Slow component apparent diffusion coefficient for prostate cancer: Comparison and correlation with pharmacokinetic evaluation from dynamic contrast-enhanced MR imaging.

PURPOSE: Dynamic contrast enhancement (DCE)-MRI has high diagnostic performance of prostate cancer. However, it is preferable to avoid the use of MRI contrast media. A study reported that the diagnosability of the wash-in index of DCE-MRI was equivalent to the intravoxel incoherent motion of the diffusion weighted image. The purpose of this study was to examine the correlation between the slow component apparent diffusion coefficient (ADC) and the wash-out index of the DCE. MATERIALS AND METHODS: Thirty-eight patients diagnosed with prostate cancer by biopsy were enrolled in this study. The fast and slow component ADCs of the DWI were calculated for 76 points of the tumor and the contralateral normal parts. Furthermore, the wash-in and wash-out indices of the DCE-MRI were calculated. The correlations for each calculated index were compared. RESULTS: There was a significant difference between the tumor and the contralateral normal parts for both fast (p = 0.03) and slow component (p < 0.01) ADCs. In addition, the slow component ADC was correlated with the wash-out index (r = 0.64). CONCLUSION: The slow component ADC was correlated with the wash-out index, and may, therefore, be a suitable substitute for DCE-MRI.

Ultrasound cardiography examinations detect victims' long-term realized and potential consequences after major disasters: a case-control study.

BACKGROUND: An increase in cardiovascular diseases has been reported following major disasters. Previous work has shown that ultrasonographic findings from ultrasound cardiography examination (UCG) increased until the 44th month after the tsunami caused by the Great East Japan Earthquake. The present study conducted UCG among victims in the tsunami disaster area and investigated the frequency of disaster-related cardiovascular diseases and changes over time until the 55th month after the disaster. METHODS: The subjects were residents of temporary housing complexes and neighboring housing in Watari-gun, Miyagi Prefecture, Japan. There were 207 subjects in the 18th month, 125 in the 30th month, 121 in the 44th month, and 106 in the 55th month after the disaster. Data were collected through UCG and self-report questionnaire. RESULTS: Significant changes were observed among subjects with clinical findings from the UCG, which increased over the study period-from 42.0 to 60.8, 72.7, and 73.6% beginning in the 18th month after the disaster (p < 0.0001). CONCLUSIONS: It is possible that the UCG can become a useful examination to visualize the potential impact of a major disaster on the cardiac function of victims. Victims with clinical findings continued increasing not only during the acute phase after a disaster but also in the long term. We therefore need to keep this in mind, and note that it is important to establish a support system to control cardiovascular diseases from the early stage of disaster. TRIAL REGISTRATION: UMIN; ID000029802. R000034050 . 2 November 2017.

The Yellow Scale Is Superior to the Gray Scale for Detecting Acute Ischemic Stroke on a Monitor Display in Computed Tomography.

RATIONALE AND OBJECTIVES: The purpose of this study was to compare the efficacy of the color scale with regard to focal detection with computed tomography in acute ischemic stroke. MATERIALS AND METHODS: Computed tomography images of the brain of 19 patients diagnosed with acute stroke, based on magnetic resonance diffusion-weighted images obtained within an onset of 24 hours, and the images of five normal patients were displayed in each color look-up table on a monitor. The detection of acute stroke was compared among 15 radiologists. The images were compared in the gray, green, yellow, red, and blue scales of the look-up tables. The observers recorded acute ischemic stroke as "present" or "absent." They also located the position of the stroke lesion and described the degree of their conviction as to whether a lesion existed. Detection was evaluated by receiver operating characteristic analysis. The area under the receiver operating characteristic curves was compared. In addition, reduced fatigue and the ease in image observation were compared. RESULTS: Compared to the other scales, the yellow scale had a significantly higher area under the receiver operating characteristic curve, which indicated that this scale allowed better detection of acute ischemic stroke. The gray scale produced the least fatigue in image observation. CONCLUSIONS: The detection of acute ischemic stroke is improved by changing the display monitor from the gray scale to the yellow scale. From the perspective of color psychology, yellow is associated with higher arousal, cheerfulness, confidence, creativity, and excitement. Therefore, the yellow scale may be suitable for a medical imaging display.

[The Usefulness of Strain Elastography for Determining Liver Fibrosis Stage in Chronic Viral Hepatitis: An Analysis Using Tissue Doppler Imaging with Manual Compression].

