Dynamic contrast-enhanced MR urography in the evaluation of pediatric hydronephrosis: Part 1, functional assessment

OBJECTIVE: The purpose of our study was to derive time-intensity curves for the renal cortex and medulla from 3D dynamic MR urography and to assess whether these curves are predictive of obstruction. MATERIALS AND METHODS: Fifty-nine examinations were performed in 53 pediatric patients and the degree of obstruction assessed using the renal transit time. The cortex and medulla were segmented using a semiautomatic method, and mean time-intensity curves were derived for the segmented volumes. The basic parameters of the curves (amplitude, washout) were assessed, as was the presence of certain characteristic features of the curves. RESULTS: The images allowed clear visualization of three phases of the uptake of contrast material in the cortex, the medulla, and the collecting system. Both the amplitude of the curves and the washout of the contrast material were predictive of obstruction. The distal tubular peak was reliably detected in the cortex of nonobstructed kidneys. CONCLUSION: Combining signal-intensity-versus-time-curve analysis with the other parameters that can be derived from the same MR urography data set provides a powerful tool for the diagnosis of obstruction.     

Giant hydronephrosis due to ureteropelvic junction obstruction in a child: CT and MR appearances

Giant hydronephrosis caused by congenital ureteropelvic junction (UPJ) obstruction is a rare urological entity in childhood. We report a case of giant hydronephrosis in a 12-year-old boy presented with abdominal distension. Radiological features of this rare entity are discussed with an overview of sonographic findings, especially including CT and MR appearances. The current literature is also reviewed.     

Time-resolved dynamic contrast-enhanced MR urography for the evaluation of ureteral peristalsis: initial experience

Purpose

To determine the feasibility of time‐resolved dynamic contrast‐enhanced magnetic resonance urography (MRU) for the evaluation of ureteral peristalsis using a data‐sharing 3D gradient echo sequence with spiral k‐space filling.

Materials and Methods

Eight patients (M = 3, F = 5, mean 48.1 years) were referred for MRU for the evaluation for renal mass (n = 3), hematuria (n = 2), urinary tract tuberculosis (n = 1), postoperative bladder cancer (n = 1), and postoperative ureteric reimplantation (n = 1). Dynamic MRU was performed for 120 seconds at 1.5T after intravenous furosemide and gadolinium administration using an oblique sagittal, time‐resolved T1 3D gradient echo sequence with 1 second effective temporal resolution. Study quality was assessed based on artifacts and extent of ureteric visualization. Frequency of peristalsis from the renal pelvis to urinary bladder was evaluated for each subject.

Results

A total of 16 ureters were examined. Image quality was good in four ureters, satisfactory in 11 ureters, and poor in one ureter. Mean peristaltic frequency was 3.5 waves per minute (range, 2.5–6.5 waves/minute) in normal ureters (n =11). Five ureters were considered abnormal (one urinary tract tuberculosis and four postsurgical ureters), and all had decreased or no peristalsis (0–1.5 waves per minute).

Conclusion

MRU using a time‐resolved, data‐sharing 3D contrast‐enhanced technique is able to demonstrate ureteral peristalsis and permits quantification of ureteral peristaltic frequency. J. Magn. Reson. Imaging 2008;28:1293–1298. © 2008 Wiley‐Liss, Inc.     

Functional, dynamic, and anatomic MR urography: feasibility and preliminary findings.

RATIONALE AND OBJECTIVES: The authors assessed the feasibility of using magnetic resonance (MR) urography to acquire functional, dynamic, and anatomic information in human subjects with normal and hydronephrotic kidneys. MATERIALS AND METHODS: In subjects known to have or suspected of having hydronephrosis, split renal filtration fractions were measured with a customized magnetization-prepared, inversion-prepared gradient-recalled echo sequence to determine the T1 of flowing blood in the inferior vena cava and aorta before and after contrast medium administration and in the renal veins and arteries after contrast medium administration. Multiple timed sets of coronal fast spoiled gradient-echo 70 degrees flip-angle images were acquired before and after contrast medium administration to derive MR renograms from changes in the signal intensity of the cortex and medulla. Precontrast T2-weighted images were obtained with a three-dimensional fast spoiled gradient-echo maximum intensity projection pulse sequence, and postcontrast T1 maximum intensity projection images were also obtained to depict the renal anatomy. RESULTS: Split filtration fraction differentiated normal from hydronephrotic kidneys. MR renograms depicted vascular, tubular, and ductal phases and differentiated between normal and hydronephrotic kidneys (P < .05, n = 20). Contrast medium dose correlated with the peak of the cortical signal intensity curves on the renogram (r = 0.7, P < .0005; n = 20). The sensitivities for the visual determination of hydronephrosis and unilateral delayed excretion of contrast material were both 100%, and the specificities were 64% and 85%, respectively. CONCLUSION: The preliminary findings show promise for the use of MR urography in the comprehensive assessment of renal function, dynamics, and anatomy.     

