Diffusion-weighted MR imaging of kidneys in healthy volunteers and patients with parenchymal diseases: initial experience

PURPOSE: To prospectively evaluate feasibility of diffusion-weighted (DW) magnetic resonance (MR) imaging in assessment of renal function in healthy volunteers and patients with various renal abnormalities and to prospectively evaluate reproducibility of DW MR imaging in volunteers. MATERIALS AND METHODS: Study protocol was approved by local ethics committee; informed consent was obtained. Eighteen healthy volunteers and 15 patients underwent transverse fat-saturated echo-planar DW MR imaging of the kidneys during normal breathing. Freehand regions of interest were delineated in the cortex and medulla of the kidneys. The following apparent diffusion coefficient (ADC) values were calculated: ADC of all b values (ADC(avg)), ADC of low b values (b = 0, 50, 100 sec/mm2; ADC(low)), and ADC of high b values (b = 500, 750, 1000 sec/mm2; ADC(high)). These values were calculated to differentiate influence of perfusion and diffusion. Reproducibility was assessed by repeating the same protocol in five randomly selected volunteers after 6 months. For statistical analysis, Student t tests were used. RESULTS: In all volunteers, ADC(avg) and ADC(high) were significantly higher in the cortex than in the medulla (P < .001). No difference between the cortex and medulla could be observed for ADC(low). Patients with renal failure had significantly lower ADC(avg) (P < .001, P = .004), ADC(low) (P = .02, P = .03), and ADC(high) (P = .02, P = .04) of cortex and medulla, respectively, than did volunteers. In the patient with pyelonephritis, all ADC values of cortex and medulla were substantially lower compared with the contralateral side, whereas patients with ureteral obstruction showed varying degrees of difference in all ADC values compared with the contralateral side. No statistically significant changes were found in the repeat study of the volunteers. CONCLUSION: DW MR imaging is feasible and reproducible in the assessment of renal function, as shown in our initial experience with a small number of patients and volunteers.     

Contrast-enhanced peripheral MR angiography at 3.0 Tesla: initial experience with a whole-body scanner in healthy volunteers

PURPOSE: To report preliminary experience with contrast-enhanced magnetic resonance angiography (CE-MRA) of the peripheral arteries on a 3.0 T whole-body scanner equipped with a prototype body coil. MATERIALS AND METHODS: Four healthy volunteers were imaged on the 3.0 T system and, for comparative purposes, two of the subjects were also imaged on a commercially available 1.5 T whole-body system. To investigate field strength influence on objective image quality, signal-to-noise (SN) and contrast-to-noise (CN) ratios were calculated for named vessels from the infrarenal aorta to the ankles at both field strengths. Comparable imaging protocols were used at both field strengths. In addition, two reviewers, blinded for field strength, gave subjective image quality scores (three-point scale). RESULTS: SN and CN ratios were approximately equal on both systems (variation < or =9%) for the iliac and proximal upper leg stations. For the popliteal and lower leg stations SN ratios were 36% and 97% higher, and CN ratios were 44% and 127% higher, at 3.0 T. Subjective image quality at 3.0 T was substantially better for the distal upper and lower legs. CONCLUSION: Contrast-enhanced peripheral MRA is possible at 3.0 T when an imaging protocol similar to a current state-of-the-art 1.5 T protocol is used. Objective and subjective image quality at 3.0 T is comparable for the iliac and upper legs but better for the popliteal and lower leg arteries.     

Usefulness of the abduction and external rotation views in shoulder MR arthrography

OBJECTIVE: The purpose of this article is to illustrate the usefulness of the abduction and external rotation position in MR arthrography of the shoulder. CONCLUSION: The use of abduction and external rotation in shoulder MR arthrography can be a helpful tool that complements sequences that use conventional positions for characterizing a variety of abnormal conditions in the shoulder.     

Displaceability of SLAP lesion on shoulder MR arthrography with external rotation position

Objective  

To investigate the usefulness of the external rotation (ER) position on magnetic resonance (MR) arthrography for the diagnosis of superior labral anterior to posterior (SLAP) lesion.     

