Brain White Matter Involvement in Hereditary Spastic Paraplegias: Analysis with Multiple Diffusion Tensor Indices

BACKGROUND AND PURPOSE:The hereditary spastic paraplegias are a group of genetically heterogeneous neurodegenerative disorders, characterized by progressive spasticity and weakness of the lower limbs. Although conventional brain MR imaging findings are normal in patients with pure hereditary spastic paraplegia, microstructural alteration in the cerebral WM can be revealed with DTI. Concomitant investigation of multiple intrinsic diffusivities may shed light on the neurobiologic substrate of the WM degeneration pattern in patients with pure hereditary spastic paraplegia across the whole brain.MATERIALS AND METHODS:Tract-based spatial statistics analysis was performed to compare fractional anisotropy and mean, axial, and radial diffusivities of the WM skeleton in a group of 12 patients with pure hereditary spastic paraplegia and 12 healthy volunteers. Data were analyzed counting age and sex as nuisance covariates. The threshold-free cluster-enhancement option was applied, and the family-wise error rate was controlled by using permutation tests for nonparametric statistics.RESULTS:In pure hereditary spastic paraplegia, group widespread fractional anisotropy decreases and radial diffusivity and mean diffusivity increases (P < .05, corrected) were found. No voxelwise difference was observed for the axial diffusivity map. Percentage of voxels within the WM skeleton that passed the significance threshold were 51%, 41.6%, and 11.9%, respectively, for radial diffusivity, fractional anisotropy, and mean diffusivity clusters. An anteroposterior pattern with preferential decrease of fractional anisotropy in the frontal circuitry was detected.CONCLUSIONS:In patients with pure hereditary spastic paraplegia, alterations in multiple DTI indices were found. Radial diffusivity seems more sensitive to hereditary spastic paraplegia–related WM pathology and, in line with the lack of axial diffusivity changes, might indicate a widespread loss of myelin integrity. A decrease of fractional anisotropy alone in the frontal circuitry may reflect subtle disruption of the frontal connections.

The hereditary spastic paraplegias (HSPs), also called familial spastic paraparesis or Strümpell-Lorrain disease, represent a genetically and clinically heterogeneous group of neurodegenerative disorders.¹ The main clinical feature is progressive spasticity due to slowly progressing “dying back” axonal degeneration, which is maximal in the terminal portions of the longest descending and ascending tracts.² On the basis of clinical symptoms, HSPs are classified into pure or uncomplicated, in which the spastic paraplegia is the major clinical manifestation; and complex or complicated forms, presenting with additional neurologic signs, such as intellectual disability or cognitive decline, deafness, cerebellar ataxia, epilepsy, dysarthria, peripheral neuropathy, optic atrophy, and visual dysfunction.³ Autosomal dominant, autosomal recessive, or X-linked inheritance is associated with multiple genes or loci and leads to genetic heterogeneity of this disorder. The HSP loci are designated as spastic paraplegia loci and are numbered 1–56 according to their discovery.⁴ There is scarce evidence about the epidemiology of HSP, though its prevalence is estimated at 1.27:100,000 population in Europe.⁵Findings of conventional MR imaging of the brain are usually normal in pure hereditary spastic paraplegia (pHSP). In contrast, nonspecific findings such as cortical atrophy and subcortical and periventricular WM alterations are present in complicated HSP.⁶ Distinct MR imaging findings may accompany complicated HSP; for instance, a common form of autosomal recessive HSP with SPG11 mutation (linked to the 15q13-q15 chromosome) is frequently associated with a thin corpus callosum.⁷ Optic nerve and cerebellar atrophy may be revealed when visual symptoms and cerebellar ataxia are present.⁸DTI is an efficient technique used to characterize the in vivo microstructural organization of the WM.⁹ The common DTI indices are fractional anisotropy (FA) (sensitive to microstructural changes and associated with the presence of oriented structures in tissue) and mean diffusivity (MD) (characterizes mean-square displacement of molecules and the overall presence of obstacles to diffusion).¹⁰ Other indices, axial diffusivity (AD) and radial diffusivity (RD), offer suggestive elements to differentiate axonal injury and demyelination.¹¹ To extend our knowledge of the neurobiologic basis of WM pathology, using multiple diffusivity matrices (FA, MD, RD, and AD) is recommended.¹²The present study was set up to investigate WM alterations across the whole brain in a group of patients with pHSP with SPG4, SPG5, SPG3a, and SPG10 mutations, applying tract-based spatial statistics (TBSS) analysis with multiple DTI indices.     