BACKGROUND/AIM: Accurate determination of the stage of liver fibrosis is an essential component in choice of treatment and assessment of cancer risk in patients with chronic viral hepatitis. The aim of this study was to evaluate the usefulness of strain elastography based on tissue Doppler imaging for liver fibrosis in chronic viral hepatitis. METHODS: A total of 37 patients with chronic viral hepatitis and 8 healthy volunteers were enrolled. Strain value was measured by using a conventional ultrasound machine that included strain imaging technolo- gy. Strain elastography was performed at the right subcostal area with manual compression. Liver fibrosis stages were assessed by using liver biopsy and compared with strain values. Diagnostic performance of the strain value for fibrosis stage 4, cirrhosis, was determined by performing a receiver-operating characteristics (ROC) curve analysis. RESULTS: Twenty-seven patients were positive for HCV RNA, 9 were positive for HBs antigen, and 1 was positive for both (Fibrosis stage F1, n=11; F2, n=7; F3, n=15; F4, n=4). The strain value of F3 and F4 was 0.066±0.02 and 0.042±0.011, respectively. These strain Values were significantly lower compared to those of healthy volunteers (0.112 ±0.018) (P< 0.05). Using a cutoff value of 0.042, the area under ROC curve was 0.88 for the diagnosis of F4. The sensitivity, specificity, positive predictive value, and negative predictive value were 75%, 92%, 50%, and 94%, respectively. CONCLUSIONS: Strain elastography based on tissue Doppler imaging with manual compression appears to be a useful tool to diagnose cirrhosis in patients with chronic viral hepatitis. [Original].

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.

Characterization of carotid artery plaque components on magnetic resonance imaging using signal intensity of the phantom as a reference.

RATIONALE AND OBJECTIVES: To evaluate the properties of plaque by the use of magnetic resonance imaging (MRI), it is necessary to use a material with stable signal intensity (eg, muscle or submandibular gland) as a reference. However, there may be differences between individuals. Therefore, we used a small phantom set on the circumference of the neck as a reference. The signal intensity ratio (SIR) methods using the phantom as a reference were reviewed for discrimination of the properties of plaque in the carotid artery. MATERIALS AND METHODS: Three phantoms (phantom 1: water; phantom 2: 5 µmol gadopentetate dimeglumine; and phantom 3: 2.5 µmol gadopentetate dimeglumine) were set around the neck. SIR was calculated for each region of interest and compared according to pathological grade. RESULTS: The method using a phantom as a reference reduced the standard deviations of tissue ratios to 0.16 from 0.27 in comparison with the method using muscle and showed a close correlation with pathological grade. In addition, the agreement rates with pathological grade and grades from each SIR using signal intensity of the phantom as a reference were higher than using signal intensity of the muscle as a reference to 0.86 from 0.63 for two-dimensional images and to 0.86 from 0.71 for three-dimensional images. CONCLUSIONS: The method described here reduced error compared to the method using muscle as a reference, and the results were closely correlated with pathological grade.

Differential diagnosis of vertebral compression fracture using in-phase/opposed-phase and short TI inversion recovery imaging.

BACKGROUND: Magnetic resonance imaging (MRI) is highly useful for detecting diseases of the bone marrow. The sensitivity for detecting compression fracture is very high, but specificity is low for differential diagnosis between malignant and benign cases. PURPOSE: To evaluate the usefulness of in-phase/opposed-phase and short TI inversion recovery (STIR) magnetic resonance imaging (MRI) of bone marrow for differentiation between benign and malignant vertebral compression fractures. MATERIAL AND METHODS: A retrospective review of 66 patients with 70 vertebral compression fractures was performed. The signal intensity ratio (SIR) defined as SIR (opposed/in) was calculated from in-phase/opposed-phase MR images, and the signal intensity ratio as SIR (STIR) was calculated from STIR MR images. The relationships between values of SIR (opposed/in) and SIR (STIR) and the differential diagnosis of malignant vs. benign fractures were considered. RESULTS: When SIR (opposed/in) was less than 1.0, bone marrow was benign. The bone marrow was malignant when both SIR (opposed/in) was greater than 1.0 and SIR (STIR) was less than 2.0. CONCLUSION: In cases of acute compression fracture, malignant bone marrow showed SIR(STIR) values less than 2.0 and SIR (in/opposed) greater than 1.0. In contrast, benign bone marrow showed SIR (STIR) values greater than 2.5. For chronic compression fracture, malignant bone marrow showed SIR (in/opposed) greater than 1.0. Bone marrow was benign in all cases with SIR (in/opposed) less than 1.0.

