Glaucoma severity affects diffusion tensor imaging (DTI) parameters of the optic nerve and optic radiation

Objectives

To evaluate whether MR diffusion tensor imaging (DTI) of the optic nerve and optic radiation in glaucoma patients provides parameters to discriminate between mild and severe glaucoma and to determine whether DTI derived indices correlate with retinal nerve fibre layer (RNFL) thickness.

Methods

3-Tesla DTI was performed on 90 subjects (30 normal, 30 mild glaucoma and 30 severe glaucoma subjects) and the FA and MD of the optic nerve and optic radiation were measured. The categorisation into mild and severe glaucoma was done using the Hodapp–Parrish–Anderson (HPA) classification. RNFL thickness was also assessed on all subjects using OCT. Receiver operating characteristic (ROC) analysis and Spearman's correlation coefficient was carried out.

Results

FA and MD values in the optic nerve and optic radiation decreased and increased respectively as the disease progressed. FA at the optic nerve had the highest sensitivity (87%) and specificity (80%). FA values displayed the strongest correlation with RNFL thickness in the optic nerve (r = 0.684, p ≤ 0.001) while MD at the optic radiation showed the weakest correlation with RNFL thickness (r = −0.360, p ≤ 0.001).

Conclusions

The high sensitivity and specificity of DTI-derived FA values in the optic nerve and the strong correlation between DTI-FA and RNFL thickness suggest that these parameters could serve as indicators of disease severity.     

Correlation study of 3T-MR-DTI measurements and clinical symptoms of cervical spondylotic myelopathy

Objective

To discuss the correlation between diffusion tensor imaging (DTI) measurements, diffusion tensor tractography and the clinical symptoms of cervical spondylotic myelopathy.

Methods

Based on the Japanese Orthopedics Association (JOA) score, 104 cervical spondylotic myelopathy cases were first divided into four groups: mild, moderate, severe and serious groups. According to lesion signal characteristics, all cases were again divided into three groups: A(N/N): normal signal in both T1WI and T2WI; B (N/H): normal signal in T1WI but high signal in T2WI; and C (L/H): low signal in T1WI and high signal in T2WI. The apparent diffusion coefficient (ADC), fractional anisotropy (FA), λ1, λ2, and λ3 were measured and diffusion tensor tractography was performed in the seriously compressed section of the spinal cord.

Results

The FA values were positively correlated with JOA scores (r = 0.883, P < 0.05), and significantly different among four JOA groups (P < 0.05). The ADC, λ2, and λ3 were significantly different among the moderate, severe and serious groups as well as among the A, B, and C groups (P < 0.05). Declining FA values were found associated with increasing fiber bundle damage.

Conclusions

The FA values and the change patterns of fiber bundle were more sensitive than T2WI for spinal cord lesion, and were positively correlated with clinical symptoms.     

Potential of diffusion tensor MR imaging in the assessment of cognitive impairments in children with periventricular leukomalacia born preterm

Purpose

To investigate MR diffusion tensor imaging (DTI) and fiber tractography (FT) in the assessment of altered major white matter fibers correlated with cognitive functions in preterm infants with periventricular leukomalacia (PVL), to explore the neural foundation for PVL children's cognitive impairments.

Materials and methods

Forty six preterm infants (16 ± 4.7 months) suffered from PVL and 16 age-matched normal controls were recruited. Developmental quotient (DQ) was recorded to evaluate PVL children's cognitive functions. According to the DQ scores, patients were divided into three groups: mild, moderate and severe cognitive impairment groups. DTI scan was performed. Fractional anisotropy (FA) values of major white matter fibers were measured and their correlation with cognitive levels was evaluated.

Results

Compared with the control group, the PVL group showed a significant mean FA reduction in bilateral corticospinal tract (CST), anterior/posterior limb of internal capsule (ICAL/ICPL), arcuate fasciculus (AF), corona radiate (CR), superior longitudinal fasciculus (SLF), splenium of corpus callosum (SCC) (p < 0.05) and bilateral posterior thalamic radiation (PTR) (p < 0.01). The FA values of left CST, bilateral AF, anterior cingulum (ACG), SLF, ICAL, ICPL, PTR, CR, genu of corpus callosum (GCC), SCC and middle cerebellar peduncle showed significant negative correlations with the cognitive levels.