Feasibility of diffusion weighted MR imaging in differentiating recurrent laryngeal carcinoma from radionecrosis

Purpose

To assess the feasibility of apparent diffusion coefficient (ADC) generated from diffusion weighted magnetic resonance imaging as a non invasive technique to differentiate tumor recurrence from radionecrosis in patients with laryngeal carcinoma.

Materials and methods

Twenty one patients suspected of tumor recurrence underwent MRI including diffusion weighted imaging (DWI) (b 0 and 1000). ADC maps were generated and ADC values were measured at the lesion sites and the normal laryngeal tissues, and were compared with the histopathological results.

Results

The mean ADC of tumor recurrence {1.04 ± 0.34 × 10⁻³ mm²/s (SD)} was significantly lower (p < 0.0001) than the mean ADC of the normal laryngeal tissues in the same patient (1.48 ± 0.099 × 10⁻³ mm²/s) while the mean ADC of radionecrosis (1.79 ± 0.41 × 10⁻³ mm²/s) was significantly higher (p < 0.04) than the mean ADC of the normal laryngeal tissues (1.49 ± 0.095 × 10⁻³ mm²). The mean ADC of tumor recurrence is significantly lower (p < 0.0001) than the mean ADC of radionecrosis with 1.16 × 10⁻³ mm²/s is the best cut value for differentiating tumor recurrence from radionecrosis.

Conclusion

ADC can differentiate tumor recurrence from radionecrosis in laryngeal carcinoma.     

SPG3A-linked hereditary spastic paraplegia associated with cerebral glucose hypometabolism

SPG3A-linked hereditary spastic paraplegia (HSP) is a rare autosomal dominant motor disorder caused by a mutation in the SPG3A gene, and is characterized by progressive motor weakness and spasticity in the lower limbs, without any other neurological abnormalities. SPG3A-linked HSP caused by a R239C mutation has been reported to present a pure phenotype confined to impairment of the corticospinal tract. However, there is still a debate about the etiology of this motor deficit with regard to whether it is peripheral or central. We herein report two patients who were heterozygous for a R239C mutation in the SPG3A gene. Two middle-aged Japanese sisters had been suffering from a pure phenotype of HSP since their childhood. Both patients had a significant decrease in glucose metabolism in the frontal cortex medially and dorsolaterally in a [¹⁸F]-fluorodeoxyglucose (FDG) positron emission photography (PET) study and low scores on the Frontal Assessment Battery. A real-time PCR analysis in normal subjects showed the frontal cortex to be the major location where SPG3A mRNA is expressed. The present finding that the frontal glucose hypometabolism was associated with frontal cognitive impairment indicates that widespread neuropathology associated with mutations in the SPG3A gene may be present more centrally than previously assumed.     

Pre-exercise alkalosis attenuates the heat shock protein 72 response to a single-bout of anaerobic exercise

The heat shock protein 72 (HSP72) response following exercise is well documented, however, little is known on whether the expression may be mediated by the ingestion of ergogenic aids prior to performance. The purpose of this research was to investigate the effect of sodium bicarbonate (NaHCO₃) ingestion on monocyte and lymphocyte expressed HSP72 and oxidative stress for 4-h post exercise. Seven active males (22.3 ± 2.9 years, 181.6 ± 4.5 cm, 78.1 ± 8.1 kg) performed a 4-min ‘all-out’ cycle test following a dose of 0.3 g kg⁻¹ body mass of NaHCO₃, or an equimolar placebo dose of sodium chloride. HSP72 was measured by flow cytometry and oxidative stress was determined via plasma thiobarbituric acid substances (TBARS) analysis. The NaHCO₃ ingestion significantly increased blood pH (p < 0.001), bicarbonate (p < 0.001) and base excess (p < 0.001) pre-exercise. Despite this there was no evidence of a significantly improved exercise performance when compared with the placebo trials (p ≥ 0.26) (means ± SD; average power 292 ± 43 W vs. 291 ± 50 W; peak power 770 ± 218 W vs. 775 ± 211 W; work completed 71 ± 10 kJ vs. 68 ± 10 kJ). Monocyte expressed HSP72 was significantly lower under experimental conditions during the 4-h post-exercise (p = 0.013), as was plasma TBARS (p < 0.001). These findings suggest that pre-exercise alkalosis can attenuate the stress response to a single bout of anaerobic exercise.     

