MR imaging evaluation of renal cell carcinoma

Textural differences in apparent diffusion coefficient between low- and high-stage clear cell renal cell carcinoma

OBJECTIVE

The purpose of this article is to evaluate differences in texture measures on apparent diffusion coefficient (ADC) maps between low- and high-stage clear cell renal cell carcinomas (RCCs).

MATERIALS AND METHODS

In this retrospective study, 61 patients with clear cell RCC at pathologic examination and who underwent preoperative MRI with diffusion-weighted imaging were included. Clear cell RCCs were clinically staged on review of preoperative MRI by a board-certified radiologist blinded to the pathologic findings. Whole lesions were segmented on ADC maps by two readers independently, from which first-order texture features (i.e., mean and skewness) and second-order texture features (i.e., cooccurrence matrix measures) were calculated. Texture metrics were compared between low- and high-stage clear cell RCC.

RESULTS

In 61 patients, there were 62 clear cell RCCs (33 low stage [stages I and II] and 29 high stage [stages III and IV]) at pathologic examination. Staging accuracy of qualitative interpretation was 100% for low-stage lesions and 37.9% (11/29) for high-stage lesions. There was no statistically significant difference in mean ADC between high- and low-stage clear cell RCCs (1.77×10(-3) vs 1.80×10(-3) mm2/s; p=0.7). However, high-stage clear cell RCCs were larger (6.96±2.93 vs 3.49±1.57 cm; p<0.0001) and had statistically significantly (p≤0.0001) higher ADC skewness (0.02±0.33 vs -0.52±0.65) and cooccurrence matrix correlation (0.64±0.11 vs 0.49±0.13). Multivariate logistic regression identified size, skewness, and cooccurrence matrix correlation as significant independent predictors of high stage (AUC=0.92). Interreader correlation in texture metrics ranged from 0.82 to 0.89.

CONCLUSION

First- and second-order ADC texture metrics differ between low- and high-stage clear cell RCCs. A model that includes size and ADC texture measures may help to stage clear cell RCCs noninvasively.

Advanced renal mass imaging: diffusion and perfusion MRI

Computed tomography (CT) is considered the imaging modality of choice in evaluation of renal lesions. The advantages of magnetic resonance imaging (MRI) compared to CT include superior soft tissue contrast, avoidance of ionizing radiation and iodinated contrast media, and the possibility of performing functional and advanced imaging techniques such as diffusion-weighted (DWI) and perfusion-weighted imaging (PWI). Although the traditional role of MRI in the evaluation of renal mass is primarily that of a problem-solving tool, DWI and PWI are expanding the role of MRI in management of renal cell cancers. DWI and PWI have shown considerable promise not only in renal lesion detection and characterization as benign or malignant, but also in assessment of renal cell cancer subtype and nuclear grade. Furthermore, these techniques have the potential to assist with tailoring patient- and disease-specific management by providing surgical planning in patients with localized renal cell cancer and assessing treatment response in patients with advanced renal cell cancer undergoing targeted chemotherapy.

Contemporary imaging of the renal mass

Renal masses increasingly are detected incidentally in asymptomatic individuals. Accurate characterization of these lesions is important for clinical management, planning intervention, and avoiding unnecessary procedures. Ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) are the mainstays of renal mass detection and characterization. Ultrasonography is useful for distinguishing cystic from solid lesions and can detect lesion vascularity, especially with use of ultrasound contrast agents, but is less sensitive, less specific, and less reproducible than CT and MRI. CT, with and without intravenous contrast, is the primary imaging test for characterization and staging of renal lesions, and is utilized more often than MRI. Current multidetector CT technology provides near isotropic acquisition, with three-dimensional reformatting capabilities. Due to lack of exposure to iodinated contrast and ionizing radiation and superior soft tissue contrast, MRI is being increasingly utilized as a problem-solving tool for diagnosis, staging, and preoperative planning for renal malignancies. Future directions for imaging of primary renal neoplasm include accurate characterization of renal cell cancer subtype, assistance with treatment planning, and evaluation of treatment response.

