Shot Echo Planar Research Articles

Generalizing Diffusion Tensor Imaging of the Physis and Metaphysis.

Current methods to predict height potential are inaccurate. Predicting height by using MRI of the physeal cartilage has shown promise but the applicability of this technique in different imaging setups has not been well-evaluated. To assess variability in diffusion tensor imaging of the physis and metaphysis (DTI-P/M) of the distal femur between different scanners, imaging parameters, tractography software, and resolution. Prospective. Eleven healthy subjects (five males and six females ages 10-16.94). 3 T; DTI single shot echo planar sequences. Physeal DTI tract measurements of the distal femur were compared between different scanners, imaging parameters, tractography settings, interpolation correction, and tractography software. Bland-Altman, Spearman correlation, linear regression, and Shapiro-Wilk tests. Threshold for statistical significance was set at P = 0.05. DTI tract values consistently showed low variability with different imaging and analysis settings. Vendor to vendor comparison exhibited strong correlation (ρ = 0.93) and small but significant bias (bias -5.76, limits of agreement [LOA] -24.31 to 12.78). Strong correlation and no significant difference were seen between technical replicates of the General Electric MRI scanner (ρ = 1, bias 0.17 [LOA -1.5 to 1.2], P = 0.42) and the Siemens MRI scanner (ρ = 0.89, bias = 0.56, P = 0.71). Different voxel sizes (1 × 1 × 2 mm3 vs. 2 × 2 × 3 mm3) did not significantly affect DTI values (bias = 1.4 [LOA -5.7 to 8.4], P = 0.35) but maintained a strong correlation (ρ = 0.82). Gap size (0 mm vs. 0.6 mm) significantly affects tract volume (bias = 1.8 [LOA -5.4 to 1.8]) but maintains a strong correlation (ρ = 0.93). Comparison of tractography algorithms generated significant differences in tract number, length, and volume while maintaining correlation (ρ = 0.86, 0.99, 0.93, respectively). Comparison of interobserver variability between different tractography software also revealed significant differences while maintaining high correlation (ρ = 0.85-0.98). DTI of the pediatric physis cartilage shows high reproducibility between different imaging and analytic parameters. 2 TECHNICAL EFFICACY: Stage 1.

Functional assessment of brain development in fetuses that subsequently deliver very preterm: An MRI pilot study.

To evaluate changes occurring in the fetal brain prior to very preterm delivery using MRI T2* relaxometry, an indirect assessment of tissue perfusion. Fetuses that subsequently delivered spontaneously <32weeks gestation and a control cohort were identified from pre-existing datasets. Participants had undergone a 3T MRI assessment including T2* relaxometry of the fetal brain using a 2D multi-slice gradient echo single shot echo planar imaging sequence. T2* maps were generated, supratentorial brain tissue was manually segmented and mean T2* values were generated. Groups were compared using quadratic regression. Twenty five fetuses that subsequently delivered <32weeks and 67 that delivered at term were included. Mean gestation at MRI was 24.5weeks (SD 3.3) and 25.4weeks (SD 3.1) and gestation at delivery 25.5weeks (SD 3.4) and 39.7weeks (SD 1.2) in the preterm and term cohorts respectively. Brain mean T2* values were significantly lower in fetuses that subsequently delivered before 32weeks gestation (p<0.001). Alterations in brain maturation appear to occur prior to preterm delivery. Further work is required to explore these associations, but these findings suggest a potential window for therapeutic neuroprotective agents in fetuses at high risk of preterm delivery in the future.

Functional MRI assessment of the lungs in fetuses that deliver very Preterm: An MRI pilot study

