MR virtual endoscopy of the upper urinary tract

MR Virtual Endoscopy of the Fetal Limb Anomalies Using Three-Dimensional Fast Imaging Employing Steady-State Acquisition Sequence

OBJECTIVE

To retrospectively investigate the feasibility of magnetic resonance virtual endoscopy (MRVE) to visualize the normal limbs and limb deformities Methods: MR sequences included two-dimensional (2D) single fast spin-echo sequence and 2D and 3D steady-state procession fast imaging sequences. MRVE reconstruction was retrospectively performed by 2 radiologists in 32 fetuses in 30 pregnant women. The correlation between the radiologists for the virtual endoscopy threshold of MRVE was determined. Image quality and limb segment visibility were independently rated. Area under the receiver operating characteristics curve (AUC) of 2D MRI and MRVE was calculated.

RESULTS

The mean virtual endoscopy threshold required for the visualization of the limb was 991.93 ± 12.13 and 991.83 ± 12.26 for 2 radiologists, respectively. The correlation between the radiologists for virtual endoscopy threshold was excellent (r = 0.933). The weighted kappa statistic was 0.96 for the evaluation of image quality of limb segments, indicating excellent interobserver agreement. Compared to that of 2D MRI alone, a higher AUC of 2D MRI with MRVE was achieved in detection of both upper and lower limb deformities (0.91 vs. 0.69 and 0.83 vs. 0.71, respectively).

CONCLUSION

MRVE may display normal and abnormal fetal limb orientation and structures from multiple perspectives and provide incremental information for obstetrics.

Establishment and Evaluation of Patient-Specific Virtual Ureteroscopy in Assisting Flexible Ureteroscopy for Urolithiasis

Objectives. To establish virtual ureteroscopy (VU) through computed tomography urography (CTU) data from patients with upper urinary tract (UUT) stones indicated for flexible ureteroscopy (fURS) and to validate its effectiveness. Methods. Patient-specific VU generation was accomplished through incorporating CTU data into specialized software (Crusher) developed on the open access Visualization Tools Kit (VTK). These were then presented to fURS experts and novice urologists for evaluation and comparison using modified Likert-type questionnaire of 10-point rating scales (1 = not at all useful/not at all realistic/poor, 10 = very useful/very realistic/ excellent). Results. Face and content validation of VU from 5 fURS experts in 3 different centers: overall usefulness 7.4 ± 0.5, graphics 7.4 ± 0.5, intrarenal anatomy 8.4 ± 0.5, stone details 7.8 ± 0.4, usefulness in surgical planning and training 7.6 ± 0.9. Significant increase of detection in the number of calyces and stones was found from using CTU only to CTU-VU combined in the novice group ( P = .000). Before VU observation, novices found much fewer calyces and stones than experts ( P = .004 and .000, respectively). However, this gap disappeared after VU observation ( P = .327 and .292, respectively). VU feedback from the novices was superb. Conclusions. Establishing patient-specific VU through CTU data from renal stone patients is feasible. The present VU can significantly improve novice urologists’ comprehension of intrarenal anatomy and stone information before fURS procedures. Face and content validity is also proved. This novel modality may serve as an important tool for fURS surgical planning, navigation, and training.

Virtual MR arthroscopy of the shoulder: image gallery with arthroscopic correlation of major pathologies in shoulder instability

BACKGROUND

The purpose of this study was to compare virtual MR arthroscopic reconstructions with arthroscopic images in patients affected by shoulder joint instability. MR arthrography (MR-AR) of the shoulder is now a well-assessed technique, based on the injection of a contrast medium solution, which fills the articular space and finds its way between the rotator cuff (RC) and the glenohumeral ligaments. In patients with glenolabral pathology, we used an additional sequence that provided virtual arthroscopy (VA) post-processed views, which completed the MR evaluation of shoulder pathology.

