomatic knee OA. Standardized response means (SRM) were calculated for each measure. Statistical analysis to determine significance of change between timepoints was performed with a two-tailed Student's t-test (JSN, global, regional analysis) and nonparametric Mann-Whitney test (ordered values). At 1 year, global cartilage volume losses of 2.3% (SRM -0.44) in the medial tibia and 6.9% in the medial femur (SRM -0.74) were recorded. SRM for JSN was -0.46. Regional analysis revealed largest reductions in cartilage thickness in the external (SRM -0.84) weight-bearing subregion of the medial femur and in the posterior subregion of the medial tibia (SRM -0.79). OV analysis in the medial compartment revealed areas of cartilage thinning (four ranked OV) and cartilage thickening (two ranked OV). The MRI OV approach proved to be a superior analysis tool for detecting changes in cartilage morphology over a 1-year period. Radiographically defined JSN was found to be the least responsive measurement method of knee OA disease progression.
Publisher: Springer International Publishing
Date: 2014
Publisher: SPIE
Date: 28-03-2013
DOI: 10.1117/12.2007697
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2005
Publisher: Wiley
Date: 19-03-2015
DOI: 10.1002/NBM.3273
Abstract: Non-Gaussian diffusion dynamics was investigated in the two distinct water populations identified by a biexponential model of diffusion in prostate tissue. Diffusion-weighted MRI (DWI) signal attenuation was measured ex vivo in two formalin-fixed prostates at 9.4 T with diffusion times Δ = 10, 20 and 40 ms, and b values in the range 0.017-8.2 ms/µm(2) . A conventional biexponential model was compared with models in which either the lower diffusivity component or both of the components of the biexponential were stretched. Models were compared using Akaike's Information Criterion (AIC) and a leave-one-out (LOO) test of model prediction accuracy. The doubly stretched (SS) model had the highest LOO prediction accuracy and lowest AIC (highest information content) in the majority of voxels at Δ = 10 and 20 ms. The lower diffusivity stretching factor (α2 ) of the SS model was consistently lower (range ~0.3-0.9) than the higher diffusivity stretching factor (α1 , range ~0.7-1.1), indicating a high degree of diffusion heterogeneity in the lower diffusivity environment, and nearly Gaussian diffusion in the higher diffusivity environment. Stretched biexponential models demonstrate that, in prostate tissue, the two distinct water populations identified by the simple biexponential model in idually exhibit non-Gaussian diffusion dynamics.
Publisher: Radiological Society of North America (RSNA)
Date: 10-2013
Abstract: To explore relationships between reader performance and reader characteristics in mammography for specific radiologist groupings on the basis of annual number of readings. The institutional review board approved the study and waived the need for patient consent to use all images. Readers gave informed consent. One hundred sixteen radiologists independently reviewed 60 mammographic cases: 20 cases with cancer and 40 cases with normal findings. Readers located any visualized cancer, and levels of confidence were scored from 1 to 5. A jackknifing free response operating characteristic (JAFROC) method was used, and figures of merit along with sensitivity and specificity were correlated with reader characteristics by using Spearman techniques and standard multiple regressions. Reader performance was positively correlated with number of years since qualification as a radiologist (P ≤ .01), number of years reading mammograms (P ≤ .03), and number of readings per year (P ≤ .0001). The number of years since qualification as a radiologist (P ≤ .004) and number of years of reading mammograms (P ≤ .002) were negatively related to JAFROC values for radiologists with annual volumes of less than 1000 mammographic readings. For in iduals with more than 5000 mammographic readings per year, JAFROC values were positively related to the number of years that the reader was qualified as a radiologist (P ≤ .01), number of years of reading mammograms (P ≤ .002), and number of hours per week of reading mammograms (P ≤ .003). Number of mammographic readings per year was positively related with JAFROC scores for readers with an annual volume between 1000 and 5000 readings (P ≤ .03). Differences in JAFROC scores appear to be more related to specificity than location sensitivity, with the former demonstrating significant relationships with four of the five characteristics analyzed, whereas no relationships were shown for the latter. Radiologists' determinants of performance are associated with annual reading volumes. Ability to recognize normal images is a discriminating factor in in iduals with a high volume of mammographic readings.