Imaging of renal cell carcinoma: state of the art and recent advances

BACKGROUND AND AIM

Renal cell carcinoma (RCC) is the 13th most common cancer worldwide and accounts for 4% of all adult malignancies. Herein the state of the art and recent advances in cross-sectional radiological imaging applied to RCC are reviewed, including ultrasonography, computed tomography, magnetic resonance imaging, and positron emission tomography.

METHODS

Literature search of peer-reviewed papers published by October 2010.

RESULTS

In front of more conventional and widespread imaging tools, such as ultrasonography and computed tomography, an array of newer and attractive radiological modalities are under investigation and show promise to improve our ability to noninvasively detect renal tumors and its recurrences, accurately assess the extent of the disease, and reliably evaluate treatment response, particularly in the era of antiangiogenetic therapy.

CONCLUSIONS

Recent major advances in radiological imaging techniques have considerably improved our ability to diagnose, stage and follow-up RCC. Further studies are needed to evaluate the potential of most recent and still investigational imaging tools.

Magnetic Resonance Imaging of Renal Disease: Recent Developments and Future Applications

Magnetic resonance imaging (MRI) offers the ability to non-invasively assess parenchymal and vascular renal disease. Indications for renal MRI include the evaluation of renal masses, urinary obstruction and infection, renal vasculature, and the health of transplant kidneys. The potential of MR angiography to replace invasive conventional x-ray angiography has been recognized for many years. Recent developments in MRI resulting from fast MR systems with faster gradients, new surface coil designs and the latest sequence developments coupled with innovative contrast agent administration strategies have prompted substantial progress of MRI in the diagnosis of renal disease. The goal of this article is to present the current state of MRI in diagnosing renal disease, with an emphasis on the latest developments in the evaluation of renal vascular disease.

Magnetic Resonance Imaging of the Kidney

High tissue contrast, multiplanar image capabilities, and tissue characterization render MR into an ideal imaging modality for effective evaluation of a wide range of renal disorders. It provides high details of anatomy and can suggest the composition of lesions. Improvements of MRI technology during the last years have made MRI increasingly attractive for body imaging. Fast imaging sequences and parallel imaging techniques have proved to be useful in minimizing artifacts from respiratory motion and magnetic susceptibility differences providing superior imaging quality. Additionally, the use of renally eliminated paramagnetic contrast agents permits assessment of parenchymal perfusion and visualization of the excretion of the contrast medium providing information on renal function.

Accuracy of Breath-Hold Magnetic Resonance Imaging in Preoperative Staging of Organ-Confined Renal Cell Carcinoma

PURPOSE

To determine the accuracy of breath-hold magnetic resonance (MR) imaging for preoperative staging of patients with organ-confined (stage I) renal cell carcinoma.

MATERIALS AND METHODS

Preoperative MR examinations of 43 patients (50 lesions) who underwent nephrectomy were reviewed. The MR examination consisted entirely of breath-hold sequences, and images were retrospectively evaluated by 2 blinded radiologists. Reviewers independently evaluated each case for findings that could affect the radiologic staging, particularly those that distinguish between organ-confined (stage I) and non-organ-confined (>stage II) disease. Each reviewer assigned a stage, and results were correlated with findings at surgery and pathologic examination.

RESULTS

The difference between both reviewers and pathologic findings in evaluating an intact renal capsule (stage I) was statistically significant (P < 0.05) and resulted in a statistically significant difference between radiologic and pathologic staging (Wilcoxon test, P < 0.05). The kappa test demonstrated moderate agreement between radiologic and pathologic staging (82% and 80% for reviewers 1 and 2, kappa = 0.54 and 0.80, respectively) and substantial agreement (90%, kappa = 0.80) between the 2 reviewers in assigning a radiologic stage.

CONCLUSION

Breath-hold MR imaging has an accuracy ranging between 80% and 82% in staging patients with organ-confined renal cell carcinoma, with substantial (90%) agreement between readers.

