1,720,967 research outputs found
MR Spectroscopy of the Breast at 3T: An Initial Clinical Experience
No full textPURPOSE
To report on an initial experience on breast MR spectroscopy (MRS) at 3T. The study was aimed at characterizing the feasibility of single-voxel choline detection at 3T in suspected
malignant breast lesions.
METHOD AND MATERIALS
22 patients (24 lesions, range 0.065-8.18cm3, mean 1.93cm3) were enrolled in the study (32-77yrs, mean 57yrs). All patients had suspicious findings on mammography or
sonography of the breast, confirmed by cytology and/or micro-biopsy. Single-voxel MRS was performed by means of a Philips Achieva STx 3.0T scanner. Iterative shimming was
restricted to the region of interest (ROI) used for spectroscopy (0.512-8.0 cm3, mean 1.097 cm3). The ROI was centred on the lesion, except in cases where a central necrotic
area was observed. The spectroscopic sequence used TE=100ms, TR=2000ms, 128 samples, water (window 100Hz) and fat (SPAIR, window 80Hz) suppression. When possible,
spectroscopy was performed before contrast agent injection and repeated thereafter. Pre-saturation was used to suppress signal from nearby regions. The local field homogeneity
was evaluated by means of the FWHM of the unsuppressed water peak. A threshold was placed at 50Hz, above which spectroscopy was not performed due to insufficient field
homogeneity. Total choline was estimated by means of the signal-to-noise ratio of the peak at 3.2ppm.
RESULTS
MRS was feasible in 54.2% of the lesions (13/24, water peak FWHM 15-44Hz, mean 29Hz). For the other 11 lesions the FWHM of the unsuppressed water peak exceeded 50Hz
(57-103Hz, mean 70.3Hz). Of the 13 feasible, 10 lesions showed choline (SNR 3.2-16.6, mean 7.5) while 3 lesions showed no detectable choline. In 2 cases no choline was
detected in the central, necrotic region while a clear signal was present at the periphery of the lesion (SNR 5.1-5.4). In 2 cases the cho signal was disrupted after contrast
injection.
CONCLUSION
High-field MR spectroscopy is expected to improve the signal-to-noise ratio of the investigated metabolites (choline in this study), however field homogeneity is more difficult to
achieve compared to 1.5T applications. The measured SNR confirmed the expected improvement, but further research is warranted to increase the fraction of cases for which
high-field MRS is feasible.
CLINICAL RELEVANCE/APPLICATION
MRS at 3T could improve the specificity of breast MR, however the possible correlation between total choline concentration and malignancy needs further investigation
Assessment of Image Quality vs Dose Using an Iterative Reconstruction Algorithm in Multislice CT
No full textPURPOSE
To assess image quality and patient dose obtained in multi slice CT studies by means of a standard Filtered Backprojection algorithm (FBP) versus a new type of iterative algorithm
called iDose4
METHOD AND MATERIALS
Various scans on a Catphan600 phantom (The Phantom Laboratory) were performed with a Brilliance iCT-256 scanner (Philips Healthcare) varying reconstruction algorithm (FBP and
iDose4 with six different levels), kernel (B-D-YB), and dose. Image quality has been compared through the following figures of merit: signal-to-noise ratio (SNR) for low-contrast
resolution and MTF-50 for high-contrast resolution. Images were analysed with IQworks. Dose was varied through the mAs/slice mean value set to scan the phantom. The fixed scan
parameters used for all the studies were: HV=120kVp, FOV=250mm, pitch=0.993, slice thickness=2.5mm, rotation time=0.75s, matrix size=512x512. 188 patients were scanned
according to an iDose4 level 3 protocol (30% dose reduction). Five radiologists performed image quality analysis with a 5 point grading scale (1 worst; 5 excellent)
RESULTS
With kernel B and 78mAs/slice the following SNR values have been measured: FBP 1.48, iDose4 (levels 1 to 6) 1.62, 1.70, 1.82, 1.98, 2.28, 2.54; for MTF-50 results were: FBP 3.5
lp/cm, iDose4 (levels 1 to 6) 3.4 to 3.5 lp/cm . With FBP (kernel B) and mAs/slice ranging from 78 to 156 results for SNR were: 1.48-2.12 (R2=0.998), and for MTF-50: 3.4-3.7
lp/cm. Equivalent values of SNR (1.81) and MTF-50 (3.5 lp/cm) were obtained with iDose4 level 3-kernel B-78mAs/slice and with FBP-kernel B-117mAs/slice. MTF-50 as a function of
the kernel varied from 3.5lp/cm (B) to 6.2lp/cm (YB), almost independently from dose and reconstruction algorithm. Quality image was 5 level in 66,5% of 188 patient examinations
and not inferior to 3 level
CONCLUSION
Phantom assessments showed that the use of the iDose4 algorithm compared to FBP allows SNR to increase up to 70% at equal patient dose and permits to reach a 33% patient
dose reduction at equal values of SNR and MTF-50, SNR being the limiting factor.
