Body Diffusion-weighted Imaging Research Articles

Utility of the Diffusion Weighted Sequence in Gynecological Imaging: Review Article.

Simple SummaryDiffusion weighted imaging (DWI) is a magnetic resonance imaging sequence with diverse clinical applications in malignant and nonmalignant gynecological conditions. It provides vital supplemental information in the diagnosis and management of various gynecological conditions. Radiologists should be aware of fundamental concepts, clinical applications and pitfalls of DWI. Additionally we briefly discuss potential scope of newer advanced techniques based on DWI including diffusion tensor imaging and diffusion-weighted whole-body imaging with background signal suppression.Functional imaging with diffusion-weighted imaging (DWI) is a complementary tool to conventional diagnostic magnetic resonance imaging sequences. It is being increasingly investigated to predict tumor response and assess tumor recurrence. We elucidate the specific technical modifications of DWI preferred for gynecological imaging, including the different b-values and planes for image acquisition. Additionally, we discuss the problems and potential pitfalls encountered during DWI interpretation and ways to overcome them. DWI has a wide range of clinical applications in malignant and non-malignant gynecological conditions. It provides supplemental information helpful in diagnosing and managing tubo-ovarian abscess, uterine fibroids, endometriosis, adnexal torsion, and dermoid. Similarly, DWI has diverse applications in gynecological oncology in diagnosis, staging, detection of recurrent disease, and tumor response assessment. Quantitative evaluation with apparent diffusion coefficient (ADC) measurement is being increasingly evaluated for correlation with various tumor parameters in managing gynecological malignancies aiding in preoperative treatment planning. Newer advanced DWI techniques of diffusion tensor imaging (DTI) and whole body DWI with background suppression (DWIBS) and their potential uses in pelvic nerve mapping, preoperative planning, and fertility-preserving surgeries are briefly discussed.

Improved geometric accuracy of whole body diffusion-weighted imaging at 1.5T and 3T using reverse polarity gradients

Whole body diffusion-weighted imaging (WB-DWI) is increasingly used in oncological applications, but suffers from misalignments due to susceptibility-induced geometric distortion. As such, DWI and structural images acquired in the same scan session are not geometrically aligned, leading to difficulties in e.g. lesion detection and segmentation. In this work we assess the performance of the reverse polarity gradient (RPG) method for correction of WB-DWI geometric distortion. Multi-station DWI and structural magnetic resonance imaging (MRI) data of healthy controls were acquired at 1.5T (n = 20) and 3T (n = 20). DWI data was distortion corrected using the RPG method based on b = 0 s/mm2 (b0) and b = 50 s/mm2 (b50) DWI acquisitions. Mutual information (MI) between low b-value DWI and structural data increased with distortion correction (P < 0.05), while improvements in region of interest (ROI) based similarity metrics, comparing the position of incidental findings on DWI and structural data, were location dependent. Small numerical differences between non-corrected and distortion corrected apparent diffusion coefficient (ADC) values were measured. Visually, the distortion correction improved spine alignment at station borders, but introduced registration-based artefacts mainly for the spleen and kidneys. Overall, the RPG distortion correction gave an improved geometric accuracy for WB-DWI data acquired at 1.5T and 3T. The b0- and b50-based distortion corrections had a very similar performance.

Kanser Tanısında Tüm Vucut MR ile PET-CT Karşılaştırması

Objective: Whole body diffusion-weighted imaging (DWI) has been increasingly used in oncological cases for detection and characterization of tumors and monitoring of treatment response. We compared the tumor detection capacity and diagnostic accuracy of DWI with positron emission tomography/computed tomography (PET/CT), which is regarded as the gold standard. Materials and Methods: The study included 29 adult patients (13 men and 16 women) aged between 38 and 86 years who had various types of cancer, and for whom PET/CT was indicated for staging or evaluating treatment response. A total of 240 lesions that were positive in FDG-PET/CT were identified in the DWI images, and DWI signal intensity and apparent diffusion coefficient (ADC) value were measured for each lesion. SUVmax, ADC, and DWI intensity values of PET-positive lesions and lesion areas for both methods were compared using Mann-Whitney U test and Spearman correlation test. Results: SUVmax and DWI intensities of the lesions showed significant correlation (Spearman correlation coefficient= -0.296, p&amp;lt;0.0001). When we analyzed whether lesion size was associated with SUVmax, ADC, or DWI intensity, we found a correlation between lesion diameter and DWI intensity (r=-0.30; p=0.0001). Conclusion: The DWI was generally correlated with PET/CT with very close specificity and sensitivity values between the two methods. Whole body DWI can be used as an alternative or complementary to PET/CT in investigation and follow-up of oncological cases.