ObjectivesTo compare mean pulmonary T2* values and pulmonary volumes in fetuses that subsequently spontaneously delivered before 32 weeks with a control cohort with comparable gestational ages and to assess the value of mean pulmonary T2* as a predictor of preterm birth < 32 weeks’ gestation. MethodsMRI datasets scanned at similar gestational ages were selected from fetuses who spontaneously delivered < 32 weeks of gestation and a control group who subsequently delivered at term with no complications. All women underwent a fetal MRI on a 3 T MRI imaging system. Sequences included T2-weighted single shot fast spin echo and T2* sequences, using gradient echo single shot echo planar sequencing of the fetal thorax. Motion correction was performed using slice-to-volume reconstruction and T2* maps generated using in-house pipelines. Lungs were manually segmented and volumes and mean T2* values calculated for both lungs combined and left and right lung separately. Linear regression was used to compare values between the preterm and control cohorts accounting for the effects of gestation. Receiver operating curves were generated for mean T2* values and pulmonary volume as predictors of preterm birth < 32 weeks’ gestation. ResultsDatasets from twenty-eight preterm and 74 control fetuses were suitable for analysis. MRI images were taken at similar fetal gestational ages (preterm cohort (mean ± SD) 24.9 ± 3.3 and control cohort (mean ± SD) 26.5 ± 3.0). Mean gestational age at delivery was 26.4 ± 3.3 for the preterm group and 39.9 ± 1.3 for the control group. Mean pulmonary T2* values remained constant with increasing gestational age while pulmonary volumes increased. Both T2* and pulmonary volumes were lower in the preterm group than in the control group for all parameters (both combined, left, and right lung (p < 0.001 in all cases). Adjusted for gestational age, pulmonary volumes and mean T2* values were good predictors of premature delivery in fetuses < 32 weeks (area under the curve of 0.828 and 0.754 respectively). ConclusionThese findings indicate that mean pulmonary T2* values and volumes were lower in fetuses that subsequently delivered very preterm. This may suggest potentially altered oxygenation and indicate that pulmonary morbidity associated with prematurity has an antenatal antecedent. Future work should explore these results correlating antenatal findings with long term pulmonary outcomes.

Amide Proton Transfer-Weighted Imaging and Multiple Models Intravoxel Incoherent Motion-Based 18F-FDG PET/MRI for Predicting Progression-Free Survival in Non-Small Cell Lung Cancer.

Amide proton transfer-weighted imaging (APTWI) and multiple models intravoxel incoherent motion (IVIM) based 18F-FDG PET/MR could reflect the microscopic information of the tumor from multiple perspectives. However, its value in the prognostic assessment of non-small cell lung cancer (NSCLC) still needs to be further explored. To determine whether pretreatment APTWI, mono-, bi-, and stretched-exponential model IVIM, and 18F-FDG PET-derived parameters of the primary lesion may be associated with progression-free survival (PFS) in NSCLC. Prospective. Seventy-seven patients (mean age, 62 years, range, 20-81 years) with 37 men and 40 women were included. 3.0 T 18F-FDG PET/MRI, single shot echo planar imaging sequences for IVIM and fast spin-echo sequences with magnetization transfer pulses for APTWI. Patient clinical characteristics (age, sex, smoke, subtype, TNM stage, and surgery), PFS (chest CT every 3 months, median follow-up was 18 months, range, 4-27 months), and APTWI (MTRasym(3.5 ppm)), IVIM (ADCstand, D, D*, f, DDC, and α), and 18F-FDG PET (SUVmax, MTV, and TLG) parameters were recorded. Proportional hazards model, concordance index, calibration curve, decision curve analysis (DCA), and Log-rank test. A P value <0.05 was considered statistically significant. Histological subtype, TNM stage, MTV, D*, and MTRasym(3.5 ppm) were all independent predictors of PFS. A prediction model based on these predictors was developed with a C-index of 0.895 (95% CI: 0.839-0.951), which was significantly superior to each of the above predictors alone (C-index = 0.629, 0.707, 0.692, 0.678, and 0.558, respectively). The calibration curve and DCA indicated good consistency and clinical utility of the prediction model, respectively. Log-rank test results showed a significant difference in PFS between the high- and low-risk groups. APTWI and multiple models IVIM based 18F-FDG PET/MRI can be used for PFS assessment in NSCLC. 3 TECHNICAL EFFICACY: Stage 2.

Graph network measures reveal distinct white matter abnormalities in motor and extra-motor brain regions of two UMN-predominant ALS subtypes