Early report: comparison of breath-hold MR excretory urography, Doppler ultrasound and isotope renography in evaluation of symptomatic hydronephrosis in pregnancy

AIM: To compare assessment by MR excretory urography (MREU), Doppler ultrasound and isotope renography of women with symptomatic hydronephrosis in pregnancy and to define its cause.MATERIALS AND METHODS: Eleven women at 19-34 weeks of gestation were studied prospectively with gadolinium-enhanced breath-hold gradient echo MREU and transabdominal Doppler ultrasound compared with a 'gold standard' of isotope renography employing frusemide challenge. All studies were performed within 24 h, were reported independently in a blinded fashion and employed clearly defined criteria. Obstetric and infant outcomes were obtained.RESULTS: There were no adverse reactions to gadolinium administration in pregnancy and no adverse obstetric or infant outcomes. Three of the 11 women were unable to tolerate the complete MREU protocol. Ultrasound indices could not be used to predict ureteric obstruction as shown by isotope renography. MREU agreed with renographic findings in five of the six cases with obstruction and in two without obstruction. MREU directly demonstrated hydronephrosis to result from extrinsic compression of the ureter between the gravid uterus and iliopsoas muscle. CONCLUSION: MR excretory urography is a promising technique which affords equivalent functional and additional anatomical information to isotope renography. It is more accurate than Doppler ultrasound in the assessment of ureteric obstruction in pregnancy.Spencer, J. A. (2000). Clinical Radiology55, 446-453.     

Morphologic and functional evaluation of duplicated renal collecting systems with MR urography: A descriptive analysis

PurposeTo describe the morphology and function of duplicated collecting systems in pediatric patients undergoing functional MR urography (fMRU).MethodsThis is a HIPAA compliant IRB approved retrospective study of all patients with duplicated renal collecting systems undergoing fMRU at our institution between 2010 and 2017. Two pediatric radiologists evaluated the studies to determine the presence, morphology and function of duplicated collecting systems using both T2-weighted and dynamic post-contrast fat saturated T1-weighted images. Assessed morphologic features included pelvic and calyceal dilation, partial or complete ureteral duplication, ureteral dilation, ectopic ureteral insertion and ureteroceles. Functional analysis was carried out per moiety.ResultsA total of 86 examinations (63 girls; 23 boys), median age 2.6 years (Standard Deviation 6.4 years, interquartile range: 0.4–10.3 years) and 107 kidneys (39 right; 30 left and 19 bilateral), which yielded 214 evaluable moieties, were included in the final sample. One hundred and sixty-three (76.1%) of the moieties had normal morphological features and normal functional results (average calyceal transit time and renal transit time of 2 min 28 s and 3 min 16 s, respectively). The remaining 51 moieties (23.8%) were hypoplastic or dysplastic. Seventy-seven (35.9%) had pelvic and calyceal dilation. Slightly more than half of the kidneys had complete ureteral duplication (60/107; 56%); 50 (50/107, 46.7%) had ectopic ureters (23 intra- and 27 extravesical) and 9 (9/107, 8.4%) had ureteroceles.ConclusionfMRU provides comprehensive information regarding the morphology and function of duplicated renal collecting systems in children. In particular, fMRU is useful for assessing barely or non-functioning renal poles and ectopic ureters.     