Use of dynamic phase subtraction (DPS) map in dynamic contrast-enhanced MRI of the breast.

BACKGROUND: The Breast Imaging Reporting and Data System (BI-RADS) of the American College of Radiology recommends careful examination of the region of interest (ROI) in areas that seem to show a washout pattern on time-intensity curve (TIC). However, it is difficult to identify malignancies because many benign lesions also show enhancement, and these include cysts, hemorrhage, fibrosis, and necrosis in the mass. PURPOSE: This study was performed to assess the performance of the dynamic phase subtraction (DPS) map for dynamic contrast-enhanced magnetic resonance imaging (MRI) of the breast. A DPS map is a map image with pixel-by-pixel subtraction of an early-phase image from a delayed-phase image obtained in a dynamic study. MATERIALS AND METHODS: The use of the DPS map was analyzed retrospectively in 53 patients (32-84 years old) who underwent dynamic contrast-enhanced MRI of the breast. Sensitivity and specificity were compared with and without a DPS map for masses diagnosed as malignant lesions by biopsy. In addition, the patterns of time-intensity curves 30 seconds, 90 seconds, and 5 minutes after injection of contrast agent were compared with and without a DPS map. RESULTS: Sensitivity increased from 0.78 to 0.95, and specificity increased from 0.71 to 0.95 with reference to the DPS map. The pattern of TIC changed from continuous to a plateau in 9 cases, from a plateau to washout in 21 cases, and from continuous to washout in 7 cases. CONCLUSION: Use of the DPS map of dynamic contrast-enhanced MRI of the breast results in high detection rates of malignant masses, allows accurate ROI setting of TIC, and reduces operator's task.

Imaging parameter effects in apparent diffusion coefficient determination of magnetic resonance imaging.

PURPOSE: Although an apparent diffusion coefficient (ADC) value is often used for differential diagnosis of tumours, it varies with scanning parameters. The present study was performed to investigate the influence of imaging parameters, i.e., b value, repetition time (TR) and echo time (TE), on ADC value. METHODS: The phantoms were scanned using diffusion weighted imaging (DWI) with changing b values (b=0-3000 s/mm(2)), TR and TE to determine the influence on ADC. Moreover, ADC of the brain in normal volunteers was determined with varying b values (b=0-1000 s/mm(2)). RESULTS: Diffusion decay curves were obtained by biexponential fitting in all phantoms. The points where fast and slow components of the biexponential decay crossed were called turning points. The b values of turning points that crossed from the biexponential curve were different in each phantom. The b values of turning points depended on ADC of fast diffusion component. When ADC is calculated using two b values of front and back for the turning point, the ADC value may be different. Therefore, it was necessary to perform calculations by b value until the turning point to obtain the ADC value of the fast component. In addition, b≥100 was recommended to avoid the influence of perfusion by blood. Furthermore, the choice of long TR and short TE was effective for accurate measurement of ADC. CONCLUSION: It is important to determine the turning point for measuring ADC.

Improvement on detectability of early ischemic changes for acute stroke using nonenhanced computed tomography: effect of matrix size.

PURPOSE: It has recently been reported that intravenous recombinant tissue plasminogen activator improves the clinical outcome after acute stroke. Computed tomography (CT) is the standard imaging method used to determine the indication for thrombolysis. However, detection of early ischemic change often results in an increase in local radiation exposure. Therefore, the effects of decreased matrix size and use of a noise reduction filter were evaluated. MATERIALS AND METHODS: The low contrast resolution was compared for different matrix sizes and imaging filters using a contrast-detail phantom. In addition, early ischemic change in clinical images with matrix sizes of 256×256 and 128×128 processed using three imaging filters (Gaussian, smoothing, and unsharp mask) from 11 patients within 3h of stroke onset was evaluated by seven radiologists in a blind manner. RESULTS: The use of images with a matrix size of 256×256 and processed with the Gaussian filter increased the detection of early signs of acute stroke. CONCLUSIONS: This study was performed to determine whether the converted matrix size and use of imaging filters could improve the detectability of early ischemic change on CT images in acute stroke. To reduce the dose of radiation exposure for patients, it was effective to use an optimal noise reduction filter and reasonable matrix size. In particular, changing the matrix size to 256×256 was the most effective for detection of early ischemic change in examinations using clinical images.

