A comparison of arterial spin labeling perfusion MRI and DCE-MRI in human prostate cancer.

Perfusion MRI has the potential to provide pathophysiological biomarkers for the evaluating, staging and therapy monitoring of prostate cancer. The objective of this study was to explore the feasibility of noninvasive arterial spin labeling (ASL) to detect prostate cancer in the peripheral zone and to investigate the correlation between the blood flow (BF) measured by ASL and the pharmacokinetic parameters K(trans) (forward volume transfer constant), kep (reverse reflux rate constant between extracellular space and plasma) and ve (the fractional volume of extracellular space per unit volume of tissue) measured by dynamic contrast-enhanced (DCE) MRI in patients with prostate cancer. Forty-three consecutive patients (ages ranging from 49 to 86 years, with a median age of 74 years) with pathologically confirmed prostate cancer were recruited. An ASL scan with four different inversion times (TI = 1000, 1200, 1400 and 1600 ms) and a DCE-MRI scan were performed on a clinical 3.0 T GE scanner. BF, K(trans), kep and ve maps were calculated. In order to determine whether the BF values in the cancerous area were statistically different from those in the noncancerous area, an independent t-test was performed. Spearman's bivariate correlation was used to assess the relationship between BF and the pharmacokinetic parameters K(trans), kep and ve. The mean BF values in the cancerous areas (97.1 ± 30.7, 114.7 ± 28.7, 102.3 ± 22.5, 91.2 ± 24.2 ml/100 g/min, respectively, for TI = 1000, 1200, 1400, 1600 ms) were significantly higher (p < 0.01 for all cases) than those in the noncancerous regions (35.8 ± 12.5, 42.2 ± 13.7, 53.5 ± 19.1, 48.5 ± 13.5 ml/100 g/min, respectively). Significant positive correlations (p < 0.01 for all cases) between BF and the pharmacokinetic parameters K(trans), kep and ve were also observed for all four TI values (r = 0.671, 0.407, 0.666 for TI = 1000 ms; 0.713, 0.424, 0.698 for TI = 1200 ms; 0.604, 0.402, 0.595 for TI = 1400 ms; 0.605, 0.422, 0.548 for TI = 1600 ms). It can be seen that the quantitative ASL measurements show significant differences between cancerous and benign tissues, and exhibit strong to moderate correlations with the parameters obtained using DCE-MRI. These results show the promise of ASL as a noninvasive alternative to DCE-MRI.

A study on small-world brain functional networks altered by postherpetic neuralgia.

Understanding the effect of postherpetic neuralgia (PHN) pain on brain activity is important for clinical strategies. This is the first study, to our knowledge, to relate PHN pain to small-world properties of brain functional networks. Functional magnetic resonance imaging (fMRI) was used to construct functional brain networks of the subjects during the resting state. Sixteen patients with PHN pain and 16 (8 males, 8 females for both groups) age-matched controls were studied. The PHN patients exhibited decreased local efficiency along with non-significant changes of global efficiency in comparison with the healthy controls. Moreover, regional nodal efficiency was found to be significantly affected by PHN pain in the areas related to sense (postcentral gyrus, inferior parietal gyrus and thalamus), memory/affective processes (parahippocampal gyrus) and emotional activities (putamen). Significant correlation (p<0.05) was also found between the nodal efficiency of putamen and pain intensity in PHN patients. Our results suggest that PHN modulates the local efficiency, and the small-world properties of brain networks may have potentials to objectively evaluate pain information in clinic.

Effect of iodinated contrast media on renal function evaluated with dynamic three-dimensional MR renography.