Diagnostic accuracy of diffusion-weighted imaging- magnetic resonance imaging compared to positron emission tomography/computed tomography in evaluating and assessing pathological response to treatment in adult patients with lymphoma: A systematic review.

The use of Positron emission tomography/computerised tomography (PET/CT) is well established in the staging and assessment of treatment response of lymphoma. Recent studies have suggested that whole body diffusion-weighted imaging -magnetic resonance imaging (WB-DW-MRI) may be an alternative to PET/CT in both staging and assessment of treatment response. A systematic review was performed to assess the ability of DW-MRI in the assessment of treatment response in lymphoma. Pubmed, Medline, Web of Science and Embase databases were queried for studies examining whole body DW-MRI compared to PET/CT in adult patients using a protocol of search terms. We carried out an extensive assessment of titles, abstracts and full texts of relevant paper as well as quality assessment with the Quality Assessment of Diagnostic Accuracy (QUADAS-2) tool. Eight studies were found to meet the criteria and were included in our review and analysis. Overall, the quality of studies was found to be moderate, with good inter-rater agreement (K=0.74). Data analysis showed that lesion-based assessment in 5 studies with pooled results had a sensitivity and specificity of 94.7% and 99.3%. Assessment with Cohen's Kappa coefficient showed agreement to be excellent (K=0.88). Three studies were included for qualitative analysis, two of which showed good equivalence between PET/CT and DW-MRI. WB-DWI-MRI can be considered a sensitive and specific method for assessing treatment response in Lymphoma without the use of ionising radiation or administration of F-18 Flurodeoxyglucose. Further studies are needed to evaluate the optimum b-values in assessing treatment response.

Non‐enhanced magnetic resonance imaging versus renal scintigraphy in acute pyelonephritis

The utility of non-enhanced magnetic resonance imaging (MRI) has not been examined extensively for diagnosing acute pyelonephritis (APN) in children. The aims of this study were to compare non-enhanced MRI with technetium-99m dimercaptosuccinic acid (99m Tc-DMSA) renal scintigraphy in detecting APN. Six boys and one girl with temperature ≥38°C and positive urine culture received both non-enhanced MRI with whole body diffusion-weighted imaging (DWI) and 99m Tc-DMSA scintigraphy ≤7days from the fever onset. The sensitivity and specificity of MRI in detecting APN lesions diagnosed on 99m Tc-DMSA scintigraphy were 80% and 100%, respectively. Non-enhanced MRI in children with suspected APN ≤7days from fever onset might be a suitable replacement for 99m Tc-DMSA scintigraphy for the detection of APN.

Diagnostic Effectiveness of whole Body Diffusion- Weighted Magnetic Resonance Imaging in Focal and Diffuse Bone Marrow Involvement in Patients with Lymphoma

Objective:to compare diagnostic effectiveness of whole body diffusion-weighted imaging (DWI), other magnetic resonance imaging (MRI) pulse sequences and iliac wing trephine biopsy in the diagnosis of focal and diffuse bone marrow (BM) involvement in patients with lymphoma.Materials and methods.Prospective study included 130 patients with lymphoma who underwent whole-body MRI-DWI and iliac wing trephine biopsy before treatment (64 (49,2%) men, 66 (50,8%) women, middle age 43,3 ± 16,3 years, interval of 18–79 years). Hodgkin's lymphoma (HL) was at 57 (44%) patients, non-Hodgkin lymphomas (NHL) – at 73 (56%). Diagnostic effectiveness of T1- weighted images (T1-WI), STIR, DWI and FIESTA was analyzed. BM apparent diffusion coefficient (ADC) values were measured.Results.BM involvement was found in 42 patients, including 9 with HL and 33 with NHL. In HL, BM involvement was only focal. Diffuse involvement occurred more often (64%) in the NHL as compared to focal one. In focal involvement, all pulse sequences showed high diagnostic sensitivity (90–100%), BM biopsy sensitivity was 33% only. The proposed new criterion for the diagnosis of diffuse BM involvement in NHL – diffuse signal increase of the spine on DWI above renal parenchyma – has the highest sensitivity (90%) compared to T1-WI and STIR (67%) and FIESTA (71%) (p &lt; 0.05). In NHL, the ADC value ≤0.575 • 10−3 mm2/s discrimi nates cases of diffuse involvement and absence of BM involvement with a sensitivity of 86% and a specificity of 68% (p &lt; 0.0001). In HL, the diffuse BM signal increase on DWI is not indicative of involvement.Conclusion.All pulse sequences showed high effectiveness in the diagnosis of focal BM involvement in patients with lymphoma, iliac wing biopsy effectiveness was low. The proposed new DWI criterion for diagnosing diffuse BM involvement in NHL is the most sensitive one. A new algorithm based on whole body MRI-DWI for the diagnosis of BM involvement allows to reduce the need for BM biopsy without reducing the diagnostic effectiveness.