MRI measurements of the pons and cerebellum in children born preterm; associations with the severity of periventricular leukomalacia and perinatal risk factors

Our purpose was to measure the size of the pons and cerebellum in preterm babies with periventricular leukomalacia (PVL), and to study their relationship with the severity of PVL and with perinatal risk factors. We examined 33 premature children, mean gestational age 31 weeks, range 26–36 weeks with PVL on MRI, and 27 full-term controls. On MRI at 0.4–5.5 years (mean 1.4 years) we measured the area of the corpus callosum and vermis, the anteroposterior diameter of the pons and the volume of the cerebellum. The area of the corpus callosum was used as a marker of white matter loss and PVL severity. All regional brain measurements except that of the vermis were significantly lower in patients than controls: corpus callosum (mm²): 239.6±92.5 vs 434.8±126.8, P <0.01; pons (mm): 14.8±3.0 vs 17.9±1.4, P <0.01]; cerebellum (cm³): 68.2±31.6 vs 100.6±28.3, P <0.01; vermis (mm²): 808.1±292.2 vs 942.2±246.2, NS. Significant reduction in the area of the vermis: 411.3±203.3 vs 935±252.6 mm²; cerebellar volume: 16.3±12.5 vs 96.6±20.2 mm³; and the diameter of the pons: 10.1±2.2 vs 17.5±1.3 mm (P <0.01) were observed in seven children with gestational age 28 weeks, severe hypotension and large patent ductus arteriosus (PDA). There was a significant correlation between the duration of mechanical ventilation and the size of the vermis, pons and cerebellum (R=–0.65, –0.57 and –0.73, respectively, P <0.01).     

Computed tomography in hereditary ataxias

Summary Cranial CT in 39 patients (23 belonged to 8 families) with four different groups of hereditary ataxia (HA) showed mainly three combinations of atrophic findings: (1) cerebellar ataxia (CA, n=17) had marked atrophy of the cerebellum and/or the brain stem combined with moderate cerebral atrophy; (2) an intermediate group consisting of hereditary spastic paraplegia (HSP, n=10) and Friedreich's ataxia (FA, n=7), both with moderate infra- and supratentorial atrophy; (3) atrophy was hardly demonstrated in the group of Charcot-Marie-Tooth disease (CMT, n=5). HA cases with atrophy could be distinguished from multiple sclerosis (MS) by CT.     

Relationships between brain water content and diffusion tensor imaging parameters (apparent diffusion coefficient and fractional anisotropy) in multiple sclerosis

Fifteen multiple sclerosis patients were examined by diffusion tensor imaging (DTI) to determine fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in a superventricular volume of interest of 8×8×2 cm³ containing gray matter (GM) and white matter (WM) tissue. Point resolved spectroscopy 2D-chemical shift imaging of the same volume was performed without water suppression. The water contents and DTI parameters in 64 voxels of 2 cm³ were compared. The water content was increased in patients compared with controls (GM: 244±21 vs. 194±10 a.u.; WM: 245±32 vs. 190±11 a.u.), FA decreased (GM: 0.226±0.038 vs. 0.270±0.020; WM: 0.337±0.044 vs. 0.402±0.011) and ADC increased [GM: 1134±203 vs. 899±28 (×10⁻⁶ mm²/s); WM: 901±138 vs. 751±17 (×10⁻⁶ mm²/s)]. Correlations of water content with FA and ADC in WM were strong (r=−0.68, P<0.02; r=0.75; P<0.01, respectively); those in GM were weaker (r=−0.50, P<0.05; r=0.45, P<0.1, respectively). Likewise, FA and ADC were more strongly correlated in WM (r=−0.88; P<0.00001) than in GM (r=−0.69, P<0.01). The demonstrated relationship between DTI parameters and water content in multiple sclerosis patients suggests a potential for therapy monitoring in normal-appearing brain tissue.     

