Purpose The purpose of this study was to investigate whether the cardiac motion artifact that regularly appears in diffusion-weighted imaging of the left liver lobe might be reduced by acquiring ...images in inspiration, when the coupling between heart and liver might be minimal. Materials and methods 43 patients with known or suspected focal liver lesions were examined at 1.5 T with breath hold acquisition, once in inspiration and once in expiration. Data were acquired with a diffusion-weighted echo planar imaging sequence and two b-values (b50 = 50 s/mm² and b800 = 800 s/mm²). The severity of the cardiac motion artifact in the left liver lobe was rated by two experienced radiologists for both b-values with a 5 point Likert scale. Additionally, the normalized signal S(b800)/S(b50) in the left liver lobe was computed. The Wilcoxon signed-rank test was used comparing the scores of the two readers obtained in inspiration and expiration, and to compare the normalized signal in inspiration and expiration. Results The normalized signal in inspiration was slightly higher than in expiration (0.349±0.077 vs 0.336±0.058), which would indicate a slight reduction of the cardiac motion artifact, but this difference was not significant (p = 0.24). In the qualitative evaluation, the readers did not observe a significant difference for b50 (reader 1: p = 0.61; reader 2: p = 0.18). For b800, reader 1 observed a significant difference of small effect size favouring expiration (p = 0.03 with a difference of mean Likert scores of 0.27), while reader 2 observed no significant difference (p = 0.62). Conclusion Acquiring the data in inspiration does not lead to a markedly reduced cardiac motion artifact in diffusion-weighted imaging of the left liver lobe and is in this regard not to be preferred over acquiring the data in expiration.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To evaluate the semi-automatic image registration accuracy of X-ray-mammography (XR-M) with high-resolution high-field (3.0T) MR-mammography (MR-M) in an initial pilot study.
MR-M was acquired on a ...high-field clinical scanner at 3.0T (T1-weighted 3D VIBE ± Gd). XR-M was obtained with state-of-the-art full-field digital systems. Seven patients with clearly delineable mass lesions >10mm both in XR-M and MR-M were enrolled (exclusion criteria: previous breast surgery; surgical intervention between XR-M and MR-M). XR-M and MR-M were matched using a dedicated image-registration algorithm allowing semi-automatic non-linear deformation of MR-M based on finite-element modeling. To identify registration errors (RE) a virtual craniocaudal 2D mammogram was calculated by the software from MR-M (with and w/o Gadodiamide/Gd) and matched with corresponding XR-M. To quantify REs the geometric center of the lesions in the virtual vs. conventional mammogram were subtracted. The robustness of registration was quantified by registration of X-MRs to both MR-Ms with and w/o Gadodiamide.
Image registration was performed successfully for all patients. Overall RE was 8.2mm (1 min after Gd; confidence interval/CI: 2.0-14.4mm, standard deviation/SD: 6.7 mm) vs. 8.9 mm (no Gd; CI: 4.0-13.9 mm, SD: 5.4mm). The mean difference between pre- vs. post-contrast was 0.7 mm (SD: 1.9 mm).
Image registration of high-field 3.0T MR-mammography with X-ray-mammography is feasible. For this study applying a high-resolution protocol at 3.0T, the registration was robust and the overall registration error was sufficient for clinical application.
Magnetic resonance mammography (MRM) has the highest sensitivity for detection of breast cancer. As opposed to x-ray mammography, MRM is unaffected by breast density, a condition fulfilled especially ...in younger women with dense breast tissue. Approximately 5-10% of all breast cancer cases will develop on the basis of genetic alterations. This high-risk group fulfils the breast density conditions above. Consequently, MRM has been used to screen for breast cancer in these individuals. This article seeks to assess the potential role of computer-aided diagnosis/detection (CAD) in a MRM screening setting. To do so, we describe screening MRI workflow conditions, possible CAD applications together with the use and limitations of available CAD systems. As differences in examination techniques present one major reason for the heterogeneity of reported results, we include our own detailed imaging protocol developed on the basis of more than 20 years of clinical MRM experience. We also provide a future perspective on CAD in MRM.
Since the introduction of contrast-enhanced breast magnetic resonance imaging (MRI) of the breast, the medical community acknowledged its high sensitivity. On the other hand, breast MRI has been ...criticized for its supposedly inherently low or at least inferior specificity as compared to mammography and ultrasound. This book chapter analyzes whether this assumption is really true and the reasons which initially led to it. After demonstrating that contrast enhancement is the basis of the high sensitivity of breast MRI, we explain why a number of benign lesions do enhance and can be misinterpreted as false positives, potentially impacting on patient management. An in-depth comparison between a paper published in 1993 showing a specificity of 37% and a paper published in 1994 showing a specificity of 97% is presented as a way to discuss the mantra of a low specificity associated with breast MRI. Factors influencing specificity such as the reference standard used, the indication to the MRI examination (and, therefore, the study population investigated), the technical characteristics of the MRI equipment, and the technical quality of the MRI examination, the reader’s experience, and the diagnostic criteria are discussed. The potential role of diffusion-weighed imaging (DWI) for improving breast MRI specificity is presented.
Objectives: To evaluate the cost-effectiveness of MR-mammography (MRM) vs. x-ray based mammography (XM) in two-yearly screening women of intermediate risk for breast cancer in the light of recent ...literature.
Methods: Decision analysis and Markov modelling were used to compare cumulative costs (in US-$) and outcomes (in QALYs) of MRM vs. XM over the model runtime of 20 years. The perspective of the U.S. healthcare system was selected. Incremental cost-effectiveness ratios (ICER) were calculated and related to a willingness to pay-threshold of $ 100,000 per QALY in order to evaluate the cost-effectiveness. Deterministic and probabilistic sensitivity analyses were conducted to test the impact of variations of the input parameters. In particular, variations of the rate of false positive findings beyond the first screening round and their impact on cost-effectiveness were assessed.
Results: Breast cancer screening with MRM resulted in increased costs and superior effectiveness. Cumulative average costs of $ 6,081 per woman and cumulative effects of 15.12 QALYs were determined for MRM, whereas screening with XM resulted in costs of $ 5,810 and 15.10 QALYs, resulting in an ICER of $ 13,493 per QALY gained. When the specificity of MRM in the second and subsequent screening rounds was varied from 92% to 99%, the ICER resulted in a range from $ 38,849 to $ 5,062 per QALY.
Conclusions: Based on most recent data on the diagnostic performance beyond the first screening round, MRM may remain the economically preferable alternative in screening women of intermediate risk for breast cancer due to their dense breast tissue.
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