Conclusions

DTI can provide more information for understanding the pathophysiology of cognitive impairment in preterm infants with PVL.     

Diagnostic performance of conventional diffusion weighted imaging and diffusion tensor imaging for the liver fibrosis and inflammation

Objective

To evaluate the diagnostic accuracy of liver apparent diffusion coefficient (ADC) measured with conventional diffusion-weighted imaging (CDI) and diffusion tensor imaging (DTI) for the diagnosis of liver fibrosis and inflammation.

Materials and methods

Thirty-seven patients with histologic diagnosis of chronic viral hepatitis and 34 healthy volunteers were included in this prospective study. All patients and healthy volunteers were examined by 3 T MRI. CDI and DTI were performed using a breath-hold single-shot echo-planar spin echo sequence with b factors of 0 and 1000 s/mm². ADCs were obtained with CDI and DTI. Histopathologically, fibrosis of the liver parenchyma was classified with the use of a 5-point scale (0–4) and inflammation was classified with use of a 4-point scale (0–3) in accordance with the METAVIR score. Quantitatively, signal intensity and the ADCs of the liver parenchyma were compared between patients stratified by fibrosis stage and inflammation grade.

Results

With a b factor of 1000 s/mm², the signal intensity of the cirrhotic livers was significantly higher than those of the normal volunteers. In addition, ADCs reconstructed from CDI and DTI of the patients were significantly lower than those of the normal volunteers. Liver ADC values inversely correlated with fibrosis and inflammation but there was only statistically significant for inflammatory grading. CDI performed better than DTI for the diagnosis of fibrosis and inflammation.

Conclusion

ADC values measured with CDI and DTI may help in the detection of liver fibrosis. They may also give contributory to the inflammatory grading, particularly in distinguishing high from low grade.     

In vivo DTI longitudinal measurements of acute sciatic nerve traction injury and the association with pathological and functional changes

Objective

To explore the feasibility of longitudinally measuring acute traction injury to the sciatic nerve using 1.5 T clinical MRI scanner of diffusion tensor imaging (DTI) and to analyze the associations of the measurements [regarding fractional anisotropy (FA), apparent diffusion coefficient (ADC), eigenvalue (λ_|| and λ_⊥)] with limb function and pathology.

Materials and methods

Acute traction injuries to the sciatic nerve were created in the right hind limbs of 32 New Zealand white rabbits, the left hind limbs were chosen as sham operation nerves. MRI scans were performed at intervals from pre-operation through 8 weeks post-operation follow up. Scanning sequences included T2WI, STIR, and single shot spin echo DTI with single shot EPI acquisition (SE-DTI-SSEPI). Parameters of FA, ADC, axial diffusivity (λ_||) and radial diffusivity (λ_⊥) were then calculated from the DTI. The limb functions and pathologic changes were evaluated and compared.

Results

Diffusion Tensor Tractography (DTT) only revealed the proximal portion of the injured nerves 1–3 days after traction injury but did not reveal the nerve of the distal and traction portions at all. Nerve fibers of the distal and traction portions were not revealed by DTT until after the 1st week. They were elongated gradually and recovered almost to the normal at 8th week. The value of FA and λ_⊥of the injured nerves, which varied in different portions, were significantly different between the traction injury nerves and the sham operation nerves, whereas the value of ADC and λ_|| were not significantly different. The curve lines of FA value-time for the proximal, traction and distal portions of the injured nerve correlated well to the functional and pathological changes of the limb affected, while the DTI parameters did not change that much in the sham-operated nerves.