Bowel MR imaging with oral Gastrografin: an experimental study with healthy volunteers

Our objective was to evaluate Gastrografin for MR bowel imaging. Twenty-three healthy volunteers in two randomised groups received 300 or 400 ml 50% Gastrografin, drunk continuously during 2 and 3 h, respectively. Images were applied during breath-hold in three orthogonal orientations. The balanced fast-field echo (BFFE) and balanced turbo field-echo (BTFE) sequences, with acquisition times from 13 to 25 s, were used before gadolinium (Gd) DTPA implying 1- to 2-mm-thick slices locally or 6-mm-thick slices through the entire gastrointestinal tract. The Gd-enhanced images were performed using a 3D T1-weighted FFE sequence with water selective excitation (Proset). Image quality, including bowel distention, homogeneity of opacification and wall conspicuity, were evaluated by two experienced reviewers, and the adverse reactions were recorded. Very good or excellent distention, homogeneity and wall conspicuity were achieved in the central segments from the ileum to the left colon flexure in 83–96% of cases, due to the adequate contrast media supply in these regions. Distention, homogeneity and delineation were good in the central segments of the remaining bowels. Diarrhoea was a major problem affecting all participants, followed by nausea. Provided that there is modern fast sequential technology, excellent MR imaging of the bowel can be achieved by the oral administration 50% diluted Gastrografin. Further studies are needed to refine the technique and optimise the quantity and concentration of Gastrografin in order to avoid or reduce adverse reactions. Electronic Publication     

Glenohumeral relationships during physiologic shoulder motion and stress testing: initial experience with open MR imaging and active imaging-plane registration.

PURPOSE: To test the hypotheses that open dynamic magnetic resonance (MR) imaging can (a) be used to evaluate and define normal shoulder motion in active joint motion and muscle contraction and (b) be used in conjunction with physical examination. MATERIALS AND METHODS: With an open-configuration, 0.5-T MR imaging system and active image-plane tracking, 10 shoulders were studied in five asymptomatic subjects to establish normal patterns of glenohumeral motion during abduction and adduction and internal and external rotation. Preliminary studies of physical examination during MR imaging, in which a physician examiner applied mechanical force to the humeral head, were also performed. RESULTS: During abduction and adduction and internal and external rotation maneuvers with active subjects muscle contraction, the humeral head remained precisely centered on the glenoid fossa in all asymptomatic subjects, which is in agreement with findings of previous radiographic studies. Application of force to the humeral head by an examiner was associated with as much as 6 mm of anterior translation and 13 mm of posterior translation. CONCLUSION: Dynamic MR imaging of the glenohumeral joint is possible over a wide range of physiologic motion in vertically open systems. Use of an MR tracking coil enabled accurate tracking of the anatomy of interest. These preliminary measurements of normal glenohumeral motion patterns begin to establish normal ranges of motion and constitute a necessary first step in characterizing pathologic motion in patients with common clinical problems such as instability and impingement.     

健康志愿者头部MR弹性成像研究

Objective To evaluate the shear stiffness of brain by MR elastography (MRE) in healthy Chinese volunteers and to assess the association between the cerebral shear stiffness and age. Methods Brain MRE studies were performed on 105 healthy volunteers. The shear stiffness of brain parencham was measured by local frequency estimation (LFE) algorithm. The differences of the shear stiffness between white matter(WM) and grey matter(GM) were analyzed by independent sample t test; the differences of brain parenchyma shear stiffness between male and female were estimated by independent sample t test. Spearman test was used to analyze the correlation between age and the shear stiffness of parenchyma; the volunteers were divided into two groups (age ≤ 40 and age > 40) and the correlation between age and shear stiffness of parencbyma in each group were analyzed separately. Results The shear stiffness of whiter matter [(23.1±5.7) kPa] was higher than that of grey matter[(11.3±2.6) kPa], and the difference was significant (t = 19.34, P < 0.01). In male, the shear stiffness of WM and GM was (23.4±5.8) kPa and (11.4±2.8) kPa respectively; while in female, it was (22.8±5.6) kPa and (11.1±2.5) kPa respectively. No sex differences were found in the stiffness of white matter or gray matter (t = - 0.534, - 0.606, P > 0.05). An age-dependent trend was observed in the stiffness of grey matter(r =0.315, P < 0.01),while not in whiter matter (r = 0.183, P > 0.05). When the shear stiffness of subjects no more than 40 years old was analysed, the age-dependent trend of shear stiffness was found both in white matter and gray matter(r = 0.251,0.235, P < 0.05); While in subjects over 40 years old, the age-dependent rend of shear stiffness was not found in white matter or gray matter(r = 0.181, - 0.001, P > 0.05). Conclusions The shear stiffness of WM is significantly higher than that of GM. No obvious sex difference was found in the stiffness of brain parenchyma. The shear stiffness of GM increases with age; the age-related increase of shear stiffness of WM was only found in subjects under 40 years old.     