BackgroundRoutine clinical magnetic resonance imaging (MRI) shows bilateral corticospinal tract (CST) hyperintensity in some patients with upper motor neuron (UMN)-predominant ALS (ALS-CST+) but not in others (ALS-CST–). Although, similar in their UMN features, the ALS-CST+ patient group is significantly younger in age, has faster disease progression and shorter survival than the ALS-CST– patient group. Reasons for the differences are unclear. MethodIn order to evaluate more objective MRI measures of these ALS subgroups, we used diffusion tensor images (DTI) obtained using single shot echo planar imaging sequence from 1.5 T Siemens MRI Scanner. We performed an exploratory whole brain white matter (WM) network analysis using graph theory approach on 45 ALS patients (ALS-CST+) (n = 21), and (ALS-CST–) (n = 24) and neurological controls (n = 14). ResultsSignificant (p < 0.05) differences in nodal degree measure between ALS patients and controls were observed in motor and extra motor regions, supplementary motor area, subcortical WM regions, cerebellum and vermis. Importantly, WM network abnormalities were significantly (p < 0.05) different between ALS-CST+ and ALS-CST– subgroups. Compared to neurologic controls, both ALS subgroups showed hubs in the right superior occipital gyrus and cuneus as well as significantly (p < 0.05) reduced small worldness supportive of WM network damage. ConclusionsSignificant differences between ALS-CST+ and ALS-CST– subgroups of WM network abnormalities, age of onset, symptom duration prior to MRI, and progression rate suggest these patients represent distinct clinical phenotypes and possibly pathophysiologic mechanisms of ALS.

Diffusion tensor imaging in evaluation of intradural spinal tumors – A case series

Diffusion tensor imaging (DTI) is an advanced magnetic resonance imaging (MRI) technique which utilizes diffusion measurements in multiple directions to provide information regarding tissue structure by parameters such as fractional anisotropy (FA) and apparent diffusion coefficient along with generation of fiber tractography maps. We investigated DTI using single shot echo planar imaging in 20 diffusion directions on 3T MRI in nine patients diagnosed with intradural spinal tumors and found significant reduWction in FA value within the lesion compared to FA value at normal cord. Tractography maps generated by DTI were useful in differentiating intramedullary from extramedullary location of tumor. Tractography also provided useful information regarding tract infiltration or displacement in cases of intramedullary neoplasms. Thus, DTI proved helpful in classification, characterization, and treatment planning of intradural spinal tumors.

Ultra-high field (10.5T) diffusion-weighted MRI of the macaque brain

Diffu0sion-weighted magnetic resonance imaging (dMRI) is a non-invasive imaging technique that provides information about the barriers to the diffusion of water molecules in tissue. In the brain, this information can be used in several important ways, including to examine tissue abnormalities associated with brain disorders and to infer anatomical connectivity and the organization of white matter bundles through the use of tractography algorithms. However, dMRI also presents certain challenges. For example, historically, the biological validation of tractography models has shown only moderate correlations with anatomical connectivity as determined through invasive tract-tracing studies. Some of the factors contributing to such issues are low spatial resolution, low signal-to-noise ratios, and long scan times required for high-quality data, along with modeling challenges like complex fiber crossing patterns. Leveraging the capabilities provided by an ultra-high field scanner combined with denoising, we have acquired whole-brain, 0.58 mm isotropic resolution dMRI with a 2D-single shot echo planar imaging sequence on a 10.5 Tesla scanner in anesthetized macaques. These data produced high-quality tractograms and maps of scalar diffusion metrics in white matter. This work demonstrates the feasibility and motivation for in-vivo dMRI studies seeking to benefit from ultra-high fields.

A fast MR-thermometry method for quantitative assessment of temperature increase near an implanted wire.

To propose a MR-thermometry method and associated data processing technique to predict the maximal RF-induced temperature increase near an implanted wire for any other MRI sequence. A dynamic single shot echo planar imaging sequence was implemented that interleaves acquisition of several slices every second and an energy deposition module with adjustable parameters. Temperature images were processed in real time and compared to invasive fiber-optic measurements to assess accuracy of the method. The standard deviation of temperature was measured in gel and in vivo in the human brain of a volunteer. Temperature increases were measured for different RF exposure levels in a phantom containing an inserted wire and then a MR-conditional pacemaker lead. These calibration data set were fitted to a semi-empirical model allowing estimation of temperature increase of other acquisition sequences. The precision of the measurement obtained after filtering with a 1.6x1.6 mm2 in plane resolution was 0.2°C in gel, as well as in the human brain. A high correspondence was observed with invasive temperature measurements during RF-induced heating (0.5°C RMSE for a 11.5°C temperature increase). Temperature rises of 32.4°C and 6.5°C were reached at the tip of a wire and of a pacemaker lead, respectively. After successful fitting of temperature curves of the calibration data set, temperature rise predicted by the model was in good agreement (around 5% difference) with measured temperature by a fiber optic probe, for three other MRI sequences. This method proposes a rapid and reliable quantification of the temperature rise near an implanted wire. Calibration data set and resulting fitting coefficients can be used to estimate temperature increase for any MRI sequence as function of its power and duration.