Tetrahydrobiopterin restores impaired coronary microvascular dysfunction in hypercholesterolaemia

Purpose Tetrahydrobiopterin (BH₄) is an essential co-factor for the synthesis of nitric oxide (NO), and BH₄ deficiency may cause impaired NO synthase (NOS) activity. We studied whether BH₄ deficiency contributes to the coronary microcirculatory dysfunction observed in patients with hypercholesterolaemia.Methods Myocardial blood flow (MBF; ml min^–1 g^–1) was measured at rest, during adenosine-induced (140 g kg^–1 min^–1 over 7 min) hyperaemia (mainly non-endothelium dependent) and immediately after supine bicycle exercise (endothelium-dependent) stress in ten healthy volunteers and in nine hypercholesterolaemic subjects using ¹⁵O-labelled water and positron emission tomography. Measurements were repeated 60 min later, after intravenous infusion of BH₄ (10 mg kg^–1 body weight over 30 min). Adenosine-induced hyperaemic MBF is considered to represent (near) maximal flow. Flow reserve utilisation was calculated as the ratio of exercise-induced to adenosine-induced hyperaemic MBF and expressed as percent to indicate how much of the maximal (adenosine-induced) hyperaemia can be achieved by bicycle stress.Results BH₄ increased exercise-induced hyperaemia in controls (2.96±0.58 vs 3.41±0.73 ml min^–1 g^–1, p<0.05) and hypercholesterolaemic subjects (2.47±0.78 vs 2.70±0.72 ml min^–1 g^–1, p<0.01) but had no influence on MBF at rest or during adenosine-induced hyperaemia in controls (4.52±1.10 vs 4.85±0.45 ml min^–1 g^–1, p=NS) or hypercholesterolaemic subjects (4.86±1.18 vs 4.53±0.93 ml min^–1 g^–1, p=NS). Flow reserve utilisation remained unchanged in controls (70±17% vs 71±19%, p=NS) but increased significantly in hypercholesterolaemic subjects (53±15% vs 66±14%, p<0.05).Conclusion BH₄ restores flow reserve utilisation of the coronary microcirculation in hypercholesterolaemic subjects, suggesting that BH₄ deficiency may contribute to coronary microcirculatory dysfunction in hypercholesterolaemia.The first two authors have contributed equally to the present project.An erratum to this article can be found at     

Involvement of pulmonary endothelial cell injury in the pathogenesis of pulmonary fibrosis: clinical assessment by 123I-MIBG lung scintigraphy

Purpose Pulmonary microvascular endothelial injury may be involved in the pathogenesis of pulmonary fibrosis (PF). The aim of this study was to evaluate the pulmonary vascular status in patients with PF by lung scintigraphic assessment of ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG), which reflects latent endothelial cell lesions.Methods We assessed lung ¹²³I-MIBG kinetics and clinical indices in 23 PF patients and 16 controls. Mean uptake ratios of lung to mediastinum (L/M) were calculated in anterior planar images at 30 (early image) and 270 (delayed image) min after intravenous injection of ¹²³I-MIBG. The pulmonary mean washout rate (WR) of ¹²³I-MIBG was also calculated.Results The L/M ratio in early images, but not in delayed images, was significantly lower in the PF patients than in the controls (L/M_early 1.41±0.14 vs 1.53±0.10, p<0.01; L/M_delayed 1.28±0.10 vs 1.33±0.07, p=NS). WR was significantly reduced in the PF patients compared with the controls (28.6%±3.1% vs 34.2%±5.1%, p<0.001). In the study subjects (PF patients plus controls) there were significant relationships between lung WR of ¹²³I-MIBG and other diagnostic parameters for the severity of PF, such as vital capacity (r=0.625, p<0.0001), total lung capacity (r=0.691, p<0.0001), carbon monoxide diffusing capacity (r=0.622, p<0.0001), serum angiotensin-converting enzyme activity (r=0.422, p<0.01), carbohydrate antigen KL-6 levels (r=–0.495, p<0.01) and surfactant protein-D levels (r=–0.461, p<0.01). When control subjects were excluded, similar significant correlations were observed between WR and %TLC (r=0.508, p<0.05), DL_CO (r=0.593, p<0.01) and serum ACE activity (r=0.515, p<0.05) in the PF patients.Conclusion These results suggest that endothelial cell injury plays a significant role in the pathogenesis of PF, and that lung WR of ¹²³I-MIBG, which is a specific marker of endothelial damage, can serve as a novel diagnostic tool to evaluate the functional severity of PF.     