Effects of iodinated contrast agent on diffusion weighted magnetic resonance imaging.

RATIONALE AND OBJECTIVES: To evaluate the effects of iodine contrast agent on diffusion signal intensity and apparent diffusion coefficient (ADC) in diffusion-weighted imaging (DWI) studies in magnetic resonance imaging (MRI) examination just after computed tomography (CT) contrast imaging. MATERIALS AND METHODS: On a 1.5 T MRI scanner, ADC was calculated from the signal intensity of DWI (b = 0 and 1000) using phantoms filled with contrast agent (0, 4.5, 6.0, 9.0, 30, and 60 mgI/mL). We evaluated the signal intensities of DWI and ADC in 10 patients (3 women, 7 men, 35-68 years old) examined by MRI study less than 40 minutes after injection of 100 mL of iopamidol (300 mgI/mL) for CT study. RESULTS: The DWI signal increased until a CT value of 190 HU, but showed no changes above this value. The ADC decreased with increases in CT value. Less than 40 minutes after injection of iopamidol (300 mgI/mL) for CT scan, the signal intensity of DWI was significantly increased and ADC was significantly decreased. CONCLUSIONS: It is necessary to recognize the rate of decrease of ADC, because it is dependent on the density of iodine contrast agents.

Differentiation of hepatic tumors by use of image contrast with T2-weighted MRI.

Differentiation of hepatic tumors is often evaluated in terms of qualitative diagnostic performance. The signal intensity patterns of hepatic masses are known to differ on certain T2-weighted imaging sequences. In this study, we investigated the quantitative analysis of hepatic masses by using an index called the "T2-shine ratio." Fast-spin-echo (FSE), half-Fourier acquisition single-shot turbo spin echo (HASTE), and true-FISP sequences obtained with quick-imaging techniques during a single breath-hold were examined in 74 patients. T2-shine ratios were calculated by use of the signals of regions of interest (ROIs) placed on a tumor and peripheral tissue: the T2-shine ratio is defined as (tumor signal-liver signal)/liver signal. The rate of change in the T2-shine ratio was compared among three sequences of FSE, HASTE, and true-FISP. The T2-shine ratio of FSE deducted from HASTE was significantly higher for hepatic cysts than for other masses. The T2-shine ratio of HASTE deducted from True-FISP was less than zero for hemangioma. For the value that deducted the T2-shine ratio of HASTE from the T2-shine ratio of true-FISP, hemangiomas had a significantly lower value than did cysts and metastases (P < 0.05), but there was no significant difference from hepatocellular carcinomas (HCCs). Although liver cysts, cavernous hemangiomas, and other lesions could be differentiated, it was virtually impossible to distinguish HCCs from metastatic tumors. In conclusion, the quantitative analysis of hepatic tumors was able to differentiate among these lesions by use of the T2-shine ratio.

The effect of susceptibility of gadolinium contrast media on diffusion-weighted imaging and the apparent diffusion coefficient.

RATIONALE AND OBJECTIVES: The development of parallel magnetic resonance imaging has resulted in the frequent use of diffusion-weighted imaging (DWI) in clinical medicine, which usually involves the use of contrast medium. However, gadolinium (Gd) contrast medium may have some effect on DWI and the apparent diffusion coefficient (ADC). The present study was performed to determine whether the magnetic susceptibility of contrast medium alters the DWI signal and the value of ADC in some imaging techniques. MATERIALS AND METHODS: Nonfat suppression DWI, short-time inversion recovery (STIR) combination, and chemical shift selective (CHESS) combination DWI were performed to examine 10 phantoms with gadolinium-meglumine gadopentetate (Gd-DTPA) dissolved at concentrations from 0.0005 to 0.1 mmol in physiologic saline as a contrast medium. The average pixel value and ADC of each method were determined. RESULTS: ADC showed no differences between before and after treatment with contrast medium for all imaging techniques with Gd considered distributed over the whole tumor. The signal intensity did not change on nonfat suppression or CHESS combination DWI, but deteriorated on STIR. CONCLUSIONS: ADC was not influenced by the magnetic susceptibility of contrast medium. In addition, it was suggested that the ability of tumor detection may be reduced if STIR is used as fat suppression.

[Effect of vibration caused by time-varying magnetic fields on diffusion-weighted MRI].

