Immediate effect of upright position on lumbar disc using multiposture MRI: Preliminary results.

Objectives: Gravity loading on lumbar intervertebral discs (IVDs) is affected by body position. Although the long-term effects of gravity on IVDs have been reported, the immediate effects of gravity on IVDs remain unclear. We considered that changes in IVD structure in the upright and supine positions provided new diagnostic information. Therefore, we compared the apparent diffusion coefficient (ADC), transverse relaxation time (T2), and morphology of the lumbar spine between the quickly changing upright and supine positions using an original magnetic resonance imaging (MRI) system that can obtain images in any position (multiposture MRI). Material and Methods: On a 0.4-T multiposture MRI, diffusion-weighted images of the lumbar spine in seven healthy volunteers were obtained using single-shot diffusion echo-planar imaging (b = 0 and 600 s/mm2) in quickly changing upright and supine positions. Moreover, spin-echo images with multiple echo times (echo time = 30, 60, 90, and 120 ms) were obtained in each position. We calculated the ADC and T2 of each IVD (L1 and S1) without any disc degeneration. In addition, the lumbar lordosis angle and length of the lumbar spine were measured to evaluate the morphology of the lumbar spine. Results: The T2 of the IVD between L4 and L5 in the upright position was significantly lower than that in the supine position (P < 0.05). No significant differences were observed in the ADC. The morphology of the lumbar spine did not differ significantly between the two positions. Conclusion: The T2 of the IVD between L4 and L5 was likely decreased by the effect of gravity due to the postural change from supine to upright.

Prediction of tissue deformation based on mechanical and physiological factors in the prone position during surgery.

AIM: This study aimed to predict tissue deformation based on the pressure applied while lying in the prone position and physiological factors. METHODS: Healthy volunteers were instructed to lie on mattresses of four different hardness levels (50, 87.5, 175, and 262.5 N). The order in which the mattresses were used was randomized per participant. Pressure at the iliac crests was measured using a pressure mapping sensor sheet. Participants were placed in the prone position for 10 min, with pressure data used from the latter 5 min. For the tissue deformation at the iliac crests, our previous study data were used. Multiple regression analysis was used to identify predictive mechanical and physiological factors. RESULTS: The distance between the left and right greater trochanters, maximum interface pressure and age were significant predictors for compression of the skin and soft tissue. Significant predictors of internal soft tissue displacement were the distances between the left and right anterior superior iliac spines and greater trochanters. No factors predicted skin surface displacement. CONCLUSIONS: Our study provided predictive factors that may be measured easily in a clinical setting to reduce the risk of pressure ulcers during surgery in the prone position.

Extrusion of the medial meniscus under a weight-loading condition in early knee osteoarthritis: an investigation using special upright magnetic resonance imaging.

BACKGROUND: Whether the medial meniscus morphology and movement occur under upright loading conditions in early knee osteoarthritis (OA) or medial meniscus posterior root tear (MMPRT) remains unknown. This study aimed to evaluate the medial and anteroposterior extrusion of the medial meniscus under unloaded and upright-loaded conditions in patients with early knee OA. METHODS: Twelve patients with early knee OA and 18 healthy adult volunteers participated in this study. Magnetic resonance imaging using special equipment was performed with the participants in the unloaded and upright-loaded conditions. Medial, anterior, and posterior extrusions of the medial meniscus against the tibial edge were evaluated and compared between the early knee OA and healthy adult control groups. Additionally, 12 patients in the early knee OA group were divided into 2 subgroups based on whether MMPRT was observed, and the extrusion of the medial meniscus was compared. RESULTS: The amount of medial extrusion of the medial meniscus in both the unloaded and upright-loaded conditions was significantly greater in the early knee OA group than in the control group (unloaded: 2.6 ± 1.0 mm vs 0.7 ± 0.5 mm; upright-loaded: 3.7 ± 0.9 mm vs 1.8 ± 0.8 mm). Similarly, the anterior and posterior extrusion of the medial meniscus in the upright-loaded condition was significantly larger in the early knee OA group (anterior: 4.6 ± 1.0 mm vs 3.7 ± 1.1 mm; posterior: -3.4 ± 1.1 mm vs -4.6 ± 1.6 mm). However, no difference was observed in meniscal extrusion between unloaded and upright-loaded conditions. The posterior extrusion of the medial meniscus in the upright-loaded condition was significantly greater in MMPRT cases than in non-MMPRT cases in the early knee OA group (MMPRT: -2.7 ± 1.1 mm; non-MMPRT -4.1 ± 1.5 mm). CONCLUSIONS: In early knee OA, significantly large meniscal extrusions of the medial meniscus in both unloaded and upright-loaded conditions were found compared with healthy adults. Among patients with early knee OA, those with MMPRT showed a large posterior extrusion of the medial meniscus in the upright-loaded condition compared with those without MMPRT. LEVEL OF EVIDENCE: Level IV.

