Diffusion weighted imaging in the detection of upper urinary tract urothelial tumors

Clinicopathologic characteristics of pulmonary ground glass opacity located preoperatively using a Hook-wire guidewire

Objective

To evaluate the relationship between the clinical and imaging features of ground glass opacity (GGO) localized using a preoperative Hook-wire guidewire and postoperative pathology.

Method

Preoperative Hook-wire guidewire localization was performed in 83 patients with GGO less than 2 ​cm, and their clinical data, imaging data, and postoperative pathology findings were retrospectively analyzed. The images were classified as pure GGO (pGGO) or mixed GGO (mGGO). The relationship between clinical and imaging features and postoperative pathology was analyzed.

Result

The 83 cases were colocalized, and the success rate of the guidewire positioning was 100%. Complications included pneumothorax (19.2% [16/83]) and the incidence of minor bleeding (30.2 [25/83]). Forty-seven patients had mGGO and 36 had pGGO. Among the 47 cases of mGGO, 18 (38.3%) were invasive adenocarcinoma (IAC), 18 (38.3%) were microinvasive adenocarcinoma (MIA), 8 (17.0%) were adenocarcinoma in situ (AIS), 2 (4.3%) were atypical adenomatous hyperplasia (AAH), and 1 (2.1%) was benign. Among the 36 cases of pGGO, 6 (16.7%) were IAC, 13 (36.1%) were MIA, 8 (22.2%) were AIS, 2 (5.6%) were AAH, and 7 (19.4%) cases were benign lesions. A significantly higher proportion of patients with IAC had mGGO than pGGO (21.7% vs. 7.2%, respectively; p ​= ​0.004). Among patients with mGGO, a higher proportion of them had a nodule diameter of ≥1 ​cm than those with a diameter of <1 ​cm (25.5% vs. 12.8%, respectively; p ​= ​0.003). There was no significant difference in age, location distribution, or pathological type.

Conclusion

Preoperative CT-guided Hook-wire guidewire positioning was safe with minor complications. A significantly higher proportion of patients with IAC had mGGO than pGGO. Patients with mGGO and a nodule diameter ≥1 ​cm require active treatment.

Update on MR urography (MRU): technique and clinical applications

Magnetic resonance imaging of the upper tract (pyelocalyces and ureters) or MR Urography (MRU) is technically possible and when performed correctly offers similar visualization of the upper tracts and for detection of non-calculous diseases of the collecting system similar specificity but with lower sensitivity compared to CTU. MRU provides the ability to simultaneously image the kidneys and urinary bladder with improved soft tissue resolution, better tissue characterization and when combined with assessment of the upper tract, a comprehensive examination of the urinary system. MRU requires meticulous attention to technical details and is a longer more demanding examination compared to CTU. Advances in MR imaging techniques including: parallel imaging, free-breathing motion compensation techniques and compressed sensing can dramatically shorten examination times and improve image quality and patient tolerance for the exam. This review article discusses updates in the MRU technique, summarizes clinical indications and opportunities for MRU in clinical practice and reviews advantages and disadvantages of MRU compared to CTU.

The value of adding diffusion-weighted images for tumor detection and preoperative staging in renal pelvic carcinoma for the reader's experience

PURPOSE

This retrospective study aimed to assess the value of adding diffusion-weighted magnetic resonance imaging (DWI) or gadolinium-enhanced fat-suppressed T1WI (CEI) to T2-weighted imaging (T2WI) for preoperative T categorization in renal pelvic carcinoma by the reader's experience using surgical specimens as the reference standard.

METHODS

Two radiologists (Reader 1; 3 years, 2; 13 years) reviewed 49 cases with urothelial carcinoma who underwent magnetic resonance imaging examination before surgery, independently, using three image sets: T2WI alone, T2WI plus DWI, and T2WI plus CEI for tumor detection and T categorization. The differences in the apparent diffusion coefficient values between tumors and renal parenchyma, histopathologic grade were analyzed.

RESULTS

T2WI plus CEI or DWI had high detection rates (93.4%) compared to T2WI alone. When discriminating T3a/T3b, for Reader 1, the use of T2WI plus DWI (88.0%) and T2WI plus CEI (92.0%) was significantly more accurate than T2WI alone (73%), with AUCs of 0.86, 0.86 and 0.77, respectively. For Reader 2, the accuracies were high on all image sets, with AUCs of 0.87-0.95, and the mean ADC of the tumors was significantly lower than that of the normal renal parenchyma. In addition, the mean ADC values of high-grade tumors were significantly lower than that of low-grade tumors.