健康志愿者头部MR弹性成像研究

目的 应用MR弹性成像(MRE)技术评估健康志愿者脑组织的剪切模量,并了解脑组织剪切模量与年龄间是否存在相关性.方法 选取105名健康志愿者,其中男42名、女63名,行头部MRE检查.通过局部频率估算法(LFE)分别测量志愿者脑灰质与脑白质的剪切模量.采用独立样本t检验评估脑灰质与脑白质剪切模量间是否存在差异,以及脑实质剪切模量是否存在性别差异;应用Spearman相关分析评估剪切模量与年龄是否存在相关性,并将志愿者分为≤40岁组(76名)和>40岁组(29名),分别进行脑实质剪切模量与年龄间的相关性分析.结果 105名健康志愿者脑白质的剪切模量[(23.1±5.7)kPa]高于脑灰质[(11.3±2.6)kPa],两者间差异具有统计学意义(t=19.34,P<0.01).男性志愿者脑白质与脑灰质的剪切模量分别为(23.4±5.8)、(11.4±2.8)kPa,女性志愿者分别为(22.8±5.6)、(11.1±2.5)kPa.男、女志愿者脑组织间剪切模量值差异无统计学意义(t值分别为-0.534、-0.606,P值均>0.05).年龄相关性分析显示,灰质的剪切模量与年龄呈正相关(r=0.315,P<0.01),白质的剪切模量与年龄无相关性(r=0.183,P>0.05);≤40岁组志愿者灰、白质剪切模量与年龄呈正相关(r值分别为0.251、0.235,P值均<0.05),而>40岁组志愿者脑灰、白质剪切模量均与年龄无相关性(r值分别为0.181、-0.001,P值均>0.05).结论 健康志愿者脑白质的剪切模量明显高于脑灰质;脑实质剪切模量男女之间无差别;脑灰质剪切模量随年龄增加而增加.     

Spin-labeling coronary MR angiography with steady-state free precession and radial k-space sampling: initial results in healthy volunteers

The purpose of this study was to prospectively compare free-breathing navigator-gated cardiac-triggered three-dimensional steady-state free precession (SSFP) spin-labeling coronary magnetic resonance (MR) angiography performed by using Cartesian k-space sampling with that performed by using radial k-space sampling. A new dedicated placement of the two-dimensional selective labeling pulse and an individually adjusted labeling delay time approved by the institutional review board were used. In 14 volunteers (eight men, six women; mean age, 28.8 years) who gave informed consent, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, vessel length, and subjective image quality were investigated. Differences between groups were analyzed with nonparametric tests (Wilcoxon, Pearson chi2). Radial imaging, as compared with Cartesian imaging, resulted in a significant reduction in the severity of motion artifacts, as well as an increase in SNR (26.9 vs 12.0, P < .05) in the coronary arteries and CNR (23.1 vs 8.8, P < .05) between the coronary arteries and the myocardium. A tendency toward improved vessel sharpness and vessel length was also found with radial imaging. Radial SSFP imaging is a promising technique for spin-labeling coronary MR angiography.     

Articular cartilage of the knee: evaluation with fluctuating equilibrium MR imaging--initial experience in healthy volunteers

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study, whose purpose was to prospectively compare three magnetic resonance (MR) imaging techniques-fluctuating equilibrium, three-dimensional (3D) spoiled gradient-recalled acquisition in the steady state (SPGR), and two-dimensional (2D) fast spin echo (SE)-for evaluating articular cartilage in the knee. The study cohort consisted of 10 healthy volunteers (four men, six women; age range, 26-42 years). Cartilage signal-to-noise ratio (SNR), SNR efficiency, cartilage-fluid contrast-to-noise ratio (CNR), CNR efficiency, image quality, cartilage visibility, and fat suppression were compared. Cartilage volume was compared for the fluctuating equilibrium and 3D SPGR techniques. Compared with 3D SPGR and 2D fast SE, fluctuating equilibrium yielded the highest cartilage SNR efficiency and cartilage-fluid CNR efficiency (P < .01 for both). Image quality was similar with all sequences. Fluctuating equilibrium imaging yielded higher cartilage visibility than did 2D fast SE imaging (P <. 01) but worse fat suppression than did 3D SPGR and 2D fast SE imaging (P < .04). Cartilage volume measurements with fluctuating equilibrium and 3D SPGR were similar. Fluctuating equilibrium MR imaging is a promising method for evaluating articular cartilage in the knee.     

MR arthrography including abduction and external rotation images in the assessment of atraumatic multidirectional instability of the shoulder

Objective

To evaluate diagnostic signs and measurements in the assessment of capsular redundancy in atraumatic multidirectional instability (MDI) of the shoulder on MR arthrography (MR-A) including abduction/external rotation (ABER) images.