Robust Self-Calibrating nCPMG Acquisition: Application to Body Diffusion-Weighted Imaging.

This paper demonstrates a robust diffusion-weighted single-shot fast spin echo (SS-FSE) sequence in the presence of significant off-resonance, which includes a variable-density acquisition and a self-calibrated reconstruction as improvements. A non-Carr-Purcell-Meiboom-Gill (nCPMG) SS-FSE acquisition stabilizes both the main and parasitic echo families for each echo. This preserves both the in-phase and quadrature components of the magnetization throughout the echo train. However, nCPMG SS-FSE also promotes aliasing of the quadrature component, which complicates reconstruction. A new acquisition and reconstruction approach is presented here, where the field-of-view is effectively doubled, but a partial k-space and variable density sampling is used to improve scan efficiency. The technique is presented in phantom scans to validate SNR and robustness against rapidly varying object phase. In vivo healthy volunteer examples and the clinical cases are demonstrated in abdominal imaging. This new approach provides comparable SNR to previous nCPMG acquisition techniques as well as providing more uniform apparent diffusion coefficient maps in phantom scans. In vivo scans suggest that this method is more robust against motion than previous approaches. The proposed reconstruction is an improvement to the nCPMG sequence as it is auto-calibrating and is justified to accurately treat the signal model for the nCPMG SS-FSE sequence.

Comparison Between 3-Scan Trace and Diagonal Body Diffusion-Weighted Imaging Acquisitions: A Phantom and Volunteer Study.

Diagonal diffusion-weighted imaging (dDWI) uses simultaneous maximized application of 3 orthogonal gradient systems as opposed to sequential acquisition in 3 directions in conventional 3-scan trace DWI (tDWI). Several theoretical advantages of dDWI vs. tDWI include reduced artifacts and increased sharpness. We compared apparent diffusion coefficient (ADC) quantification and image quality between monopolar dDWI and tDWI in a dedicated diffusion phantom (b = 0/500/900/2000 s/mm2) and in the abdomen (b = 50/400/800 s/mm2) and pelvis (b = 50/1000/1600 s/mm2) of 2 male volunteers at 1.5 T and 3.0 T. Phantom estimated signal-to-noise ratio (eSNR) was also measured. Two independent observers assessed the image quality on a 5-point scale. In the phantom, image quality was similar between tDWI and dDWI, with equivalent ADC quantification (mean coefficient of variation [CV] between sequences: 1.4% ± 1.2% at 1.5 T and 0.7% ± 0.7% at 3.0 T). Phantom eSNR was similar for both tDWI and dDWI, except for a significantly lower eSNR for b900 of dDWI at 3.0 T (P = .006). In the volunteers, the CV values between tDWI and dDWI were higher than those in the phantom (CV range: abdominal organs, 1.3%–13.3%; pelvic organs, 0.6%–5.7%). A trend toward significant better image quality for dDWI compared with tDWI was observed for b800 (abdomen) at 3.0 T and for b1000 and b1600 (pelvis) at 1.5 T (P = .063 to .066). Our data suggest that dDWI may provide better image quality than tDWI without affecting ADC quantification, needing confirmation in a future clinical study.

Abstract 3973: Diffusion-weighted imaging of bone metastases as treatment response biomarker in prostate cancer