MRI for Preoperative Staging of Renal Cell Carcinoma Using the 1997 TNM Classification:Comparison with Surgical and Pathologic Staging

OBJECTIVE

The purpose of our study was to determine the accuracy of MRI for preoperative staging of renal cell carcinoma using the 1997 TNM classification.

MATERIALS AND METHODS

We conducted a retrospective review of MRI performed in 40 consecutive patients with 42 renal cell carcinomas before radical (n = 35) or partial (n = 4) nephrectomy or exploratory laparotomy (n = 3). The interval between imaging and surgery ranged from 1 to 59 days (mean, 17.9 days). Imaging was performed with T1- and T2-weighted, dynamic gadolinium-enhanced, and time-of-flight sequences. MRI and surgical-pathologic staging was performed using the 1997 TNM staging system. MRI staging was compared with surgical-pathologic staging as the gold standard. Agreement between the two staging methods was assessed using the kappa statistic.

RESULTS

Agreement between MRI and surgical-pathologic staging was good for T staging (kappa = 0.72 and 0.78 for reviewers 1 and 2 respectively), poor for N staging (kappa = 0.13, both reviewers), good for M staging (kappa = 0.66, both reviewers), and excellent for the assessment of venous involvement (kappa = 0.93, both reviewers). MRI overestimated the T stage in five patients and the N stage in five and underestimated the T stage in three, the N stage in four, the M stage in one, and the extent of venous thrombosis in two patients.

CONCLUSION

MRI is a reliable method for preoperative staging of renal cell carcinoma using the 1997 TNM classification, in particular for assessing venous involvement.

Body MR venography

MRV offers unique diagnostic possibilities for detection and characterization of venous disease. It allows evaluation of perivascular and vascular anatomy, evolution of thromboembolic events, and assessment of vascular flow. MRI is a diagnostic tool that can be tailored for a variety of clinical dilemmas, not only DVTs. Continued improvements in hardware and software will expand the role of MRV.

Fast breath-hold T2-weighted MRI of the kidney by means of half-Fourier single-shot turbo spin echo: comparison with high resolution turbo spin echo sequence

PURPOSE

The value of the fast half-Fourier single-shot turbo spin echo (HASTE) sequence in T2-weighted MRI of the kidney was evaluated as a substitute for the conventional turbo spin echo (TSE) sequence.

METHOD

Forty-five patients with suspected abnormalities of the kidney underwent MRI with a 1.5 T system. Breath-hold HASTE and respiratory-triggered TSE sequences were performed. Qualitative and quantitative analyses were performed for comparison of these sequences.

RESULTS

The signal-to-noise ratio (SNR) with HASTE was higher than that with TSE. The lesion-to-kidney contrast-to-noise ratio for solid masses with HASTE was almost equal to that with TSE. For cystic masses, the CNR with HASTE was significantly higher than that with TSE (p < 0.05). Respiratory and chemical shift artifacts were significantly smaller on HASTE than on TSE (p < 0.01). However, the blurring artifact was higher on HASTE than on TSE (p = 0.01).

CONCLUSION

The HASTE sequence generates high contrast images and is free of motion and chemical shift artifacts, with much better time efficacy. The sequence provides comparable diagnostic information to TSE sequences.

Carcinoma of the kidney, testis, and rare urologic malignancies

The purpose of this symposium was to provide a forum for discussion on current information on the etiology and diagnosis of, and therapy for, tumors of the kidney, testis, and several uncommon malignancies of the genitourinary tract. The most recent contributions in epidemiology and molecular genetics were discussed with specific reference to their importance for clinical practice. Contemporary treatment approaches with the emphasis on multidisciplinary patient management of tumors commonly seen in the clinic as well as those that are only rarely diagnosed by urooncologists were presented. Major stress was given to the management optimization as it pertains to short- and long-term quality of life issues of patients treated for these tumors. Methods to reduce treatment toxicity including carcinogenic potential of chemotherapy, radiotherapy, or their combination were found to be of nearly equal importance to patient survival. Symposium participants reached consensus on a number of important points: 1) The management of patients with several malignancies discussed requires the presence of a multidisciplinary team of specialist who are interested in diagnosis and treatment of genitourinary tumors; 2) Patients managed in such an environment are expected to have optimal survival and the best possible quality of life; 3) Real advances in the management of patients can be best obtained through well-designed prospective clinical trials; and 4) There is a need for timely introduction of relevant advances in epidemiology and molecular genetics to clinics.

