Comparison of Virtual Cystoscopy, Multiplanar Reformation, and Source CT Images with Contrast Material-Filled Bladder for Detecting Lesions

Role of imaging techniques in the diagnosis and follow-up of muscle-invasive bladder carcinoma

INTRODUCTION

Muscle-invasive bladder malignancies represent 20-30% of all bladder cancers. These patients require imaging tests to determine the regional and distant staging.

OBJECTIVE

To describe the role of various imaging tests in the diagnosis, staging and follow-up of muscle-invasive bladder cancer. To assess recent developments in radiology aimed at improving the sensitivity and specificity of local staging and treatment response.

ACQUISITION OF EVIDENCE

We conducted an updated literature review.

SYNTHESIS OF THE EVIDENCE

Computed tomography and magnetic resonance imaging (MRI) are the tests of choice for performing proper staging prior to surgery. Computed tomography urography is currently the most widely used technique, although it has limitations in local staging. Ultrasonography still has a limited role. Recent developments in MRI have improved its capacity for local staging. MRI has been suggested as the test of choice for the follow-up, with promising results in assessing treatment response. Positron emission tomography could improve the detection of adenopathies and extrapelvic metastatic disease.

CONCLUSIONS

Imaging tests are essential for the diagnosis, staging and follow-up of muscle-invasive bladder cancer. Recent technical developments represent important improvements in local staging and have opened the possibility of assessing treatment response.

Computed tomography virtual cystoscopy for follow-up of patients with superficial bladder tumours in comparison to conventional cystoscopy: An exploratory study

Objective

To evaluate and analyse the efficacy of computed tomography (CT) virtual cystoscopy in comparison to conventional cystoscopy for the follow-up of patients with non-muscle-invasive bladder cancer.

Patients and methods

The study was done over 3 years, from April 2010 to June 2013, and included 30 patients who all had non-muscle-invasive transitional cell carcinoma (Ta, T1). The patients all underwent complete transurethral resection of the tumour and presented for first follow-up check cystoscopy. The examination was performed using a 16-slice multi-detector (MD) CT scanner. The results were compared for sensitivity and specificity in relation to the site, size, and shape of the tumour.

Results

In all, 20 lesions were detected by CT virtual cystoscopy in 18 patients, whilst the remaining 12 were lesion free. Conventional cystoscopy, detected 23 lesions in 19 patients. The sensitivity of the virtual images was 87%; its specificity in identifying lesions was 100%, with a positive predictive value of 100% and negative predictive value of 78.5%.

Conclusion

CT virtual cystoscopy is a promising technique for detecting bladder tumours and some other bladder lesions. However, the detection rate for recurrent NMIBC does not appear to be adequate to replace conventional cystoscopy.

Can CT Virtual Cystoscopy Replace Conventional Cystoscopy in Early Detection of Bladder Cancer?

Aim. To correlate findings of conventional cystoscopy with CT virtual cystoscopy (CTVC) in detecting bladder tumors and to evaluate accuracy of virtual cystoscopy in early detection of bladder cancer. Material and Method. From June 2013 to June 2014, 50 patients (46 males, four females) with history and investigations suggestive of urothelial cancer, with mean age 62.76 ± 10.45 years, underwent CTVC by a radiologist as per protocol and subsequently underwent conventional cystoscopy (CPE) the same day or the next day. One urologist and one radiologist, blinded to the findings of conventional cystoscopy, independently interpreted the images, and any discrepant readings were resolved with consensus. Result. CTVC detected 23 out of 25 patients with bladder tumor(s) correctly. Two patients were falsely detected as negative while two were falsely labeled as positive in CTVC. Virtual and conventional cystoscopy were comparable in detection of tumor growth in urinary bladder. The sensitivity, specificity, positive predictive value, and negative predictive value of virtual cystoscopy were 92% each. Conclusion. CTVC correlates closely with the findings of conventional cystoscopy. Bladder should be adequately distended and devoid of urine at the time of procedure. However, more studies are required to define the role of virtual cystoscopy in routine clinical practice.