Methods

Twenty-one MR-A including ABER position of 20 patients with clinically diagnosed MDI and 17 patients without instability were assessed by three radiologists. On ABER images, presence of a layer of contrast between the humeral head (HH) and the anteroinferior glenohumeral ligament (AIGHL) (crescent sign) and a triangular-shaped space between the HH, AIGHL and glenoid (triangle sign) were evaluated; centring of the HH was measured. Anterosuperior herniation of the rotator interval (RI) capsule and glenoid version were determined on standard imaging planes.

Results

The crescent sign had a sensitivity of 57 %/62 %/48 % (observers 1/2/3) and specificity of 100 %/100 %/94 % in the diagnosis of MDI. The triangle sign had a sensitivity of 48 %/57 %/48 % and specificity of 94 %/94 %/100 %. The combination of both signs had a sensitivity of 86 %/90 %/81 % and specificity of 94 %/94 %/94 %. A positive triangle sign was significantly associated with decentring of the HH. Measurements of RI herniation, RI width and glenoid were not significantly different between both groups.

Conclusions

Combined assessment of redundancy signs on ABER position MR-A allows for accurate differentiation between patients with atraumatic MDI and patients with clinically stable shoulders; measurements on standard imaging planes appear inappropriate.

Key Points

? MR arthrography has the possibility to accurately identify patients with atraumatic MDI. ? Imaging of the shoulder in abduction and external rotation provides additive information. ? Capsular enlargement of the shoulder can be diagnosed on MR arthrography.     

Development of a short and effective shoulder external rotation strength program in handball: A delphi study

BackgroundWeakness of the shoulder external rotators (ER) is one of the main risk factors for shoulder pain in handball. Short, effective shoulder ER strength programs the players will adhere to are lacking.Objectivesto develop a short and effective shoulder ER strength program, handball players will adhere to.MethodsWe conducted a modified Delphi study, including experts in the field of shoulder, strength training and handball. In the first round, the experts were asked to rate eight pre-defined shoulder ER exercises on efficacy and adherence and to suggest other preferred exercises. In round two, they were asked to rate the new exercises from round one. In round three, they received a statistical summary of the panels scores, their own score and a summary of the suggestions. Based on the feedback, the experts were asked to revise their response.ResultsSixteen experts completed three rounds with 100% response rate. Twenty-eight exercises were rated. We reached consensus for both efficacy and adherence for two exercises, ER in 90° abduction in a bent-over squat position and ER in 90° abduction combined with horizontal abduction and trunk rotation in a push-up position.ConclusionWe reached consensus for both efficacy and adherence for two exercises.     

Pituitary gland MR: a comparative study of healthy volunteers and patients with microadenomas.

PURPOSETo compare the MR appearance of the pituitary glands of healthy volunteers with that of patients with microadenomas.METHODSUnenhanced coronal T1-weighted MR of the pituitary gland was performed on 52 healthy adult volunteers and 14 consecutive patients with evidence of pituitary adenomas. The MRs were interpreted in a randomized, blinded fashion. Notation was made of pituitary gland size, symmetry, stalk position, and the gland''s signal uniformity.RESULTSFocal pituitary gland hypointensities were seen in 20 of 52 volunteers and in all 14 patients. In the volunteers, on average the areas of low signal were smaller and not as dark as in the patient group, but there was some overlap between the two groups. Pituitary gland size, symmetry, and stalk position did not differ between the two groups.CONCLUSIONSFocal hypointensities are common incidental MR findings in the healthy population. On average they appear smaller and not as dark as microadenomas.     

MR cisternography: initial experience in 41 cases.

PURPOSETo present our initial experience with MR cisternography, an application of fast spin-echo MR with fat suppression, and compare it with routine MR cranial studies in the evaluation of the subarachnoid cisterns and their contents.METHODSMR cisternography is a heavily T2-weighted fast spin-echo technique with high spatial resolution; it uses fat suppression and video reversal of the images. A small number of individual sections (two to four) are compressed into a composite image by a maximum-intensity projection algorithm, providing better depiction of anatomy in three dimensions. MR cisternography enhances the signal intensity of the cerebrospinal fluid (CSF) with suppression and subtraction of the background. A total of 41 patients were examined during a period of 6 months. MR cisternography was performed as an additional one (n = 31) or two (n = 10) sequences after conventional MR study.RESULTSTwenty-one cases of disease were examined by MR cisternography, including 8 neoplasms, 4 CSF fistulas, and 3 large intracranial aneurysms. MR cisternography provided information unavailable by conventional MR studies in 17 cases. These included visualization of fistulous tracks in patients with CSF rhinorrhea, origin of a large suprasellar aneurysm, an additional loculus of a posterior fossa aneurysm and its relation to surrounding structures, and proper location of three tumors (intraaxial versus extraaxial). Clear depiction of the pituitary gland separate from the cavernous sinus was noted in 60% of the cases, and a new observation of a CSF sleeve around the third nerve in the posterior cavernous sinus was made in 85% of the cases.CONCLUSIONMR cisternography is superior to conventional MR studies in depicting anatomic structures within the subarachnoid spaces. This technique is recommended in the evaluation of cranial CSF fistulas and suprasellar and posterior fossa masses and in diagnosis of intraaxial versus extraaxial location of intracranial tumors.     