MATERIALS AND METHODS

We enrolled 36 patients, from whom MR arthrographic sequence data (SE T1w and GRE T1 FAT SAT) were obtained using a GE 0.5 T Signa--before any surgical or arthroscopic planned treatment; the protocol included a supplemental 3D, spoiled GE T1w positioned in the coronal plane. Dedicated software loaded on a work-station was used to elaborate VAs. Two radiologists evaluated, on a semiquantitative scale, the visibility of the principal anatomic structures, and then, in consensus, the pathology emerging from the VA images.

RESULTS

These images were reconstructed in all patients, except one. The visualization of all anatomical structures was acceptable. VA and MR arthrographic images were fairly concordant with intraoperative findings.

CONCLUSIONS

Although in our pilot study the VA findings did not change the surgical planning, the results showed concordance with the surgical or arthroscopic images.

Diagnostic potential of virtual pneumoendoscopy of the urinary tract

OBJECTIVE

To evaluate the diagnostic possibilities of CT virtual pneumoendoscopy, in various vesical and extra-vesical urinary tract abnormalities and suggest possible indications for this examination.

PATIENTS AND METHODS

Thirty-three patients (26 men and 7 women, aged 30-91, mean-61 years) were referred by the urologists for specific further evaluation of the urinary tract with virtual pneumoendoscopy for various indications. All patients except three underwent conventional endoscopy within a week either before or after the virtual examination, but the endoscopy was either equivocal or limited. The urinary tract was insufflated with room air.

RESULTS

Successful CT pneumoendoscopy was achieved in 31 of the 33 patients. The indications for the virtual study included obstructive uropathy (22), hematuria (15), and suspected fistula (2). The virtual examination findings included urethral stricture, recto-urethral fistula, multiple bladder tumors, bladder tumor invading the distal ureter or urethra, bladder diverticula containing a tumor, ureteral stricture, renal transitional cell carcinoma, and renal calculi with inflammation. Virtual CT endoscopy had added value to the diagnostic process in all our patients.

CONCLUSION

In selected cases virtual CT pneumoendoscopy may serve as an important adjunctive diagnostic aid for urologic pathologies.

Contrast-enhanced multislice pneumo-CT-cystography in the evaluation of urinary bladder neoplasms

PURPOSE

To evaluate the accuracy of contrast-enhanced multislice CT (MSCT) in the study of urothelial tumors after distension of the bladder with air.

MATERIALS AND METHODS

We evaluated 43 consecutive patients with endoscopically proven bladder lesions. After air distension of the bladder, unenhanced pelvic and enhanced abdomino-pelvic scans were obtained with the following protocol: thickness 2.5mm x 4mm, increment 1mm, scan delay 40'' and 7-10 min. For each patient we considered the number, size, aspect (papillary or sessile) and contrast enhancement of lesions. Ureteral involvement and the presence of synchronous lesions in the excretory scan were also evaluated. MPR and virtual endoscopy images were reviewed in all cases.

RESULTS

Bladder lesions were visualized in 39/43 cases. Compared to conventional cystoscopy, MSCT recognized single lesions in 31/33 patients, two lesions in 4/6, three in 2/2 and more than five foci in 2/2 patients. A papillary aspect was described in 44 cases while 11 lesions were sessile. Conventional Cystoscopy recognized six more lesions as compared with MSCT (four flat and two small papillary lesions). The detection rate for protruding lesions was 100% (52/52) for lesions>5mm and 60% (3/5%) for lesions<5mm. In four patients hydronephrosis was present, while in one case a synchronous lesion was evident in the renal pelvis.

CONCLUSION

Contrast-enhanced MSCT with air distension of the urinary bladder is a safe and complete investigation to evaluate the local stage of bladder cancer and to evaluate the ureteral extension of the tumor, as well as the presence of synchronous lesions.

Magnetic resonance urography in pediatric urology

PURPOSE OF REVIEW

Magnetic resonance urography (MRU) has emerged as a powerful diagnostic tool in the evaluation of the pediatric genitourinary tract. The purpose of this review is to familiarize the reader with the basic techniques, strengths and limitations, as well as the current and potential future applications of MRU in pediatric urology.