Tri- and bi-exponential diffusion analyses of the kidney: effect of respiratory-controlled acquisition on diffusion parameters.

This study examined whether respiratory-controlled acquisition influences diffusion parameters obtained with intravoxel incoherent motion (IVIM) analysis using tri-exponential and bi-exponential models. Ten healthy volunteers were examined on a 3.0 T MRI system to obtain coronal diffusion-weighted images of both kidneys. The participants were scanned twice using respiratory-triggering (RT) and free-breathing (FB) acquisition to assess the repeatability of the measurements. We determined mean signal intensities in the renal cortex at each b value. Then, perfusion-related diffusion coefficient (Dp), fast-free diffusion coefficient (Df), slow-restricted diffusion coefficient (Ds), and their corresponding fractions (Fp, Ff, and Fs, respectively) were calculated using tri-exponential function. Moreover, perfusion-related diffusion coefficient (D*), the fraction (F), and perfusion-independent diffusion coefficient (D) were calculated using bi-exponential function. Normalized root-mean-square errors for the tri- and bi-exponential analyses (nRMSEtri and nRMSEbi, respectively) were determined to assess the deviation of the fitted to measured data, i.e., the fitting accuracy. Additionally, repeatability coefficients (RCs) were calculated from Bland-Altman plots to evaluate the repeatability of each diffusion parameter. These values were compared between the RT and FB groups. Dp and D* in the RT group were significantly lower than those in the FB group (P < 0.05). In addition, the RT group showed significantly lower nRMSEtri and nRMSEbi values than those in the FB group (P < 0.05). Moreover, Dp, Ds, Fs, and D* at RT showed lower RC values than those at FB. Respiratory-controlled acquisition affects perfusion-related diffusion parameters of the kidney obtained using tri-exponential and bi-exponential analyses.

Validating scapular motion measurements using an optical motion analyzer and gravity magnetic resonance imaging.

[Purpose] This study aimed to validate whether scapular motion measured using a pad with retroreflective markers and optical motion analyzer (VICON MX) can reflect the motion calculated by images using multi-posture (gravity) magnetic resonance imaging. [Participants and Methods] The participants were 12 healthy males (12 dominant-side shoulders). The measurement items were the scapular angle at shoulder flexion 140° and 160° and abduction 100°, 120°, 140°, and 160°. The scapular angle changes were extracted from the upward/downward and internal/external rotations. Angular changes were calculated by subtracting the scapular angle in static position (drooped upper limb and external shoulder rotation) during resting chair sitting from the scapular angle in each of the six limb positions and subtracting it at shoulder abduction 100° from the scapular angle at shoulder abduction 120°, 140°, and 160°. [Results] The results showed no agreement in most cases and no consistent bias. [Conclusion] The result questions the validity of scapular motion analysis using pads with optical markers. However, the facility environment imposes many study limitations, and this method requires further validation eventually.

Spatial analysis of acoustic noise transfer function with a human-body phantom in a clinical MRI scanner.