PURPOSE: To assess the hemodynamic effect of iodinated contrast media (CM) on glomerular filtration rate (GFR) by using dynamic three-dimensional magnetic resonance (MR) renography in a rabbit model. MATERIALS AND METHODS: This study was approved by the university animal care and use committee. Twelve healthy male New Zealand rabbits (body mass range, 2.5-3.0 kg) were included. Two of them were sacrificed before MR examination to obtain renal histologic samples as controls. The other ten rabbits completed 4-minute dynamic contrast material-enhanced MR imaging 24 hours before and 20 minutes after intravenous injection of iopamidol (370 mg of iodine per milliliter) at a dose of 6 mL per kilogram of body weight. Blood volume (V(B)), GFR, and tubule volume (V(E)) of the renal cortex were determined with a two-compartment kinetic model. Maximum upslope (K(m)), peak concentration (P(c)), and initial 60-second area under the curve (IAUC) of the whole kidney renogram curve were measured with semiquantitative analysis. The self-control data were compared by using the Student paired t test. RESULTS: Iopamidol significantly decreased cortical V(B) (mean, 42.53% ± 10.16 [standard deviation] before CM administration vs 27.23% ± 16.13 after CM administration; P < .01), V(E) (mean, 22.40% ± 11.69 before CM administration vs 11.51% ± 6.58 after CM administration; P < .01), and GFR (mean, 31.92 mL/100 g per minute ± 12.52 before CM administration vs 21.48 mL/100 g per minute ± 10.02 after CM administration; P < .01). Results of whole-kidney renogram analysis showed a decrease in K(m), P(c), and IAUC caused by iopamidol administration. CONCLUSION: High-dose iopamidol resulted in a marked decrease in renal function, which could be detected at dynamic three-dimensional MR renography.

Low-contrast agent dose dual-energy CT monochromatic imaging in pulmonary angiography versus routine CT.

OBJECTIVE: This study aimed to retrospectively evaluate the feasibility and reliability of low-contrast agent dose dual-energy computed tomography (DECT) monochromatic imaging in pulmonary angiography. METHODS: Computed tomography pulmonary angiography was performed in 86 patients, 41 in 120-kVp computed tomography (CT) and 45 in DECT with low-contrast agent dose. The images in DECT were reconstructed at optimal kiloelectron-voltage (keV), demonstrating the best contrast-to-noise ratio between pulmonary artery and soft tissue, and at 70 keV. Image quality was compared by quantitative and subjective indexes. The radiation doses were recorded. RESULTS: Compared with 120-kVp CT, optimal keV showed superior quantitative indexes with inferior subjective image quality, whereas 70 keV demonstrated no statistical difference in quantitative indexes with superior subjective image quality. All suspicious pulmonary embolisms in DECT were diagnosed confidently by combination of 2 kinds of monochromatic imaging. The radiation dose in DECT is almost twice as 120-kVp CT. CONCLUSIONS: Low-contrast agent dose DECT monochromatic imaging in pulmonary angiography accommodates superior intravascular enhancement and contrast in pulmonary arteries, and improves diagnostic confidence with compatible radiation dose.

Quantitative assessment of acute kidney injury by noninvasive arterial spin labeling perfusion MRI: a pilot study.

The kidneys are essential for maintaining homeostasis, are responsible for the reabsorption of water, glucose and amino acids, and filter the blood by removing waste. Acute kidney injury (AKI) is a syndrome characterized by the rapid loss of renal excretory function and the accumulation of end metabolic products of urea and creatinine. AKI is associated with the later development of chronic kidney disease and end-stage kidney disease, and may eventually be fatal. Early diagnosis of AKI and assessments of the effects of treatment, however, are challenging. The pathophysiological mechanism of AKI is thought to be the imbalance between oxygen supply and demand in the kidneys. We have assessed the ability of arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI), without the administration of contrast media, to quantify renal blood flow (RBF) non-invasively. We found that RBF was significantly lower in AKI patients than in healthy volunteers. These results suggest that ASL perfusion MRI, a noninvasive measurement of RBF, may be useful in the early diagnosis of AKI.

Quantitative cerebral blood flow mapping and functional connectivity of postherpetic neuralgia pain: a perfusion fMRI study.