RECENT FINDINGS

MRU can provide detailed anatomical information and assess renal function and drainage in a single study. MRU does not employ ionizing radiation and may be utilized in patients with iodine-based contrast allergy or impaired renal function. MRU has been most often applied to the evaluation of hydronephrosis and provides valuable insight into a wide range of obstructive uropathies. MRU was shown to be superior to renal scintigraphy for the diagnosis of pyelonephritis and renal scarring. The use of MRU for the assessment of urolithiasis and vesicoureteral reflux is limited and technical refinements are required. Potential future applications include fetal MRU, virtual endoscopy, and MRU-guided procedures. The development of new contrast agents and new image-processing software will further enhance the diagnostic potential of MRU in pediatric urology.

SUMMARY

MRU is currently thought of as a problem-solving tool to define anatomy and function when conventional methods fall short. This technique is likely to emerge as the imaging modality of choice for children with complex genitourinary pathology.

Application of Magnetic Resonance Virtual Endoscopy as a Presurgical Procedure Before Sialoendoscopy

OBJECTIVES

The objectives of this study were to investigate the feasibility of clinical application of magnetic resonance (MR) virtual endoscopy as a presurgical procedure before sialoendoscopy and to evaluate its value in the diagnosis of obstructive salivary gland diseases and preoperative visualization of endoluminal views.

STUDY DESIGN

This study presents our initial experience to use MR virtual endoscopy for the presurgical visualization of salivary duct lumen and ductal pathologies in comparison to the sialoendoscopy findings in a feasibility study.

METHODS

Six consecutive patients with suspected obstructive salivary gland diseases underwent MR sialography with a three-dimensional fast imaging using steady-state acquisition. The three-dimensional MR data were transferred to an independent workstation and were postprocessed with navigator software to generate three-dimensional reconstruction and virtual endoscopic images. The fly-through mode was used to imitate the sialoendoscopic exploratory procedure. Then the patients underwent sialoendoscopy and the endoscopic findings were compared with the preoperative virtual endoscopic images.

RESULTS

The MR data acquisition and postprocessing protocol were feasible. The virtual endoscopy created clear endoluminal views of salivary duct and the ductal pathologies. The diagnoses were all confirmed by surgical sialoendoscopy. The virtual endoscopic images showed close resemblance to the sialoendoscopic findings.

CONCLUSIONS

MR virtual endoscopy is an effective and noninvasive diagnostic method for evaluating the endoluminal anatomy and pathologies of the salivary duct. The clinical application of MR virtual endoscopy as a presurgical procedure before sialoendoscopy is a valuable and promising approach, which can provide surgeons useful morphologic and pathologic information.

Retroperitoneal Fibrosis, Today: An Updating of Knowledges on this Subjet

Retroperitoneal fibrosis (RPF) is characterized, at first, by a replacement of the normal retroperitoneal tissue by an active granulomatosis inflammation (cellular phase), and at a later stage by a fibrous scar tissue (established fibrotic phase). The aetiology of secondary RPFs includes several drugs (notably methysergide, ergotamine, pergolide, hydralazine), both chronic atherosclerotic aortitis-periaortitis and inflammatory aortic aneurisms, autoimmune diseases such as different forms of systemic vasculitis and collagen diseases, histiocytosis such as Erdheim-Chester syndrome, desmoplastic reactions to retroperitoneal malignancy carcinoid syndrome, retroperitoneal accidentally and surgically occurred traumas, abdominal radiation therapy.

On the contrary, the causes of idiopathic RPF remain uncertain; its pathogenesis is associated to immuno-mediated mechanisms. The inflammatory process can involve retroperitoneal vessels, ureters, peri- and pararenal spaces, mesenteric small intestine, duodenum, psoas muscles, and can spread to mediastinal space. Diagnosis and characterization of the polyphase inflammatory evolution require integrated approaches including laboratory tests, morpho-functional imaging and, sometimes, histopathologic assessment. In the early stages, the management of RPF ranges from the removal of identifiable etiologic agents to the interfering with the inflammatory immuno-mediated process by means of several drugs. Unfortunately, many effective immunosuppressive drugs induce adverse reactions unrelated to their specific immunosuppressive action; this is the reason why the biopharmacology research today is struggling towards the identification of molecular targets having their expression restricted to immune cells and/or cytokines. Moreover, the progression of atheromatous aortitis to RPF could be prevented by statins which are able to interfere with the inflammatory pathway as well as to induce the well-known reduction in the levels of atherogenic lipoproteins. In the late established fibrotic stage, either open surgery or endourologic, laparoscopic procedures are performed; nevertheless neoadiuvant and adiuvant corticosteroid-immunosuppressive treatments are mandatory in order to avoid any relapse of the disease.