Can Quantitative and Qualitative DWI Differentiate between Benign and Malignant Ovarian Masses?

Abstract Background: Pre-operative diagnosis of ovarian represents diagnostic challenge as it affects the lines of treatment and patient's prognosis. Previous studies studied the role of the Diffusion Weighted Imaging (DWI) in discrimination between benign and malignant ovarian masses with controversial results. Aim of Study: The aim of this study was to evaluate the role of qualitative and quantitative Diffusion Weighted Imaging (DWI) in the discrimination between benign and malignant ovarian tumors. Material and Methods: The study included 82 patients. All patients underwent MRI with a 1.5T unit. Conventional MRI both pre and post contrast. Before administration of the contrast, the DWI sequence, single shot echo planar sequence in the axial plane was done for all patients. Analysis of the MRI findings, the signal intensity on DWI and the ADC value for solid and cystic components was done for all lesions. Results: For conventional MRI, the overall sensitivity, specificity, PPV, NPV and accuracy of MRI was 85.71%, 85.71%, 87.80%, 83.33% and 85.71% respectively. Hyperin-tense signal on DWI of the solid component was observed in 17/18 (94.4%) of malignant tumors. The restricted diffusion in the solid components had a sensitivity of 94.44%, specificity 85.71%, PPV 94.44% and NPV of 85.71% with overall accu-racy of 92.% in prediction of malignancy. Using 1.2 X 10–3 mm2/sec) as a cut off value between benign an malignant lesion had sensitivity 88.89%, specificity 85.71% and accuracy 88% in differentiation between benign and malignant masses. Conclusion: Diffusion weighted imaging especially the qualitative component have high diagnostic accuracy in differentiation between benign and malignant ovarian masses and should be integrated into the pelvic MRI.

Usefulness of Respiratory Suppression for Abdominal Using EPI Sequences

The upper abdomen was imaged with diffusion weighted images for free breathing and respiratory suppression using single shot-echo planar imaging (SS-EPI) and readout segmented-EPI (RS-EPI). We examined the usefulness of respiratory suppression imaging for the subject of healthy volunteers. Motion artifacts, apparent diffusion coefficient (ADC) values, and organs movement distances were evaluated. As a result, motion artifacts and organs movement distances were reduced in respiratory suppression than free breathing. The ADC values did not change. Respiratory suppression was simple and useful. In addition, it was found that RS-EPI imaging could be used for imaging the upper abdomen in the same way as SS-EPI by respiratory suppression.

Aberrant gray matter volumes and functional connectivity in adolescent patients with ADHD.

Altered gray matter (GM) volumes and functional connectivity (FC) happens in attention-deficit/hyperactivity disorder (ADHD) patients and the intelligence quotient (IQ) of ADHD patients is generally lower than healthy subjects, while few studies have focused on the association among the three. To investigate the abnormal changes of GM volumes and FC in ADHD patients compared with typically-developing control (TD-C), as well as the association between the changes and IQ. Case control. 36 ADHD patients and 36 TD-C, aged 8-17. 3.0T/single shot echo planar imaging (EPI). Preprocessing of fMRI data and seed-based FC calculation using DPABI4.0, and VBM was performed by CAT12. Comparison between groups of smoothed GM volumes was performed using two-sample t-test within SPM 12, age and total intracranial volume (TIV) were returned as covariates. Comparison between groups of FCs was performed using a two-sample t-test within RESTplus; age was returned as a covariate. False discovery rate (FDR)-corrected and P < 0.05 was considered statistically significant. Compared with TD-C, reduced GM volumes occurred in the left superior frontal gyrus (t = -3.61, P < 0.001), right middle frontal gyrus (t = -3.97, P < 0.001), left middle cingulum (t = -3.93, P < 0.001), and left cuneus (t = -4.42, P < 0.001). Decreased FC was found between the left precuneus and left middle cingulum (t = -5.86, P < 0.001), left middle temporal gyrus, and left superior frontal gyrus (t = -5.67, P < 0.001), as well as left medial superior frontal gyrus and left superior frontal gyrus (t = -6.73, P < 0.001). The results confirmed that FCs between the regions with declined GM volumes and others were altered in ADHD patients. We speculated that abnormal changes of GM volume and FC maybe used as an imaging metric of ADHD. 2 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2020;51:719-726.

Paraspinal Muscle DTI Metrics Predict Muscle Strength.