Conclusions

DTI obtained on a 1.5 T clinical MRI scanner can demonstrate early abnormal changes following traction injury to the sciatic nerve in rabbits. The curve lines of FA-time and λ_⊥-time for nerve traction injury are consistent with the pathological and functional changes of the limb affected. DTI may thus be a sensitive and reliable method to evaluate degeneration and regeneration of the nerve after traction injury.     

A comparison of the performance of anatomical MRI and DTI in diagnosing carpal tunnel syndrome

Purpose

To compare the performance of anatomical magnetic resonance imaging (MRI) with that of diffusion tensor imaging (DTI) in the diagnosis of carpal tunnel syndrome (CTS).

Materials and methods

We performed 3T anatomical MRI and DTI on 42 patients and 42 age-matched controls. The median nerve cross-sectional area (CSA), relative median nerve signal intensity, and palmar bowing of the flexor retinaculum, assessed with anatomical MRI, and fractional anisotropy (FA) and apparent diffusion coefficient of the median nerve, assessed with DTI, were measured at four locations: the hamate level, the pisiform level (P0), the level located 1 cm proximal to the P0 level (P1), and the distal radioulnar joint level (DR). Adding the ratios and differences of the median nerve parameters between the measurements at the DR and other locations to the diagnostic parameters, we evaluated the area under the receiver operating characteristic curves (AUCs) of all the diagnostic parameters of both scans.

Results

The AUCs of FA(P1) (0.814) and FA(P0) (0.824) in DTI were larger than the largest AUC for anatomical MRI, CSA(P1) (0.759). However, the receiver operating characteristics of the three parameters were not significantly different (P > 0.1). The sensitivity and specificity of CSA(P1) (76.2% and 73.8%) and FA(P1) (73.8% and 76.2%) increased after inclusive and exclusive combination to 90.5% each.

Conclusion

The individual performances of both scans were not significantly different in diagnosing CTS. Measuring both CSA and FA at P1 may be useful and efficient to utilize the merits of both scans and to increase the CTS diagnostic performance.     

Diffusion tensor imaging of the median nerve at 3.0 T using different MR scanners: Agreement of FA and ADC measurements

Objective

To assess the agreement of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of the median nerve on 3.0 T MR scanners from different vendors.

Materials and methods

IRB approved study including 16 healthy volunteers (9 women; mean age 30.6 ± 5.3 years). Diffusion tensor imaging (DTI) of the dominant wrist was performed on three 3.0 T MR scanners (GE, Siemens, Philips) using similar imaging protocols and vendor-proprietary hard- and software. Intra-, inter-reader and inter-vendor agreements were assessed.

Results

ICCs for intra-/inter-reader agreements ranged from 0.843–0.970/0.846–0.956 for FA, and 0.840–0.940/0.726–0.929 for ADC, respectively.ANOVA analysis identified significant differences for FA/ADC measurements among vendors (p < 0.001/p < 0.01, respectively). Overall mean values for FA were 0.63 (SD ± 0.1) and 0.999 × 10⁻³ mm²/s (SD ± 0.134 × 10⁻³) for ADC. A significant negative measurement bias was found for FA values from the GE scanner (−0.05 and −0.07) and for ADC values from the Siemens scanner (−0.053 and −0.063 × 10⁻³ mm²/s) as compared to the remainder vendors

Conclusion

FA and ADC values of the median nerve obtained on different 3.0 T MR scanners differ significantly, but are in comparison to the standard deviation of absolute values small enough to not have an impact on larger group studies or when substantial diffusion changes can be expected. However, caution is warranted in an individual patient when interpreting diffusion values from different scanner acquisitions     

Comparison of the diagnostic performances of diffusion parameters in diffusion weighted imaging and diffusion tensor imaging of breast lesions

Purpose

To evaluate the diagnostic efficiency of the diffusion parameters measured by conventional diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) for discrimination of malignant breast lesions from benign lesions and the normal breast.