Virtual endoscopy of the urinary tract

Technological breakthroughs have advanced the temporal and spatial resolutions of diagnostic imaging, and 3 dimensional (3-D) reconstruction techniques have been introduced into everyday clinical practice. Virtual endoscopy (VE) is a non-invasive technique that amplifies the perception of cross-sectional images in the 3-D space, providing precise spatial relationships of pathological regions and their surrounding structures. A variety of computer algorithms can be used to generate 3-D images, taking advantage of the information inherent in either spiral computed tomography or magnetic resonance imaging (MRI). VE images enable endoluminal navigation through hollow organs, thus simulating conventional endoscopy. Several clinical studies have validated the diagnostic utility of virtual cystoscopy, which has high sensitivity and specificity rates in the detection of bladder tumor. Published experience in the virtual exploration of the renal pelvis, ureter and urethra is encouraging but still scarce. VE is a safe, non-invasive method that could be applied in the long-term follow-up of patients with ureteropelvic junction obstruction, urinary bladder tumors and ureteral and/or urethral strictures. Its principal limitations are the inability to provide biopsy tissue specimens for histopathologic examination and the associated ionizing radiation hazards (unless MRI is used). However, in the case of endoluminal stenosis or obstruction, VE permits virtual endoluminal navigation both cephalad and caudal to the stenotic segment. To conclude, VE provides a less invasive method of evaluating the urinary tract, especially for clinicians who are less familiar with cross-sectional imaging than radiologists.

[Virtual multislice computed tomography cystoscopy for evaluation of urinary bladder lesions]

The introduction of multislice computed tomography (MDCT) with the possibility of acquiring isotropic datasets has been an ideal prerequisite for development of virtual MDCT cystoscopy. Remarkable technical progress regarding post-processing of high-resolution 3D datasets as well as a considerable reduction of the time required for post-processing made it possible to introduce virtual MDCT cystoscopy into the clinical routine. 3D post-processing that often required 7-8 h when virtual endoscopy techniques were first developed can now be performed in less than 5 min after transfer of data to the 3D workstation. With the limitations and contraindications of conventional cystoscopy in mind, virtual MDCT cystoscopy may be seen as a valuable alternative to conventional cystoscopy for evaluation of hematuria.

Virtual endoscopy in renal artery stenosis: an innovative approach for diagnosis and follow-up

PURPOSE

We investigated the utility of virtual endoscopy (VE) as a diagnostic and follow-up tool in patients with renal artery stenosis, especially as a means of defining vascular patency.

PATIENTS AND METHODS

We performed VE in 24 patients with ostial atherosclerotic renal artery stenosis and correlated the results with those of conventional angiography. The patients were treated successfully by placement of metal stents and conventional catheter angiography and VE for patency assessment 6 and 12 months after stent insertion.

RESULTS

In all patients, the stenotic segment was identified, and VE findings were concordant with those of angiography. The average degree of stenosis was estimated to be 70% +/- 20% when angiography was used and 62% +/- 15% when VE was used. After metal stent insertion, the 12-month patency rate was 83.3% (20 patients). Angiography and VE findings remained concordant during the follow-up period, but VE provided more information beyond the stenotic segment, allowing examination of the arterial lumen both cephalad and caudal to the point of obstruction.

CONCLUSION

Virtual endoscopy provided a more dynamic, direct, minimally invasive approach that was equal to or better than angiography for both the verification of the vascular stenosis and the evaluation of the arterial lumen.

Three-Dimensional CT Virtual Endoscopy in the Detection of Simulated Tumors in a Novel Phantom Bladder and Ureter Model

BACKGROUND AND PURPOSE

Cystoscopy and ureteroscopy have limitations in the evaluation for urothelial tumors, and both are invasive. We studied the utility of three-dimensional (3D) CT virtual endoscopy in phantom models.