High-resolution myocardial perfusion imaging at 3 T: comparison to 1.5 T in healthy volunteers

The purpose of this study was to evaluate high-resolution (HR) myocardial first-pass perfusion in healthy volunteers at 3 T compared to a typical clinical imaging protocol at 1.5 T, with respect to overall image quality and the presence of subendocardial dark rim artifacts. Myocardial first-pass rest perfusion studies were performed at both field strengths using a T1-weighted saturation-recovery segmented k-space gradient-echo sequence combined with parallel imaging (Gd-DTPA 0.05 mmol/kg). Twenty-six healthy volunteers underwent (1) a HR perfusion scan at 3 T(pixel size 3.78 mm²) and (2) a standard perfusion approach at 1.5 T(pixel size 9.86 mm²). The contrast enhancement ratio (CER) and overall image quality (4-point grading scale: 4: excellent; 1: non-diagnostic) were assessed, and a semiquantitative analysis of dark rim artifacts was performed for all studies. CER was slightly higher (1.31 ± 0.32 vs. 1.14 ± 0.34; p<0.01), overall image quality was significantly improved (3.03 ± 0.43 vs. 2.37 ± 0.39; p<0.01), and the number of dark rim artifacts (139 ± 2.09 vs. 243 ± 2.33; p<0.01) was significantly reduced for HR perfusion imaging at 3 T compared to the standard approach at 1.5 T. HR myocardial rest perfusion at 3 T is superior to the typical clinical perfusion protocol performed at 1.5 T with respect to the overall image quality and presence of subendocardial dark rim artifacts.     

Apparent diffusion coefficient values as an adjunct to dynamic contrast enhanced MRI for discriminating benign and malignant breast lesions presenting as mass and non-mass like enhancement

Purpose

The purpose of our study was to evaluate the diagnostic value of an imaging protocol that combines dynamic contrast-enhanced MRI (DCE-MRI) and apparent diffusion coefficient (ADC), measured by diffusion weighted MRI, in discriminating benign and malignant breast lesions presenting as mass and non mass like enhancement (NMLE).

Methods and materials

80 patients with 110 breast lesions identified with dynamic contrast MRI. Diffusion-weighted images were obtained at b values of 0 and 750 S/mm², differences in the apparent diffusion coefficients (ADCs) are included in the study and malignant lesions were compared by lesion type (mass or NMLE), and the analysis was performed to evaluate diagnostic performance based on ADC thresholds. All lesions have pathological results. The study has been done retrospectively 50 patients underwent surgical excision with preoperative localization, while the 30 cases underwent stereotactic biopsies either US or mammographically guided techniques specially if associated with micro calcifications.

Results

The mean ADC value of all benign lesions is 1.41 ± 0.36 × 10⁻³ mm²/s, which is higher than the mean ADC of all malignant lesions (1.05 ± 0.30 × 10⁻³ mm²/s, p < 0.05). In the MASS type, the mean ADC is higher in the benign group (1.34 ± 0.30 × 10⁻³ mm²/s) than in the malignant group (1.02 ± 0.29 × 10⁻³ mm²/s, p < 0.01). In the NMLE type, the mean ADC is also higher in the benign group (1.54 ± 0.45 × 10⁻³ mm²/s) than in the malignant group (1.11 ± 0.32 × 10⁻³ mm²/s, p < 0.01). Therefore, benign lesions have higher ADC values than malignant lesions, regardless of the lesion morphology.

Conclusion

Diffusion-weighted MRI shows adequate help in differentiation of benign and malignant masses and lesions with non-mass like enhancement found at breast MRI.     