Materials and methods

The study included 52 women with 55 breast lesions (30 malignant, 25 benign). DTI and DWI were performed complementary to dynamic contrast MRI at 3T. Apparent diffusion coefficient (ADC) of DWI, mean diffusivity (MD) and fractional anisotropy (FA) values of DTI were measured for lesions and contralateral breast parenchyma in each patient. We used b factors of 0, 50, 850, 1000 and 1500 s/mm² for DWI and b 0 and 1000 s/mm² for DTI. ADC, MD and FA values were compared between malignant and benign lesions, and the normal parenchyma by univariate and multivariate analyses.

Results

Diffusion parameters showed no difference according to menopausal status in the normal breast. ADC and MD values of the malignant lesions were significantly lower than benign lesions and normal parenchyma (p = 0.001). The FA showed no statistical significance. With the cut-off values of ≤1.23 × 10⁻³ mm²/s (b 0–1000 s/mm²) and ≤1.12 × 10⁻³ mm²/s (b 0–1500 s/mm²), ADC showed 92.85% and 96.15% sensitivity; 72.22% and 73.52% PPV, respectively. With a cut-off value of ≤1.27 × 10⁻³ mm²/s (b 1000 s/mm²), MD was 100% sensitive with a PPV of 65.90%. Comparing the diagnostic performance of the parameters in DTI with DWI, we obtained similar efficiency of ADC with b values of 0,1000 and 0,1500 s/mm² and MD with a b value of 0, 1000 s/mm² (AUC = 0.82 ± 0.07).

Conclusion

ADC of DWI and MD of DTI values provide significant discriminative factors for benign and malignant breast lesions. FA measurement was not discriminative. Supported with clinical and dynamic contrast MRI findings, DWI and DTI findings provide significant contribution to the final radiologic decision.     

Microstructural abnormalities in the trigeminal nerves of patients with trigeminal neuralgia revealed by multiple diffusion metrics

Objective

To investigate microstructural tissue changes of trigeminal nerve (TGN) in patients with unilateral trigeminal neuralgia (TN) by multiple diffusion metrics, and correlate the diffusion indexes with the clinical variables.

Methods

16 patients with TN and 6 healthy controls (HC) were recruited into our study. All participants were imaged with a 3.0 T system with three-dimension time-of-flight (TOF) magnetic resonance angiography and fluid attenuated inversion recovery (FLAIR) DTI-sequence. We placed regions of interest over the root entry zone of the TGN and measured fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). The mean values of FA, MD, AD and RD were compared between the affected and unaffected sides in the same patient, and to HC values. The correlation between the side-to-side diffusion metric difference and clinical variables (disease duration and visual analogy scale, VAS) was further explored.

Results

Compared with the unaffected side and HC, the affected side showed significantly decreased FA and increased RD; however, no significant changes of AD were found. A trend toward significantly increased MD was identified on the affected side comparing with the unaffected side. We also found the significant correlation between the FA reduction and VAS of pain (r = −0.55, p = 0.03).

Conclusion

DTI can quantitatively assess the microstructural abnormalities of the affected TGN in patients with TN. Our results suggest demyelination without significant axonal injury is the essential pathological basis of the affected TGN by multiple diffusion metrics. The correlation between FA reduction and VAS suggests FA as a potential objective MRI biomarker to correlate with clinical severity.     

MR neurography of the median nerve at 3.0T: optimization of diffusion tensor imaging and fiber tractography

Objectives

The purpose of this study was to systematically assess the optimal b-value and reconstruction parameters for DTI and fiber tractography of the median nerve at 3.0 T.

Methods

Local ethical board approved study with 45 healthy volunteers (15 men, 30 women; mean age, 41 ± 3.4 years) who underwent DTI of the right wrist at 3.0 T. A single-shot echo-planar-imaging sequence (TR/TE 10123/40 ms) was acquired at four different b-values (800, 1000, 1200, and 1400 s/mm²). Two independent readers performed post processing and fiber-tractography. Fractional anisotropy (FA) maps were calculated. Fiber tracts of the median nerve were generated using four different algorithms containing different FA thresholds and different angulation tolerances. Data were evaluated quantitatively and qualitatively.

