Multi-detector row CT of the kidneys and urinary tract: techniques and applications in the diagnosis of benign diseases

Survival analysis of clear cell renal cell carcinoma based on radiomics and deep learning features from CT images

PURPOSE

To create a nomogram for accurate prognosis of patients with clear cell renal cell carcinoma (ccRCC) based on computed tomography images.

METHODS

Eight hundred twenty-two ccRCC patients with contrast-enhanced computed tomography images involved in this study were collected. A rectangular region of interest surrounding the tumor was used to extract quantitative radiomics and deep-learning features, which were filtered by Cox proportional hazard regression model and least absolute shrinkage and selection operator. Then the selected features formed a fusion signature, which was assessed by Cox proportional hazard regression model method, Kaplan-Meier analysis, receiver operating characteristic curves, and concordance index (C-index) in different clinical subgroups. Finally, a nomogram constructed with this signature and clinicopathologic risk factors was assessed by C-index and survival calibration curves.

RESULTS

The fusion signature performed better than the radiomics signature. Then we combined this signature and 2 clinicopathologic risk factors. This nomogram showed an increase of about 20% in C-index values when compared to clinical nomogram in both datasets. Its prediction probability was also in good agreement with the actual ratio.

CONCLUSION

The proposed fusion nomogram provided a noninvasive and easy-to-use model for survival prognosis of ccRCC patients in future clinical use, without the requirement to perform a detailed segmentation for radiologists.

Scientific Status Quo of Small Renal Lesions: Diagnostic Assessment and Radiomics

Background: Small renal masses (SRMs) are defined as contrast-enhanced renal lesions less than or equal to 4 cm in maximal diameter, which can be compatible with stage T1a renal cell carcinomas (RCCs). Currently, 50-61% of all renal tumors are found incidentally. Methods: The characteristics of the lesion influence the choice of the type of management, which include several methods SRM of management, including nephrectomy, partial nephrectomy, ablation, observation, and also stereotactic body radiotherapy. Typical imaging methods available for differentiating benign from malignant renal lesions include ultrasound (US), contrast-enhanced ultrasound (CEUS), computed tomography (CT), and magnetic resonance imaging (MRI). Results: Although ultrasound is the first imaging technique used to detect small renal lesions, it has several limitations. CT is the main and most widely used imaging technique for SRM characterization. The main advantages of MRI compared to CT are the better contrast resolution and tissue characterization, the use of functional imaging sequences, the possibility of performing the examination in patients allergic to iodine-containing contrast medium, and the absence of exposure to ionizing radiation. For a correct evaluation during imaging follow-up, it is necessary to use a reliable method for the assessment of renal lesions, represented by the Bosniak classification system. This classification was initially developed based on contrast-enhanced CT imaging findings, and the 2019 revision proposed the inclusion of MRI features; however, the latest classification has not yet received widespread validation. Conclusions: The use of radiomics in the evaluation of renal masses is an emerging and increasingly central field with several applications such as characterizing renal masses, distinguishing RCC subtypes, monitoring response to targeted therapeutic agents, and prognosis in a metastatic context.

Computed Tomography Urography: State of the Art and Beyond

Computed Tomography Urography (CTU) is a multiphase CT examination optimized for imaging kidneys, ureters, and bladder, complemented by post-contrast excretory phase imaging. Different protocols are available for contrast administration and image acquisition and timing, with different strengths and limits, mainly related to kidney enhancement, ureters distension and opacification, and radiation exposure. The availability of new reconstruction algorithms, such as iterative and deep-learning-based reconstruction has dramatically improved the image quality and reducing radiation exposure at the same time. Dual-Energy Computed Tomography also has an important role in this type of examination, with the possibility of renal stone characterization, the availability of synthetic unenhanced phases to reduce radiation dose, and the availability of iodine maps for a better interpretation of renal masses. We also describe the new artificial intelligence applications for CTU, focusing on radiomics to predict tumor grading and patients' outcome for a personalized therapeutic approach. In this narrative review, we provide a comprehensive overview of CTU from the traditional to the newest acquisition techniques and reconstruction algorithms, and the possibility of advanced imaging interpretation to provide an up-to-date guide for radiologists who want to better comprehend this technique.

CT of the urinary tract revisited

Computed tomography (CT) of the abdomen is usually appropriate for the initial imaging of many urinary tract diseases, due to its wide availability, fast scanning and acquisition of thin slices and isotropic data, that allow the creation of multiplanar reformatted and three-dimensional reconstructed images of excellent anatomic details. Non-enhanced CT remains the standard imaging modality for assessing renal colic. The technique allows the detection of nearly all types of urinary calculi and the estimation of stone burden. CT is the primary diagnostic tool for the characterization of an indeterminate renal mass, including both cystic and solid tumors. It is also the modality of choice for staging a primary renal tumor. Urolithiasis and urinary tract malignancies represent the main urogenic causes of hematuria. CT urography (CTU) improves the visualization of both the upper and lower urinary tract and is recommended for the investigation of gross hematuria and microscopic hematuria, in patients with predisposing factors for urologic malignancies. CTU is highly accurate in the detection and staging of upper tract urothelial malignancies. CT represents the most commonly used technique for the detection and staging of bladder carcinoma and the diagnostic efficacy of CT staging improves with more advanced disease. Nevertheless, it has limited accuracy in differentiating non-muscle invasive bladder carcinoma from muscle-invasive bladder carcinoma. In this review, clinical indications and the optimal imaging technique for CT of the urinary tract is reviewed. The CT features of common urologic diseases, including ureterolithiasis, renal tumors and urothelial carcinomas are discussed.