Potential impact of pediatric MR urography on the imaging algorithm in patients with a functional single kidney

OBJECTIVE: The purpose of this study was to evaluate the potential of MR urography in the assessment of children with a suspected "functional single kidney." SUBJECTS AND METHODS: Sixty patients (age range, 2.7 weeks to 15.7 years) who had been referred for assessment of a suspected functional single kidney underwent MR urography in addition to detailed sonography of the urinary tract and the currently indicated standard imaging. The results of the conventional imaging ((99m)Tc-dimer captosuccinic acid scintigraphy, voiding cystourethrography, and genitography) were compared with the results of sonography and MR urography; surgical findings served as the gold standard if available. RESULTS: Twenty-six patients had a single kidney. The other diagnoses were six contralateral multicystic dysplastic kidneys, two normal ectopic kidneys, one crossfused double system, and 25 ectopic or dysplastic renal buds. Scintigraphy detected all normal kidneys, two ectopic kidneys, and two dysplastic renal buds. Detailed sonography missed two ectopic kidneys and two orthotopic dysplastic renal buds, but one additional renal bud that could not be confirmed on other imaging techniques (accuracy, 91.7%; sensitivity, 88.2%; specificity, 96.2%) was suspected. MR urography results were correct in all patients and verified in all 13 with surgical correlation. CONCLUSION: MR urography allows a reliable assessment of renal and ureteral anatomy and of dysplastic or ectopic renal buds, even in non- or poorly functioning systems. MR urography therefore has the potential to replace the currently used excretory urography and scintigraphy. In patients with a suspected functional single kidney a detailed sonographic study and MR urography should be considered the diagnostic algorithm of choice.     

MR urography: evaluation of different techniques in non-dilated tracts

OBJECTIVE: To assess the effectiveness of different MRI sequences for the visualisation of the different components of the non-dilated urinary tract. METHOD: 20 asymptomatic individuals were prospectively evaluated using 2 different heavily T2 weighted sequences, and after the injection of 2 different doses of gadolinium (Gd-DTPA). Images were independently scored. RESULTS: The low dose Gd-DTPA enhanced MR urography (MRU) sequence was the best overall sequence for the visualisation of both the pelvicalyceal systems and ureters. The combination of information from the other sequences was additive. CONCLUSIONS: Combined use of heavily T2 weighted and Gd-DTPA enhanced MRU produces diagnostic images and does not require pre-imaging preparation other than oral hydration.     

尿路梗阻磁共振水成像技术与IVU及CT检查对照研究

磁共振尿路成像(MR)是国外近年开展的一项泌尿系影像学检查新方法.现将我院MR检查与CT及IVU检查结果对比如下.     

Microvascular obstruction and myocardial function after acute myocardial infarction: assessment by using contrast-enhanced cine MR imaging

This study was approved by the Human Investigation Committee of William Beaumont Hospital, and all patients gave informed consent. The purpose of this study was to prospectively compare contrast material-enhanced cine magnetic resonance (MR) imaging with more-standard MR imaging for the evaluation of microvascular obstruction and myocardial function in 80 patients (56 men, 24 women; mean age, 57 years; range, 29-80 years) with acute myocardial infarction after reperfusion therapy. Findings at contrast-enhanced cine MR imaging agreed with the global and transmural extent of microvascular obstruction at first-pass perfusion (intraclass correlation coefficient [IC] of 0.96 [P < .001] and 0.88 [P < .001], respectively) and inversion-recovery gradient-echo (IC of 0.90 [P < .001] and 0.93 [P < .001], respectively) MR imaging. There was no significant difference between myocardial function parameters before and after contrast material enhancement. Contrast-enhanced cine MR imaging reduced imaging time by 34% (11 of 32 minutes) and improved spatial resolution. Supplemental material: radiology.rsnajnls.org/cgi/content/full/240/2/529/DC1     

MSCTA和MSCTU对肾盂输尿管连接部梗阻的诊断价值

目的：探讨MSCT血管成像（MSCTA）及尿路成像（MSCTU）在肾盂输尿管连接部梗阻（UPJO）诊断中的价值。方法：回顾性分析经手术病理证实的16例UPJO患者的MSCTA及MSCTU影像资料,利用多种后处理重组技术（MPR、CPR、MIP、VR）进行重组。结果：16例肾盂输尿管连接部梗阻中,梗阻位置全部诊断正确。梗阻原因诊断为输尿管息肉1例,血管压迫3例,炎性狭窄12例。术前诊断与手术探查及病理结果基本一致。结论：MSCTU和MSCTA可作为UPJO术前评估的常规方法,在诊断引起UPJO的疾病方面具有重要价值。     

Dynamic contrast-enhanced MR evaluation of prostate cancer before and after endorectal high-intensity focused ultrasound

Purpose

The authors sought to determine the diagnostic performance of dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging in the evaluation of prostate cancer before and after transrectal high-intensity focused ultrasound (HIFU) treatment.