Results

Tracking algorithms using a minimum FA threshold of 0.2 and a maximum angulation of 10° were significantly better than other algorithms. Fiber tractography generated significantly longer fibers in DTI acquisitions with higher b-values (1200 and 1400 s/mm² versus 800 s/mm²; p < 0.001). The overall quality of fiber tractography was best at a b-value of 1200 s/mm² (p < 0.001).

Conclusions

In conclusion, our results indicate use of b-values between 1000 and 1400 s/mm² for DTI of the median nerve at 3.0 T. Optimal reconstruction parameters for fiber tractography should encompass a minimum FA threshold of 0.2 and a maximum angulation tolerance of 10.     

Rectal tumour volume (GTV) delineation using T2-weighted and diffusion-weighted MRI: Implications for radiotherapy planning

Purpose

To compare the rectal tumour gross target volume (GTV) delineated on T2 weighted (T2W MRI) and diffusion weighted MRI (DWI) images by two different observers and to assess if agreement is improved by DWI.

Material and methods

27 consecutive patients (15 male, range 27.1–88.8 years, mean 66.9 years) underwent 1.5 T MRI prior to chemoradiation (45 Gy in 25 fractions; oral capecitabine 850 mg/m²), including axial T2W MRI (TR = 6600 ms, TE = 90 ms) and DWI (TR = 3000 ms, TE = 77 ms, b = 0, 100, 800 s/mm²). 3D tumour volume (cm³) was measured by volume of interest (VOI) analysis by two independent readers for the T2W MRI and b800 DWI axial images, and the T2W MRI and DWI volumes compared using Mann–Whitney test. Observer agreement was assessed using Bland–Altman statistics. Significance was at 5%.

Results

Artefacts precluded DWI analysis in 1 patient. In the remaining 26 patients evaluated, median (range) T2W MRI MRI and DWI (b = 800 s/mm²) 3D GTVin cm³ were 33.97 (4.44–199.8) and 31.38 (2.43–228), respectively, for Reader One and 43.78 (7.57–267.7) and 42.45 (3.68–251) for Reader Two. T2W MRI GTVs were slightly larger but not statistically different from DWI volumes: p = 0.52 Reader One; p = 0.92 Reader Two. Interobserver mean difference (95% limits of agreement) for T2W MRI and DWI GTVs were −9.84 (−54.96 to +35.28) cm³ and −14.79 (−54.01 to +24.43) cm³ respectively.

Conclusion

Smaller DWI volumes may result from better tumour conspicuity but overall observer agreement is not improved by DWI.     

Can diffusion tensor imaging predict motor power affection after moderate traumatic brain injury?

Objective

To determine whether commissural and projection fibers fractional anisotropy (FA) abnormalities can help in the prediction of long-term outcome of motor power affection after moderately severe traumatic brain injury (TBI).

Methods

MRI protocol included diffusion tensor imaging (DTI) and was performed for 32 patients with moderate TBI and 32 matched control subjects. Regions of interests were applied in the FA maps in the corpus callosum, internal capsules posterior limb, and cerebral peduncles. Results were compared in patients with motor power affection and patients without motor power affection to the control group.

Results

All patients had FA values lower than the control group with significance differences in the corpus callosum. Patient group with weakness had FA values lower than the control groups with significance differences in the posterior limb of the left internal capsules (p = 0.001) and left cerebral peduncles (p < 0.001). Significant differences were found when comparing the posterior limb of the left internal capsule (p = 0.002) and left cerebral peduncle (p = 0.022) to the right side in the weakness group.

Conclusion

FA values measured in the acute stage provided information about associated and projectional fibers disruptions, which have a prognostic value about motor power affection.     

Comparison of 3D turbo spin-echo SPACE sequences with conventional 2D MRI sequences to assess the shoulder joint

Purpose

To determine the accuracy and reliability of three-dimensional (3D) T1- and proton density (PD)-weighted turbo spin-echo (TSE) sampling perfection with application-optimized contrasts using different flip-angle evolution (SPACE) compared with conventional 2D sequences in assessment of the shoulder-joint.

