Masanori Ozaki

Diffusion-weighted Imaging of the Breast: Principles and Clinical Applications

Diffusion-weighted imaging provides a novel contrast mechanism in magnetic resonance (MR) imaging and has a high sensitivity in the detection of changes in the local biologic environment. A significant advantage of diffusion-weighted MR imaging over conventional contrast material-enhanced MR imaging is its high sensitivity to change in the microscopic cellular environment without the need for intravenous contrast material injection. Approaches to the assessment of diffusion-weighted breast imaging findings include assessment of these data alone and interpretation of the data in conjunction with T2-weighted imaging findings. In addition, the analysis of apparent diffusion coefficient (ADC) value can be undertaken either in isolation or in combination with diffusion-weighted and T2-weighted imaging. Most previous studies have evaluated ADC value alone; however, overlap in the ADC values of malignant and benign disease has been observed. This overlap may be partly due to selection of b value, which can influence the concomitant effect of perfusion and emphasize the contribution of multicomponent model influences. The simultaneous assessment of diffusion-weighted and T2-weighted imaging data and ADC value has the potential to improve specificity. In addition, the use of diffusion-weighted imaging in a standard breast MR imaging protocol may heighten sensitivity and thereby improve diagnostic accuracy. Standardization of diffusion-weighted imaging parameters is needed to allow comparison of multicenter studies and assessment of the clinical utility of diffusion-weighted imaging and ADC values in breast evaluation.

X‐ray Radiation Causes Electromagnetic Interference in Implantable Cardiac Pacemakers

Background: X‐rays are not thought to cause electromagnetic interference (EMI) in implantable cardiac pacemakers. However, x‐ray radiation during computed tomography (CT) scanning has been reported to cause EMI in some implantable cardiac pacemakers. The objectives of this study were to identify the location within the pacemakers where x‐ray radiation causes EMI and to investigate the association of EMI with the x‐ray radiation conditions.

Motion artifact reduction of diffusion‐weighted MRI of the liver: Use of velocity‐compensated diffusion gradients combined with tetrahedral gradients

To assess the effect of motion artifact reduction on the diffusion‐weighted magnetic resonance imaging (DWI‐MRI) of the liver, we compared velocity‐compensated DWI (VC‐DWI) and VC‐DWI combined with tetrahedral gradients (t‐VC‐DWI) to conventional DWI (c‐DWI) in the assessment of apparent diffusion coefficients (ADCs) of the liver.

Apparent Diffusion Coefficient Value Is Not Dependent on Magnetic Resonance Systems and Field Strength Under Fixed Imaging Parameters in Brain.

Objective The aim of the study was to investigate the causes of apparent diffusion coefficient (ADC) measurement errors and to determine the optimal scanning parameters that are independent of the field strength and vendors of the magnetic resonance (MR) system. Materials and Methods Brain MR images of 10 healthy volunteers were scanned using 6 MR scanners of different field strengths and vendors in 2 different institutions. Ethical review board approvals were obtained for this study, and all volunteers gave their informed consents. Coefficient of variation (CV) of ADC values were compared for their differences in various MR scanners and in the scanned subjects. Results The CV of ADC values for 6 different scanners of 6 brains was 3.32%. The CV for repeated measurements in 1 day (10 scans per day) and in 10 days (scan per day for 10 days) for 1 subject was 1.72% and 2.96%, respectively (n = 5, P < 0.001). The CV of measurements for 10 healthy subjects was 5.22%. The measurement errors of the ADC values for 6 different MR units in 1 subject were higher than the intrascanner variance for the same subject but were lower than the intersubject variance for the same scanner. Conclusions The variance in the ADC values for different MR scanners is reasonably small if appropriate scanning parameters (repetition time, >3000 ms; echo time, minimum; and high enough signal-to-noise ratio of high-b diffusion-weighted image) are used.

Diffusion weighted imaging: A long way to clinical routine

Diffusion weighted image (DWI) of the breast is characterized by high signal contrast of breast cancer against the normal breast parenchyma without the use of contrast material. A number of studies have shown that the apparent diffusion coefficient (ADC) value can be distinguished between benign and malignancy with high sensitivity [1–4]. In our country, DWI is already used in the routine protocol of breast MRI. However, DWI of the breast does not seem to be globally accepted as a routine protocol. The introduction of DWI to clinical routine protocol in the breast seems delayed compared to other organs. The biggest obstacle for this issue is considered to be the lack of evidence about the contribution of breast DWI to the diagnosis and treatment of breast disease. Some studies have shown the utility of DWI in diagnostic improvement by adding breast DWI to MMG or conventional MRI [5,6]. However, the scan protocol of each study differs and there is no consensus about the optimal scan parameters for breast DWI yet. The diversity of protocol is a barrier to further progress of breast DWI, as the signal intensity and ADC is significantly influenced by scan parameters. Thus the criteria of diagnosis on DWI cannot be defined. This study will discuss the current status and issue of the breast DWI at the clinical practice. There are two approaches to evaluate the breast DWI. One of them is a combination of signal intensity of DWI and T2WI, and the other one is the analysis of the ADC value [7]. Generally, the signal intensity of DWI becomes lower as b value increases, but a higher b value emphasizes contrast resolution between breast cancer and normal breast tissue. Mass type breast cancer can be detected on DWI using any b-values. However, non-mass type breast cancer, typically DCIS, in the dense breast tissue may be obscured with lower b-value around 500 to 750 s/mm. This is because of the high signal intensity of surrounding normal breast tissue from T2 shine through effect. The visibility of DCIS will improve with