Diffusion-weighted images (DWIs) with high b-factor in the body are often used to detect and diagnose cancer at MRI. The echo planar imaging (EPI) sequence and high motion probing gradient pulse are used at diffusion weighted imaging, causing high table vibration. The purpose of this study was to assess whether the diffusion signal and apparent diffusion coefficient (ADC) values are influenced by this vibration because of time-varying magnetic fields. Two DWIs were compared. In one, phantoms were fixed on the MRI unit's table transmitting the vibration. In the other, phantoms were supported in air, in the absence of vibration. The phantoms called "solution phantoms" were made from agarose of a particular density. The phantoms called "jelly phantoms" were made from agarose that was heated. The diffusion signal and ADC value of each image were compared. The results showed that the signal of DWI units using the solution phantom was not affected by vibration. However, the signal of DWI and ADC were increased in the low-density jelly phantom as a result of vibration, causing the jelly phantom to vibrate. The DWIs of vibrating regions such as the breast maybe be subject to error. A countermeasure seems to be to support the region adequately.

[Effects of slice thickness and matrix size on MRI for signal detection].

High-resolution MRI with increased matrix size is becoming widely used. When matrix size is increased, the signal-to-noise ratio (SNR) decreases. To compensate for a poor SNR, a thick slice is often used. The purpose of this study was to assess whether slice thickness affects the signal detectability of MR images. Signal detectability was evaluated for various slice thicknesses using a contrast-detail phantom. The results showed that thinning slices led to increased signal detection but to decreased SNR because of higher contrast in the partial volume effect. In addition, increasing matrix size and slice thickness for high-resolution imaging led to a decrease in signal detection. It is necessary to consider voxel form for two-dimensional MR images and to recognize that cuboid voxels lead to increased signal detection.

[Accuracy of contrast-to-noise ratio measurement for magnetic resonance clinical images].

The contrast-to-noise ratio (CNR) is often used to evaluate magnetic resonance images, because it has two components, contrast and SNR, and indicates the detectability of clinical lesions. Two methods (using a phantom and using clinical images) are employed to measure CNR. In addition, there are some methods of measurement that use clinical images. In this report, the accuracy of measurement and correlation for signal detectability were evaluated in four methods of measuring CNR using clinical images. The results indicated that the inter-tissue method using an air signal provided good accuracy and was consistent with signal detectability using observer performance. In addition, a small region of interest (ROI) was better suited as the target for CNR measurement using clinical images.

[Signal detectability of mammography depends on film-screen system and luminance of view box].

High-density film and the high-luminance view-box system are being recommended for mammograms owing to the improved detection of masses. However, this system causes an increase in radiation. Therefore, the purpose of this study was to assess whether the detection of masses would improve using the normal-luminance view box and normal-density film with different types of contrast systems. Low-contrast detection using ROC analysis and high-contrast detection using an ACR phantom were evaluated for the following systems: high-density film and high-luminance view box, normal-density film and normal-luminance view box, and normal-density film with wide latitude and normal-luminance view box. The results showed no significant variation in the detectability of the system with high-density film and high-luminance view box and the normal-density film with wide latitude and normal-luminance view box. However, in terms of low-contrast visibility, the system using normal-density film and normal-luminance view box was significantly reduced in comparison with the others. Therefore, the system with normal-density film with wide latitude and the normal-luminance view box is recommended because of reduced radiation dose.

[Accuracy of signal-to-noise ratio measurement method for magnetic resonance images].

The signal-to-noise ratio (SNR) of a magnetic resonance image is a common measure of imager performance. However, evaluations for the calculation of the SNR use various methods. A problem with measuring SNR is caused by the distortion of noise statistics in commonly used magnitude images. In this study, measurement accuracy was compared among four methods of evaluating SNR according to the size and position of regions of interest (ROIs). The results indicated that the method that used the difference between two images showed the best agreement with the theoretical value. In the method that used a single image, the SNR calculated by using a small size of ROI showed better agreement with the theoretical value because of noise bias and image artifacts. However, in the method that used the difference between two images, a large size of ROI was better in reducing statistical errors. In the same way, the methods that used air noise and air signal were better when applied to a large ROI. In addition, the image subtraction process used to calculate pixel-by-pixel differences in images may reach zero on a minus pixel value when using an image processor with the MRI system and apparatuses associated with it. A revised equation is presented for this case. It is important to understand the characteristics of each method and to choose a suitable method carefully according to the purpose of the study.