Computed tomography-virtual cystoscopy in the evaluation of a bladder mass: Could it replace standard conventional cystoscopy?

Objective

To determine the role of computed tomography-virtual cystoscopy (CT-VC) in the detection and evaluation of bladder cancer, compared to standard conventional cystoscopy (CC).

Patients and methods

Twenty-five patients with a clinical presentation of a bladder mass(es) were selected from an outpatient urology clinic between May 2011 and August 2012. All patients were then assessed using multi-slice CT of the bladder, CT-VC and CC. The results were then compared amongst axial CT images, multiplanar reconstruction (MPR) images, CT-VC and CC, and compared with the pathological results.

Results

Forty lesions were found at CC in the 25 patients. MPR images had a greater sensitivity for detecting small masses of ⩽5 mm, and for identifying the location of the masses, especially basal (100%), than had axial images. The diagnostic results varied significantly (P = 0.031 and 0.039) between CC and axial images. The difference was slightly significant (P = 0.063) for MPR images and was not significant (P = 0.99) for virtual images.

Conclusions

Compared to CC, CT-VC was much less invasive, but it was not possible to take a biopsy and provide tissue for histopathology, and it could not depict flat lesions or mucosal colour changes. Therefore, CT-VC could be considered for bladder mapping before CC, in the follow-up of patients with superficial transitional cell carcinoma after transurethral resection of the tumour, in combination with urine cytology, and for patients in whom CC is difficult or contraindicated.

A unified EM approach to bladder wall segmentation with coupled level-set constraints

Magnetic resonance (MR) imaging-based virtual cystoscopy (VCys), as a non-invasive, safe and cost-effective technique, has shown its promising virtue for early diagnosis and recurrence management of bladder carcinoma. One primary goal of VCys is to identify bladder lesions with abnormal bladder wall thickness, and consequently a precise segmentation of the inner and outer borders of the wall is required. In this paper, we propose a unified expectation-maximization (EM) approach to the maximum-a posteriori (MAP) solution of bladder wall segmentation, by integrating a novel adaptive Markov random field (AMRF) model and the coupled level-set (CLS) information into the prior term. The proposed approach is applied to the segmentation of T(1)-weighted MR images, where the wall is enhanced while the urine and surrounding soft tissues are suppressed. By introducing scale-adaptive neighborhoods as well as adaptive weights into the conventional MRF model, the AMRF model takes into account the local information more accurately. In order to mitigate the influence of image artifacts adjacent to the bladder wall and to preserve the continuity of the wall surface, we apply geometrical constraints on the wall using our previously developed CLS method. This paper not only evaluates the robustness of the presented approach against the known ground truth of simulated digital phantoms, but further compares its performance with our previous CLS approach via both volunteer and patient studies. Statistical analysis on experts' scores of the segmented borders from both approaches demonstrates that our new scheme is more effective in extracting the bladder wall. Based on the wall thickness calibrated from the segmented single-layer borders, a three-dimensional virtual bladder model can be constructed and the wall thickness can be mapped onto the model, where the bladder lesions will be eventually detected via experts' visualization and/or computer-aided detection.