Diffusion weighted magnetic resonance imaging of kidneys in children with vesicoureteral reflux

Purpose

The apparent diffusion coefficient (ADC) which obtain from diffusion-weighted magnetic resonance imaging (DWI), is a quantitative parameter representing the renal function and parenchymal damage in some renal disorders. The primary aim of this study was to investigate whether renal tissue alterations associated with vesicoureteral reflux (VUR) can be displayed by DWI. The secondary aim was to assess how ADC values change with age in kidneys with and without VUR.

Materials and methods

This prospective study included 46 patients (8 boys, 38 girls; mean age 7.3 ± 4.2; range 1–15 years) with VUR and 54 control subjects (21 boys, 33 girls; mean age 7.7 ± 5.2; range 1–17 years). All subjects underwent DWI of the kidneys using b value of 600 s/mm² in addition to MR urography. The ADC values of 71 kidneys with VUR were compared with those of 81 kidneys without VUR.

Results

The mean ADC values were (1.93 ± 0.36) × 10⁻³ mm²/s, (1.97 ± 0.24) × 10⁻³ mm²/s, (1.83 ± 0.37) × 10⁻³ mm²/s, (1.98 ± 0.20) × 10⁻³ mm²/s and (2.08 ± 0.42) × 10⁻³ mm²/s in normal kidneys, and in those with grade 1, grade 2, grade 3 and grade 4 VUR, respectively. There was no significant difference in ADC values between kidneys with and without VUR. There was a significant positive correlation between the age and ADC values both in kidneys with and without VUR (r = 0.79, p < 0.001 and r = 0.82; p < 0.001, respectively).

Conclusion

DWI does not reveal probable parenchymal alterations in reflux nephropathy. ADC values increase with age during childhood not only in normal kidneys but also in kidneys with VUR.     

Influence of a small field-of-view size on the detection of coronary artery calcifications with MSCT: in vitro and in vivo study

The purpose of this study is to asses the impact of small field-of-view (FOV) sizes on the detection of coronary artery calcifications using multislice-spiral computed tomography (MSCT). First, a static chest phantom containing calcium inserts was scanned 10 times using a standardized scan protocol. Secondly, 50 patients (28 male, 63.6±10.6 years) underwent cardiac MSCT using the same protocol. Images were reconstructed with three different FOV sizes (180×180, 220×220, 380×380 mm²). Coronary calcium scoring and risk stratification were performed for each image series. In the phantom study, the Agatston score calculated with a FOV size of 180×180 mm² was 657.80±20.05. At a FOV of 220×220 mm² and 380×380 mm², the corresponding values were 657.04±21.36 and 655.04±20.74, respectively. The corresponding values in the patient study were 541.65±869.87, 541.91±872.57 and 536.61±867.81. No statistically significant differences in the calcium score were found comparing different FOV sizes. Significantly more lesions (p=0.00149) were detected in the patient study. Comparing the different FOV sizes of 180×180 mm² and 220×220 mm² (380×380 mm²), four (six) patients had to be assigned to different risk groups. The use of small FOV sizes resulted in an improved detection of coronary calcifications influencing the risk stratification for further cardiac events in MSCT coronary calcium scoring.     

Neck lymph nodes: Characterization with diffusion-weighted MRI

Purpose

To evaluate the role of diffusion-weighted imaging (DWI) in differentiating the various causes of enlarged neck lymph nodes.

Materials and methods

Thirty-four patients with enlarged neck lymph nodes clinically suggestive of malignancy underwent DWI with b values (0 and 1000). Apparent diffusion coefficient (ADC) maps are generated from DWI and ADC values were calculated for the enlarged lymph nodes and compared with histopathological results.

Results

The patients were divided into nine patients with benign neck lymphadenopathy, 14 patients with metastasis from head and neck cancer and 11 patients with nodal lymphoma. The mean ADC of the benign neck lymph nodes (1.51 ± 0.36 × 10⁻³ mm²/s) was significantly higher than those of the metastatic (0.92 ± 0.13 × 10⁻³ mm²/s) and lymphomatous (0.74 ± 0.14 × 10⁻³ mm²/s) lymph nodes (p < 0.0001) and the mean ADC of the metastatic nodes was significantly higher than that of nodal lymphoma (p = 0.04). The mean ADC of well- and moderately differentiated metastasis (0.98 ± 0.14 × 10⁻³ mm²/s) was significantly higher than that of poorly differentiated metastasis (0.83 ± 0.06 × 10⁻³ mm²/s) (p = 0.03). The mean ADC of non-Hodgkin lymphoma (0.65 ± 0.06 × 10⁻³ mm²/s) was significantly lower than that of Hodgkin lymphoma (0.86 ± 0.11 × 10⁻³ mm²/s) (p = 0.004). The best threshold for differentiating malignant from benign lymph nodes was 1.15 × 10⁻³ mm²/s.