BACKGROUND: The acoustic noise in magnetic resonance imaging (MRI) potentially depends on the measurement position and presence of a patient inside the scanner bore. PURPOSE: To analyze the spatial characteristics of the acoustic noise by using the gradient-pulse-to-acoustic-noise transfer function (GPAN-TF) with and without a human-body phantom on the examination table. MATERIAL AND METHODS: Acoustic noise waveforms were acquired at 80 and 110 measurement positions with and without a phantom. The GPAN-TFs µPa/(mT/m) in the coils were calculated by deconvolution. The phantom effect on the spatial distribution of the acoustic noise was assessed using the peak sound pressure levels (SPLs), mean values, peak values, and peak frequencies of the GPAN-TFs. RESULTS: The peak SPLs in all positions for the X-, Y-, and Z-gradient coils were increased by 11.1 dB, 1.4 dB, and 6.1 dB, respectively, compared with the peak SPL of the magnetic isocenter. The maximum peak SPLs among all positions of the X-, Y-, and Z-gradient coils with the phantom were increased by 4.9 dB, 7.4 dB, and 6.9 dB, respectively, relative to those without the phantom. However, the peak SPLs decreased at some positions with the phantom placed on the table (X-gradient coil = 4.6 dB, Y-gradient coil = 5.0 dB, Z-gradient coil = 8.4 dB). The most common peak frequencies were in the range of 2000-3000 Hz. CONCLUSION: "Hotspot" areas with and without the phantom were associated with acoustic noise sources in the clinical MRI scanner and were enhanced by the phantom's presence.

Diffusion-weighted Imaging of the Abdomen during a Single Breath-hold Using Simultaneous-multislice Echo-planar Imaging.

PURPOSE: This multi-scanner study aimed to investigate the validity of single breath-hold (BH) diffusion-weighted imaging (DWI) using simultaneous-multislice (SMS) echo-planar imaging in multiple abdominal organs to enable faster acquisition and reliable quantification of apparent diffusion coefficient (ADC). METHODS: SNR, geometric distortion (GD), and ADC in a phantom; the ADC in the liver, renal cortex, paraspinal muscle, spleen, and pancreas; and the signal intensity ratio of the portal vein-to-muscle (SIRPV-M) in healthy volunteers were compared between BH- and respiratory-triggered (RT) DWI with b-values of 0 and 800 s/mm2 in two different MRI scanners. RESULTS: The phantom study showed that the SNR of BH-DWI was significantly lower than that of the RT-DWI (P < 0.05 for both scanners), whereas the GD and ADC of BH-DWI did not differ significantly from those of the RT-DWI (P = 0.09-0.60). In the volunteer study, the scan times were 23 seconds for BH-DWI and 184±33 seconds for RT-DWI, respectively. The ADC of the liver in BH-DWI was significantly lower than that in RT-DWI (P < 0.05 for both scanners), whereas there were no significant differences in the ADCs of the renal cortex, paraspinal muscle, spleen, or pancreas between BH-DWI and RT-DWI (P = 0.07-0.86). The SIRPV-M in BH-DWI was significantly smaller than in RT-DWI (P < 0.05 for both scanners). CONCLUSION: The proposed method enables the acquisition of abdominal diffusion-weighted images in a single BH.

Relationship between pelvic floor muscle function and changes in lumbar spine and hip motion due to pelvic floor muscle contraction.