Abstract INTRODUCTION: Response assessment of bone metastases (BM) remains a challenge for drug development in metastatic castration resistant prostate cancer (mCRPC) as standard imaging techniques, computed tomography and bone scintigraphy, fail to characterize BM. Diffusion-weighted imaging (DWI) is a functional MRI technique that studies the motion of water molecules within a tissue informing on cellularity. We hypothesized that changes in whole body (WB) DWI informs on BM response to treatment in mCRPC. METHODS: We conducted a phase II trial of the PARP inhibitor olaparib in mCRPC (TOPARP-A; CRUK/11/029); the primary endpoint was response rate defined using RECIST 1.1, PSA falls of ≥50% and conversion of circulating tumour cell (CTC) counts from ≥5 to &amp;lt;5. Optional WB-DWI in patients (pt) was performed prior to starting olaparib and after 12 weeks (w) of treatment on a 1.5 T MRI (Siemens Avanto). Images were analyzed with open-access imaging software (Osirix v5.6). Areas of DWI signal abnormality consistent with BM in the axial skeleton (C4 to mid-thigh) were delineated. We estimated disease volume and apparent diffusion coefficient (ADC), a parameter derived from DWI correlated with cellularity. BM volume and median ADC (mADC) changes between baseline and 12w were associated with binary response to treatment using Mann-Whitney tests and logistic regression; associations with best percentage PSA and CTC change after treatment were assessed using Spearman's correlation. RESULTS: Overall, 33/42 pt consented to the WB-DWI substudy of whom 21 had WB-DWI at baseline and at 12w. Of these 29% (6/21) were classified as responders to olaparib as per the primary endpoint definition and had not progressed prior to 12w. At baseline, median CTC count was 46 CTC/7.5ml blood and median PSA was 411 ng/ml for this cohort. When assessing all the areas of DWI signal abnormality, median volume of BM per patient was 445ml and mADC was 782 x10-6 mm2/s. Baseline CTC counts and PSA were significantly associated with volume of BM (ρ = 0.59, p = 0.005; ρ = 0.64, p = 0.002 respectively). All pts who responded to olaparib showed a decrease in volume of BM (median -41.1%, range -58.8%, -6.3%), whilst in non-responders a decrease was not observed in any pt (median 20.7%, range 0.0%, 76.9%); the difference between responders and non-responders was statistically significant (p = 0.001). Increases in mADC after 12 weeks of treatment were associated with increased odds of response (Odds Ratio: 1.08, 95% CI 1.00, 1.15, p = 0.04). Additionally, we detected a significant positive association between changes in volume of BM estimated by DWI and best percentage change in PSA and CTC (ρ = 0.63, p = 0.002 and ρ = 0.77, p&amp;lt;0.001 respectively). CONCLUSION: Decrease in volume and increase in mADC of BM assessed by WB-DWI are indicators of response to olaparib in BM from mCRPC. These data require validation but support the use of WB-DWI for assessing BM during treatment. Citation Format: Raquel Perez-Lopez, Matthew D. Blackledge, Helen Mossop, Joaquin Mateo, David Collins, Veronica A. Morgan, Alison McDonald, Shahneen Sandhu, Aurelius Omlin, Diletta Bianchini, Zafeiris Zafeiriou, Pasquale Rescigno, Michael Kolinsky, Daniel Nava Rodrigues, Penny Flohr, Berni Ebbs, Gemma Fowler, Nuria Porta, Emma Hall, Martin Leach, Johann S. de Bono, Dow-Mu Koh, Nina Tunariu. Diffusion-weighted imaging of bone metastases as treatment response biomarker in prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3973.

Simultaneous whole body (18)F-fluorodeoxyglucose positron emission tomography magnetic resonance imaging for evaluation of pediatric cancer: Preliminary experience and comparison with (18)F-fluorodeoxyglucose positron emission tomography computed tomography.

To describe our preliminary experience with simultaneous whole body (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography and magnetic resonance imaging (PET-MRI) in the evaluation of pediatric oncology patients. This prospective, observational, single-center study was Health Insurance Portability and Accountability Act-compliant, and institutional review board approved. To be eligible, a patient was required to: (1) have a known or suspected cancer diagnosis; (2) be under the care of a pediatric hematologist/oncologist; and (3) be scheduled for clinically indicated (18)F-FDG positron emission tomography-computed tomography (PET-CT) examination at our institution. Patients underwent PET-CT followed by PET-MRI on the same day. PET-CT examinations were performed using standard department protocols. PET-MRI studies were acquired with an integrated 3 Tesla PET-MRI scanner using whole body T1 Dixon, T2 HASTE, EPI diffusion-weighted imaging (DWI) and STIR sequences. No additional radiotracer was given for the PET-MRI examination. Both PET-CT and PET-MRI examinations were reviewed by consensus by two study personnel. Test performance characteristics of PET-MRI, for the detection of malignant lesions, including FDG maximum standardized uptake value (SUVmax) and minimum apparent diffusion coefficient (ADCmin), were calculated on a per lesion basis using PET-CT as a reference standard. A total of 10 whole body PET-MRI exams were performed in 7 pediatric oncology patients. The mean patient age was 16.1 years (range 12-19 years) including 6 males and 1 female. A total of 20 malignant and 21 benign lesions were identified on PET-CT. PET-MRI SUVmax had excellent correlation with PET-CT SUVmax for both benign and malignant lesions (R = 0.93). PET-MRI SUVmax > 2.5 had 100% accuracy for discriminating benign from malignant lesions using PET-CT reference. Whole body DWI was also evaluated: the mean ADCmin of malignant lesions (780.2 + 326.6) was significantly lower than that of benign lesions (1246.2 + 417.3; P = 0.0003; Student's t test). A range of ADCmin thresholds for malignancy were evaluated, from 0.5-1.5 × 10(-3) mm(2)/s. The 1.0 × 10(-3) ADCmin threshold performed best compared with PET-CT reference (68.3% accuracy). However, the accuracy of PET-MRI SUVmax was significantly better than ADCmin for detecting malignant lesions compared with PET-CT reference (P < 0.0001; two-tailed McNemar's test). These results suggest a clinical role for simultaneous whole body PET-MRI in evaluating pediatric cancer patients.