BackgroundThe paraspinal muscles play an important role in the onset and progression of lower back pain. It would be of clinical interest to identify imaging biomarkers of the paraspinal musculature that are related to muscle function and strength. Diffusion tensor imaging (DTI) enables the microstructural examination of muscle tissue and its pathological changes.PurposeTo investigate associations of DTI parameters of the lumbar paraspinal muscles with isometric strength measurements in healthy volunteers.Study TypeProspective.SubjectsTwenty‐one healthy subjects (12 male, 9 female; age = 30.1 ± 5.6 years; body mass index [BMI] = 27.5 ± 2.6 kg/m2) were recruited.Field Strength/Sequence3 T/single‐shot echo planar imaging (ss‐EPI) DTI in 24 directions; six‐echo 3D spoiled gradient echo sequence for chemical shift encoding‐based water–fat separation.AssessmentParaspinal muscles at the lumbar spine were examined. Erector spinae muscles were segmented bilaterally; cross‐sectional area (CSA), proton density fat fraction (PDFF), and DTI parameters were calculated. Muscle flexion and extension maximum isometric torque values [Nm] at the back were measured with an isokinetic dynamometer and the ratio of extension to flexion strength (E/F) calculated.Statistical TestsPearson correlation coefficients; multivariate regression models.ResultsSignificant positive correlations were found between the ratio of extension to flexion (E/F) strength and mean diffusivity (MD) (P = 0.019), RD (P = 0.02) and the eigenvalues (λ1: P = 0.026, λ2: P = 0.033, λ3: P = 0.014). In multivariate regression models λ3 of the erector spinae muscle λ3 and gender remained statistically significant predictors of E/F (R2 adj = 0.42, P = 0.003).Data ConclusionDTI allowed the identification of muscle microstructure differences related to back muscle function that were not reflected by CSA and PDFF. DTI may potentially track subtle changes of back muscle tissue composition. Level of Evidence: 3 Technical Efficacy: Stage 2J. Magn. Reson. Imaging 2019;50:816–823.

Role of MRI in Characterization of Benign Hepatic Focal Lesions

Background: nowadays, magnetic resonance plays a key role in management of liver lesions, using a radiation-free technique and a safe contrast agent profile. The heightened soft-tissue resolution and sensitivity to intravenous contrast agents provided by magnetic resonance imaging (MRI) makes it an invaluable problem-solving tool for fully characterizing focal liver lesions (FLL). Diffusion-weighted imaging (DWI) sequences have been shown to be an emerging contributor for liver MRI and are being incorporated in most abdominal MR protocols. Aims: To determine the role of MRI in characterization of benign hepatic focal lesions. Patients and methods: This study included 30 patients (11 M, 19 F with mean age of 47.7 years) with benign hepatic focal lesions. They were simple cyst (n =6), hemangioma (n = 11), abscess (n = 4), adenoma (n = 2), focal nodular hyperplasia (n = 3), Hydatid cyst (n=1) and regenerative nodules (n = 3). They underwent routine MR imaging and diffusion MR weighted imaging using 1.5 tesla MR unit (Philips Achieva). Diffusion MR imaging was done using spin echo type of single shot echo planar imaging (EPI) with b value of 0, &800 mm2/sec. The apparent diffusion coefficient (ADC) map was reconstructed and ADC value was measured. The mean ADC values correlated with histopathological results as well as followup imaging results. Results: The mean ADC values were significantly different within benign hepatic focal lesions (P < 0.001). There was highly statically significant relation between cyst and hemangioma (p-value < 0.001), cyst and abscess (p-value <0.001), hemngioma and abscess (p-value < 0.001), while there was no statically significance relation between adenoma and focal nodular hyperplasia (p-value < 0.74), adenoma and regenerative nodules (p-value < 0.67) and focal nodular hyperplasia and regenerative nodules (p-value < 0.41). Conclusions: benign liver lesions are frequently encountered in clinical practice and their characterization may be sometimes difficult. The problem of lesion characterization is mainly crucial and may influence therapeutic decisions and patient’s management. The role of imaging is therefore a mainstay and MRI, with its multi parametric potentialities, is a highly accurate method for lesion detection and characterization. Nevertheless, benign lesions may be sometimes “non-typic” in their cellular content and vascular behavior and lesions biopsy can be necessary for definitive characterization.