CONCLUSIONS

DWI and CEI could be more helpful than T2WI alone for preoperative T categorization by less-experienced reader and DWI could be used for preoperative T categorization and for predicting the histopathologic grade of renal pelvic carcinoma.

Multidetector CT imaging features of invasive renal parenchyma urothelial carcinoma

OBJECTIVE

To characterize the multidetector CT imaging features of invasive renal parenchyma urothelial carcinoma (IRPUC).

METHODS

29 patients with IRPUC were retrospectively evaluated. Tumour location, density, cystic or solid appearance, calcification, capsule sign, enhancement pattern and metastases were assessed.

RESULTS

IRPUC involved the right kidney in 82.7% of patients. Medullary involvement was observed in 93.1% of patients. In 89.6% of patients, the reniform contour of the kidney was preserved. Tumours showed an infiltrative appearance (100%) with a poorly defined margin (100%), but an expansile component was also present (20.7%). Linear calcification was present (20.7%). Evidence of intra-abdominal metastatic disease (in 37.9% of cases) and regional lymphadenopathy (in 27.5% of cases) was present. Tumour attenuation was less or equal compared with the renal cortex or medulla on unenhanced CT (p-value> 0.05), after i.v. contrast administration; 100% were of homogeneous low attenuation compared with the normal renal cortex and medulla (p-value< 0.05).

CONCLUSION

IRPUC tends to be more prevalent in the right kidney, poorly defined margin, medullary involvement, with homogeneous enhancement less than the cortex and medulla in all phases.

ADVANCES IN KNOWLEDGE

IRPUC was more prevalent in the right kidney. IRPUC enhancement was less than that of the cortex and medulla on all phases. IRPUC showed poorly defined margin with medullary involvement and preserved reniform contour.

Are we closer to seeing carcinoma in situ in the upper urinary tract?

INTRODUCTION

There is observed increase in detection rate of upper urinary tract urothelial cancer worldwide. This is a result of improved imaging as well as implementation of novel technologies of direct visualization of upper urinary tract. Standard techniques still remain insufficient to diagnose flat urothelial lesions. Carcinoma in situ is characterized by flat disordered proliferation of urothelial cells with marked cytologic abnormality, which occur within one cell layer as well as full thickness urothelium and therefore requires a better technology to pick up early and subtle mucosal changes.

MATERIAL AND METHODS

The review presents available diagnostic tools in detection of upper urinary tract urothelial cancer and their ability to depict carcinoma in situ.

RESULTS

Ureterorenoscopy is an investigation of choice as various promising techniques are under pilot investigations to enhance visualization of upper urinary tract carcinoma in situ. So far only photodynamic diagnosis has been reported to be as effective in detection of carcinoma in situ in the upper as within the lower urinary tract.

CONCLUSIONS

Although we are close to see upper urinary tract carcinoma in situ all new promising diagnostic techniques still require further validation in multicenter clinical trials to indicate any change to current recommendations.

DWI in the Etiologic Diagnosis of Excretory Upper Urinary Tract Lesions: Can It Help in Differentiating Benign From Malignant Tumors? A Retrospective Study of 98 Patients

OBJECTIVE

The objective of this study was to evaluate the diagnostic performance of high-field DWI in distinguishing benign from malignant lesions of the upper urinary tract (UUT).

MATERIALS AND METHODS

Ninety-eight patients who underwent 3-T DWI (b = 1000 s/mm(2)) for assessment of a UUT lesion were retrospectively included in the study. Data on the size, location, and mean apparent diffusion coefficient (ADC) value of the lesions were collected and correlated with the final diagnosis. ROC curve analysis was used to determine the best threshold value of the mean ADC for characterization of the lesions.

RESULTS

A total of 66 carcinomas and 33 benign lesions were identified. The mean (± SD) ADC value was statistically significantly lower for the malignant lesions than for the benign lesions (0.984 ± 0.048 vs 1.536 ± 0.067 × 10(-3) mm(2)/s; p = 0.000007). For characterization of malignant lesions, the best cutoff ADC value on the ROC curve was found to be less than or equal to 0.996 10(-3) mm(2)/s. On the basis of this value, the sensitivity and specificity of 3-T DWI for the identification of malignant UUT lesions were 78.3% and 95.5%, respectively, with a positive predictive value of 94.7% and a negative predictive value of 80.8% (p = 0.0001). The thickness of the smallest lesion was 3 mm. The mean ADC value of high-grade tumors was not statistically significantly lower than that of low-grade tumors. The best cutoff value for predicting benignancy was greater than or equal to 1.100 × 10(-3) mm(2)/s with sensitivity of 90.9%, specificity of 82.6%, positive predictive value of 83.3%, and negative predictive value of 90.5%.