Conclusion

DWI is a non-invasive technique that can help in the identification of the cause of enlarged neck lymph nodes.     

Parallel-transmit-accelerated spatially-selective excitation mri for reduced-fov diffusion-weighted-imaging of the pancreas

Objectives

To find out whether the use of accelerated 2D-selective parallel-transmit excitation MRI for diffusion-weighted EPI (pTX-EPI) offers advantages over conventional single-shot EPI (c-EPI) with respect to different aspects of image quality in the MRI of the pancreas.

Materials and methods

The MRI examinations of 33 consecutive patients were evaluated in this prospective and IRB-approved study. PTX-EPI was performed with a reduced (zoomed) FOV of 230 × 118 mm². The 2D-RF pulse of pTX-EPI was accelerated, i.e. shortened by a factor of 1.7 (pTX-acceleration factor). C-EPI used a full-FOV of 380 × 285 mm². In a qualitative analysis, two experienced readers evaluated 3 different aspects of image quality on 3- to 5-point Likert scales. Additionally, apparent diffusion coefficients (ADCs) were determined in both c-EPI and pTX-EPI in normal-appearing pancreatic tissue using regions of interests (ROIs). Mean ADC values and standard deviations were compared between the two techniques.

Results

The reduced-FOV pTX-EPI was superior to c-EPI with respect to overall image quality (p < 0.0001) and identifiability of the pancreatic ducts (p < 0.01). Artifacts were significantly less severe in pTX-EPI (p < 0.01). The mean ADC values of c-EPI (1.29 ± 0.19 × 10⁻³ mm²/s) and pTX-EPI (1.27 ± 0.17 × 10⁻³ mm²/s) did not differ significantly between the two techniques (p = 0.44). The variation within the ROIs as measured by the standard deviation was significantly lower in pTX-EPI (0.095 × 10⁻³ mm²/s) than in c-EPI (0.135 × 10⁻³ mm²/s), p < 0.05.

Conclusions

PTX-accelerated EPI with spatially-selective excitation and reduced FOV leads to substantial improvements in DWI of the pancreas with respect to different aspects of image quality without significantly influencing the ADC values.     

Neuronal changes in the arcuate and hypoglossal nuclei of brain stem induced by head injury

In head injury, assessing the damage not only to the cerebrum and the cerebellum but also to the brain stem is very important. In this paper, we report neuronal changes of the arcuate nucleus (ARC) and the hypoglossal nucleus (HN) in the brain stem. We investigated these changes immunohistochemically with antibodies against microtubule-associated protein 2 (MAP2), muscarinic acetylcholine receptor (mAChR), c-fos gene product (c-Fos), and the 72 kD heat-shock protein (HSP70). We measured the percentage of immunopositive neurons among the total neurons of the ARC and the HN. The investigation of neuronal changes in relation to the type of head injury showed different results. In cases of tonsillar herniation, immunoreactivity to MAP2 and mAChR in the ARC was significantly lower than in the HN (p < 0.01). Moreover, MAP2, HSP70 and c-Fos reactivities in the ARC were significantly lower than in other types of head injuries (p < 0.01). In the HN, diffuse axonal injury produced slightly higher immunoreactivity to mAChR and c-Fos (p < 0.1). Our observations indicate that immunohistochemical examination of brain stem nuclei can provide useful information for estimating damage to the brain stem. Received: 20 March 2000 / Accepted: 19 September 2000     

Apparent diffusion coefficient in cervical cancer of the uterus: comparison with the normal uterine cervix