Diffusion-weighted imaging of the brains of dogs with idiopathic epilepsy

BackgroundIdiopathic epilepsy is one of the most common neurological disorders in dogs. Unfortunately, up to 30% of dogs with idiopathic epilepsy show no improvement under antiepileptic drug treatment. Diffusion-weighted imaging is used in human medicine to identify epileptogenic foci in the brain to allow for more invasive treatments such as deep brain stimulation or surgical removal.The aim of this study was to ass the feasibility of interictal diffusion-weighted MRI in dogs and to evaluate the distribution of diffusion in the brains of dogs with idiopathic epilepsy (IE) and to compare these values to previously published values from healthy beagle dogs.Client-owned dogs with the final diagnosis of IE were included in this study. MRI examination was carried out using a 1.0Tesla superconductive magnet. Diffusion-weighted images using a single shot echo planar imaging sequence (SSh-EPI) with a b value of b = 0 s/mm2 and b = 800 s/mm2 were acquired in a dorsal and transverse plane with diffusion gradients in all three planes (x-, y- and z-plane). An ADC (apparent diffusion coefficient) map of the isometric image of each acquired slice was generated.Regions of interest (ROIs) were manually drawn around the caudate nucleus, the thalamus, the piriform lobe including the amygdala, the hippocampus, the semioval center and the temporal cerebral cortex by one of the authors. ROI drawings were repeated 5 times at different time points to assess intra-obersver variability. A multi-way mixed-model analysis of variance (ANOVA) and two-way ANOVA were used during statistical analysis. A p value of p < 0.05 was considered significant.ResultsDogs with IE showed a significantly increased ADC in the amygdala within the piriform lobe and in the semioval center (p < 0.05) compared with the healthy control group.ConclusionChanges in the piriform lobe in cases of epilepsy are reported infrequently in human and veterinary medicine. Similar to our results, ADC changes in the interictal phase usually include an increase in ADC due to cell loss and increased intercellular spaces. Diffusion MRI might be a promising technique for the examination of canine epileptic patients lacking other gross neuromorphological abnormalities.

The Importance of Diffusion Weighted Imaging in Breast MRI

Objectives: The aim of this study was to evaluate the value of diffusion weighted imaging in Diffusion weighted imaging in distinguishing between in benign and malignant breast lesion Methods: There were 37 female patients with 47 lesions. Sixty seven female subjectd (40 mean age ) ,age ranges 17-69 , with histopathologically proven breast lesions underwent DWI of breasts with a single shot echo planar imaging (EPI )sequence .the computed mean apparent diffusion cofficients (ADCs) of the breasts lesion and cell density were then correlated. Results: The ADC varied substantially between benign breast lesions ((1.52 0.26) 10 -3 mm2 / second). And malignant breast lesions ((0.94 0.21) 10 -3 mm2 / second) .The AUC with ROC analysis was 0.896 and the threshold for ADC was 1.17 10-3 mm2 /second with a sensitivity and specificity of 90% and 85%, respectively. The mean ADC of malignant breast lesions was statistically lower for benign lesions (P value less than 0.01) Conclusions: The ADC would be a effective parameter in distinguishing between malignant and benign breast lesions.