Publisher: Elsevier BV
Date: 03-2005
DOI: 10.1016/J.EJRAD.2004.03.016
Abstract: In vivo magnetic resonance (MR) spectroscopy at 1.5T was performed on a large polypoid cutaneous melanoma, and two enlarged lymph nodes containing metastatic melanoma, from three patients. Spectra were acquired in vivo from voxels wholly within the primary tumour or secondary lymph node and were thus uncontaminated by signals from adjacent tissue. Tissue biopsies taken after resection of primary tumours and secondary lymph nodes were examined by 8.5T magnetic resonance spectroscopy (MRS) and the results compared with the in vivo spectra, and with spectra from normal skin and a benign skin lesion. There was good agreement between the dominant features of 1.5T spectra acquired in vivo and 8.5T spectra acquired from resected tissue. However, less intense resonances observed at 8.5T in malignant biopsy tissue were not consistently observed at 1.5T in vivo. In vivo spectra from primary and metastatic melanoma showed high levels of choline metabolites. An intense lactate resonance was also present in the in vivo spectrum of primary melanoma. All 8.5T spectra of biopsies from primary and secondary melanoma showed high levels of choline metabolites and lactate, and additional resonances consistent with elevated levels of taurine, alanine, lysine, and glutamate/glutamine relative to normal and benign tissue. Elevated levels of choline, lactate, taurine, and amino acids appear to be clinically useful markers for identifying the pathology of primary and metastatic melanoma.
Publisher: Wiley
Date: 02-11-2013
DOI: 10.1002/JMRI.23898
Abstract: To assess the utility of knee cartilage volumetry using an unspoiled fat-suppressed 3D fast gradient echo (FGRE) sequence at 3T. Sagittal magnetic resonance (MR) images were obtained with an unspoiled fat-suppressed 3D FGRE sequence in eight porcine knees. Manual segmentation was used to derive the cartilage volume. This volume was compared to a volume measurement of cartilage scraping specimens obtained by water displacement. Imaging was repeated five times in four of the knees to assess interscan volume measurement reproducibility and calculate precision error. A single 3D dataset was manually segmented five times at weekly intervals to assess intraobserver volume measurement reproducibility. Total cartilage volume obtained from MRI and water displacement correlated well (r = 0.75). The interscan reproducibility of total volume measurements, expressed as the coefficient of variation (CV), was 4.2%, and the precision error (root mean square [RMS] CV) was 4.1%. The CV of intraobserver estimates of total cartilage volume by MRI was 3.6%. Interscan reproducibility of quantification of total cartilage volume and reproducibility of the manual segmentation technique were both high (>95%). Accurate and reproducible cartilage volumetry can be obtained by using a clinical unspoiled fat-suppressed 3D FGRE acquired at 3T MRI.
Publisher: SPIE
Date: 03-03-2011
DOI: 10.1117/12.877964
Publisher: Radiological Society of North America (RSNA)
Date: 2022
Publisher: Wiley
Date: 08-2003
Publisher: Wiley
Date: 07-10-2016
DOI: 10.1002/MRM.25908
Abstract: To investigate diffusion anisotropy in whole human prostate specimens Seven whole radical prostatectomy specimens were obtained with informed patient consent and institutional ethics approval. Diffusion tensor imaging was performed at 9.4 Tesla. Diffusion tensors were calculated from the native acquired data and after progressive downs ling Fractional anisotropy (FA) decreased as voxel volume increased, and differed widely between prostates. Fixation decreased mean FA by ∼0.05-0.08 at all voxel volumes but did not alter principle eigenvector orientation. In unfixed tissue high FA (> 0.6) was found only in voxels of volume 0.25. FA decreased at longer diffusion times (Δ = 60 or 80 ms compared with 20 ms), but only by ∼0.02 at typical clinical voxel volume. Peripheral zone FA was significantly lower than transition zone FA in five of the seven prostates FA varies widely between prostates. The very small proportion of clinical size voxels with high FA suggests that in clinical DWI studies ADC based on three-direction measurements will be minimally affected by anisotropy. Magn Reson Med 76:626-634, 2016. © 2015 Wiley Periodicals, Inc.
Publisher: Radiological Society of North America (RSNA)
Date: 12-2015
DOI: 10.1148/RADIOL.2015142414
Abstract: To investigate the hypothesis that the clinically observed decrease in apparent diffusion coefficient (ADC) at diffusion-weighted magnetic resonance imaging with increasing prostate cancer Gleason grade can be attributed to an increasing volume of low-diffusivity epithelial cells and corresponding decreasing volumes of higher-diffusivity stroma and lumen space rather than to increased cell density. Tissue s les were acquired after institutional ethics review committee approval and informed consent from patients were obtained. Nuclear count, nuclear area, and gland component volumes (epithelium, stroma, lumen space) were measured in tissue from 14 patients. Gland component volumes and cellularity metrics were correlated with Gleason pattern (Spearman rank correlation coefficient) and measured ADC (Pearson correlation coefficient) in six prostates ex vivo. Differences between metrics for cancerous tissue and those for normal tissue were assessed by using a two-tailed two-s le t test. Linear mixed models with a post hoc Fisher least significant difference test were used to assess differences between gland component volumes and cellularity metrics for multiple groups. To adjust for a clustering effect due to repeated measures, the organ mean value of the measured metric for each tissue type was used in the analysis. There were significant differences between Gleason patterns for gland component volumes (P < .05) but not nuclear count (P = .100) or area (P = .141). There was a stronger correlation of Gleason pattern with gland component volumes (n = 553) of epithelium (Spearman ρ = 0.898, P < .001), stroma (ρ = -0.651, P < .001), and lumen space (ρ = -0.912, P = .007) than with the cellularity metrics (n = 288) nuclear area (ρ = 0.422, P = .133) or nuclear count (ρ = 0.082, P = .780). There was a stronger correlation between measured ADC and lumen volume (r = 0.688, P < .001) and epithelium volume (r = -0.647, P < .001) than between ADC and nuclear count (r = -0.598, P < .001) or nuclear area (r = -0.569, P < .001) (n = 57). Differences in the gland compartment volumes of prostate tissue having distinct diffusivities, rather than changes in the conventionally cited "cellularity" metrics, are likely to be the major contributor to clinically observed variations of ADC in prostate tissue.