Materials and methods

We analysed 25 patients with prostate cancer. The prostate-specific antigen (PSA) value was evaluated 1, 4 and 6 months after treatment. DCE-MR imaging was performed the day prior to and 1, 4 and 6 months after HIFU treatment. Transrectal prostate biopsies were obtained at the time of diagnosis and 6 months after treatment.

Results

Before treatment, intraglandular lesions were considered to be potential sites of neoplasm and subsequently confirmed as sites of prostate adenocarcinoma in all 25 patients based on prostatespecific antigen (PSA) values and histological examinations (rho=1; p<0.001). Using histology as the gold standard, DCE-MR imaging displayed 100% sensitivity, 100% specificity, 100% positive predictive value and 100% negative predictive value before treatment. After HIFU treatment, DCE-MR imaging showed 100% sensitivity and 96% specificity.

Conclusions

DCE-MR imaging can be used to visualise prostate adenocarcinoma. Several morphological and postgadolinium modifications in the follow-up DCE-MR images after HIFU treatment were also observed.     

Anterior bundle of ulnar collateral ligament: evaluation of anatomic relationships by using MR imaging, MR arthrography, and gross anatomic and histologic analysis

PURPOSE: To evaluate the gross and microscopic anatomy and the magnetic resonance (MR) imaging and MR arthrographic appearance of the anterior bundle of the ulnar collateral ligament (UCL) of the elbow. MATERIALS AND METHODS: The origin and insertion of the anterior bundle of the UCL, the bundle's relationship to the overlying flexor tendons, and the presence of a layered configuration were assessed through inspection and dissection of an elbow specimen. T1-weighted spin-echo MR imaging and MR arthrography in standard imaging planes and a coronal oblique plane were performed in eight other elbow specimens. Additional MR arthrography was performed in four specimens by using the coronal plane with the elbow in 20 degrees of flexion. The specimens were then cut in planes corresponding to those of the MR images. Histologic analysis of two specimens was performed. RESULTS: The anterior bundle of the UCL appeared as a low-signal-intensity structure on T1-weighted spin-echo MR and MR arthrographic images. It consisted of a uniform layer of parallel collagen fibers attaching proximally to the base of the medial epicondyle of the humerus and distally to the medial aspect of the coronoid process of the ulna (sublime tubercle). A layer of synovium separated the anterior bundle from the more superficial tendon of the flexor digitorum superficialis muscle. MR imaging-anatomic comparison in four (50%) specimens revealed separation between the anterior bundle of the UCL and the sublime tubercle. Results of histologic analysis of two of these specimens confirmed insertion of the anterior bundle of the UCL 3 and 4 mm distal to the articular margin. Ligamentous degeneration was detected in only one of these specimens. CONCLUSION: There is variability in the distal insertion of the anterior bundle, and this suggests that caution should be exercised in the diagnosis of its partial detachment from the sublime tubercle of the ulna.     

Value of contrast-enhanced MR enterography in pediatric Crohn's disease: preliminary study

OBJECTIVE: Feasibility study of contrast enhanced MR enterography without enteroclysis as a new diagnostic tool for children with known or suspected Crohn's disease. METHODS: We prospectively included 15 children, 8-18 years old, with clinical suspicion of Crohn's disease. MR enterography without enteroclysis was performed on a 1,5 T clinical MR system. A total of 1000 ml of mannitol 5% was orally administered 60 minutes prior to MRI. Coronal and axial breath-hold sequences were acquired. The following sequences were obtained: True-FISP, FLASH T1 2D/3D with Fat saturation before and after gadolinium injection. Two radiologists, blinded to patient information, independently reviewed all examinations to record image quality, the degree of distension of the distal ileum, the presence of abnormal bowel segments and the presence of extra-intestinal complications. MRI findings were correlated to sonographic, endoscopic and biological results (sensitivity, specificity, Kappa test). RESULTS: The examinations were considered of satisfactory diagnostic quality in 93.3% of patients. Respiratory artifacts were present in one case. The entire GI tract could be identified on all sequences. Distention of the distal ileum was recorded as good to excellent in 89% of healthy subjects. Five MR examinations were considered abnormal with isolated ileal involvement in 2 cases, ileocolic involvement in 2 cases, and isolated colonic involvement in 1 case. The sensitivity and specificity of MR for the positive diagnosis of Crohn's disease were 100% and 83% respectively. Three extra-intestinal complications were detected: one case of ileo-ileal fistula, not identified on ultrasonography, an asymptomatic anal fistula and a symptomatic inflammatory stricture. CONCLUSION: MR enterography without enteroclysis is a well tolerated, effective non invasive method in the evaluation of known or suspected Crohn's disease. Because of the absence of ionizing radiation, MR enterography should become the gold standard in pediatric patients.     