Motion correction for MR cystography by an image processing approach

Magnetic resonance (MR) cystography or MR-based virtual cystoscopy is a promising new technology to evaluate the entire bladder in a fully noninvasive manner. It requires the anatomical bladder images be acquired at high spatial resolution and with adequate signal-to-noise ratio (SNR). This often leads to a long-time scan (>5 min) and results in image artifacts due to involuntary bladder motion and deformation. In this paper, we investigated an image-processing approach to mitigate the problem of motion and deformation. Instead of a traditional single long-time scan, six repeated short-time scans (each of approximately 1 min) were acquired for the purpose of shifting bladder motion from intrascan into interscans. Then, the interscan motions were addressed by registering the short-time scans to a selected reference and finally forming a single average motion-corrected image. To evaluate the presented approach, three types of images were generated: 1) the motion-corrected image by registration and average of the short-time scans; 2) the directly averaged image of the short-time scans (without motion correction); and 3) the single image of the corresponding long-time scan. Six experts were asked to blindly score these images in terms of two important aspects: 1) the definition of the bladder wall and 2) the overall expression on the image quality. Statistical analysis on the scores suggested that the best result in both the aspects is achieved by the presented motion-corrected average. Furthermore, the superiority of the motion-corrected average over the other two is statistically significant by the measure of a linear mixed-effect model with p -values < 0.05. Our findings may facilitate the detection of bladder abnormality in MR cystography by mitigating the motion challenge. The effectiveness of this approach depends on the noise level of acquired short-time scans and the robustness of image registration, and future effort on these two aspects is needed.

Imaging of the female urethral diverticulum

Female urethral diverticulum is a localized out-pouching of the urethra that is becoming increasingly prevalent, but often poses a diagnostic challenge. Traditionally, conventional voiding cystourethrography has been used to make the preoperative diagnosis. With the development of higher-resolution images acquired through ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI), the anatomy and various abnormalities of the female urethra can be better elucidated. This article focuses on the imaging features of female urethral diverticulum, with emphasis on diagnostic pearls, particularly using MRI. Female urethral diverticulum can be best identified by their location in the posterolateral urethra and by their communication with the urethral lumen. Improved imaging techniques combined with increased physician awareness of urethral diverticulum will lead to more prompt and accurate diagnosis of this entity, leading to better treatment of affected patients.

Investigating the relationship between virtual cystoscopy image quality and CT slice thickness

OBJECTIVE

To investigate the effect of reconstruction slice thickness on image quality at CT virtual cystoscopy (VC).

METHODS

Pelvic CT examinations in bladder cancer patients were reconstructed at different slice thicknesses (0.6-5 mm) and intervals, and resulting VC images assessed. Quality indicators were ridging, holes, floaters and dimpling artefacts, tumour definition, and an overall score, ranked 1 (best) to 7 (worst). CT number and standard deviation (SD) for bladder contents and bladder wall were recorded. The mean SD was used as a measure of noise, and the contrast-to-noise ratio (CNR) was calculated as the CT number difference between them divided by the average image noise. The mean CNR across the three levels was used for analysis. Each qualitative image quality measure was compared with CT number, noise and CNR measurements.

RESULTS

Dimpling artefacts increased with thinner slice reconstruction and correlated with increased noise, often resulting in poor tumour definition. The best overall image quality score was seen for VC images reconstructed at 1.2 mm slice thickness, probably because of the competing effects of spatial resolution and CNR.

CONCLUSION

A slice thickness reconstruction <1.2 mm does not provide for better image quality at VC owing to the presence of increased noise.

Comparison of virtual cystoscopy and ultrasonography for bladder cancer detection: a meta-analysis

BACKGROUND AND PURPOSE

Bladder cancer is the most commonly diagnosed malignancy in patients presenting with haematuria. Early detection is crucial for improving patient prognosis. We therefore performed a meta-analysis to evaluate and compare the detection validity (sensitivity and specificity) of virtual cystoscopy (VC) and ultrasonography (US).

METHODS

We searched MEDLINE, EMBASE, PubMed and the Cochrane Library for studies evaluating diagnosis validity of VC and US between January 1966 and December 2009. Meta-analysis methods were used to pool sensitivity and specificity and to construct a summary receiver-operating characteristic (SROC) curve.