A relation between apparent diffusion coefficient (ADC) values and tumor cellular density has been reported. The purpose of this study was to measure the ADC values of cervical cancers in the uterus and compare them with those of normal cervical tissues, and to test whether ADC could differentiate between normal and malignant cervical tissues in the uterus. Twelve consecutive female patients with cervical cancer of the uterus and ten female patients with other pelvic abnormalities were included in this study. ADC was measured at 1.5 T with b-factors of 0, 300 and 600 s/mm² using single-shot echo-planar diffusion-weighted imaging and a parallel imaging technique. The mean ADC value of cervical cancer lesions was 1.09±0.20×10^–3 mm²/s, and that of normal cervix tissue was 1.79±0.24×10^–3 mm²/s (P<0.0001). In nine patients treated by chemotherapy and/or radiation therapy, the mean ADC value of the cervical cancer lesion increased significantly after therapy (P<0.001). The present study showed, with a small number of patients, that ADC measurement has a potential ability to differentiate between normal and cancerous tissue in the uterine cervix. Further study is necessary to determine the accuracy of ADC measurement in monitoring the treatment response.     

Optimization of b value in diffusion-weighted MRI for the differential diagnosis of benign and malignant vertebral fractures

Objective The objective was to explore the optimal b value in diffusion-weighted imaging (DWI) of MRI for differential diagnosis of benign and malignant vertebral fractures. Materials and Methods Thirty-four consecutive patients with vertebral compression fractures underwent sagittal diffusion-weighted imaging (DWI) with different b values. The group included 14 patients with 18 benign vertebral fractures due to osteoporosis and/or trauma and 20 patients with 27 malignant vertebral fractures due to malignancy. The quality of the images was analyzed qualitatively on a three-point scale and quantitatively by measurement of the signal-to-noise ratio (SNR). Apparent diffusion coefficient (ADC) values were also calculated. Results Smaller b values correlated with better DW image quality. We found significant differences in the qualitative points values among the DW images with different b values (F = 302.18, p < 0.001). The mean SNR of the images ranged from 21.75 ± 3.64 at a b value of 0 s/mm² to 5.31 ± 3.17 at a b value of 800 s/mm². The SNR of DWI with a b value of 300 s/mm² (18.62 ± 2.47) was significantly different from that with other b values (p < 0.01). The mean combined ADC values of malignant fractures were significantly lower than those of benign ones on DWI with a b value of 300 s/mm² (t = 9.097, p < 0.01). Four cases of benign vertebral fractures were misdiagnosed as being malignant when b values of 0 s/mm² and 100 s/mm² were used. Conclusions When DWI with multiple b values is used to differentiate benign from malignant vertebral compression fractures, b values within the range of around 300 s/mm² are recommended, taking into account both SNR and diffusion weighting of water molecules.     

Diffusion-weighted MR imaging of pleural fluid: differentiation of transudative vs exudative pleural effusions

The aim of this study was to evaluate the ability of diffusion-weighted MRI in differentiating transudative from exudative pleural effusions. Fifty-seven patients with pleural effusion were studied. Diffusion-weighted imaging (DWI) was performed with an echo-planar imaging (EPI) sequence (b values 0, 1000 s/mm²) in 52 patients. The apparent diffusion coefficient (ADC) values were reconstructed from three different regions. Subsequently, thoracentesis was performed and the pleural fluid was analyzed. Laboratory results revealed 20 transudative and 32 exudative effusions. Transudates had a mean ADC value of 3.42±0.76×10^–3 mm²/s. Exudates had a mean ADC value of 3.18±1.82×10^–3 mm²/s. The optimum cutoff point for ADC values was 3.38×10^–3 mm²/s with a sensitivity of 90.6% and specificity of 85%. A significant negative correlation was seen between ADC values and pleural fluid protein, albumin concentrations and lactate dehydrogenase (LDH) measurements (r=–0.69, –0.66, and –0.46, respectively; p<0.01). The positive predictive value, negative predictive value, and diagnostic accuracy of ADC values were determined to be 90.6, 85, and 88.5%, respectively. The application of diffusion gradients to analyze pleural fluid may be an alternative to the thoracentesis. Non-invasive characterization of a pleural effusion by means of DWI with single-shot EPI technique may obviate the need for thoracentesis with its associated patient morbidity.