Publisher: Oxford University Press (OUP)
Date: 18-02-2016
DOI: 10.1093/RPD/NCW005
Abstract: This phantom-based study aimed to examine radiation dose from digital breast tomosynthesis (DBT) and digital mammography (DM) and to assess the potential for dose reductions for each modality. Images were acquired at 10-60 mm thicknesses and four dose levels and mean glandular dose was determined using a solid-state dosemeter. Eleven readers assessed image quality and compared simulated lesions with those on a reference image, and the data produced was analysed with the Friedman and Wilcoxon signed-rank tests. For a phantom thickness of 50 mm (typical breast thickness), DBT dose was 13 % higher than DM, but this differential is highly dependent on thickness. Visibility of masses was equal to a reference image (produced at 100 % dose) when dose was reduced by 75 and 50 % for DBT and DM. For microcalcifications, visibility was comparable with the reference image for both modalities at 50 % dose. This study highlighted the potential for reducing dose with DBT.
Publisher: Frontiers Media SA
Date: 24-03-2017
Publisher: Springer Science and Business Media LLC
Date: 19-09-2005
Publisher: SPIE
Date: 22-03-2016
DOI: 10.1117/12.2216492
Publisher: Springer Science and Business Media LLC
Date: 04-06-2013
DOI: 10.1007/S00330-013-2919-6
Abstract: To investigate pulmonary vasculature opacification during CTPA using an optimised patient-specific protocol for administering contrast agent. CTPA was performed on 200 patients with suspected PE. Patients were assigned to two protocol groups: protocol A, fixed 80 ml contrast agent protocol B used a patient-specific approach. The mean cross-sectional opacification profile of 8 central and 11 peripheral pulmonary arteries and veins was measured and the arteriovenous contrast ratio (AVCR) calculated. Protocols were compared using Mann-Whitney U non-parametric statistics. Jack-knife alternative free-response receiver-operating characteristic (JAFROC) analyses assessed diagnostic efficacy. Interobserver variations were investigated using kappa methods. A number of pulmonary arteries demonstrated increases in opacification (P < 0.03) for protocol B compared to A, whilst opacification in the heart and veins was reduced in protocol B (P = 0.05). Increased AVCR in protocol B compared with A was observed at all anatomic locations (P < 0.0002). Increased JAFROC (P < 0.0002) and kappa variation were observed with protocol B (κ = 0.78) compared to A (κ = 0.25). Mean contrast volume was reduced in protocol B (33 ± 9 ml) compared to A (80 ± 1 ml). Significant improvements in visualisation of the pulmonary vasculature can be achieved with a low volume of contrast agent using injection timing based on a patient-specific contrast formula. • Optimal opacification of the pulmonary arteries is essential for CT pulmonary angiography. • Matching timing with vessel dynamics significantly improves vessel opacification. • This leads to increased arterial opacification and reduced venous opacification. • This can also lead to a reduced volume of contrast agent.
Publisher: Elsevier BV
Date: 02-2013
DOI: 10.1016/J.EJRAD.2012.09.016
Abstract: To investigate enhancement of head and neck arteries during carotid computed tomography angiography using a reduced volume contrast regimen and craniocaudal scan acquisition. Two hundred and two patients underwent carotid angiography using a 64 channel computed tomography scanner. Patients were allocated to one of two acquisition/contrast regimens: regimen A, the department's standard protocol, consisting of a caudocranial scan direction with 100mL of contrast intravenously regimen B, involving a craniocaudal scan direction and approximately 50 mL of contrast using a timing dictated by patient hemodynamics. Attenuation profiles of cranial arteries and veins in 6 anatomical segments were assessed and arteriovenous contrast ratios (AVCR) calculated. Receiver operating characteristic (ROC) analysis was performed using DBM methodology. Arterial attenuation was up to 54% (p<0.01) higher following regimen B compared with A. Attenuation in the veins were significantly lower in regimen B than in regimen A with a maximum reduction of up to 93% (p<0.0001). With regimen B, there were significant (p<0.0001) improvements in AVCR at a variety of anatomical sites. The ROC analysis demonstrated a significantly higher Az score for the novel regimen compared with regimen A (p<0.002) with inter-neuroradiologist agreement increasing from poor to moderate. Significant improvements in visualisation of head and neck arterial vasculature can be achieved with a CT acquisition regimen using low contrast volume and injection timing based on patient specific contrast formula and craniocaudal scan direction.