This article investigates the effects of postherpetic neuralgia (PHN) on resting-state brain activity utilizing arterial spin labeling (ASL) techniques. Features of static and dynamic cerebral blood flow (CBF) were analyzed to reflect the specific brain response to PHN pain. Eleven consecutive patients suffering from PHN and 11 age- and gender-matched control subjects underwent perfusion functional magnetic resonance imaging brain scanning during the resting state. Group comparison was conducted to detect the regions with significant changes of CBF in PHN patients. Then we chose those regions that were highly correlated with the self-reported pain intensity as "seeds" to calculate the functional connectivity of both groups. Absolute CBF values of these regions were also compared across PHN patients and control subjects. Significant increases in CBF of the patient group were observed in left striatum, right thalamus, left primary somatosensory cortex (S1), left insula, left amygdala, left primary somatomotor cortex, and left inferior parietal lobule. Significant decreases in CBF were mainly located in the frontal cortex. Regional CBF in the left caudate, left insula, left S1, and right thalamus was highly correlated with the pain intensity, and further comparison showed that the regional CBF in these regions is significantly higher in PHN groups. Functional connectivity results demonstrated that the reward circuitry involved in striatum, prefrontal cortex, amygdala, and parahippocampal gyrus and the circuitry among striatum, thalamus, and insula were highly correlated with each element in PHN patients. In addition, noninvasive brain perfusion imaging at rest may provide novel insights into the central mechanisms underlying PHN pain.

Hemodynamic effects of furosemide on renal perfusion as evaluated by ASL-MRI.

RATIONALE AND OBJECTIVES: The aim of this study was to investigate the short-term effects of furosemide on renal perfusion by using arterial spin labeling (ASL) magnetic resonance imaging. MATERIALS AND METHODS: Eleven healthy human subjects were enrolled in the study. The measurement of renal blood flow (RBF) was performed by applying an ASL technique with flow-sensitive alternating inversion recovery spin preparation and a single-shot fast spin-echo imaging strategy on a 3.0-T magnetic resonance scanner. For all subjects, the ASL magnetic resonance images were obtained before agent injection as a baseline scan. Then 20 mg of furosemide was injected intravenously. Postfurosemide ASL images were acquired following administration to evaluate the renal hemodynamic response. RESULTS: Postinjection scans showed that cortical RBF decreased from 366.59 ± 41.19 mL/100 g/min at baseline to 314.33 ± 48.83 mL/100 g/min at 10 minutes after the administration of furosemide (paired t test, P = .04 vs baseline), and medullary RBF decreased from 118.59 ± 24.69 mL/100 g/min at baseline to 97.38 ± 18.40 mL/100 g/min at 10 minutes after the administration of furosemide (paired t test, P = .01 vs baseline). There was a negative correlation between the furosemide-induced diuretic effect and the reduction of RBF (Spearman's r = -0.61). CONCLUSIONS: The dominant hemodynamic effect of furosemide on the kidney is associated with a decrease in both cortical and medullary blood perfusion. Furthermore, the quantitative ASL technique may provide an alternative way to noninvasively monitor the change in renal function due to furosemide administration.

Measuring diagnostic accuracy of imaging parameters in pelvic lipomatosis.

OBJECTIVES: To study whether the individual radiological findings can help predict diagnosis of pelvic lipomatosis (PL) or, specifically appreciate its progression. METHODS: Data from 32 clinically proven cases of PL and 25 controls were collected. Two reviewers were recruited for a blinded evaluation, image features were recorded in terms of: (1) bladder shape; (2) bladder-rectosigmoid morphological indexes including ratio of superior-inferior to anterior-posterior length of bladder (SI/AP), angle between anterior and posterior wall (AAP), relative length of posterior urethra (rLPU), angle between bladder and seminal vesicle (ABS) and rectosigmoid morphological index (RMI); (3) secondary complications. Results were evaluated by an unpaired t test and ROC analysis. RESULTS: The sensitivity and specificity were 40.6% and 100% for pear and banana-shaped bladder, 62.5% and 100% for SI/AP, 40.6% and 100% for AAP, 62.5% and 100% for ABS, 78.1% and 72% for rLPU, 59.4% and 96% for RMI, respectively. These radiological findings partially correlated with the severity of disease weighted by hydronephrosis and treatment grade. Image analysis demonstrated high prevalence of glandular cystitis (100%) and hydronephrosis (73.4%). CONCLUSION: We conclude that PL is a progressive disease involving multiple pelvic organs with high prevalence of intractable cystitis and hydronephrosis. The imaging characteristics can help predict diagnosis and, specifically appreciate progression.

