CT cystography and virtual cystoscopy in the assessment of new and recurrent bladder neoplasms

PET/CT limitations and pitfalls in urogenital cancers

Hybrid FDG PET/CT plays a vital role in oncologic imaging and has been widely adopted for the staging and restaging of a variety of malignancies. Its diagnostic value in urogenital malignancies is less well-known, not at least because of the variable FDG avidity of these tumor entities, the sites of these tumors, and technical challenges associated with sequential imaging of CT and PET. PET/CT interpretation thus can be especially challenging and is associated with many pitfalls, which can lead to both false-positive and false-negative diagnoses as well as incorrect assessment of metabolic change following therapy. Currently, FDG PET/CT is not the standard of care for the initial diagnosis or staging of early-stage or low-risk urogenital cancers; however, it can help evaluate distant metastatic disease, response to therapy, and disease recurrence in high-risk patients. Knowledge of imaging features of tumor metabolic avidity and pitfalls is essential for accurate interpretation.

ACR Appropriateness Criteria® Post-Treatment Surveillance of Bladder Cancer

Urothelial cancer is the second most common cancer, and cause of cancer death, related to the genitourinary tract. The goals of surveillance imaging after the treatment of urothelial cancer of the urinary bladder are to detect new or previously undetected urothelial tumors, to identify metastatic disease, and to evaluate for complications of therapy. For surveillance, patients can be stratified into one of three groups: (1) nonmuscle invasive bladder cancer with no symptoms or additional risk factors; (2) nonmuscle invasive bladder cancer with symptoms or additional risk factors; and (3) muscle invasive bladder cancer. This article is a review of the current literature for urothelial cancer and resulting recommendations for surveillance imaging. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Nonionizing photoacoustic cystography with near-infrared absorbing gold nanostructures as optical-opaque tracers

AIM

The objectives of this study were to demonstrate nonionizing photoacoustic tomography (PAT) of bladders with near-infrared absorbing gold nanocages (GNCs) as an optical-turbid tracer and to investigate the fate of GNCs after photoacoustic imaging.

MATERIALS & METHODS

The rats' bladders were visualized using PAT after transurethral injection of 2-nM GNCs. The fate of GNCs in the bladders was investigated. Spectroscopic PAT was applied to identify GNC-filled bladders in vivo and study biodistribution ex vivo.

RESULTS

Rats' bladders filled with GNCs were successfully imaged using a PAT system. The photoacoustic amplitude was enhanced by approximately 2240%. Both in vivo and ex vivo PAT results reveal that no accumulation of GNCs in the bladder and kidney was observed, and were validated with inductively coupled plasma mass spectrometry.

CONCLUSION

The PAT with transurethral injection of GNCs provides two crucial safety features for clinical translation: no radiation exposure and no long-term heavy metal accumulation.

Detection of bladder cancer recurrence with real-time three-dimensional ultrasonography-based virtual cystoscopy

This prospective study evaluated the accuracy of grey-scale two-dimensional (2D) ultrasonography and real-time threedimensional (3D) ultrasonography-based virtual cystoscopy for detecting early recurrence of bladder cancer in previously treated patients (n = 40). Real-time 3D ultrasonography-based virtual cystoscopy images were compared with both 2D ultrasonography and interval conventional cystoscopy pathology results. Ultrasound examinations were performed before routine follow-up with conventional cystoscopy. Overall sensitivity for real-time 3D ultrasonography-based virtual cystoscopy was lower than for 2D ultrasonography, indicating it did not provide additional information. The results of combined (2D and 3D) ultrasonography and conventional cystoscopy differed significantly. Where lesions were detected with combined ultrasonography, the number of previous cystoscopies was lower and the tumour stage was significantly higher at initial diagnosis, compared with cases where no lesions were detected. The results suggest that ultrasonography before cystoscopy can be performed more frequently - or, if no lesions are detected by ultrasonography, the interval between cystoscopies can be prolonged - in patients at high risk of bladder cancer recurrence.

An adaptive window-setting scheme for segmentation of bladder tumor surface via MR cystography

This paper proposes an adaptive window-setting scheme for noninvasive detection and segmentation of bladder tumor surface in T(1)-weighted magnetic resonance (MR) images. The inner border of the bladder wall is first covered by a group of ball-shaped detecting windows with different radii. By extracting the candidate tumor windows and excluding the false positive (FP) candidates, the entire bladder tumor surface is detected and segmented by the remaining windows. Different from previous bladder tumor detection methods that are mostly focusing on the existence of a tumor, this paper emphasizes segmenting the entire tumor surface in addition to detecting the presence of the tumor. The presented scheme was validated by ten clinical T(1)-weighted MR image datasets (five volunteers and five patients). The bladder tumor surfaces and the normal bladder wall inner borders in the ten datasets were covered by 223 and 10,491 windows, respectively. Such a large number of the detecting windows makes the validation statistically meaningful. In the FP reduction step, the best feature combination was obtained by using receiver operating characteristics or ROC analysis. The validation results demonstrated the potential of this presented scheme in segmenting the entire tumor surface with high sensitivity and low FP rate. This study inherits our previous results of automatic segmentation of the bladder wall and will be an important element in our MR-based virtual cystoscopy or MR cystography system.