Publisher: MDPI AG
Date: 27-05-2016
Publisher: Wiley
Date: 28-12-2012
DOI: 10.1002/MRM.23244
Abstract: MR microimaging at 16.4 T with 40-μm isotropic voxels was used to investigate compartmentation of water diffusion in formalin-fixed prostate tissue. Ten tissue s les (~ 28 mm(3) each) from five organs were imaged. The mean diffusivity of epithelial, stromal, and ductal/acinar compartments was estimated by two methods: (1) manual region of interest selection and (2) Gaussian fitting of voxel diffusivity histograms. For the region of interest-method, the means of the tissue s le compartment diffusivities were significantly different (P < 0.001): 0.54 ± 0.05 μm(2)/ms for epithelium-containing voxels, 0.91 ± 0.17 μm(2)/ms for stroma, and 2.20 ± 0.04 μm(2)/ms for saline-filled ducts. The means from the histogram method were also significantly different (P < 0.001): 0.45 ± 0.08 μm(2)/ms for epithelium-containing voxels, 0.83 ± 0.16 μm(2)/ms for stroma, 2.21 ± 0.02 μm(2)/ms for duct. Estimated partial volumes of epithelial, stromal, and ductal/acinar compartments in a "tissue only" subvolume of each s le were significantly different (P < 0.02) between cancer and normal tissue for all three compartments. It is concluded that the negative correlation between apparent diffusion coefficient and cancer Gleason grade observed in vivo results from an increase of partial volume of epithelial tissue and concomitant decrease of stromal tissue and ductal space.
Publisher: SPIE
Date: 28-03-2013
DOI: 10.1117/12.2007360
Publisher: Wiley
Date: 27-01-2012
DOI: 10.1002/MRM.24179
Abstract: Diffusion tensor microimaging at 16.4 T with 40 μm isotropic voxels was used to investigate anisotropic water diffusion in prostate tissue at spatial resolution approaching the cellular scale. Nine normal glandular tissue s les were collected from the peripheral zone of six formalin fixed radical prostatectomy specimens. Fibromuscular stromal tissue exhibited microscopic diffusion anisotropy (mean fractional anisotropy range 0.47-0.66) significantly higher (P < 0.01, Student's t-test) than in epithelium-containing voxels (mean fractional anisotropy range 0.31-0.54) in six of the seven normal tissue s les in which both compartments could be measured. Fiber tracking demonstrated principle stromal fiber directions consistent with myocyte orientation seen on light microscopy of the same s le. Diffusion tensor microimaging may be valuable for investigation of variable results from attempts to measure diffusion anisotropy in the prostate in vivo.
Publisher: Wiley
Date: 15-11-2013
DOI: 10.1002/MRM.24549
Abstract: To evaluate the effect of formalin fixation on biexponential modeling of diffusion decay in prostate tissue. Three whole prostate specimens were imaged unfixed immediately postsurgery, and again after formalin fixation. Diffusion-weighted imaging was performed over an extended range of b-values and a biexponential model fitted to the signal decay curves. Tissue fixation resulted in a 35%, 20%, and 20% reduction in mean apparent diffusion coefficient of the higher diffusivity fit component for the three organs, respectively, and a 64%, 57%, and 45% reduction in mean apparent diffusion coefficient of the lower diffusivity component. The mean signal fraction of the higher diffusivity component was increased by 23%, 5%, and 1%, respectively. The effect of fixation did not appear to vary according to tissue type or glandular zone. Formalin fixed tissue appears to provide a stable model for detailed investigation of the microscopic biophysical basis of diffusion phenomena observed in vivo. Diffusivity changes that result from fixation may provide information about the microscopic environments of the biexponential components.
Publisher: SPIE
Date: 11-03-2014
DOI: 10.1117/12.2043321
Publisher: Wiley
Date: 20-05-2015
DOI: 10.1002/JMRS.110
Publisher: SPIE
Date: 17-03-2015
DOI: 10.1117/12.2081838
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.JMIR.2011.05.002
Abstract: Contrast medium (CM) administration for multidetector computed tomography angiography (CTA) requires using a power injector. Power injectors deliver viscous CM at different flow rates up to a maximum pressure of 300 lb per square inch (psi), provide features that benefit patient safety, improve arterial and parenchymal opacification, and allow flexible and complex injection protocols to be administered. The use of power injectors not only includes contrast but also saline, which is primarily responsible for reducing the overall volume of contrast administration while maintaining peak vessel opacification over a longer duration during the CTA acquisition. CTA faces multiple challenges with advanced scanner hardware. There is an increased need to inject small volumes of CM at fast injection rates over a short duration. This technical overview is to increase the understanding of parameters that influence optimal contrast enhancement and bolus geometry, and to enable the user to modify and optimize scanner and contrast protocols.