The serial effect of iodinated contrast media on renal hemodynamics and oxygenation as evaluated by ASL and BOLD MRI.

Contrast-induced nephropathy is a prevalent cause of renal failure, and the mechanisms underlying this injury are not fully understood. We utilized noninvasive functional MRI in order to determine the serial effect of a single administration of iodinated contrast media (CM) on renal hemodynamics and oxygenation. Fifteen rabbits were randomized to receive an intravenous injection of CM (i.e. iopamidol-370; 6 ml kg(-1) body weight) or an equivalent amount of 0.9% saline. Both arterial spin-labeling and blood oxygen level-dependent imaging sequences were performed at 24 h before and at intervals of 1, 24, 48 and 72 h after injection to obtain serial renal blood flow (RBF) and relative spin-spin relaxation rate (R(2)*). Results showed that, in the iopamidol group, the mean cortical RBF decreased at 1 h (p = 0.04 vs baseline), reached its minimum at 24 h (p = 0.01) and gradually returned to baseline by 48 h (p = nonsignificant, NS). The outer medullary RBF decreased to its minimum by 24 h (p = 0.00) and remained less than baseline until 72 h. R(2)* in inner stripes was dramatically increased at 1 h (p = 0.00), remained elevated at 24 h (p = 0.05), but returned to baseline by 48 h (p = NS). R(2)* values within the cortex and outer stripes and inner medulla were slightly increased, but the changes did not reach a statistical significance (p = NS). Saline did not produce positive change in either RBF or R(2)* within different compartments of the kidney. We conclude that iopamidol is associated with a relatively longer-term hypoperfusion in whole kidney and decreased oxygen level in the inner stripes of the outer medulla.

Feasibility study of exploring a T1-weighted dynamic contrast-enhanced MR approach for brain perfusion imaging.

PURPOSE: To investigate the feasibility of T(1) -weighted dynamic contrast-enhanced (DCE) MRI for the measurement of brain perfusion. MATERIALS AND METHODS: Dynamic imaging was performed on a 3.0 Tesla (T) MR scanner by using a rapid spoiled-GRE protocol. T(1) measurement with driven equilibrium single pulse observation of T(1) (DESPOT1) was used to convert the MR signal to tracer concentration. Cerebral perfusion maps were obtained by using an improved gamma-variate model in 10 subjects and compared with those with arterial spin label (ASL) approach. RESULTS: The cerebral blood volume (CBV) values were calculated as 4.74 ± 1.09 and 2.29 ± 0.58 mL/100 g in gray matter (GM) and whiter matter (WM), respectively. Mean transit time (MTT) values were 6.15 ± 0.59 s in GM and 6.96 ± 0.79 s in WM. The DCE values for GM/WM cerebral blood flow (CBF) were measured as 53.41 ± 9.23 / 25.78 ± 8.91 mL/100 g/min, versus ASL values of 49.05 ± 10.81 / 23.00 ± 5.89 mL/100 g/min for GW/WM. Bland-Altman plot revealed a small difference of CBF between two approaches (mean bias = 3.83 mL/100 g/min, SD = 11.29). There were 6 pairs of samples (5%, 6/120) beyond the 95% limits of agreement. The correlation plots showed that the slop of Y (CBF_(_DCE)) versus X intercept (CBF_(_ASL)) is 0.95 with the intercept of 4.53 mL/100 g/min (r = 0.74; P < 0.05). CONCLUSION: It is feasible to evaluate the cerebral perfusion by using T(1)-weighted DCE-MRI with the improved kinetic model.

Time course study on the effects of iodinated contrast medium on intrarenal water transport function using diffusion-weighted MRI.