Renal neoplasms amenable to partial nephrectomy: MR imaging

PURPOSE

To determine the magnetic resonance (MR) imaging characteristics of renal lesions in patients who undergo technically successful partial nephrectomy.

MATERIALS AND METHODS

Between February 1991 and September 1997, 38 patients (41 lesions) who underwent partial nephrectomy at a single institution were preoperatively evaluated with contrast material-enhanced, multiplanar, surface-coil MR imaging. Imaging findings that could affect the decision to perform partial nephrectomy were retrospectively evaluated: tumor size; tumor location; presence of pseudocapsule; suspected tumor invasion of renal sinus fat, renal collecting system, renal vein, or perinephric fat; and morphologic and physiologic status of the contralateral kidney. Correlation was made with surgical and pathologic findings.

RESULTS

Thirty-three of 41 lesions (80%) were renal cell carcinomas, five were oncocytic neoplasms (12%), two were hemorrhagic cysts (5%), and one was an angiomyolipoma (2%). Twenty-four of 41 (59%) lesions had pseudocapsules. In most cases, the perinephric fat (n = 38 [93%]), the renal sinus fat (n = 31 [76%]), and the renal collecting system (n = 39 [95%]) were correctly interpreted as being uninvolved by tumor.

CONCLUSION

Renal neoplasms amenable to partial nephrectomy can be identified and characterized with contrast-enhanced, multiplanar, surface-coil MR imaging.

Surgical strategy in late‐stage renal cell cancer with intracaval extension

During the past two years several reports have substantially contributed to the surgical stratification of patients with late-stage renal cell cancer and simultaneously occurring intracaval neoplastic extension, and our knowledge about the clinical prognosis of the patients after nephrectomy with complete removal of the tumour thrombosis has been extended. Recognizing the importance of a tolerable perioperative and postoperative morbidity and mortality, it is now well documented in the literature that a multidisciplinary approach involving the combined use of deep hypothermia, cardiac arrest and cardiopulmonary bypass has dramatically improved the feasibility of surgical treatment of the venous extension above the hepatic veins. Furthermore, the diagnostic approach for patients with intracaval thrombosis, aiming at the reliable delineation of the cranial margin of venous extension, has been rationalized without compromising important diagnostic information required for the surgical stratification. This review assesses the current opinion of the surgical stratification of patients with renal cell cancer and intracaval neoplastic extension, the most reliable and least invasive diagnostic approach for the preoperative staging and, finally, the independent prognostic value of neoplastic venous extension for the clinical course of the disease.

Small renal cell carcinoma: MRI with pathologic correlation

The MRI features of small renal cell carcinomas (RCCs) were retrospectively reviewed and correlated with histology in 24 patients. MRI features on both T1- and T2-weighted images were classified into hypointensity, isointensity, and hyperintensity. Each tumor was pathologically classified into four types: alveolar, papillary, tubular, and cystic. These findings were correlated with MR signal intensities. Alveolar tumors showed hypointensity to isointensity on T1-weighted image and isointensity to hyperintensity on T2-weighted image. In contrast, all papillary tumors showed hypointensity on T2-weighted image. Four of six tumors with hypointensity on T2-weighted image were caused by hemosiderin deposition, hemorrhage, and necrosis. However, there were two papillary RCCs that showed hypointensity on T2-weighted image despite no hemosiderin deposition and no hemorrhage. We conclude that papillary RCC is associated with T2-hypointense appearance as well as hemosiderin deposition, hemorrhage, and necrosis.