Publisher: Wiley
Date: 02-12-2013
DOI: 10.1002/MRM.25032
Abstract: To compare the theoretical information content of four popular models of diffusion-weighted signal attenuation. Four whole prostates were imaged fresh unfixed and fixed at 9.4T. Biexponential, kurtosis, stretched exponential, and monoexponential models were ranked using Akaike's Information Criterion (AIC) with validation by a leave-one-out test of model prediction error. For unfixed tissue measurements (b-value range: 17-2104 s/mm(2)) the biexponential and kurtosis models had similar information content to each other and this was distinctly higher than for the stretched and monoexponential models. In fixed-tissue measurements (b-value range: 17-8252 s/mm(2)), the biexponential model had much higher information content than the three other models. AIC-based model ranking is consistent with an independent prediction accuracy test. Biexponential and kurtosis models consistently perform better than stretched and monoexponential models. The biexponential model has increasing superiority over all three other models as maximum b-value increases above ∼2000 s/mm(2).
Publisher: Wiley
Date: 09-12-2012
DOI: 10.1002/MRM.23291
Abstract: Magnetic resonance microimaging was used to measure diffusion decay over an extended b-factor range in a formalin-fixed normal prostate s le and a Gleason pattern 3+4 cancer tissue s le. The coefficients of biexponential fits to diffusion decay data from 1600 voxels of dimension 160 × 160 × 160 μm(3) in each s le were correlated with underlying epithelial and stromal compartment partial volumes estimated from high-resolution apparent diffusion coefficient (ADC) data (40 × 40 × 40 μm(3) voxels) from the same tissue. In the normal tissue s le, the signal fractions of the low and high ADC components of the biexponential fits correlated linearly with partial volumes of epithelial tissue (R(2) = 0.6) and stromal tissue (R(2) = 0.5), respectively. Similar but weaker correlations were observed in the cancer s le. Epithelium-containing high spatial resolution voxels appeared to be composed of ∼60% low ADC and ∼40% high ADC component. Stromal voxels appeared to be composed of ∼20% low ADC and ∼80% high ADC component. This preliminary report suggests that distinctly different diffusion properties in microscopically adjacent cell types contribute to the multiexponential diffusion decay phenomenon in prostate tissue.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2003
DOI: 10.1097/00008390-200306000-00006
Abstract: Accurate staging of patients with primary cutaneous melanoma includes assessment of regional lymph nodes for the presence of micrometastatic disease. Sentinel lymph node biopsy is highly accurate but is an invasive surgical procedure with a 5-10% complication rate, and requires labour-intensive and expensive histological examination to identify disease. A rapid, accurate and cost-effective non-surgical technique able to detect micrometastatic deposits of melanoma in regional lymph nodes would be of great benefit. Fine needle aspiration biopsies and tissue specimens were obtained from lymph nodes from 18 patients undergoing node resection for metastatic melanoma and five patients undergoing radical retropubic prostatectomy. One-dimensional proton magnetic resonance spectroscopy was undertaken at 360 MHz (8.5 T). Lymph nodes were cut into 3 mm thick slices and embedded. Four sequential 5 microm tissue sections were cut from each block and stained, with haematoxylin and eosin, for S100 protein, for HMB45, and again with haematoxylin and eosin, respectively. Proton magnetic resonance spectroscopy distinguished between benign and malignant lymph node tissue (P < 0.001, separate t-test) and benign and malignant lymph node fine needle aspiration biopsy (P < 0.012) based on the ratio of the integrals of resonances from lipid/other metabolites (1.8-2.5 p.p.m. region) and 'choline' (3.1-3.3 p.p.m. region). In conclusion, one-dimensional proton magnetic resonance spectroscopy on a simple fine needle aspiration biopsy can distinguish lymph nodes containing metastatic melanoma from uninvolved nodes, providing a rapid, accurate and cost-effective non-surgical technique to assess regional lymph nodes in patients with melanoma.
Publisher: American Society for Microbiology
Date: 08-2001
DOI: 10.1128/JCM.39.8.2916-2923.2001
Abstract: A new fingerprinting technique with the potential for rapid identification of bacteria was developed by combining proton magnetic resonance spectroscopy ( 1 H MRS) with multivariate statistical analysis. This resulted in an objective identification strategy for common clinical isolates belonging to the bacterial species Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae , and the Streptococcus milleri group. Duplicate cultures of 104 different isolates were examined one or more times using 1 H MRS. A total of 312 cultures were examined. An optimized classifier was developed using a bootstrapping process and a seven-group linear discriminant analysis to provide objective classification of the spectra. Identification of isolates was based on consistent high-probability classification of spectra from duplicate cultures and achieved 92% agreement with conventional methods of identification. Fewer than 1% of isolates were identified incorrectly. Identification of the remaining 7% of isolates was defined as indeterminate.