Materials and methods

Ninety-three subjects were examined on a 3-T MRI system with both conventional 2D-TSE sequences in T1-, T2- and PD-weighting and 3D SPACE sequences in T1- and PD-weighting. All examinations were assessed independently by two reviewers for common pathologies of the shoulder-joint. Agreement between 2D- and 3D-sequences and inter-observer-agreement was evaluated using kappa-statistics.

Results

Using conventional 2D TSE sequences as standard of reference, sensitivity, specificity, and accuracy values of 3D SPACE were 81.8%, 95.1%, and 93.5% for injuries of the supraspinatus-tendon (SSP), 81.3%, 93.5%, and 91.4% for the cartilage layer and 82.4%, 98.5%, and 97.5% for the long biceps tendon. Concordance between 2D and 3D was almost perfect for tendinopathies of the SSP (κ = 0.85), osteoarthritis (κ = 1), luxation of the biceps tendon (κ = 1) and adjacent bone marrow (κ = 0.92). Inter-observer-agreement was generally higher for conventional 2D TSE sequences (κ, 0.23–1.0), when compared to 3D SPACE sequences (κ, −0.33 to 1.0) except for disorders of the long biceps tendon and supraspinatus tendon rupture.

Conclusion

Because of substantial and almost perfect concordance with conventional 2D TSE sequences for common shoulder pathologies, MRI examination-time can be reduced by nearly 40% (up to 11 min) using 3D-SPACE without loss of information.     

3D dynamic pituitary MR imaging with CAIPIRINHA: Initial experience and comparison with 2D dynamic MR imaging

Objectives

To evaluate the validity of 3D dynamic pituitary MR imaging with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA), with special emphasis on demarcation of pituitary posterior lobe and stalk.

Methods

Participants comprised 32 patients who underwent dynamic pituitary MR imaging due to pituitary or parasellar lesions. 3D dynamic MR with CAIPIRINHA was performed at 3 T with 20-s-interval, precontrast, 1st to 5th dynamic images. Normalized values and enhanced ratios (dynamic postcontrast image values divided by precontrast ones) were compared between 3D and 2D dynamic MR imaging for patients with visual identification of posterior lobe and stalk.

Results

In 3D, stalk was identified in 29 patients and unidentified in 3, and posterior lobe was identified in 28 and unidentified in 4. In 2D, stalk was identified in 26 patients and unidentified in 6 patients, and posterior lobe was identified in 15 and unidentified in 17. Normalized values of pituitary posterior lobe and stalk were higher in 3D than 2D (P < 0.001). No significant difference in enhancement ratio was seen between 3D and 2D.

Conclusions

3D dynamic pituitary MR provided better identification and higher normalized values of pituitary posterior lobe and stalk than 2D.     

Magnetic resonance fiber density mapping of age-related white matter changes

Objectives

To introduce fiber density mapping (FDM) for investigation of age-related white matter (WM) changes and to compare its capabilities with conventional diffusion tensor imaging (DTI) post-processing.

Methods

DTI data with 1.9 mm³ isotropic voxels were acquired from 44 healthy volunteers (18–88 years) at 3 T. FDM is a 3-step approach which includes diagonalization of the diffusion tensor, fiber reconstruction for the whole brain, and calculation of fiber density (FD) values. Maps of fractional anisotropy (FA) and mean diffusivity (MD) were additionally calculated. Voxel-based analyses were performed to determine volume clusters of significant correlation with age. Bivariate linear regression models and Hotelling–Williams tests were used to detect significant differences between correlations.

Results

FDM detected a larger WM volume affected by age-related changes concomitant with fewer significant clusters compared to FA and MD. This indicates that WM alterations due to normal aging occur rather globally than locally. FD values showed a significant stronger correlation with age in frontal lobes (prefrontal and precentral gyrus), limbic lobes (cingulate and parahippocampal gyrus), the corpus callosum (genu) and temporal lobes.