Role of diffusion-weighted imaging in early ankylosing spondylitis

Background With the advanced MRI techniques, pathologic features can be detected at an early stage and quantitatively evaluated, resulting in the advantages of early diagnosis and prompt treatment. This study aimed to determine the value of diffusion-weighted MR imaging (DWI) in detection of early ankylosing spondylitis (AS) and investigate the characteristic manifestations of AS on whole body DWI (WB-DWI). Methods Twenty patients with the diagnosis of early AS, twenty patients with low back pain (LBP), and twenty-five healthy volunteers were included in this study. The subchondral bone apparent diffusion coefficients (ADC) among these groups in the bilateral ilia and sacrum along the sacroiliac joints were compared. An independent sample t-test was utilized to analyze ADC value differences among groups. P-values less than 0.05 denoted statistical significance. The mean ADC values of focal DWI lesions in AS patients were also measured. Whole body diffusion-weighted imaging was performed in fifteen additional AS patients, and analyzed with MIP and MPR techniques in comparison to conventional MR images in order to evaluate the ability to detect AS lesions with whole body DWI. Results Mean ADC values in AS patients were (0.518±0.122)×10-3 mm2/s in the ilium and (0.503±0.168)×10-3 mm2/s in the sacrum. These were significantly greater than the values measured in the ilium and sacrum of LBP patients, (0.328±0.053)×10-3 mm2/s in the ilium and (0.311±0.081)×10-3 m2/s in the sacrum, and control group, (0.325±0.015)×10-3 mm2/s in the ilium and (0.318±0.011)×10-3 mm2/s in the sacrum respectively. No statistically significant differences were found between LBP group and control group. The mean ADC value of focal DWI lesions in early AS patients was (0. 899±0.265)×10-3 mm2/s, which was significantly higher than that of adjacent normal-appearance areas ((0.454±0.079)×10-3 mm2/s). WB-DWI detected abnormalities in the 15 additional AS patients both within the sacroiliac joints and at other sites, corresponding to the clinical symptoms of the patients. The mean ADC value of focal DWI lesions of this patient cohort was (1.286±0.311)×10-3 mm2/s in the sacrum and (1.220±0.299) ×10-3 mm2/s in the ilium. Conclusions Subchondral marrow ADC values of subchondral marrows near the sacroiliac joints allow for the differentiation of patients with early AS from normal volunteers and LBP patients. Combined with post-processing techniques such as MIP and MPR, WB-DWI allows for the comprehensive assessment of AS patients, an evaluation potentially helpful in determining prognosis and following the therapeutic response.

Abdominal applications of diffusion-weighted magnetic resonance imaging: Where do we stand

Diffusion-weighted imaging (DWI) is one of the magnetic resonance imaging (MRI) sequences providing qualitative as well as quantitative information at a cellular level. It has been widely used for various applications in the central nervous system. Over the past decade, various extracranial applications of DWI have been increasingly explored, as it may detect changes even before signal alterations or morphological abnormalities become apparent on other pulse sequences. Initial results from abdominal MRI applications are promising, particularly in oncological settings and for the detection of abscesses. The purpose of this article is to describe the clinically relevant basic concepts of DWI, techniques to perform abdominal DWI, its analysis and applications in abdominal visceral MR imaging, in addition to a brief overview of whole body DWI MRI.