BACKGROUND: Pelvic floor muscles (PFM) are important for lumbar stability. However, the relationship between lumbar and hip motion angle changes (MAC) caused by PFM contraction and each PFM's function remains unclear. OBJECTIVE: To clarify the lumbar spine and hip motion changes produced by PFM contraction and the relationship between MAC and PFM function. METHODS: In 21 healthy females, motion angle was measured for prone hip extension movement using natural movement (NM), PFM contracting movement (PM), and reducing lumbar movement (RM) methods. The PFM functional indices were bladder base elevation distance, continuous bladder base elevation time, and pelvic floor location. RESULTS: The PM showed no significant difference in lumbar motion angle but had significantly smaller hip motion than the NM (NM; 26.1 ± 8.3, PM; 29.2 ± 11.0). MAC was significantly greater in RM (lumbar spine; 4.4 ± 3.2, hip; 5.9 ± 8.7) than in PM (lumbar spine; 0.4 ± 4.4, hip; 3.1 ± 5.1) for both the lumbar spine and hip. Lumbar spine and hip MAC of PM was significantly correlated with pelvic floor location (lumbar spine; r=-0.44, hip; r= 0.54). CONCLUSION: PFM contraction does not attenuate lumbar spine motion but reduces hip motion. MAC due to PFM contraction during lumbar movement tasks is related to the PFM functional index.

Evaluation of Brain Tumors Using Amide Proton Transfer Imaging: A Comparison of Normal Amide Proton Transfer Signal With Abnormal Amide Proton Transfer Signal Value.

OBJECTIVE: The aim of the study was to evaluate the relationship of amide proton transfer (APT) signal characteristics in brain tumors and uninvolved brain tissue for patients with glioblastoma and those with brain metastases. METHODS: Using the mDIXON 3D-APT sequence of the fast spin echo method, an APT image was obtained. The mean APT signal values of tumor core, peritumor edema, ipsilateral normal-appearing white matter (INAWM), and contralateral normal white matter (CNAWM) were obtained and compared between glioblastoma and brain metastases. Receiver operating characteristic curves were used to evaluate parameters for distinguishing between glioblastoma and brain metastases. In addition, the difference and change rate in APT signal values between tumor core and peritumoral edema (PE) and CNAWM were evaluated, respectively. RESULTS: The APT signal values of glioblastoma were the highest in tumor core (3.41% ± 0.49%), followed by PE (2.24% ± 0.29%), INAWM (1.35% ± 0.15%), and CNAWM (1.26% ± 0.12%, P < 0.001). The APT signal value of brain metastases was the highest in tumor core (2.74% ± 0.34%), followed by PE (1.86% ± 0.35%), INAWM (1.17% ± 0.13%), and CNAWM (1.2% ± 0.09%, P < 0.01). The APT change rate (between PE and CNAWM) was not significantly different at 78% and 56% for glioblastoma and brain metastases, respectively ( P > 0.05). CONCLUSIONS: Performing APT imaging under the same parameters used in this study may aid in the identification of brain tumors.

Reliability of lower leg muscle thickness measurement along the long axis of the muscle using ultrasound imaging, in a sitting position.

[Purpose] To verify the reliability and validity of lower leg muscle thickness (MT) assessment along the muscle's long axis using ultrasound imaging (USI) in a sitting position. [Participants and Methods] Twenty healthy adult female participants (aged, 20.3 ± 0.9 years) were included in the study. Intra- and inter-examiner reliability of the proximal, middle, and distal MT of the tibialis anterior (TA) and medial head of the gastrocnemius (GM) were verified using USI in a sitting position. Additionally, the relationship between MT measurement using USI and muscle cross-sectional area (MCSA) measurement using magnetic resonance imaging (MRI), as well as the ankle joint's maximum muscle strength, were examined. [Results] The reliability of TA and GM MT measurement using USI was high for all regions. The relationship between MCSA measurement using MRI and MT measurement using USI showed a significant correlation in all the regions for both muscles. The relationship between ankle muscle strength and USI of MT was not significantly correlated in any region for both muscles. [Conclusion] Measurement of MT using USI is reliable and valid for MCSA, but must be combined with assessments of other factors for muscle strength.

Prediction of pathological complete response to neoadjuvant chemotherapy in breast cancer using radiomics of pretreatment dynamic contrast-enhanced MRI.