Dynamic MR assessment of the anorectal angle and puborectalis muscle in pediatric patients with anismus: technique and feasibility

PURPOSE: To assess the feasibility of dynamic breath-hold MRI for evaluating changes in the anorectal angle and movements of the pelvic-floor musculature (puborectalis) during resting and straining states in pediatric patients presenting with anismus. MATERIALS AND METHODS: Six pediatric patients (7-13 years old) with chronic constipation and manometric evidence of anismus were assessed by dynamic breath-hold MRI. Changes in the anorectal angle, the degree of pelvic-floor descent, and the thickness and length of the puborectalis muscles were measured during rest and straining. The findings were compared with those obtained in six age- and sex-matched controls. RESULTS: The children with anismus had a smaller anorectal angle during straining, and the angle decreased from rest to defecation. The puborectalis also became paradoxically shortened and thickened during straining in the anismus group. There were significant differences between the two groups in terms of the change of degree of the anorectal angle, and the thickness and length of the puborectalis muscle during straining. CONCLUSION: Fast dynamic MRI is feasible for evaluating pelvic-floor movement in pediatric patients. Preliminary results suggest that children with anismus have a smaller anorectal angle and a different puborectalis configuration compared to controls.     

Dynamic contrast-enhanced MR angiography and MR imaging of the carotid artery: high-resolution sequences in different acquisition planes

BACKGROUND AND PURPOSE: First-pass contrast-enhanced MR angiography has become the technique of choice for studying the carotid bifurcation, but this method has some limitations. We evaluated the clinical utility of performing 3D contrast-enhanced MR angiography in the axial plane immediately after performing angiography in the coronal plane. METHODS: Cervical carotid arteries of 80 consecutive patients were studied on a 1.5-T MR imager with phased-array coils. Coronal 3D MR angiography was performed after administering a bolus injection of contrast material (20 mL) with automatic triggering. This was immediately followed by an axial acquisition. We measured carotid diameters on the contrast-enhanced MR angiograms as well as on intra-arterial digital subtraction angiograms according to established criteria. We also evaluated original source MR angiograms. RESULTS: Angiograms obtained in the axial plane correlated better with the intra-arterial digital subtraction angiograms than did the coronal angiograms. When first-pass contrast-enhanced MR angiography was incomplete because of a failure of triggering, the second-phase acquisition provided sufficient image quality. Original source images suffered from ring artifacts, low axial resolution, and a low level of soft-tissue visualization. Axial-based source images showed flow-independent contrast filling to the patent lumen with sufficient visualization of plaque morphology, thickened arterial wall, and surrounding disease processes, such as tumors. CONCLUSION: With the addition of a 1-minute second-phase 3D acquisition in a different plane immediately after first-pass contrast-enhanced MR angiography, one can obtain a more accurate depiction of the carotid bifurcation, insurance against failure of triggering, and diagnostic source images.     

Dynamic contrast-enhanced MR imaging of the upper abdomen: Enhancement properties of gadobutrol,gadolinium-DTPA-polylysine,and gadolinium-DTPA-cascade-polymer

The enhancement properties of gadobutrol (40 and 80 μmol/kg body weight, 550 daltons), gadolinium-DTPA-polylysine (20 μmol/kg body weight, 53,000 daltons) and gadolinium-DTPA-cascade-polymer (20 μmol/kg body weight, < 30,000 Daltons) were investigated in abdominal MR imaging using a pig model (n = 24). Signal intensities before and after contrast media application were assessed using a fast single slice FLASH sequence. Measurements were made every 4 s within the first 116 s, every minute between 4 and 10 min and after 15,20,30,40, 50,60,90, and 120 min after contrast media injection. Injection of gadobutrol resulted in typical signal intensity curves characterizing it as an extracellular agent similar to gadopentetate dimeglumine. Significant enhancement was found in all tissues except the trunk muscles when the lower dose was administered. Gadolinium-DTPA-polylysine injection resulted also in significant enhancement of the liver, the pancreas, and the renal cortex, but not of the trunk muscle, reflecting its blood pool properties known also from other macromolecular contrast agents. The signal intensity curves obtained after gadolinium-DTPA-cascade-polymer injection were similar to those obtained after polylysine injection, stressing the blood pool character of this new type of blood pool agent.