Whole body diffusion weighted imaging pattern of normal bone marrow

Objective To analyze the pattern of normal bone marrow on whole body diffusionweighted imaging (WB-DWI) and its influence factors.Methods A total of 98 healthy volunteers (male 47 and female 51). All volunteers underwent WB-DWI at 1.5 T MR scan. The ADC value,the signal intensity on DWI obtained with a b value of 800 s/mm2 ( SIDWI ),and the signal intensity on short time inversion recovery images ( SISTIR ) of thoracic vertebrae,lumber vertebrae,bilateral head of femur,bilateral neck of femur,bilateral superior segment of femur,bilateral inferior segment of femur,bilateral ilium,bilateral head of humerus,bilateral scapula were measured and compared with ANOVA test and StudentNewmar-Keuls test.The normal appearance of bone marrow on WB-DW[ was assessed. The relationship between the SIDwI and the ADC,and the SIDWI and the SISTIR of bone marrow were analyzed.The ADC of bone marrow between male and femaIe were compared. Spearman correlation analysis was performed for different age groups.Results ( 1 ) Bone marrow signal intensity was different among 98 healthy volunteers.Bone marrow in 69 healthy volunteers (female 24,male 45 ) showed low to intermediate signal intensity,whereas in the remaining 29 healthy volunteers (female 27,male 2) showed high signal intensity.(2) The SIDWI of thoracic vertebrae ( median 44.54),lumber vertebrae ( median 35.01 ),head of femur ( median 13.61 ),neck of femur ( median 16.00),superior segment of femur ( median 21.45 ),ilium ( median 25.77),head of humerus (median 18.35),scapula (median 36.12) was positively correlated with the ADC [ (0.55 ±0.08) × l0-3,(0.53 ±0.08) × 10-3,(0.30 ± 0.10) × 10-3,(0.42 ± 0.16) × 10-3,(0.74±0.14) ×l0- 3,(0.49±0.10) ×10-3,(0.36±0.13) ×10-3,(0.49±0.11) × 10-3mm2/s]and the SISTIR ( median 61.81,64.99,53.27,69.08,73.10,66.35,73.16,79.81 ),r =0.513 and 0.695,0.741 and 0.764,0.443 and 0.489,0.641 and 0.656,0.510 and 0.648,0.475 and 0.715,0.366 and 0.446,0.437 and 0.739 ;P ＜ 0.01. (3) There was significant difference of the ADC of bone marrow in different bone,F =138.69,P ＜ 0.01. Student-Newman-Keuls test revealed that no significant difference was found in the ADC between thoracic vertebrae and lumbar vertebrae,ilium and scapula,head of humerus and inferior segment of femur ( P ＞ 0.05 ),and significant difference was found in the ADC values between the remaining two groups ( P ＜ 0.05 ). The bones associated with decreasing ADC values were superior segment of femur,thoracic vertebrae and lumber vertebrae,ilium and scapula,neck of femur,head of humerus,head of femur and inferior segment of femur. ( 4 ) The ADC values of bone marrow of female subjects in thoracic vertebrae [ (0.59 ±0.07) × 10-3 mm2/s],lumber vertebrae [ (0.58 ±0.06) × 10 -3 mm2/s],head of femur ( median 0.33 × 10 -3 mm2/s),neck of femur ( median 0.53 × 10 -3 mm2/s),superior segment of femur ( median 0.81 × 10-3 mm2/s),inferior segment of femur ( median 0.32 ×10-3 mm2/s),ilium [ (0.52 ± 0.09 ) × 10-3 mm2/s ],head of humerus (median 0.42 × 10-3 mm2/s),scapula [ (0.53 ± 0.09) × 10-3 mm2/s] were significantly higher than those of male subjects [ (0.51 ±0.07) × 10-3,(0.48 ±0.07) × 10-3,median 0.23 × 10-3,median 0.31 × 10-3,median 0.66 × 10-3,median 0.23 × 10-3,(0.46 ±0.10) × 10-3,median 0.27 × 10-3,(0.45 ±0.11 ) × 10 3mm2/s].(5)There was significant negative correlation between the ADC values of bone marrow and age in thoracic vertebrae,lumber vertebrae,head of femur,neck of femur,superior segment of femur,ilium,head of humerus for female subjects,r =-0.549, -0.629, -0.329, -0.524, -0.338, -0.548 and -0.416,respectively,P ＜ 0.05.There was no significant correlation between ADC values and age in inferior segment of femur and scapula for female subjects and all the regions for male subjects ( P ＞ 0.05 ).Conclusions The ADC and the SIsTIR of bone marrow correlates with the SIDW1.The ADC values of bone marrow is affected by age and sex,and is different for different bones. Key words: Diffusion magnetic resonance imaging; Bone marrow; Reference values

Intravoxel Incoherent Motion in Body Diffusion-Weighted MRI: Reality and Challenges