PURPOSE: To assess the effects of intravenous-injected iodinated contrast medium (CM) on intrarenal water diffusion using noninvasive diffusion-weighted MRI (DW-MRI). MATERIALS AND METHODS: Ten New Zealand White rabbits were randomized to receive a 6 mL/kg body weight intravenous injection of clinically used iopamidol-370 (n = 7) or an equivalent amount of 0.9% physiological saline (n = 3). A sequential DW-MRI was performed to estimate the intrarenal apparent diffusion coefficient (ADC) at 24 h before and 1 h, 24 h, 48 h, and 72 h after administration. RESULTS: Iopamidol produced a progressive ADC reduction in inner stripes of the renal outer medulla (IS) by 13.92% (P = 0.05) at 1 h, 17.52% (P = 0.02) at 24 h, 20.23% (P = 0.01) at 48 h and 16.31% (P = 0.04) at 72 h after injection. Cortical ADC was decreased by 14.14% (P = 0.01) at 48 h and 14.12% (P = 0.01) at 72 h after injection. Iopamidol produced slight decrease of ADCs in outer stripes of the outer medulla (OS) and inner medulla (IM) of kidney but without statistical difference. In control group, no significant ADC changes was observed in each anatomic compartment due to saline injection (P > 0.05). CONCLUSION: As demonstrated by DW-MRI, intravenous iopamidol injection resulted in a successive reduction of intrarenal water diffusion, particularly in IS of kidney. This MR technique may be used as a noninvasive tool to perform a time course study of the pathogenesis associated with contrast-induced nephropathy (CIN).

Preliminary study of whole-body diffusion-weighted imaging in detecting pulmonary metastatic lesions from clear cell renal cell carcinoma: comparison with CT.

BACKGROUND: Whole-body diffusion-weighted imaging (DWI) has been widely used in detecting malignant metastases, including pulmonary metastases. PURPOSE: To evaluate the possible utility of whole-body DWI in detecting pulmonary metastases of patients with clear cell renal cell carcinoma (ccRCC) and compare the exact differences between MR and CT in detecting pulmonary lesions. MATERIAL AND METHODS: Whole-body DWI and chest CT examinations were performed on nine consecutive patients (8 men and 1 woman) with histologically confirmed ccRCC and possible metastatic lesions before chemotherapy. RESULTS: CT and MR demonstrated pulmonary metastases in seven patients and no metastatic lesions in two patients. The numbers of pulmonary metastases detected on CT, DWI-only, T1WI-only and DWI in combination with T1WI were 83, 35, 34 and 39, respectively. Metastases with a diameter above 1.0 cm could all be detected by DWI and a diameter above 0.7 cm could all be detected by DWI in combination with T1WI. Significant differences were obtained both for correlationship between diameter and detection rates of DWI and T1WI by using Spearman rank correlation analysis. CONCLUSION: Although MR cannot be considered a replacement for CT in pulmonary metastases from ccRCC, whole-body DWI, with the combination of T1 dual echo, might be helpful for the evaluation of tumor response to chemotherapy in the follow-up of patients when the diameter of the pulmonary metastases is over 1.0 cm.

The appearance of ADCs in the non-affected areas of the patients with MELAS.

INTRODUCTION: The exact mechanism of the mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) remain unclear. Diffusion-weighted imaging (DWI) is a magnetic resonance (MR) imaging technique for studying the pathophysiologic change of the MELAS. The purpose of the study is to see whether the apparent diffusion coefficient (ADC) of MELAS in the non-affected areas is different from the ADC of the normal subjects and to speculate the pathophysiological mechanisms of the MELAS. METHODS: Sixteen cases of MELAS were retrospectively analyzed. Thirty healthy subjects were chosen to constitute the control group. All of them were performed on the 3.0T whole-body MR scanner with axial view T2 fluid attenuated inversion recovery (flair), T2-weighted imaging, T1flair, and DWI. An ADC map was reconstructed in the workstation. Two to five regions of interest were put in the non-affected frontal lobe and basal ganglia. All data took statistical analysis. RESULTS: There were significant differences between the ADC of the patients with MELAS and the controls in the non-affected areas, including the superior frontal gyrus, precentral gyrus, corpus striatum, thalamus, and white matter of the semi-oval centrum. CONCLUSION: ADCs in the non-affected areas of the patients with MELAS are higher than those of the normal subjects. Pathological changes take place in the non-affected areas of the patients with MELAS.