Publisher: Wiley
Date: 2003
DOI: 10.1002/NBM.815
Abstract: The leakage of metabolites from frozen and thawed tissue biopsies was measured semi-quantitatively by high-field (8.5 T) proton MRS. Human prostate and rat brain tissue specimens, frozen within 1 min of collection, lost significant and variable amounts of diagnostic metabolites immediately upon thawing. For prostate tissue 30-50% of initial total choline compounds, total creatines and citrate were detected in the collection buffer immediately after thawing. The widely used protocol for MR assessment of tissue biopsies, which involves washing of thawed tissue s les in fresh buffer, results in loss of large and unpredictable amounts of possibly diagnostic metabolites prior to MRS. This reduces the reproducibility of MR analysis of tissue biopsies and compromises the reliable identification of MR spectral patterns diagnostic of tissue pathology. The problem can be avoided by minimizing the volume of storage buffer, omitting tissue washing and performing MRS measurements on the tissue immersed in the original storage buffer.
Publisher: Springer Science and Business Media LLC
Date: 06-09-2014
DOI: 10.1007/S00330-014-3409-1
Abstract: The objectives are To to compare the diagnostic performance of combined digital breast tomosynthesis (DBT) and digital mammography (DM) with that of DM alone, as a function of radiologists' experience with DBT. Ethical committee approval was obtained. Fifty cases (27 cancer, 23 normal), each containing both digital mammography (DM) and digital breast tomosynthesis (DBT) images, were reviewed by 26 radiologists, ided into three groups according to level of experience with DBT (none, workshop experience, and clinical experience). The radiologists' diagnostic performance using DM was compared with that using DM + DBT, and evaluated by area under receiver-operating characteristic curve (AUC), jackknife free-response receiver-operator characteristics figure of metric (JAFROC FOM), sensitivity, location sensitivity, and specificity. For all readers combined, performance using DM + DBT was significantly higher than for DM alone by both AUC (0.788 vs 0.681, p < 0.001) and JAFROC FOM (0.745 vs 0.621, p < 0.001). Similar results were obtained for readers with no DBT experience (AUC 0.775 vs 0.682, p = 0.004 JAFROC FOM 0.695 vs 0.603, p = 0.016) and with clinical DBT experience (AUC 0.789 vs 0.681, p = 0.042 and JAFROC FOM 0.764 vs 0.632, p = 0.031). Addition of DBT to DM significantly improves radiologists' diagnostic performance whether or not they have prior DBT experience. • Adding DBT to DM increased the number of detected cancers • DBT + DM led to more accurate localization of breast cancers than DM • Addition of DBT improved radiologists' performance regardless of prior DBT experience • High-volume radiologists with different DBT experience levels performed similarly on DM + DBT.
Publisher: Wiley
Date: 17-12-2015
DOI: 10.1002/MRM.25555
Abstract: To investigate the microscopic diffusion properties of formalin-fixed breast tissue. Diffusion microimaging was performed at 16.4T with 40-μm isotropic voxels on two normal and two cancer tissue s les from four patients. Results were correlated with histology of the s les. Diffusion-weighted images and mean diffusivity maps demonstrated distinct diffusivity differences between breast tissue components. Mean diffusivity (MD) in normal tissue was 0.59 ± 0.24 μm(2) /ms for gland lobule (voxels containing epithelium and intralobular stroma) and 1.23 ± 0.34 μm(2) /ms for interlobular fibrous stroma. In the cancer s les, MD = 0.45 ± 0.23 μm(2) /ms for invasive ductal carcinoma (voxels contain epithelium and intralobular stroma) and 0.61 ± 0.35 μm(2) /ms for ductal carcinoma in situ. There were significant MD differences between all tissue components (P < 0.005), except between gland lobule and ductal carcinoma in situ (P = 0.71). The low diffusivity of epithelium-rich cancer tissue and of normal epithelium relative to its supporting fibrous stroma was similar to that reported for prostate tissue and the esophageal wall. Diffusion microimaging demonstrates distinct diffusivity differences between breast tissue glandular structures. Low diffusivity may be a distinctive feature of mammalian epithelia.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2013
Publisher: Wiley
Date: 08-02-2011
DOI: 10.1002/MRM.22778
Abstract: Diffusion tensor microimaging was used to investigate the water diffusion properties of formalin-fixed prostate tissue at spatial resolution approaching the cellular scale. Diffusion tensor microimaging was performed at 16.4 T with 40 μm isotropic voxels. Diffusion tensor microimaging clearly demonstrated distinct microscopic diffusion environments and tissue architecture consistent with that seen on light microscopy of the same tissue. The most restricted diffusion environment is the secretory epithelial cell layer (voxel bulk mean diffusivity, D = 0.4 ± 0.1 × 10(-3) mm(2)/sec). Diffusion in the fibromuscular stromal matrix is relatively less restricted (D = 0.7 ± 0.1 × 10(-3) mm(2)/sec). In tumor tissue (Gleason pattern 4+4) distinct glandular and ductal structures are absent in the diffusion-weighted images and diffusivity is low (D = 0.5 ± 0.1 × 10(-3) mm(2)/sec). Distinct stromal and epithelial diffusion compartments are the most likely origin of biexponential diffusion decay observed in vivo.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2010
DOI: 10.1097/CMR.0B013E32833BD0EC