MATERIALS AND METHODS

A phantom pelvis was constructed of Plexiglas, porcine pelvic bones, and processed animal fat and scanned at various table speeds in a four detector-row CT machine for ability to detect "tumors" of Solidwater plastic polymer. Images were reconstructed at slice thicknesses of 2.5 to 5.0 mm and reconstructed in 3D for evaluation by two radiologists with no knowledge of the scanning parameters or tumor location. Similar studies were performed with a ureter model.

RESULTS

With 5-mm slices, the sensitivity for bladder tumors ranged from 67% for 2-mm tumors to 100% for 4-mm tumors, with 12 false-positive findings. The overall sensitivity was 86% with 3.75-mm slices with one false positive, and with 2.5-mm slices, the sensitivity was 93%, again with one false positive. For the ureteral tumors, the overall sensitivities and numbers of false positives were 88.9% and eight with 5.0-mm collimation, 88.9% and four with 3.75-mm collimation, and 100% and three with 2.5-mm collimation. The effective radiation dose for all studies was equivalent to that of a standard abdomen/pelvis scan.

CONCLUSIONS

Although virtual endoscopy traditionally has had difficulty detecting tumors <5 mm, the multidetector-row CT protocols used in this study could detect most lesions smaller than this. The scan also depicts the other tissues of the pelvis, which is valuable for staging. The 3D images were produced using data from the CT urogram parameters standard at our institution.

Virtual Endoscopy: Navigation within Pelvicaliceal System

PURPOSE

To evaluate the use of virtual endoscopy (VE) for the investigation of the pelvicaliceal unit and the depiction of its anatomic deformities.

PATIENTS AND METHODS

Two study groups were prospectively enrolled in our protocol: ten patients with nonurologic pathologies, and thus without any known deformity of the pelvicaliceal unit (group A), and five patients with caliceal obstruction (group B). Virtual endoscopy represented a non-invasive technique providing amplification of the image in three-dimensional space.

RESULTS

Virtual endoscopy was feasible in all patients, and in all cases succeeded in demonstrating the threedimensional morphology of the region of interest. The entire processing time ranged from 10 to 15 minutes (mean 12.6 minutes), and the three-dimensional image could be viewed from different angles, allowing better evaluation of the collecting system and its deformities than is possible with conventional intravenous urography or percutaneous nephrostomography.

CONCLUSION

Virtual endoscopy enabled the creation of endoluminal views of the renal pelvis and calices from spiral tomographic images, thereby allowing diagnostic-preoperative and postoperative evaluation of the pelvicaliceal unit.

MR techniques for renal imaging

This article describes the principles, attributes, and pitfalls of the many MR imaging approaches available for assessment of renal-related disorders. Tables 1 and 2 summarize the specific approach and rationale.

Value of selective upper tract cytology for recognition of upper tract tumors after treatment of superficial bladder cancer

BACKGROUND

The value of selective upper urinary tract (UT) cytology in patients who are asymptomatic and tumor free at control cystoscopy after being treated for superficial bladder carcinoma has not been studied. The present study was performed to evaluate the value of selective UT cytology in patients who are tumor free at control cystoscopy after being treated for superficial bladder cancer.

METHODS

Forty-seven consecutive patients who had undergone definitive surgical treatment for superficial bladder cancer at least 24 months prior and were tumor free at control cystoscopy were evaluated with bladder wash for cytology as well as selective UT urine cytology by catheterization of both ureteral orifices. Of the 47 patients, disease was stage Ta in 30 (63.8%), T1 in 15 (31.9%) and Ta/Tcis in 2 (4.3%). Primary tumor was unifocal in 24 (51.1%) and multifocal in 23 (48.9%) patients. The time elapsed from the initial diagnosis to the last evaluation ranged from 2 to 21 years (mean 5.39).