Blood oxygen level-dependent MRI for the monitoring of neoadjuvant chemotherapy in breast carcinoma: initial experience.

PURPOSE: To determine the feasibility of using R2* map MRI for pretreatment diagnosis and monitoring of tumor response to neoadjuvant chemotherapy (NAC) in patients with breast cancer. MATERIAL AND METHODS: Twenty-eight women with breast cancer, as evidenced by pathology, underwent MR imaging prior to and after chemotherapy. All patients were examined by conventional MRI and R2* map imaging. Subjects were divided into major histological response (MHR) and non-major histological response (NMHR) groups. Mean R2* values of cancerous and normal glandular tissues were measured before and following NAC. Differences in R2* and ΔR2*% values between these two groups were compared with paired or independent t tests. The relationship between ΔR2*% and histological response was examined using Spearman's correlation test. RESULTS: Before NAC, the average R2* values in carcinoma were lower than in normal glandular tissue (P<.05). After two to four cycles of NAC, the R2* values in carcinoma were increased (P<.05 ), but this change was not significant in normal glandular tissue. After NAC, ΔR2*% was significantly higher in MHR as compared to NMHR (P<.05). The ΔR2*% correlated with the histological response (r=0.581, P<.01). CONCLUSION: In women undergoing NAC for breast cancer treatment, R2* and ΔR2*% appear to provide predictive information of tumor response which is probably associated with changes in tumor angiogenesis and tissue oxygenation. R2* map imaging of breasts may therefore be useful in monitoring tumor response to NAC.

[Small hepatocellular carcinoma in patients with hepatitis B-induced cirrhosis: a comparison between MRI and MDCT].

OBJECTIVE: To compare efficacy of plain and contrast enhancement MRI (1.5T or 3T) and dynamic contrast enhanced multidetector CT (MDCT, 16- or 64 -slice) for the detection of small hepatocellular carcinoma (HCC) in patients with hepatitis B-induced cirrhosis. METHODS: A total of 21 patients (18 men, 3 women; age range, 44-74 years) with 22 small HCC and liver cirrhosis were enrolled, all having undergone MDCT and MRI within one month. The diagnosis of small HCC was established at surgical resection (n=4), percutaneous biopsy (n=1), with positive tumor staining at intervention or from combined clinical data, typical imaging features and follow-up for a period of at least one year. Triple-phase or dual-phase dynamic contrast enhancement was performed on a 16- or 64-slice MDCT. MRI sequences included transverse T1-weighed images acquired as fast spoiled gradient (FSPGR) in-phase and out-of-phase dual-echo, transverse T2-weighed images with respiratory triggering acquired as fat-suppressed fast spin echo (FSE) or fast recovery fast spin echo (FRFSE), and breath-hold coronal T2-weighed images acquired as single shot fast spin echo (SSFSE) or fast imaging employing steady-state acquisition (FIESTA). CT and MRI observers independently analyzed each image in random order and marked each lesion detected with a score, ranking from 1 to 5 (1 definitely benign, 2 possibly benign, 3 undetermined, 4 possible HCC, and 5 definite HCC), then receiver operating characteristic (ROC) curve and Chi-square analysis were adopted to compare the efficacy for MDCT and MRI imaging. RESULTS: Although no significant difference was demonstrated at the comparison of sensitivity and specificity (sensitivity and specificity of MDCT: 70%, 50%; sensitivity and specificity of MRI 86.36%, 100%; sensitivity χ2=0.835, P=0.360; specificity χ2=1.379, P=0.240), the Az (area under the ROC curve) for MRI imaging (mean, 0.974) was much higher than that for MDCT (mean, 0.795) with significant difference (P<0.05). CONCLUSION: MRI imaging shows better diagnostic accuracy for the detection of small HCC in patients with hepatitis B-induced cirrhosis and is recommended to improve the detection and diagnosis.