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.

Virtual cystoscopy: the evaluation of bladder lesions with computed tomographic virtual cystoscopy

PURPOSE

Our objective was to assess the accuracy of computed tomographic virtual cystoscopy (CTVC) in the detection of urinary bladder lesions.

METHODS

Twenty-five patients were examined using CTVC. Bladder scanned using multislice CT at a slice thickness of 1 mm. The data were transferred to a workstation for interactive navigation using surface rendering. Findings obtained from CTVC were compared with results from conventional cystoscopy and with pathological findings.

RESULTS

Thirty-eight lesions were identified. The smallest was 0.2 × 0.3 cm; the largest was 7 × 4.5 cm. Both CTVC and conventional cystoscopy were used. Conventional cystoscopy detected the same number of lesions that were detected by CTVC. On morphological examination, 26 of the lesions were polypoid, 7 were sessile and 5 were bladder wall-thickening. While one of the polypoid lesions was reported as an inverted papilloma, 2 of the 5 lesions that were identified as wall-thickening were malignant and 3 were benign. The sensitivity of using CTVC to identify neoplasias was 100%; the accuracy was 89%.

CONCLUSION

Although the definitive diagnosis of some suspected urinary bladder tumours is only possible with conventional cystoscopy and biopsy, CTVC is a minimally invasive technique which provides beneficial information about urinary bladder lesions.

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.

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.

Detection of bladder tumors with 3-dimensional sonography and virtual sonographic cystoscopy

OBJECTIVE

Bladder tumors are among the most common types of malignant neoplasms of the urinary tract. The purpose of this study was to evaluate the potential value of 3-dimensional (3D) sonography and sonographic cystoscopy in detection of bladder tumors.

METHODS

Thirty-one patients with suspected or known bladder tumors were included this study. All patients underwent 3D sonography and conventional cystoscopy within 15 days. The number, size, location, and morphologic features of the lesions were evaluated on gray scale, 3D virtual, and multiplanar reconstruction images obtained from the patients. The results of 3D sonographic cystoscopy were compared with the findings from conventional cystoscopy, which was considered the reference standard.

RESULTS

Twenty-eight (90.3%) of 31 3D virtual sonographic cystoscopic studies had good or excellent image quality. Conventional cystoscopy revealed 47 lesions in 22 of 28 patients; 3D sonographic virtual cystoscopy showed 41 (87.2%) of 47 lesions. Three-dimensional virtual sonography alone had sensitivity of 96.2%, specificity of 70.6%, a positive predictive value of 93.9%, and a negative predictive value of 80% for tumor detection. The combination of gray scale sonography, multiplanar reconstruction, and 3D virtual sonography had sensitivity of 96.4%, specificity of 88.8%, a positive predictive value of 97.6%, and a negative predictive value of 84.2% for tumor detection.

CONCLUSIONS

Three-dimensional sonography is a promising alternative noninvasive technique for use in detection of bladder tumors, their localization, and perivesical spreading. The location, size, and morphologic features of the tumors shown on 3D sonography agreed well with the findings of conventional cystoscopy.

Virtual Cystoscopy by Intravesical Instillation of Dilute Contrast Medium: Preliminary Experience

PURPOSE

We determined whether virtual cystoscopy based on helical data sets can yield urinary capabilities similar to those achieved by fiber-optic cystoscopy.

MATERIALS AND METHODS

A total of 11 patients with ultrasound detected bladder tumors underwent pelvic CT as a single volumetric scan after preliminary bladder distention with saline mixed with contrast medium using a 6Fr infant feeding tube. Cystoscopy was simulated based on a 3-dimensional helical CT data set in real time. Source raw CT data for virtual cystoscopy were reconstructed and navigation was done in real time using surface rendering navigation software. These images and findings were then compared with conventional cystoscopy findings.

RESULTS

An attenuation gradient of 350 HU between the vesical mucosa and urine was noted. Two of the 14 tumors (11 patients) were missed and each was 0.7 cm. All tumors greater than 0.9 cm were detected. Overall sensitivity was 85.7%. There were no false-positive findings. There was good correlation with tumor location and size. The ureteral orifices and their relationship to the tumor were also well appreciated. Subtle mucosal changes on conventional cystoscopy were not delineated by virtual cystoscopy.

CONCLUSIONS

Our method of instilling dilute contrast medium in the bladder offers an excellent attenuation gradient. The overall sensitivity of tumor detection is better than that reported for intravenous contrast medium and pneumocystoscopy.