Conclusions

FDM shows higher sensitivity for detection of age-related WM changes because it includes all surrounding fiber structures into the evaluation of each DTI data voxel.     

Comparison of acquired diffusion weighted imaging and computed diffusion weighted imaging for detection of hepatic metastases

Objective

To compare the accuracy of acquired diffusion weighted imaging (DWI) (b = 1000 s/mm²) with that of computed DWI (b = 1000 s/mm²) for the detection of hepatic metastases.

Methods

Two hundred and sixty patients underwent abdominal magnetic resonance imaging (MRI) at 3.0 T for the evaluation of hepatic metastasis, including T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), heavily T2WI, DWI with b-values of 0, 500, 1000 s/mm², and three-dimensional dynamic contrast-enhanced MRI with gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA), and 190 patients were included in the final study. Computed DWI (=1000 s/mm²) was synthesized from lower b-values (b = 0 and 500 s/mm²). Two groups were assigned and compared: group A (acquired DWI) and group B (computed DWI). Diagnostic performance using each imaging set was evaluated by receiver operating characteristic (ROC) curve analysis.

Results

A total of 76 hepatic metastases were confirmed. The area under the ROC curve (Az) of group A was larger than that of group B (Observer 1; 0.919–0.915, Observer 2; 0.926–0.901), but there were no significant differences (observer 1, P = 0.500; observer 2, P = 0.190). There were 5 metastases visualized in group A, but these were difficult to detect in group B. However, there were 2 metastases that were better visualized in group B than in group A.

Conclusion

There were no significant differences between acquired DWI and computed DWI in the detection of hepatic metastasis.     

Diffusion tensor imaging of periventricular leukomalacia – Initial experience

Aim of the study

To investigate the role of MR diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) in the assessment of altered major white matter fibers in preterm infants and children with PVL.

Patients and methods

We used diffusion tensor imaging to evaluate the major white matter tract fibers in 15 children with periventricular leukomalacia in correlation with cognitive and motor disability. Mean age of the patients was 28.5 months (range: 9–84 months). 5 normal control children were recruited (mean age: 21.4, range: 11–60 months). MR imaging was obtained by using a 1.5-T, whole-body scanner. DTI was acquired after the routine sequences. Then, data post-processing and fiber-tracking method was applied.

Results

This study demonstrated the existence of the WM tract injury in PVL patients using the DTI tractography approach in correlation with neurodevelopmental delay in patients with various degrees of cognitive and motor impairment. Compared with the normal control group, the following abnormalities were detected on qualitative analysis of the white matter tracts.

Corticospinal tracts

Decreased volume and cross-sectional area on the affected side.

Ascending sensorimotor tracts

Thinning of sensory fiber tracts and posterior thalamic radiations.

Commissural and association tracts

Significant damage of the callosal fibers was reported in cases with partial agenesis of the corpus callosum.

Conclusion

DTI proved to be a promising noninvasive method for assessing the severity of white matter tract injury in patients with PVL. This is owing to the capability of fiber-tracking techniques to provide more information for understanding the pathophysiologic features of sensorimotor and cognitive disability associated with PVL. This will allow for the early intervention and initiation of rehabilitation programs aiming for minimizing the associated neurological deficit.     

Diffusion tensor tractography as a supplementary tool to conventional MRI for evaluating patients with myelopathy

Purpose

The aim of this study was to assess the clinical utility of DTI including apparent diffusion coefficient (ADC), fractional anisotropy (FA), in patients with symptoms of spinal cord myelopathy.

Patients and methods

Fifteen subjects with clinical symptoms of acute (n = 3) or slowly progressive (n = 12) spinal cord myelopathy and 11 healthy volunteers were prospectively selected. They all underwent magnetic resonance imaging of the spine at 3.0 T machine. In addition to conventional MRI, DTI was performed; maps of the apparent diffusion coefficient and of fractional anisotropy were reconstructed. Diffusion tensor tractography was used to visualize the morphological features of normal and impaired white matter at the level of the pathological lesions in the spinal cord. The patients were divided into two groups according to the signal intensity on T2WI (group A with no change in signal intensity and group B with high signal intensity).