Comparison of diffusion-weighted with T2-weighted Imaging for detection of small hepatocellular carcinoma in cirrhosis: preliminary quantitative study at 3-T.

RATIONALE AND OBJECTIVES: To compare diffusion-weighted (DW) with standard T2-weighted imaging for quantitative evaluation of small hepatocellular carcinoma (HCC) in cirrhosis. MATERIALS AND METHODS: Fourteen patients (all men; mean age, 58.6 years; age range, 45-69 years) with 22 small HCCs (<3 cm and >1 cm in diameter) in cirrhosis were included in the study. DW imaging with breath-hold single-shot echo planar imaging (b = 0, 800 seconds/mm(2)) and T2-weighted imaging with respiratory triggering fat-suppressed fast spin-echo sequence were performed on a 3-T magnetic resonance unit using an eight-channel torso phased-array coil. The signal intensity (SI) of HCC and liver were measured at workstation. Contrast-to-noise ratio (CNR), contrast ratio (CR, SI(lesion)/SI(liver)), and apparent diffusion coefficient (ADC) values were calculated. CNRs and CRs obtained with DW and T2-weighted images, and ADCs of HCC and liver were compared using nonparametric tests. RESULTS: Two lesions were excluded because of artifacts on DW images. Thus 20 lesions were analyzed. The CNRs obtained with T2-weighted images (27.12 + or - 21.12) were significantly higher (P = .02) than those with DW images (17.52 + or - 13.50). There were no significant difference between the CRs obtained with T2-weighted images (1.83 + or - 0.56) and DW images (2.01 + or - 0.67). There were no significant difference between the mean ADCs of HCC (1.22 x 10(-3) mm(2)/second + or - 0.24) and the cirrhotic liver (1.17 x 10(-3) mm(2)/second + or - 0.17), either. CONCLUSION: DW imaging with high b value was not superior to standard T2-weighted imaging in terms of lesion conspicuity of small HCC in cirrhosis.

CT angiography of pulmonary embolism using a 64 slice multi-detector scanner.

BACKGROUND: Multi-detector computed tomography (MDCT) has already been the first line investigation method for diagnosis of pulmonary embolism (PE). Reducing the amount of contrast medium used during CT scanning could decrease the incidental rate of adverse reactions. Our study amied to evaluate the image quality of pulmonary arteries using 64 slice multi-detector CT with small volumes of contrast media injection. METHODS: Forty nonconsecutive patients without PE or other lung diseases were randomly assigned to two groups. Group A underwent CT scanning with 16 x 1.25 mm collimation and a 70 ml contrast injection, while group B had CT with 64 x 0.625 mm collimation and 20 ml of contrast injection. Two readers independently depicted the segmental and subsegmental pulmonary arteries. Reasons we could not analyze the pulmonary artery or that led to misdiagnosis of pulmonary embolism were evaluated, including the degree of contrast enhancement of the main pulmonary artery, and factors that caused misdiagnosis of PE (flow-related artifacts, partial volume artifact, beam-hardening artifacts and enhancement of pulmonary vein). The independent samples t-test, Mann-Whitney U test and Pearson chi-square test were applied. RESULTS: There were no significant differences in image quality of segmental and subsegmental arteries between the two groups. No significant difference was found for factors that made pulmonary arteries non-analyzable or in the misdiagnosis of PE, except the degree of contrast enhancement. CONCLUSION: 64 x 0.625 mm collimation with 20 ml contrast injection could depict the pulmonary arteries well.

Evaluation of renal oxygenation in rat by using R2' at 3-T magnetic resonance: initial observation.