Diffusion-weighted MRI is increasingly applied in the body. It has been recognized for some time, on the basis of scientific experiments and studies in the brain, that the calculation of apparent diffusion coefficient by simple monoexponential relationship between MRI signal and b value does not fully account for tissue behavior. However, appreciation of this fact in body diffusion MRI is relatively new, because technologic advancements have only recently enabled high-quality body diffusion-weighted images to be acquired using multiple b values. There is now increasing interest in the radiologic community to apply more sophisticated analytic approaches, such as those based on the principles of intravoxel incoherent motion, which allows quantitative parameters that reflect tissue microcapillary perfusion and tissue diffusivity to be derived. In this review, we discuss the principles of intravoxel incoherent motion as applied to body diffusion-weighted MRI. The evidence for the technique in measuring tissue perfusion is presented and the emerging clinical utility surveyed. The requisites and challenges of quantitative evaluation beyond simple monoexponential relationships are highlighted.

Preliminary study on the validity of whole body diffusion-weighted imaging for the detection of malignant lesions

To evaluate the validity of whole body diffusion-weighted imaging (WBDWI) for the detection of malignant lesions. Nine healthy volunteers, 4 postoperative cases of malignant tumor and 16 malignant tumor cases were included in this study. 29 cases underwent whole body diffusion-weighted imaging on GE Signa Excite HD MR scanner within one week after or before PET examination. The images were double-blindly evaluated by two radiologists without the knowledge of the original PET results. Clinical diagnoses of malignant lesions were mainly based on PET results taken as gold standard. The malignant lesions were evaluated according to nine locations: lymph node; central nervous system; lung; liver, gallbladder, pancreas and spleen; digestive tract; kidney and adrenal gland; pelvic; skeleton, and soft tissue of each subject. The sensitivity, specificity, positive predicative value, negative predicative value, Youden's index and likelihood ratio of WBDWI were analyzed. The images of all the 9 healthy volunteers were normal. 57 malignant lesions were found in the 20 malignant cases by PET, among whom 48 lesions were detected by WBDWI including 2 false positive lesions. Among the 261 locations of 29 cases, the WBDWI examination showed 21 true positive locations, 2 false positive locations and 3 false negative locations. The sensitivity, specificity, positive predicative value, negative predicative value, Youden's index and likelihood ratio of WBDWI were 87.5%, 99.2%, 91.3%, 98.7%, 86.7%, and 103.7, respectively. The validity of WBDWI is high, and it could be a new whole body imaging technique for staging of malignant tumors.

Characterization of Genitourinary Lesions with Diffusion-weighted Imaging

Diffusion-weighted imaging has been widely accepted as a powerful imaging technique in neuroradiology. Until recently, the inclusion of diffusion-weighted sequences in body imaging protocols has been hindered by technical limitations. However, with advances in magnetic resonance (MR) imaging technology and technique, these limitations are being overcome. The addition of diffusion-weighted sequences to routine abdominopelvic MR imaging protocols has been found to yield diagnostically useful information with only a minimal increase in imaging time. More specifically, the use of diffusion-weighted imaging in the genitourinary system can facilitate the detection and characterization of genitourinary tract lesions that demonstrate equivocal signal intensity characteristics with routine MR imaging sequences. Diffusion-weighted imaging is not only helpful in differentiating benign from malignant processes, but it can also be used to assess meta-static lesions, possible tumor recurrence, and treatment response. Because it does not require injection of a gadolinium-based contrast agent, diffusion-weighted imaging can be used in patients with renal insufficiency or contrast material allergy. Most of the body diffusion-weighted imaging studies reported in the literature to date have been conducted with 1.5-T magnets. However, the feasibility of body diffusion-weighted imaging at 3.0 T is currently under investigation in an effort to determine the efficacy of the routine inclusion of diffusion-weighted imaging sequences in 3.0-T body MR imaging protocols.

加算処理による腹部Ｄｉｆｆｕｓｉｏｎ ｉｍａｇｅ改善の方法

It is difficult to obtain body diffusion weighted images (BDWI) using MRI that does not support parallel imaging and multi-NEX in clinical usage. Therefore, we evaluated whether a multiple image additions technique on the workstation could improve BDWI image quality and be good for clinical use by considering SNR and image distortion. We added 2 to 5 images on the same slice location with changing FOV, slice thickness, or reconstruction matrix in the phantom studies, and confirmed SNR improvement under all conditions. We also confirmed that this addition technique did not affect image distortion. We found that in 16 of the 18 clinical cases, BDWI with 5 images addition match pathology and T2 weighted images. We believe that this addition technique in available in the clinical practice.