CLINICAL RELEVANCE/APPLICATION
30% dose reduction not compromise image quality. Higher dose reductions seem to be achievable, possibly up to 70%, if high-contrast resolution is the most critical factor (e.g.
vascular studies
The Use of Novel Model-based Iterative Reconstruction (MBIR) Technique in Ultra-Low Dose CT Scanning in Clinical Practice – A Preliminary Study in 30 Patients
No full textPURPOSE
To compare image quality on computed tomographic (CT) images acquired with adaptive statistical iterative reconstruction (ASIR) and novel model-based iterative reconstruction
(MBIR) techniques in the context of oncological surveillance using ultra-low dose scanning parameters.
METHOD AND MATERIALS
30 patients scheduled for standard of care CT chest/abdomen/pelvis were scanned using ASIR reconstruction and in addition were scanned at 2 pre-selected ultra-low dose scans
(using noise index of 60 and 70) with images reconstructed using MBIR. Objective and subjective image qualities were compared. Effective doses for each scans were recorded.
Quantitative data such as objective image noise and mean attenuation were analyzed by comparing standard deviations, 95% confidence interval and calculating percentage
difference. Mean image noise values and attenuation values were compared between different reconstruction algorithms using ANOVA. The interobserver variation and percentage
agreement between the two radiologists for each of the assessed subjective image quality and lesion assessment parameters were estimated by using weighted k-statistics.
Kruskal-Wallis rank sum test was used to test for equality of median scores among all subjective parameters
RESULTS
Objective image analysis supports significant noise reduction with low dose scans using MBIR technique (p<0.05). There was no significant change in the mean CT numbers between
different reconstructions (p>0.05). There was no significant difference between subjective image quality of ultra-low dose MBIR scan compared with standard dose scan using ASIR
(p>0.05). Dose recorded were substantially lower for low dose MBIR protocol (up to 75% reduction compared with ASIR). Average effective doses were 8.5mSv, 3.8mSv and 2.4mSv
for standard scan NI33, NI60 and NI70 respectively.
CONCLUSION
MBIR shows superior reduction in noise and improved image quality and most importantly substantial dose reduction can be achieved by increasing the noise index parameters as
tested in this study. This is a preliminary study, and part of a much larger study of which the results will be available in full at the RSNA 2012.
CLINICAL RELEVANCE/APPLICATION
To combat against increase use of CT and concerns associated with radiation, MBIR offers another tool in the radiology armoury offering substantial dose reduction without affecting
image quality
The role of high-field MR spectroscopy in the multiparametric evaluation of breast lesions
No full textno availabl
3T MR spectroscopy in the multi-parametric MRI evaluation of breast lesions: a pattern recognition approach
No full textposter B-125
Benefits of double reading of screening mammograms: retrospective study on a consecutive series.
No full textPURPOSE:
The purpose of this study was to assess the performance of delayed second reading of screening mammograms when added to real-time reading plus immediate assessment.
MATERIAL AND METHODS:
The study setting was the mammography screening programme of an Italian Local Health Unit. Recall rate and cancer detection rate at first reading or informed second reading only were assessed in a cohort of 23,629 women aged 50-69 years screened during 2007-2008. Incremental recall rate, incremental cancer detection rate and incremental cost of second reading were determined.
RESULTS:
Recall rate was 13.0% at first and 2.7% at second reading (incremental recall rate +21.1%). Overall, recalls were more frequent in the younger decade and in the presence of denser breasts. Cancer detection rate was 7.06‰ (n=167) at first and 0.93‰ (n=22) at second reading (incremental cancer detection rate +13.1%). Compared with first reading, second reading detected more cancers depicted as isolated microcalcifications and distortions (40.9% vs. 16.2%, p=0.02) and at a lower stage (stage 0-I 81.8% vs. 69.5%, p=0.34). The cost of adding delayed second reading was + 3.65 per screened individual or 3,926.61 per incremental cancer detected.
CONCLUSIONS:
The study confirms the efficacy of second reading, even as an adjunct to real-time single reading plus immediate assessment. Incremental recall rate is acceptable in view of the incremental cancer detection rate, and both figures are within the range of literature reports on double-reading performance
Spettroscopia RM della mammella a 3T: ottimizzazione del protocollo ed esperienza clinica
No full textExtended abstra
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