RESULTS

A total of 26 studies that included 3084 patients who fulfilled all of the inclusion criteria were considered for inclusion in the analysis. The pooled sensitivity for bladder cancer detection using CT virtual cystoscopy (CTVC), MR virtual cystoscopy (MRVC) and US was 0.939 (95% CI, 0.919-0.956), 0.908 (95% CI, 0.827-0.959) and 0.779 (95% CI, 0.744-0.812), respectively. The pooled specificity for bladder cancer detection using CTVC, MRVC and US was 0.981 (95% CI, 0.973-0.988), 0.948 (95% CI, 0.884-0.983) and 0.962 (95% CI, 0.953-0.969), respectively. The pooled diagnostic odd ratio (DOR) estimate for CTVC (604.22) were significantly higher than for MRVC (144.35, P<0.001) and US (72.472, P<0.001).

CONCLUSION

Our results showed that both CTVC and MRVC are better imaging methods for diagnosing bladder cancer than US. CTVC has higher diagnostic value (sensitivity, specificity and DOR) for the detection of bladder cancer than either MRCT or US.

Development of an Automated Steering Mechanism for Bladder Urothelium Surveillance

Given the advantages of cystoscopic exams compared with other procedures available for bladder surveillance, it would be beneficial to develop an improved automated cystoscope. We develop and propose an active programmable remote steering mechanism and an efficient motion sequence for bladder cancer detection and postoperative surveillance. The continuous and optimal path of the imaging probe can enable a medical practitioner to readily ensure that images are produced for the entire surface of the bladder in a controlled and uniform manner. Shape memory alloy (SMA) based segmented actuators disposed adjacent to the distal end of the imaging probe are selectively activated to bend the shaft to assist in positioning and orienting the imaging probe at a plurality of points selected to image all the interior of the distended bladder volume. The bending arc, insertion depth, and rotational position of the imaging probe are automatically controlled based on patient-specific data. The initial prototype is tested on a 3D plastic phantom bladder, which is used as a proof-of-concept in vitro model and an electromagnetic motion tracker. The 3D tracked tip trajectory results ensure that the motion sequencing program and the steering mechanism efficiently move the image probe to scan the entire inner tissue layer of the bladder. The compared experimental results shows 5.1% tip positioning error to the designed trajectory given by the simulation tool. The authors believe that further development of this concept will help guarantee that a tumor or other characteristic of the bladder surface is not overlooked during the automated cystoscopic procedure due to a failure to image it.

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.

Hematuria: portal venous phase multi detector row CT of the bladder--a prospective study

PURPOSE

To prospectively determine the accuracy of portal venous phase helical multi-detector row computed tomography (CT) for bladder lesion evaluation in patients with hematuria by using cystoscopy as the reference standard.

MATERIALS AND METHODS

The study was approved by the institutional review board for human investigation, and informed consent was obtained from all patients. This study included 118 patients (91 male, 27 female; age range, 15-87 years; mean age +/- standard deviation, 62 years +/- 14) who underwent portal venous phase multi-detector row CT (scanning delay, 70 seconds; section thickness, 2 mm) and conventional cystoscopy because of painless gross hematuria or recurrent microscopic hematuria. Two reviewers with different experience levels independently evaluated the bladder for lesions at CT in a prospective fashion. The kappa statistic was used to determine the per lesion and per patient agreement between the two reviewers and between the CT and cystoscopic findings. The sensitivity and specificity of multi-detector row CT for bladder lesion detection were analyzed for numbers of lesions and for numbers of patients.

RESULTS

Multi-detector row CT showed excellent per lesion (kappa = 0.839) and per patient (kappa = 0.881) agreement between the two reviewers. Respective per lesion and per patient agreement between the CT and cystoscopic findings was also excellent in the first (kappa = 0.866 and kappa = 0.881) and second (kappa = 0.802 and kappa = 0.863) reviewers. The sensitivity and specificity of multi-detector row CT were 89%-92% and 88%-97%, respectively, in the per lesion analysis and 95% and 91%-93%, respectively, in the per patient analysis for both reviewers. All statistical parameters of diagnostic accuracy were similar between the two reviewers (P > .05).