Contrast-enhanced MR cholangiography: comparison of Gd-EOB-DTPA and Mn-DPDP in healthy volunteers

Objective The purpose of this study was to compare the biliary enhancement dynamics of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic-acid (Gd-EOB-DTPA) and mangafodipir trisodium (Mn-DPDP) for contrast-enhanced MR cholangiography (MRC) in healthy subjects. Methods 15 healthy volunteers underwent MRI at 1.5 T with volumetric interpolated breath-hold examination sequence. Each volunteer was scanned once for each contrast agent. The signal-to-noise ratio (SNR) of the liver parenchyma and common hepatic duct (CHD) and the contrast-to-noise ratio (CNR) of CHD to liver parenchyma were evaluated and compared before and at several time points (5, 15, 30, 45, 60, 90, and 120 min) after injection of each agent. Results SNR was significantly higher for Gd-EOB-DTPA than for Mn-DPDP in liver parenchyma after 5 min and in CHD after 15 min (p<0.05). CNR of CHD to liver parenchyma using Gd-EOB-DTPA showed an initial decrease at 5 min post-injection followed by a steep increase to a peak at 15 min post-injection. CNR using Mn-DPDP showed a steady increase to a peak at 15 min post-injection without an initial decrease. At 15 min, the value of CNR was significantly higher for Gd-EOB-DTPA than for Mn-DPDP (p<0.05). Conclusion For both contrast agents, CNR reached a peak at 15 min after contrast injection. At this time point, CNR of Gd-EOB-DTPA was significantly higher than that of Mn-DPDP. Therefore, Gd-EOB-DTPA may provide better contrast-enhanced MRC than Mn-DPDP at 15 min after contrast administration.     

Breathhold MR urography: comparison between HASTE and RARE in healthy volunteers

The purpose of our study was to determine relative values of rapid acquisition relaxation enhancement (RARE) and half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences in breathhold magnetic resonance (MR) urography in healthy volunteers under nonobstructive conditions of the urinary tract. A total of 20 healthy volunteers underwent MR urography with breathhold RARE and HASTE sequences at 1.5 T. For evaluation, the urinary tract was divided into nine segments on each side. Visualization of segments and artifacts was scored and the intensity ratios (InR) were determined. The upper five urinary segments were sufficiently visualized with RARE and significantly better with HASTE (renal calices, p = 0.002–0.037). The middle and lower ureter was sufficiently delineated both with RARE and HASTE, but HASTE images were statistically superior (p = 0.009–0.041). Both in RARE and HASTE images, the lower ureter was frequently superimposed by bowel contents and bowel motion. Superimposition of genital organs degraded image quality in eight of ten female volunteers. InRs were superior with HASTE in the kidney and ureter (p = 0.0003–0.0125). RARE InRs were higher in the bladder (p = 0.0008–0.014). We concluded that neither the RARE nor the HASTE sequences allowed the evaluation of the entire urinary tract under nonobstructive conditions. Although it cannot entirely replace intravenous urography, MR urography seems to lend itself to combination with other MR techniques, particularly in the investigation of pelvic or retroperitoneal disease. Received 28 October 1996; Revision received 7 November 1997; Accepted 29 December 1997     

Optimal protocol for injection of contrast material at MR angiography: study of healthy volunteers

Forty healthy volunteers, matched for age and body weight, underwent abdominal magnetic resonance angiography with gadopentetate dimeglumine administered by using a power injector. Injection rates were 0.3, 1.0, 2.0, or 3.0 mL/sec. Contrast material doses were 0.1 (single dose) or 0.2 (double dose) mmol/kg. Increased contrast enhancement in the aorta and minimum arteriovenous overlap can be achieved with high flow rate and double-dose injection.