CONCLUSION

The ADC measurement is a useful additional parameter in the differentiation of benign from malignant UUT lesions.

Diffusion-weighted imaging in urinary tract lesions

Diffusion-weighted imaging (DWI) utilizes the signal contrast provided by the regional differences in the Brownian motion of water molecules, which is a direct reflection of the cellular micro-environment. DWI emerged as a revolutionary magnetic resonance imaging (MRI) technique in the field of stroke imaging. As far as body imaging is concerned, DWI has come a long way from being an experimental technique to an essential element of almost all abdominal MRI examinations. This progress has been made possible by technical advancements in MRI systems, as well as a better understanding of MRI physics. DWI is quick to perform and has the potential to provide crucial information about the disease process without adding much to the total imaging time. This article provides a brief review of the basic principles of DWI with insights to the information that DWI provides in the evaluation of various diseases of the urinary tract at both 1.5 and 3 T. DWI is helpful for differentiation of various histopathological subtypes of renal cell carcinoma (RCC). Prediction of histopathological grade of RCC is also becoming possible solely based on DWI. Assessment of response to chemotherapeutic agents is possible based on the change in the ADC (apparent diffusion coefficient) value. DWI performed with high b-values increases the confidence in diagnosing prostatic carcinoma. This article highlights the emerging role of DWI in the evaluation of urinary tract lesions.

Diffusion-weighted imaging of focal renal lesions: a meta-analysis

OBJECTIVES

Contrast-enhanced MRI can only distinguish to a limited extent between malignant and benign focal renal lesions. The aim of this meta-analysis is to review renal diffusion-weighted imaging (DWI) to compare apparent diffusion coefficient (ADC) values for different renal lesions that can be applied in clinical practice.

METHODS

A PubMed search was performed to identify relevant articles published 2004-2011 on renal DWI of focal renal lesions. ADC values were extracted by lesion type to determine whether benign or malignant. The data table was finalised in a consensus read. ADC values were evaluated statistically using meta-regression based on a linear mixed model. Two-sided P value <5 % indicated statistical significance.

RESULTS

The meta-analysis is based on 17 studies with 764 patients. Renal cell carcinomas have significant lower ADC values than benign tissue (1.61 ± 0.08 × 10(-3) mm(2)/s vs 2.10 ± 0.09 × 10(-3) mm(2)/s; P < 0.0001). Uroepithelial malignancies can be differentiated by lowest ADC values (1.30 ± 0.11 × 10(-3) mm(2)/s). There is a significant difference between ADC values of renal cell carcinomas and oncocytomas (1.61 ± 0.08 × 10(-3) mm(2)/s vs 2.00 ± 0.08 × 10(-3) mm(2)/s; P < 0.0001).

CONCLUSIONS

Evaluation of ADC values can help to determine between benign and malignant lesions in general but also seems able to differentiate oncocytomas from malignant tumours, hence potentially reducing the number of unnecessarily performed nephrectomies.

KEY POINTS

• This meta-analysis assesses the role of diffusion-weighted MRI in renal lesions. • ADC values obtained by DW MRI have been compared for different renal lesions. • ADC values can help distinguish between benign and malignant tumours. • Differentiating oncocytomas from malignant tumours can potentially reduce inappropriate nephrectomies.

Apparent diffusion coefficient as a prognostic biomarker of upper urinary tract cancer: a preliminary report

OBJECTIVES

To investigate the role of apparent diffusion coefficient (ADC) as a biomarker reflecting the aggressiveness of upper urinary tract urothelial cell carcinoma (UUT-UCC).

METHODS

Thirty-four consecutive patients treated with nephroureterectomy for non-metastatic disease were prospectively enrolled in this study. ADC was compared with clinicopathological variables including Ki-67 labelling index (LI) and cancer-specific survival (CSS).