PURPOSE: To investigate if the pretreatment dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)-based radiomics machine learning predicts the pathological complete response (pCR) to neoadjuvant chemotherapy (NAC) in breast cancer patients. METHODS: Seventy-eight breast cancer patients who underwent DCE-MRI before NAC and confirmed as pCR or non-pCR were enrolled. Early enhancement mapping images of pretreatment DCE-MRI were created using subtraction formula as follows: Early enhancement mapping = (Signal 1 min - Signal pre)/Signal pre. Images of the whole tumors were manually segmented and radiomics features extracted. Five prediction models were built using five scenarios that included clinical information, subjective radiological findings, first order texture features, second order texture features, and their combinations. In texture analysis workflow, the corresponding variables were identified by mutual information for feature selection and random forest was used for model prediction. In five models, the area under the receiver operating characteristic curves (AUC) to predict the pCR and several metrics for model evaluation were analyzed. RESULTS: The best diagnostic performance based on F-score was achieved when both first and second order texture features with clinical information and subjective radiological findings were used (AUC = 0.77). The second best diagnostic performance was achieved with an AUC of 0.76 for first order texture features followed by an AUC of 0.76 for first and second order texture features. CONCLUSIONS: Pretreatment DCE-MRI can improve the prediction of pCR in breast cancer patients when all texture features with clinical information and subjective radiological findings are input to build the prediction model.

Sigmoid model analysis of breast dynamic contrast-enhanced MRI: Distinguishing between benign and malignant breast masses and breast cancer subtype prediction.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is performed to distinguish between benign and malignant lesions by evaluating the changes in signal intensity of the acquired image (kinetic curve). This study aimed to verify whether the existing breast DCE-MRI analyzed by the sigmoid model can accurately distinguish between benign and invasive ductal carcinoma (IDC) and predict the subtype. A total of 154 patients who underwent breast MRI for detailed breast mass examinations were included in this study (38 with benign masses and 116 with IDC. The sigmoid model involved the acquisition of images at seven timepoints in 1-min intervals to determine the change in signal intensity before and after contrast injection. From this curve, the magnitude of the increase in signal intensity in the early phase, the time to reach the maximum increase, and the slopes in the early and late phases were calculated. The Mann-Whitney U-test was used for the statistical analysis. The IDC group exhibited a significantly larger and faster signal increase in the early phase and a significantly smaller rate of increase in the late phase than the benign group (P < 0.001). The luminal A-like group demonstrated a significantly longer time to reach the maximum signal increase rate than other IDC subtypes (P < 0.05). The sigmoid model analysis of breast DCE-MRI can distinguish between benign lesions and IDC and may also help in predicting luminal A-like breast cancer.

Comparison of each bundle of the spring ligament complex between the standing and supine positions: A multiposture magnetic resonance imaging study.

BACKGROUND: The spring ligament complex (SLC) supports the medial longitudinal arch of the foot, particularly in standing. We evaluated posture-related changes in the thickness and length of the three SLC bundles and their histology. METHODS: The thickness and length of the supramedial calcaneonavicular ligament (smCNL), medioplantar oblique calcaneonavicular ligament (mpoCNL), and inferoplantar calcaneonavicular ligament (iplCNL) were measured in the supine and standing positions, using a multiposture magnetic resonance imaging system, in 72 healthy adult feet. Histological examination was performed for 10 feet from five cadavers. RESULTS: The smCNL thickness decreased and its length increased from the supine to the standing position (P < 0.001); no other posture-related effects were noted. Histologically, smCNL fibers overlapped along multiple directions while mpoCNL and iplCNL, fibers were oriented horizontally along the longitudinal axis and vertically along the short axis, respectively. CONCLUSION: The complex, multidirectional, orientation of the smCNL allows an adaptive response to changes in loading.

Combined maximum b-value and echo time: A practical method for determining the signal-to-noise ratio for magnetic resonance images.