CONCLUSION

Portal venous phase multi-detector row CT can provide high accuracy and reader agreement for bladder lesion detection in patients with painless gross hematuria and recurrent microscopic hematuria; these results indicate that multi-detector row CT can be used as the initial bladder examination in such patients.

Imaging of Bladder Cancer

Bladder cancer is a heterogeneous and frequently multifocal disease with a variable clinical course. The management of bladder cancer is therefore challenging and complicated. CT and MR imaging have replaced the traditional excretory urography and are emerging as the imaging modalities of choice for work-up of patients who have bladder cancer. Imaging provides essential diagnostic information for detection, staging, and post-treatment follow-up of bladder cancer.

Computed tomography urography for diagnosing bladder cancer

OBJECTIVE

To evaluate the use of computed tomography urography (CTU) for diagnosing bladder tumours in patients with macroscopic haematuria and aged >40 years.

PATIENTS AND METHODS

In all, 200 consecutive patients attending a fast-track haematuria clinic were assessed using 'same-day' CTU and flexible cystoscopy. Patients were aged >40 years and had macroscopic haematuria with no urine infection. CTU studies were reported by one uroradiologist and scored on a 3-point scale to quantify the probability of bladder cancer. All flexible cystoscopies were performed by the same cystoscopist with no knowledge of the findings of CTU, and scored using a 3-point scale. Cystoscopy, pathological findings and CTU were then compared.

RESULTS

The prevalence of bladder tumours was 24%; when CTU was compared with the histopathological findings, there was one false-positive and three false-negative diagnoses, indicating a sensitivity of 0.93 and a specificity of 0.99, with a 0.98 positive and 0.97 negative predictive value for detecting bladder cancer. A review of the three false-negative cases showed that one was missed on original CTU reporting, the second had the appearance of prostate cancer on CTU and the third was a squamous metaplasia.

CONCLUSION

CTU is an accurate method of detecting bladder tumours in the present patients, and is reliable and accurate for assessing the bladder. Our results support the use of CTU as a first-line screening tool for this high-risk group, the use of which will obviate the need for flexible cystoscopy in patients with a negative CTU and allow those with an obvious tumour to be referred directly for rigid cystoscopy and resection. The remaining patients should be referred for flexible cystoscopy. Such a pathway would accelerate patient assessment by using fewer tests and provide a true 'one-stop' clinic, allowing a comprehensive evaluation with a single test for the upper and lower urinary tract.

Virtual computed tomography cystoscopy in bladder pathologies

OBJECTIVE

Assessed the usefulness of virtual cystoscopy performed with multidetector computed tomography (CT) in patients with different urinary bladder pathologies compared to the conventional cystoscopy.

MATERIALS AND METHODS

Eighteen patients with different bladder pathologies, which consisted of 11 tumors, 3 diverticula, 2 trabecular changes and 2 stones, were assessed with conventional cystoscopy and virtual CT cystoscopy. The results of virtual CT cystoscopy were compared with the findings of conventional cystoscopy. We determined the detection rate and positive predictive value of CT imaging based virtual cystoscopy in the diagnosis of urinary bladder lesions.

RESULTS

CT scanning was well tolerated by all patients, and no complications occurred. Images in 16 (88%) of the 18 virtual cystoscopic examinations were either of excellent or good quality. All tumors except one, 2 trabecular changes and 2 stones were characterized with similar findings in the both of methods. The masses ranged from 0.4 to 7.0 cm in diameter. While conventional cystoscopy could not evaluate interior part of the diverticulum, virtual CT cystoscopy could demonstrate clearly within it. There were no false-positive findings in our series.

CONCLUSION

Virtual CT cystoscopy is a promising technique to be used in the detection of bladder lesions. It should be considered especially at the evaluation of bladder diverticula. In the future, it may be possible or even advantageous to incorporate into the imaging algorithm for evaluation of bladder lesion.