A preliminary study of blood-oxygen-level-dependent MRI in patients with chronic kidney disease.

BACKGROUND: Blood-oxygen-level-dependent (BOLD) magnetic resonance imaging (MRI) can provide regional measurements of oxygen content using deoxyhemoglobin paramagnetic characteristics. The apparent relaxation rate or R2*(=1/T2*) can be determined from the slope of log (intensity) versus echo time and is directly proportional to the tissue content of deoxyhemoglobin. Thus, as the level of deoxyhemoglobin increases, T2* will decrease, leading to an increase in R2*. Chronic kidney disease (CKD) can affect oxygenation levels in renal parenchyma, which influences the clinical course of the disease. The goal of this study was to detect and assess renal oxygenation levels in CKD using BOLD MRI. METHODS: Fifteen healthy subjects and 11 patients with CKD underwent a renal scan using multigradient-recalled-echo sequence with eight echoes. R2* (1/s) of the renal cortex and medulla was measured on BOLD images. Of the 11 patients, nine had biopsy-proven chronic glomerulonephritis, and two had a similar diagnosis based on clinical symptoms and investigations. RESULTS: Mean medullary R2* (MR2*) and cortex R2* (CR2*) levels were significantly higher in patients (22 kidneys, MR2*=24.79±4.84 s(-1), CR2*=18.97±2.72 s(-1)) than in controls (30 kidneys, MR2*=19.98±1.19 s(-1), CR2*=16.03±1.23 s(-1)) (P<.01), and MR2* was increased more than CR2*. Medullary to cortical R2* ratios (MCR2*) of patients were significantly increased when compared with those of controls (P<.01). In the patient group, estimated glomerular filtration rate levels were greater than or equal to 60 ml/min/1.73 m(2) in six patients (12 kidneys), whose MR2* and CR2* were also significantly higher than those of controls (P<.01). Serum creatinine levels were normal in seven patients (14 kidneys), whose MR2*, CR2* and MCR2* were also higher than those of controls (P<.01). CONCLUSIONS: BOLD MRI can be used to evaluate changes in renal oxygenation in CKD, suggesting that it has the potential to be an excellent noninvasive tool for the evaluation of renal function.

Cerebrospinal fluid dynamics in Chiari malformation associated with syringomyelia / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>About 50% - 70% of patients with Chiari malformation I (CMI) presented with syringomyelia (SM), which is supposed to be related to abnormal cerebrospinal fluid (CSF) flow around the foramen magnum. The aim of this study was to investigate the cerebrospinal fluid dynamics at levels of the aqueduct and upper cervical spine in patients with CMI associated with SM, and to discuss the possible mechanism of formation of SM.</p><p><b>METHODS</b>From January to April 2004, we examined 10 adult patients with symptomatic CMI associated with SM and 10 healthy volunteers by phase-contrast MRI. CSF flow patterns were evaluated at seven regions of interest (ROI): the aqueduct and ventral and dorsal subarachnoid spaces of the spine at levels of the cerebellar tonsil, C2 - 3, and C5 - 6. The CSF flow waveforms were analyzed by measuring CSF circulation time, durations and maximum velocities of cranial- and caudal-directed flows, and the ratio between the two maximum velocities. Data were analyzed by t test using SPSS 11.5.</p><p><b>RESULTS</b>We found no definite communication between the fourth ventricle and syringomyelia by MRI in the 10 patients. In both the groups, we observed cranial-directed flow of CSF in the early cardiac systolic phase, which changed the direction from cranial to caudal from the middle systolic phase to the early diastolic phase, and then turned back in cranial direction in the late diastolic phase. The CSF flow disappeared at the dorsal ROI at the level of C2 - 3 in 3 patients and 1 volunteer, and at the level of C5 - 6 in 6 patients and 3 volunteers. The durations of CSF circulation at all the ROIs were significantly shorter in the patients than those in the healthy volunteers (P = 0.014 at the midbrain aqueduct, P = 0.019 at the inferior margin of the cerebellar tonsil, P = 0.014 at the level of C2 - 3, and P = 0.022 at the level of C5 - 6). No significant difference existed between the two groups in the initial point and duration of the caudal-directed CSF flow during a cardiac cycle at all the ROIs. The maximum velocities of both cranial- and caudal-directed CSF flows were significantly higher in the patients than those in the volunteers at the aqueduct (P = 0.018 and P = 0.007) and ventral ROI at the inferior margin of the cerebellar tonsil (P < 0.001 and P = 0.002), as so did the maximum velocities of the caudal-directed flow in the ventral and dorsal ROIs at the level of C2 - 3 (P = 0.004; P = 0.007).</p><p><b>CONCLUSIONS</b>The direction of CSF flow changes in accordance with cardiac cycle. The syringomyelia in patients with CMI may be due to the decreased circulation time and abnormal dynamics of the CSF in the upper cervical segment. The decompression of the foramen magnum with dural plasty is an alternative for patients with CMI associated with SM.</p>

MRI diagnosis of Hirayama disease / 中华放射学杂志

Objective To investigate the dynamic changes of the spinal cord during neck flexion in Hirayama disease for diagnosis.Methods MRI examinations in neutral neck position and a fully flexed neck position were performed on 18 cases of Hirayama disease and 31 young normal control subjects.We measured an antero-posterior diameter(APD)and transverse diameter(TD)of the cervical cord at the superior margin of the C6 vertebral body for each position,and investigate the dynamic changes.The different in frequency of these findings between the control and patient groups was examined by means of the x~2 test.The group means were compared by independent-sample t-test.Significance was defined as P