RATIONALE AND OBJECTIVES: We sought to initially evaluate the feasibility of R2' on a 3-T magnetic resonance (MR) scanner for assessment of renal oxygenation changes following administration of furosemide in rats. MATERIALS AND METHODS: Eight intact male Wistar rats were involved in experimental group. The experiment was performed at a 3-T MR scanner using a multiple gradient-echo (mGRE) sequence for R2* map and a multiecho fast spin-echo (FSE) sequence for R2 map. R2' values of cortex and medulla were calculated using the equation R2* = R2 + R2'. The values of R2 and R2* were measured and R2' was calculated before and after administration of furosemide, and the changes (delta values) were calculated. RESULTS: Both R2* and R2 values decreased significantly after administration of furosemide (P < .001) in both the cortex and medulla. DeltaR2* in the medulla was significantly higher than in the cortex (P < .05). DeltaR2 was not significantly different between the cortex and medulla (P > .05). The baseline R2' value was 12.13 +/- 0.59 1/s in the cortex and 19.52 +/- 3.44 1/s in the medulla. R2' value decreased significantly in the medulla after administration of furosemide (P < .05), but there was no significant difference in the cortex before and after administration of furosemide (P > .05). CONCLUSION: R2' may be more appropriate than R2* to indicate the change of oxygenation after administration of furosemide in intact rats at 3-T MR. Further studies are needed for both intact animals and experimental models in comparison with non-MR imaging methods to validate this initial observation.

Relationship between the renal apparent diffusion coefficient and glomerular filtration rate: preliminary experience.

PURPOSE: To investigate the relationship between ADC values measured by diffusion-weighted MRI (DWI) and the split glomerular filtration rate (GFR). MATERIALS AND METHODS: DWI (b = 0 and 500 seconds/mm(2)) was performed with a 1.5 T MR unit in 55 patients. The ADCs were calculated with ROIs positioned in the renal parenchyma, and the split GFRs were measured by (99)Tc(m)-DTPA scintigraphy using Gates' method. The 110 kidneys were divided into four groups: normal renal function (GFR 40 mL x minute(-1)), mild renal impairment (40 > GFR > or = 20 mL x minute(-1)), moderate renal impairment (20 > GFR > or = 10 mL x minute(-1)), and severe renal impairment (GFR < 10 mL x minute(-1)). The renal ADCs between four groups were statistically compared by analysis of variance (ANOVA), and the relationship between ADCs and GFR was examined using Pearson's correlation test. RESULTS: The mean renal ADCs of the four groups were 2.87 +/- 0.11, 2.55 +/- 0.17, 2.29 +/- 0.10, and 2.20 +/- 0.11 x 10(-3)mm(2)/second, respectively. There was a statistically significant difference in renal ADCs among the four groups (P < 0.001). There was a positive correlation between the ADCs and split GFR (r = 0.709). CONCLUSION: The ADCs were significantly lower in impaired kidneys than in normal kidneys, and there was a positive correlation between the ADCs and GFR.

[Analysis of the clinical information of 1,066 cases undergoing prostate magnetic resonance examination].

OBJECTIVE: To evaluate the variation of clinical data and referred purpose of prostate magnetic resonance (MR) examination in the past 12 years in Peking University First Hospital. METHODS: One thousand and sixty-six patients underwent prostate MR examination (1,296 exams) from May 1992 to Sept. 2004. The clinical data of the patients were retrospectively analyzed. The number of patients was counted and three groups were classified (diagnosing group, staging group and follow-up group) according to the purpose of prostate MR examination per year. For the diagnosing group, the clinical data of patient's age, symptom, level of serum prostate specific antigen (PSA), and the result of ultrasound or digital rectal examination (DRE) were evaluated. RESULTS: (1)The number of patients increased year by year in the past 12 years, and the majority of the increased patients required differential diagnosis. (2) Diagnosing group: the percentage of patients with the symptom of BPH increased year by year. The average level of serum PSA dropped and the percentage of patients with elevated PSA or with nodules detected by ultrasound or DRE referred for detection of prostate cancer or with the symptom of metastasis decreased. CONCLUSION: With the widespread screening of prostate cancer, more patients of early prostate carcinoma and non-tumoral lesion in prostate gland are examined by MR imaging.