PURPOSE: The aim of the present study is to develop a simple and practical method for measuring the signal-to-noise ratio (SNR) of magnetic resonance images called combined maximum b-value and echo time (COMBET) that could be suitable for pulse sequences to which a diffusion gradient can be applied. METHODS: In the COMBET method, we first obtain a signal image using the objective pulse sequence. Then, we obtain the noise image of this sequence using the diffusion gradient with the largest b-value and longest echo time. However, other imaging parameters are the same as those used for the signal image acquisition. The SNR is calculated from the mean signal intensity in the region of interest (ROI) of the signal image divided by the signal standard deviation in the ROI of the noise image after the required corrections. We compared SNRs determined using the COMBET and double echo with the longest second echo time (DELSET) methods for single-shot echo-planar imaging and fast spin-echo sequences in white mineral oil phantom, purified water phantom, human head, and upper abdomen. We used the subtraction method as the reference standard. RESULTS: The COMBET method could obtain the optimal noise image, whereas the DELSET method could not sufficiently suppress the long T2 signal in the purified water phantom, cerebrospinal fluid, and digestive fluid. Therefore, the DELSET method afforded incorrect results for the long T2 regions in the noise and SNR maps, while the COMBET method enabled the in vivo evaluation of the SNR even in the long T2 regions. CONCLUSION: The COMBET method allows simple and practical SNR measurement, which is applicable to tissues with long T2 relaxation time.

Quantification of Regional Cerebral Blood Flow Using Diffusion Imaging With Phase Contrast.

BACKGROUND: The perfusion-related diffusion coefficient obtained from triexponential diffusion analysis is closely correlated with regional cerebral blood flow (rCBF), as assessed by arterial spin labeling (ASL) methods. However, this provides only a semiquantitative measure of rCBF, thereby making absolute rCBF quantification challenging. PURPOSE: To obtain rCBF in a noninvasive manner using a novel diffusion imaging method with phase contrast (DPC), in which the total CBF from phase-contrast (PC) MRI was utilized to convert perfusion-related diffusion coefficients to rCBF values. STUDY TYPE: Prospective. SUBJECTS: Eleven healthy volunteers (nine men and two women; mean age, 23.9 years) participated in this study. FIELD STRENGTH/SEQUENCE: A 3.0 T, single-shot diffusion echo-planar imaging with multiple b-values (0-3000 s/mm2 ), PC-MRI, pulsed continuous ASL, and 3D T1 -weighted fast field echo. ASSESSMENT: rCBF and its correlations in the gray matter (GM) and white matter (WM) were compared between DPC and ASL methods. rCBF in the GM and WM and the GM/WM ratio were compared with the literature values obtained using [15 O]-water positron emission tomography (15 O-H2 O PET). STATISTICAL TESTS: Spearman's correlation coefficient and Wilcoxon signed-rank test were used. Significance was set at P < 0.05. RESULTS: A significant positive correlation between DPC and ASL in terms of rCBF was observed in GM (R = 0.9), whereas the correlation between the two methods was poor in WM (R = 0.09). The rCBF in GM and WM and the GM/WM ratio obtained using DPC were consistent with the literature values assessed using 15 O-H2 O PET. The rCBF value obtained using DPC was significantly higher in the GM and WM than that using ASL. DATA CONCLUSION: DPC enabled noninvasive quantification of rCBF. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 1.

Epidemiology of urinary tract infections in children: Causative bacteria and antimicrobial therapy.