Abstract: Proton magnetic resonance spectroscopy at 8.5 T ex vivo was used to investigate skin lesions for metabolic signatures to predict malignancy or indicate malignant potential. Magnetic resonance spectroscopy was performed on biopsy tissue obtained from 63 skin lesions and five melanoma metastases from 55 patients. S les were grouped and compared according to five clinically significant distinctions: melanoma (n=38) or nonmelanoma (n=30), primary melanoma (n=33) or secondary melanoma (involved nodes and distant metastases, n=5), primary melanoma (n=33) or nevi (n=8), malignant (n=46) or nonmalignant (n=22), and melanocytic (n=46) or nonmelanocytic (n=22). In all comparisons, the average magnetic resonance spectrum of each class lay within 1 standard deviation of the average spectrum of the other class. There was a higher average choline metabolite signal intensity in melanoma-containing biopsies compared with nonmelanoma biopsies. Discriminant analysis based on the intensity of the choline resonance alone achieved 69% accuracy in separation of melanoma and nonmelanoma tissue. Inclusion of other metabolite resonances in the analysis did not increase discrimination accuracy. Tissue heterogeneity in conventionally collected full thickness skin biopsies and possible biochemical variance within in idual tissue types limit classification accuracy using the methods and magnetic field strength that were earlier reported to provide accurate discrimination in other cancer types.
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.CRAD.2013.01.007
Abstract: The aim of this article is to review the major limitations in current mammography and to describe how these may be addressed by digital breast tomosynthesis (DBT). DBT is a novel imaging technology in which an x-ray fan beam sweeps in an arc across the breast, producing tomographic images and enabling the production of volumetric, three-dimensional (3D) data. It can reduce tissue overlap encountered in conventional two-dimensional (2D) mammography, and thus has the potential to improve detection of breast cancer, reduce the suspicious presentations of normal tissues, and facilitate accurate differentiation of lesion types. This paper reviews the latest studies of this new technology. Issues including diagnostic efficacy, reading time, radiation dose, and level of compression cost and new innovations are considered.
Publisher: Springer Science and Business Media LLC
Date: 03-01-2008
Publisher: Springer International Publishing
Date: 2016
Publisher: Wiley
Date: 19-12-1994
DOI: 10.1016/0014-5793(94)01275-X
Abstract: Oligonucleotide probes based on the N-terminal amino acid sequences of the NqrA and NqrC subunits were used to clone genes for the Na(+)-dependent NADH-ubiquinone oxidoreductase complex from Vibrio alginolyticus. Four consecutive ORFs were identified encoding subunit proteins of 48.6, 46.8, 27.7 and 22.6 kDa, respectively (NqrA-D). A further ORF, showing 71% homology to the BolA protein of Escherichia coli, was located upstream. From sequence comparisons, we conclude that the Na(+)-dependent NADH-ubiquinone oxidoreductase complex of V. alginolyticus is clearly distinct from the corresponding H(+)-dependent enzymes of both prokaryotes and eukaryotes.
Publisher: Springer International Publishing
Date: 2016
Publisher: Wiley
Date: 21-09-2013
DOI: 10.1111/J.1754-9485.2012.02447.X
Abstract: Multidetector computed tomographic angiography is becoming the modality of choice for evaluation of the supra-aortic circulation in acute stroke imaging. Variations of the supra-aortic circulation, in particular of the extracranial arteries, are common. This article aims to provide a pictorial description of the variant anatomy of the aortic arch and extracranial arteries. Knowledge of the presence and clinical relevance of normal variants such as anomalies, duplications and embryological persistence plays a clinically relevant role in the diagnosis and management of neurological and surgical conditions, particularly as we enter an era of increasing extracranial intervention.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2006
DOI: 10.1213/01.ANE.0000198333.22687.A6
Abstract: Magnetic resonance (MR) spectroscopy is a noninvasive technique that can be used to detect and measure the concentration of metabolites and neurotransmitters in the brain and other organs. We used in vivo (1)H MR spectroscopy in subjects with low back pain compared with control subjects to detect alterations in biochemistry in three brain regions associated with pain processing. A pattern recognition approach was used to determine whether it was possible to discriminate accurately subjects with low back pain from control subjects based on MR spectroscopy. MR spectra were obtained from the prefrontal cortex, anterior cingulate cortex, and thalamus of 32 subjects with low back pain and 33 control subjects without pain. Spectra were analyzed and compared between groups using a pattern recognition method (Statistical Classification Strategy). Using this approach, it was possible to discriminate between subjects with low back pain and control subjects with accuracies of 100%, 99%, and 97% using spectra obtained from the anterior cingulate cortex, thalamus, and prefrontal cortex, respectively. These results demonstrate that MR spectroscopy, in combination with an appropriate pattern recognition approach, is able to detect brain biochemical changes associated with chronic pain with a high degree of accuracy.