뇌줄기 확산강조 자기공명영상검사 시 뒤틀림을 줄이기 위한 SS-TSE 기법의 신호대잡음비 연구

본 연구는 뇌줄기 확산강조영상검사 시 뒤틀림을 줄이기 위한 SS-TSE 기법의 신호대잡음비 감소를 수치적으로 정량화하여, 낮은 신호대잡음비로 인한 SS-TSE 기법의 문제점을 지적하고자 하였다. 연구방법은 2015년 7월부터 10월까지 뇌줄기 확산강조영상검사를 검사한 35명을 대상으로 하였으며, 기존의 SS-EPI 기법과 SS-TSE 기법을 적용하여 기법별 숨뇌의 신호대잡음비을 비교하였다. 연구결과 b=0 영상의 신호대잡음비는 새로운 SS-TSE 기법(<TEX>$314.41{\pm}42.96$</TEX>) 적용 시 SS-EPI 기법(<TEX>$514.84{\pm}48.97$</TEX>) 보다 38.9% 감소하였으며, b=1,000 영상의 경우도 SS-TSE 기법(<TEX>$117.33{\pm}14.04$</TEX>) 적용 시 SS-EPI 기법(<TEX>$208.65{\pm}25.70$</TEX>) 보다 43.8% 감소하였다. 결론적으로, 미세 병변을 진단하기 위한 뇌줄기의 확산강조 자기공명영상 검사 시 뒤틀림을 줄이기 위해 SS-TSE 기법을 적용할 경우 신호대잡음비가 저하됨으로 기존의 SS-EPI 기법이나 MS-EPI 기법을 병행하여 검사하는 것이 진단의 정확성을 높일 수 있으리라 사료된다. The purpose of this study was to investigate the problems of low signal-to-noise ratio(SNR) of single-shot turbo spin echo(SS-TSE) by quantifying numerically decreased signal to noise ratio. Thirty five patients without brain disease underwent diffusion MRI in 3T scanner from July to October in 2015. Single shot echo planar imaging(SS-EPI) which is conventionally used in MRI was taken to compared SS-TSE in SNR of medulla oblongata. As a result, SNR of SS-TSE diffusion(b0=<TEX>$314.41{\pm}42.96$</TEX>, b1000=<TEX>$117.33{\pm}14.04$</TEX>) is than SS-EPI diffusion(b0=<TEX>$514.84{\pm}48.97$</TEX>, b=<TEX>$208.65{\pm}25.70$</TEX>) lower in b=0 image(38.9%) and b=1,000 image(43.8%). Thus, diffusion MR using SS-EPI of MS-EPI should be taken for diagnosis of disease in brain stem due to decreased SNR of diffusion using SS-TSE.

Diffusion Weighted Magnetic Resonance Imaging for the Characterization of Solitary Pulmonary Lesions.

We evaluated the differential diagnosis of solitary pulmonary lesions on magnetic resonance imaging. To investigate the value of diffusion weighted imaging on the differential diagnosis of solitary pulmonary lesions. Randomized prospective study. This prospective study included 48 solitary pulmonary nodules and masses (18 benign, 30 malignant). Single shot echo planar spin echo diffusion weighted imaging (DWI) was performed with two b factors (0 and 1000 s/mm(2)). Apparent diffusion coefficients (ADCs) were calculated. On diffusion weighted (DW) trace images, the signal intensities (SI) of the lesions were visually compared to the SI of the thoracic spinal cord using a 5-point scale: 1: hypointense, 2: moderately hypointense, 3: isointense, 4: moderately hyperintense, 5: significantly hyperintense. For the quantitative evaluation, the lesion to thoracic spinal signal intensity ratios and the ADCs of the lesions were compared between groups. On visual evaluation, taking the density of the spinal cord as a reference, most benign lesions were found to be hypointense, while most of the malignant lesions were evaluated as hyperintense on DWI with a b factor of 1000 s/mm(2). In contrast, on T2 weighted images, it was seen that the distinction of malignant lesions from benign lesions was not statistically significant. The ADCs of the malignant lesions were significantly lower than those of benign lesions (mean ADC was 2.02×10(-3) mm(2)/s for malignant lesions, and 1.195×10(-3)±0.3 mm(2)/s for benign lesions). Setting the cut-off value at 1.5×10(-3), ADC had a sensitivity of 86.7% and a specificity of 88.9% for the differentiation of benign lesions from malignant lesions. DWI may aid in the differential diagnosis of solitary pulmonary lesions. (ClinicalTrials.gov Identifier: NCT02482181).

In vivo 3 T and ex vivo 7 T diffusion tensor imaging of prostate cancer: Correlation with histology

The purpose of this work was to test whether fractional anisotropy (FA) can contribute to the diagnosis and grading of prostate cancer.Turbo spin echo T2-weighted (T2W) and single shot echo planar imaging diffusion tensor imaging (EPI DTI) data were collected from 13 subjects with biopsy proven prostate cancer prior to surgical removal of the gland. Rapid acquisition with relaxation enhancement (RARE) T2W and spin-echo DTI data were acquired ex-vivo from the fixed prostatectomy specimens. Digitized whole mount histology sections, examined and annotated by a pathologist, were registered to the in-vivo and ex-vivo DTI data, and the average values of apparent diffusion coefficient (ADC) and FA were calculated from ROIs encompassing normal and cancerous peripheral zone (PZ). In addition, Monte Carlo simulations were carried out to assess the dependence of the apparent FA on the ADC values for different signal to noise ratios (SNRs).ADC values were significantly lower in tumors than in normal PZ both in-vivo and ex-vivo, while the difference in FA values between tumors and normal PZ was significant only in-vivo. Paired t-test showed significant difference between in-vivo and ex-vivo FA values in tumors, but not in the normal PZ. The simulations showed that lower SNR results in an increasing overestimation of the FA values with decreasing ADC. These results suggest that the in-vivo increase in FA values in tumors is due to low SNR, rather than the presence of cancer.The results of this study suggest that FA does not contribute significantly to the diagnostic capabilities of DTI in prostate cancer.