Results

There were no statistically significant differences in the apparent diffusion coefficient and fractional anisotropy values between the different spinal cord segments of the normal subjects. All of the patients in group B had increased apparent diffusion coefficient values and decreased fractional anisotropy values at the lesion level compared to the normal controls. However, there were no statistically significant diffusion index differences between group A patients and the normal controls.

Conclusion

Diffusion tensor imaging is a reliable method for the evaluation of the diffusion properties of normal and compressed spinal cords. Furthermore, this technique can be used as an important supplementary tool to conventional MRI for the quantification of fiber damage in spinal cord compression, thus has the potential to be of great utility for treatment planning and follow up.     

90°-Flip-angle three-dimensional double-echo steady-state (3D-DESS) magnetic resonance imaging of the knee: Isovoxel cartilage imaging at 3 T

Purpose

The purpose of this study was to investigate whether 3D-double echo steady state (3D-DESS) with improved contrast by setting the FA (Flip angle) at 90° is useful in 3D isotropic cartilage imaging of the knee at 3 T.

Materials and methods

Imaging was performed in 10 healthy volunteers using 3 methods: with 3D-DESS using FA of 25° and 90°, and with true fast imaging with steady-state precession (True-FISP). The signal-to-noise ratio (SNR) of the synovial fluid and cartilage, and contrast-to-noise ratio (CNR) were measured, and mean values were compared. Visual assessment of artifacts was performed with the cartilage divided into 6 regions.

Results

There were no significant differences in synovial fluid SNR in the comparison between FA-90° 3D-DESS and True-FISP (P = 0.364). A significantly higher cartilage SNR was observed with FA-90° 3D-DESS than with True-FISP (P = 0.031). There were no significant differences in synovial fluid-cartilage CNR between FA-90° 3D-DESS and True-FISP (P = 0.892). In the evaluation of artifacts, FA-90° 3D-DESS imaging showed a significantly higher score than True-FISP imaging in the patella and trochlea cartilage (P < 0.001, P < 0.002).

Conclusions

FA-90° 3D-DESS is useful in 3D isotropic cartilage imaging of the knee at 3 T.     

Diffusion-weighted MR imaging and ADC measurement in normal prostate,benign prostatic hyperplasia and prostate carcinoma

Purpose

Our aim was to investigate the diffusion-weighted Imaging (DWI) appearance and apparent diffusion coefficient (ADC) values of normal prostatic gland, prostate carcinoma (PCa) and benign prostate hyperplasia (BPH) and to determine the utility of DWI in their characterization.

Materials and methods

During a period of 16 months, 40 consecutive patients, with elevated PSA level and 12 healthy volunteers with no clinical symptoms or history of prostate disease were prospectively evaluated with DWI of the prostate. MRI was performed using a 1.5T MR scanner equipped with a pelvic phased array coil. For anatomical imaging, T2W FSE in the three orthogonal planes, and T1WI in axial plane were obtained. DWI with b values of 0, 300, 500 and 800 s/mm² were performed in axial plane. The results were confirmed by TRUS-guided biopsy or prostatectomy.

Results

Patients ranged in age from 45 to 85 years (mean 66.6 ± 7.9 year). Twenty patients were confirmed to have BPH, whereas 20 patients had PCa. The mean and SD of ADC values for the peripheral zone (PZ), central gland (CG), BPH nodules and PCa were 1.839 ± 0.233, 1.469 ± 0.239, 1.359 ± 0.201 and 0.87 ± 0.13 respectively. The mean ADC value of PCa was significantly lower than that of CG, PZ, and BPH nodule, with p value <0.05.

Conclusion

DW MR imaging characteristics and ADC values can differentiate PCa and BPH. DWI with ADC may be used as a complementary method to conventional MRI in diagnosis of PCa and BPH.