RESULTS

The overall 3-year CSS rate was 82 % (median follow-up, 36 months). ADC was significantly lower in grade 3 disease than in grades 1-2 disease (P = 0.011) and significantly and inversely correlated with Ki-67 LI (ρ = -0.59, P = 0.0002). Low ADCs (<1.10 × 10(-3) mm(2)/s) were significantly associated with shorter CSS (P = 0.039). Multivariate analysis of preoperative variables identified ADC and MRI-based clinical T stage as independent indicators of shorter CSS; the patients were stratified into high-risk (8 patients with low ADC and at least clinical T3) and low-risk (26 patients with high ADC or not more than clinical T2) groups with 3-year CSS rates of 43 % and 93 % (P = 0.0003).

CONCLUSIONS

Our preliminary data suggest the potential role of ADC as a quantitative biomarker reflecting the aggressiveness of UUT-UCC. ADC might be useful for preoperative risk stratification of UUT-UCC patients.

KEY POINTS

• Diffusion-weighted MRI offers new information about the aggressiveness of urinary tract cancers. • The apparent diffusion coefficient acts as a quantitative biomarker for upper urinary tract cancers. • ADC inversely correlates with immunohistochemical and histological grading of UUT-UCC. • ADC offers a prognosis for UUT-UCC patients treated with nephroureterectomy.

Clinicopathologic significance of high signal intensity on diffusion-weighted MR imaging in the ureter, urethra, prostate and bone of patients with bladder cancer

RATIONALE AND OBJECTIVES

The aim of this study was to determine the clinicopathologic significance of high-intensity areas in the ureter, urethra, prostate, and bone incidentally found on diffusion-weighted magnetic resonance imaging (DWI) for the staging of bladder cancer.

MATERIALS AND METHODS

Axial and sagittal DWI and T2-weighted imaging of the pelvis were evaluated in 157 patients with bladder cancer. Two observers assessed T2-weighted imaging with DWI independently. The observers pointed out 67 areas showing abnormal high signal intensity on DWI in the ureter (n = 17), urethra (n = 8), prostate (n = 20), and bone (n = 22). Of the 67 high-intensity areas, 33 lesions were confirmed histopathologically (ureter, n = 10; urethra, n = 7; prostate, n = 16), and 22 bone lesions were diagnosed using T1-weighted imaging and follow-up computed tomography. Thus, 55 lesions were evaluable for correlation with DWI findings.

RESULTS

Of the 55 high-intensity areas, 28 (53%) were synchronous or metastatic urothelial cancer or invasion of urothelial cancer. The remaining 27 (47%) were a ureteral clot in one, a ureteral stone granuloma in one, prostatic cancer in six, granulomatous prostatitis in three, and normal red bone marrow in 16.

CONCLUSIONS

DWI is useful to comprehend the extent of bladder cancer and to detect incidentally coexisting diseases. Other imaging, endoscopic, and clinical findings would be useful to reduce false positivity.

Investigation of renal lesions by diffusion-weighted magnetic resonance imaging applying intravoxel incoherent motion-derived parameters--initial experience

PURPOSE

Usefulness of biexponentially fitted signal attenuation at different b-values for differentiating the histological characteristics of renal tumors.

MATERIALS AND METHODS

A total of 26 patients with 28 renal masses (histologically proven: 20 clear cell renal cell carcinomas [ccRCC], three transitional cell carcinomas, two oncocytomas, and one papillary RCC) and 30 volunteers with healthy kidneys were examined at 1.5 Tesla using an echo-planar DWI sequence. Using the IVIM model, we calculated the perfusion fraction f and the diffusion coefficient D. Furthermore, the ADC was obtained. These tumor parameters were compared to healthy renal tissue nonparametrically, and a receiver operating characteristic (ROC) analysis was performed.

RESULTS

Healthy renal parenchyma showed higher ADC and D values (p<0.001) than ccRCC (ADC 1.95±0.10 [SD] μm2/ms, f 18.32±2.52%, and D 1.88±0.11 μm2/ms versus ADC 1.45±0.38 μm2/ms, f 18.59±6.16%, and D 1.34±0.38 μm2/ms). When detecting malignancies the area under the curve for D was higher than for ADC. The f values for ccRCC were higher (p<0.001) than for non-ccRCC (ADC 1.52±0.47 μm2/ms, f 8.44±1.24%, and D 1.30±0.18 μm2/ms). Both f and D correlated with ccRCC grading.

CONCLUSION

IVIM imaging is able to provide reliable diffusion values in the human kidney and may enhance the accuracy of tumor diagnosis. The D value was the best parameter to distinguish renal tumors from healthy renal tissue. The f value is promising for determining the histological subgroups.