RESULTS

UT cytology was positive in 2 cases. Although, excretory urography (IVP) revealed mild pelvicalicectasis in 1 of these 2 patients, ureterorenoscopy (URS) revealed no abnormality. In the other patient with normal IVP and retrograde pyelography (RGP), URS revealed a ureteral tumor 5 mm in diameter. Although the UT cytology was normal in the remaining 45 patients, IVP revealed right hydronephrosis in 1 patient and URS revealed multiple ureteral tumors.

CONCLUSION

Given the normal appearance of the UT, it is highly unlikely that these patients have tumor in the UT. Thus, during the follow-up of patients with superficial bladder cancer, it is not useful to perform UT select cytology in the absence of any identifiable filling defects in the upper urinary tract.

Magnetic resonance cystometry: accurate assessment of bladder volume with magnetic resonance imaging

OBJECTIVES

To evaluate magnetic resonance hydrometry for the calculation of bladder volume. The reference standard to assess bladder volume is urethral catheterization, which may be linked with the risk of trauma and infection. Hence, ultrasonography is the preferred diagnostic method. However, ultrasonography is investigator dependent and inaccurate in the hands of an inexperienced operator.

METHODS

Investigations were performed in a 1.0-Tesla clinical scanner with a manufacturer-provided single-shot turbo spin-echo sequence. We examined 30 healthy volunteers (21 males and 9 females) with a mean age of 26.4 years. To quantify the volume of fluid in a magnetic resonance image, a histogram algorithm was used and a calibration phantom applied. Prevoid and postvoid images were acquired. The bladder volume was calculated as the difference between the prevoid and postvoid image fluid volumes. The magnetic resonance-calculated data were compared with the actually voided volumes.

RESULTS

The measured voided bladder volume was 400 +/- 33 mL, whereas magnetic resonance hydrometry yielded 390 +/- 31 mL. The difference between both measurements was not statistically significant. The 95% confidence interval for the difference of both measurements ranged from -22.6 to 2.4 mL. The regression had an r2 of 0.97.

CONCLUSIONS

The feasibility of magnetic resonance hydrometry to quantify the bladder volume noninvasively was demonstrated.

Detection of upper urinary tract transitional cell carcinoma with ImmunoCyt: a preliminary report

OBJECTIVES

To assess the clinical performance of ImmunoCyt in the detection of upper urinary tract transitional cell carcinoma (UT-TCC). This newly developed immunocytochemical test detects three cellular markers specific for TCC.

METHODS

Thirty-seven patients with symptoms and/or findings on imaging suggestive of UT tumors were prospectively evaluated. All patients underwent a standard cytologic evaluation and ImmunoCyt testing of voided urine, as well as imaging studies. Urine samples were also obtained from the UT of 32 patients by ureteral catheterization and tested by cytologic analysis and ImmunoCyt.

RESULTS

Sixteen patients had UT-TCC as documented by the final histologic evaluation. The sensitivity of testing the voided urine from 37 patients was 50% for cytologic analysis, 75% for ImmunoCyt, and 87% for both methods combined. The cytologic evaluation detected no G1, 1 (17%) of 6 G2, and 7 (100%) of 7 G3 tumors. ImmunoCyt detected 1 (33%) of 3 G1, 6 (100%) of 6 G2, and 5 (71%) of 7 G3 tumors. The sensitivity in the 32 urine samples obtained from the UT was 82% for cytologic analysis, 91% for ImmunoCyt, and 100% for both methods combined. Cytologic analysis detected all G2 and G3 (100% sensitivity) and no G1 tumors. ImmunoCyt detected 2 (100% sensitivity) of 2 G1, 4 (100%) of 4 G2, and 4 (80%) of 5 G3 tumors. The test specificity, calculated in 21 patients free of TCC, was 100% for cytologic analysis in voided and ureteral urine specimens and 95% and 100% for ImmunoCyt in voided and ureteral urine samples, respectively.

CONCLUSIONS

The results of this preliminary study show that ImmunoCyt complements cytologic analysis in detecting UT-TCC, mainly because of its high sensitivity to low-grade TCC. The combination of cytologic testing and ImmunoCyt gives 100% sensitivity in detecting UT-TCC in UT urine samples.