BACKGROUND: Urinary tract infections (UTIs) are the most common bacterial infections in children. This study aimed to review characteristics of causative bacteria and the effectiveness of antimicrobial therapy in children with febrile UTIs. METHODS: Clinical records of 108 patients (130 episodes) with febrile UTIs admitted to the Kawasaki Medical School Hospital between July 2009 and October 2016 were retrospectively reviewed. The characteristics of the causative bacteria, antibacterial therapy, and therapeutic effect were verified. RESULTS: Patients were aged between 0 and 183 months (median age: 3 months). Seventy-three (67.6%) were males. Sixty-three episodes (48.5%) were diagnosed with complicated UTIs. Forty-seven episodes (36.2%) were observed in patients aged <3 months; 15 of them had complicated UTIs. Escherichia coli (E. coli) was the most common pathogen, followed by Enterococcus faecalis (E. faecalis). Blood cultures were positive in three episodes. Among the 130 episodes, 62 (47.7%) were treated with a combination of ampicillin and third-generation cephalosporins, followed by third-generation cephalosporins (31 episodes, 23.8%) and sulbactam sodium / ampicillin sodium (15 episodes, 11.5%). In case of patients with uncomplicated/complicated UTIs and patients aged <3 and ≥3 months, the most common pathogen was E. coli, followed by E. faecalis. There was no difference in therapeutic effects between "combination ampicillin and third-generation cephalosporins" and "third-generation cephalosporin monotherapy" administered for the treatment of UTIs caused by E. coli. CONCLUSIONS: Escherichia coli is the most common pathogen among pediatric UTIs. For antibacterial therapy, third-generation cephalosporin monotherapy is effective and may not require combination therapy with ampicillin.

Triexponential Diffusion Analysis of Diffusion-weighted Imaging for Breast Ductal Carcinoma in Situ and Invasive Ductal Carcinoma.

PURPOSE: To obtain detailed information in breast ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) using triexponential diffusion analysis. METHODS: Diffusion-weighted images (DWI) of the breast were obtained using single-shot diffusion echo-planar imaging with 15 b-values. Mean signal intensities at each b-value were measured in the DCIS and IDC lesions and fitted with the triexponential function based on a two-step approach: slow-restricted diffusion coefficient (Ds) was initially determined using a monoexponential function with b-values > 800 s/mm2. The diffusion coefficient of free water at 37°C was assigned to the fast-free diffusion coefficient (Df). Finally, the perfusion-related diffusion coefficient (Dp) was derived using all the b-values. Furthermore, biexponential analysis was performed to obtain the perfusion-related diffusion coefficient (D*) and the perfusion-independent diffusion coefficient (D). Monoexponential analysis was performed to obtain the apparent diffusion coefficient (ADC). The sensitivity and specificity of the aforementioned diffusion coefficients for distinguishing between DCIS and IDC were evaluated using the pathological results. RESULTS: The Ds, D, and ADC of DCIS were significantly higher than those of IDC (P < 0.01 for all). There was no significant correlation between Dp and Ds, but there was a weak correlation between D* and D. The combination of Dp and Ds showed higher sensitivity and specificity (85.9% and 71.4%, respectively), compared to the combination of D* and D (81.5% and 33.3%, respectively). CONCLUSION: Triexponential analysis can provide detailed diffusion information for breast tumors that can be used to differentiate between DCIS and IDC.

Recent acute reduction in macrolide-resistant Mycoplasma pneumoniae infections among Japanese children.

INTRODUCTION: Mycoplasma pneumoniae contributes to numerous pneumonia cases among children and young adults. Therefore, this study aimed to investigate the prevalence of M. pneumoniae infections among Japanese children, occurring since 2008. METHODS: Nasopharyngeal swab specimens were obtained from all cases, following which real-time PCR was performed to identify M. pneumoniae. Further, the p1 genotypes of isolates were determined using the PCR restriction fragment length polymorphism typing method. RESULTS: The annual rate of macrolide-resistant M. pneumoniae (MRMP) infections peaked at 81.8% in 2012 and decreased annually until 2015. Although the infection rate increased to 65.3% in 2016, it decreased again to 14.3% in 2018. Although >90% of isolates harbored the type 1 genotype until 2012, this rate decreased, and approximately 80% harbored p1 genotypes other than type 1 in 2018. Furthermore, the occurrence rate of MRMP among the type 1 isolates was very high (82.4%), whereas that among p1 genotypes other than type 1 was very low (6.5%). CONCLUSIONS: MRMP occurrence potentially decreased owing to changes in not only antibiotic usage but also in the distribution of p1 genotype among isolates.