Diffusion-Weighted MR Imaging of the Benign Hepatic Focal Lesions

Purpose: To determine the role of diffusion weighted MR imaging and apparent diffusion coefficient (ADC) in benign hepatic focal lesions. Method and Materials: This study included 47 patients (29 M, 18 F with mean age of 43 years) with benign hepatic focal lesions. They were cyst (n = 8), hemangioma (n = 23), abscess (n = 5), adenoma (n = 5), focal nodular hyperplasia (n = 4) and nodular regenerative hyperplasia (n = 2). They underwent routine MR imaging and diffusion MR weighted imaging using 1.5 tesla MR unit (Symphony-Siemens). Diffusion MR imaging was done using spin echo type of single shot echo planar imaging (EPI) with b value of 0, 500 & 1000 sec/mm2. The apparent diffusion coefficient (ADC) map was reconstructed and ADC value was measured. The mean ADC values correlated with histo-pathological results as well as follow-up imaging results. Results: Adequate ADC maps were obtained in 47 patients. The mean ADC values were 3.4 ± 0.12 × 10-3 mm2/sec in cystic lesion, 2.23 ± 0.08 × 10-3 mm2/sec in hemangioma, 1.94 ± 0.05 × 10-3 mm2/sec in abscess, 1.72 ± 0.07 × 10-3 in focal nodular hyperplasia, 1.65 ± 0.06 × 10-3 mm2/sec in adenoma, 1.62 ± 0.07 × 10-3 mm2/sec in nodular regenerative hyperplasia. The mean ADC values were significantly different within benign hepatic focal lesions (P < 0.001). The differences between the mean ADC values of FNH, adenoma and NRH were not statistically significant (P < 0.23). Conclusion: Diffusion weighted MR imaging is a new imaging modality for diagnosis and characterization of different benign hepatic focal lesions, particularly in patient with renal dysfunction.

Study of apparent diffusion coefficient value in breasts of different ages and different menstrual phases

Objective To analyze the differences of ADC values in breasts of women of different ages and different menstrual phases, so as to direct the choice of the examination time of MR DWI. MethodsThe breasts of 65 healthy volunteers were scanned with the routine MRI plain scan and DWI in the menstrual, proliferative and secretary phases. DWI was conducted with single shot echo planar imaging technique and b value were 0, 1000 s/mm2. The women were divided into three groups: Group 1(aged 20 to 29 years, 21 cases), Group 2 (aged 30 to 39, 21cases), and Group 3 (aged 40 to 49, 23 cases). The ADC values of all 130 breasts at nipple level in the different phases were measured. The ADC values in the three age groups and in the different menstrual phases were compared using ANOVA. Results The mean ADC values of Group 1 were (2.14±0.14) ×10-3, (2.03±0.18) ×10-3and (2.10±0.19)×10-3mm2/s for left breast, and (2.08±0.17) ×10-3, (2.02±0.16) ×10-3and (2.09±0.17) ×10-3mm2/s for right breast in the menstrual, proliferative and secretary phases. They were slightly higher than Group 3, which were (2.02±0.27) ×10-3, (1.97±0.25) ×10-3and (2.03±0.22)×10-3 mm2/s for left breast and (1.99±0.29) ×10-3, (1.93±0.26) ×10-3and (2.03±0.28)×10-3 mm2/s for right breast. The mean ADC values of Group 2 [left breast: (1.94±0.25) ×10-3, (1.91±0.21) ×10-3and (1.97±0.21)×10-3 mm2/s ; right breast: (1.97±0.26)×10-3, (1.89±0.25)×10-3and (1.96±0.22)×10-3 mm2/s) were the lowest among the three age groups. There were significant differences in different menstrual phases (F= 23.600, P＜0.01), but no statistical difference was found among the three age groups or between left breasts and right breasts (F= 1.683, 2.248;P＞0.05).Conclusions The mean ADC values of breasts decrease markedly in the proliferative phase.The effects of the menstrual cycle on the breast ADC values should be considered in the evaluation of breast diseases with DWI. Key words: Breast; Diffusion magnetic resonance imaging; Menstrual cycle