The preliminary study of searching primary tumors in patients with metastases using MR whole body diffusion weighted imaging

Objective To evaluate the availability and sensitivity of MR whole body diffusion weighted imaging (DWI) in searching primary tumors in patients with metastases.Methods Thirty-four patients with symptoms of metastases and unknown primary leasions were scanned by whole body DWI.All the metastases cases were diagnosed by CT,single photon emission computed tomography(SPECT) or MRL For the cases of suspected primary tumors,apparent diffusion coefficient (ADC) values of the primary and metastatic lesions were measured respectively.For the cases with primary lung cancers and metastases proved by pathology of biopsy or surgical specimens,statistics analysis of ADC values of primary and metastatic lesions was performed with paired samples t-test.The detection rate and sensitivity of this technique for screening primary tumors were evaluated.Results By whole body DWI,24 cases were found with suspected primary lesions,in which 23 cases were proved primary tumors,and 1 case was proved benign lesion.Ten cases were not identified with primary lesions on whole body DWI,but in which 2 cases were proved primary malignant tumor by biopsy later,and the other 8 cases remained unknown within follow-up of half a year to one year.For the 14 definite cases of lung cancers,the average ADC values of primary and metastatic lesions was (1.24±0.18)×10-3 and(1.16±0.27)×10-3mm2/s,respectively (t=1.28,P>0.05).The detection rate and sensitivity of whole body DWI for searching primary tumors was 67.6% (23/34) and 92.0% (23/25),respectively.Conclusion The sensitivity of whole body DWI for searching primary tumors is relatively high,and it can be used to search primary tumors in patients with metastases. Key words: Diffusion magnetic resonance imaging; Neoplasm,unknown primary; Neoplasm metastasis

Feasibility of Whole Body Diffusion Weighted Imaging in Detecting Bone Metastasis on 3.0T MR Scanner

To evaluate the feasibility of whole body diffusion weighted imaging (DWI) in bone metastasis detection using bone scintigraphy as comparison. Forty-five patients with malignancy history were enrolled in our study. All the patients received the whole body DWI and bone scintigraphy scan within 1 week. The magnetic resonance (MR) examination was performed on 3.0T MR scanner using embedded body coil. The images were reviewed separately by two radiologists and two nuclear medicine physicians, who were blinded to the results of the other imaging modality. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the two techniques for detecting bone metastasis were analyzed. A total of 181 metastatic lesions in 77 regions of 34 patients were detected by whole body DWI, and 167 metastatic lesions in 76 regions of 31 patients were identified by bone scintigraphy. The patient-based sensitivity and PPV of whole body DWI and bone scintigraphy were similar (89.5% vs. 81.6%, 97.1% vs. 91.2%), whereas, the patient-based specificity and NPV of whole body DWI were obviously higher than those of bone scintigraphy (85.7% vs. 57.1%, 60.0% vs. 36.4%). Ten regions negative in scintigraphy but positive in whole body DWI, mainly located in spine, pelvis, and femur; nine regions only detected by scintigraphy, mainly located in skull, sternum, clavicle, and scapula. The region-based sensitivity and specificity of whole body DWI were slightly higher than those of bone scintigraphy (89.5% vs. 88.4%, 95.6% vs. 87.6%). Whole body DWI reveals excellent concordance with bone scintigraphy regarding detection of bone metastasis, and the two techniques are complementary for each other.

Preliminary Study of Feasibility of Whole Body Diffusion Weighted Imaging in Diagnosis of Metastasis of Tumor

To evaluate the feasibility of whole body diffusion weighted imaging (DWI) in the diagnosis of metastatic tumor. Fifty-six patients (40 males and 16 females, age ranging from 29 to 84 years with a mean age of 57 years) with a variety of primary tumors were investigated by whole body DWI combined with computed tomography (CT) and/or conventional magnetic resonance imaging (MRI) scans. Twelve patients underwent positron emission tomography. The final diagnosis was made on the basis of CT or high resolution CT result for lung lesion and MRI or CT result for skull, abdomen and other parts. All tumors were classified into four groups by their diameter: below 1.0 cm, 1.0-1.9 cm, 2.0-2.9 cm, and above 3.0 cm. The sensitivity and specificity of whole body DWI in the detection of metastatic tumor were analyzed. The sensitivities of whole body DWI for screening metastasis of the four groups were 38%, 75%, 97%, and 100%, respectively. Whole body DWI showed the highest sensitivity and specificity for detecting metastasis of the skeletal system. It was difficult to find metastatic tumor whose diameter was below 1.0 cm, or lymph nodes located in the pelvis with diameter below 2.0 cm. Whole body DWI is a promising method in the diagnosis of metastastic tumors. With the perfection of scanning parameter, whole body DWI should be a new effective whole body technique for tumor detection.