Publisher: Elsevier BV
Date: 06-2013
DOI: 10.1016/J.ACRA.2013.01.021
Abstract: To investigate the effect of the Joint Photographic Experts Group (JPEG2000) 30:1 and 60:1 lossy compression on the detection of cranial vault fractures when compared to JPEG2000 lossless compression. Fifty cranial computed tomography (CT) images were processed with three different level of JPEG2000 compression (lossless, 30:1 lossy, and 60:1 lossy) creating three sets of images. These were presented to five musculoskeletal specialists and five neuroradiologists. Each reader read at two of the three compression levels. Twenty-two cases contained a single fracture the remaining 28 cases contained no fractures. Observers were asked to identify the presence or absence of a fracture, to locate its site, and rate their degree of confidence. Receiver operating characteristic (ROC), jackknife free-response receiver operating characteristic (JAFROC) and the Dorfman-Berbaum-Metz multiple reader multiple case (DBM-MRMC) analyses were used to explore differences between the lossless and lossy compressed images. JPEG2000 lossless and 30:1 lossy compression demonstrated no significant difference in their performance with JAFROC and DBM-MRMC analysis (P < .416) however, JPEG2000 30:1 lossy compression demonstrated significantly better performance than 60:1 lossy compression (P < .016). A significant increase in misplaced confidence ratings was also seen with 60:1 (P < .037) over 30:1 lossy and lossless compression. JPEG2000 60:1 compression degrades the detection of skull fractures significantly while increasing the confidence with which readers rate fractures compared with 30:1 lossy and lossless compression. JPEG2000 30:1 lossy compression does not significantly change performance when compared to JPEG2000 lossless for the detection of skull fractures on CT.
Publisher: Wiley
Date: 19-02-2019
DOI: 10.1002/NBM.4073
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.ACRA.2012.12.010
Abstract: To identify specific mammographic appearances that reduce the mammographic detection of breast cancer. This study received institutional board review approval and all readers gave informed consent. A set of 60 mammograms each consisting of craniocaudal and mediolateral oblique projections were presented to 129 mammogram Breastscreen readers. The images consisted of 20 positive cases with single and multicentric masses in 16 and 4 cases, respectively (resulting in a total of 24 cancers), and readers were asked to identify and locate the lesions. Each lesion was then ranked according to a detectability rating (ie, the number of observers who correctly located the lesion ided by the total number of observers), and this was correlated with breast density, lesion size, and various descriptors of lesion shape and texture. Negative and positive correlations between lesion detection and density (r = -0.64, P = .007) and size (r = 0.65, P = .005), respectively, were demonstrated. In terms of lesion size and shape, there were significant correlations between the probability of detection and area (r = 0.43, P = .04), perimeter (r = 0.66, P = .0004), lesion elongation (r = 0.49, P = .02), and lesion nonspiculation (r = 0.78, P < .0001). The results of this study have identified specific lesion characteristics associated with shape that may contribute to reduced cancer detection. Mammographic sensitivity may be adversely affected without appropriate attention to spiculation.
Publisher: Elsevier BV
Date: 10-1990
DOI: 10.1016/0167-4889(90)90084-Q
Abstract: The recovery of Candida utilis from phosphate starvation was studied using 31P-NMR. The phosphate analogue methylphosphonate was found to be a useful indicator of cytosol pH. Added orthophosphate was rapidly accumulated by the cells and stored mainly In a stable pool of polyphosphate of mean chain-length at least 200 units. Observed pH changes in the medium and cytosol during uptake of orthophosphate and methylphosphonate are consistent with the transport of these compounds across the plasma membrane by a proton hosphate symport. However, transport of phosphate across the vacuole membrane occurs by a mechanism for which methylphosphonate is not a substrate. In the cytosol pH changes are strongly correlated with changes in orthophosphate concentration, however, this is not the case in the vacuole.
Start Date: 05-2014
End Date: 05-2015
Amount: $1,064,000.00
Funder: Australian Research Council
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