Quantitative assessment of renal obstruction in multi-phase CTU using automatic 3D segmentation of the renal parenchyma and renal pelvis: A proof of concept

Purpose

Quantitative evaluation of renal obstruction is crucial for preventing renal atrophy. This study presents a novel method for diagnosing renal obstruction by automatically extracting objective indicators from routine multi-phase CT Urography (CTU).

Material and methods

The study included multi-phase CTU examinations of 6 hydronephrotic kidneys and 24 non-hydronephrotic kidneys (23,164 slices). The developed algorithm segmented the renal parenchyma and the renal pelvis of each kidney in each CTU slice. Following a 3D reconstruction of the parenchyma and renal pelvis, the algorithm evaluated the amount of the contrast media in both components in each phase. Finally, the algorithm evaluated two indicators for assessing renal obstruction: the change in the total amount of contrast media in both components during the CTU phases, and the drainage time, "T1/2", from the renal parenchyma.

Results

The algorithm segmented the parenchyma and renal pelvis with an average dice coefficient of 0.97 and 0.92 respectively. In all the hydronephrotic kidneys the total amount of contrast media did not decrease during the CTU examination and the T1/2 value was longer than 20 min. Both indicators yielded a statistically significant difference (p < 0.001) between hydronephrotic and normal kidneys, and combining both indicators yielded 100% accuracy.

Conclusions

The novel algorithm enables accurate 3D segmentation of the renal parenchyma and pelvis and estimates the amount of contrast media in multi-phase CTU examinations. This serves as a proof-of-concept for the ability to extract from routine CTU indicators that alert to the presence of renal obstruction and estimate its severity.

Immunotherapy-related renal toxicity causes reversible renal enlargement

PURPOSE

Prior case reports have noted an increase in renal size and perinephric stranding accompanying immunotherapy-related renal toxicity due to checkpoint-inhibitor therapy. The purpose of this investigation was to systematically evaluate if immunotherapy-related renal toxicity affects renal size and possible associated imaging findings.

METHODS

This retrospective multi-hospital study included 25 patients (13 men), mean age 67 years (range 46-83) who received immune-checkpoint inhibitors for cancer treatment, developed biopsy-proven immunotherapy-related nephritis, and who also had abdominal imaging before, during, and after nephritis was diagnosed. Long axis renal diameter, renal corticomedullary differentiation/enhancement and perinephric stranding were evaluated by two readers at three timepoints: (1) prior to checkpoint inhibitor therapy (baseline), (2) after biopsy-proven immunotherapy-related nephritis (post-treatment), and (3) following renal function recovery (follow-up). Intraclass correlation coefficient and Cohen's Kappa were calculated to quantify agreement. Logistic regression analysis was implemented to measure the association between each timepoint and imaging features.

RESULTS

Reader agreement on kidney measurements was excellent (ICC = 0.87). There was an increase in renal size between baseline and post-treatment (p = 0.001), followed by a decrease between post-treatment to follow-up (p < 0.001). Agreement was perfect for abnormal renal corticomedullary differentiation/enhancement (Kappa = 1, p < 0.001) and almost perfect for perinephric stranding (Kappa = 0.97, p < 0.001). Neither post-treatment nor follow-up imaging findings were significantly associated with these findings compared to the baseline (p = 0.2-0.6).

CONCLUSION

Immunotherapy-related renal toxicity was associated with an increase in renal size coincident with acute renal dysfunction.

Findings on intraprocedural non-contrast computed tomographic imaging following hepatic artery embolization are associated with development of contrast-induced nephropathy

BACKGROUND

Contrast-induced nephropathy (CIN) is a reversible form of acute kidney injury that occurs within 48-72 h of exposure to intravascular contrast material. CIN is the third leading cause of hospital-acquired acute kidney injury and accounts for 12% of such cases. Risk factors for CIN development can be divided into patient- and procedure-related. The former includes pre-existing chronic renal insufficiency and diabetes mellitus. The latter includes high contrast volume and repeated exposure over 72 h. The incidence of CIN is relatively low (up to 5%) in patients with intact renal function. However, in patients with known chronic renal insufficiency, the incidence can reach up to 27%.

AIM

To examine the association between renal enhancement pattern on non-contrast enhanced computed tomographic (CT) images obtained immediately following hepatic artery embolization with development of CIN.

METHODS

Retrospective review of all patients who underwent hepatic artery embolization between 01/2010 and 01/2011 (n = 162) was performed. Patients without intraprocedural CT imaging (n = 51), combined embolization/ablation (n = 6) and those with chronic kidney disease (n = 21) were excluded. The study group comprised of 84 patients with 106 procedures. CIN was defined as 25% increase above baseline serum creatinine or absolute increase ≥ 0.5 mg/dL within 72 h post-embolization. Post-embolization CT was reviewed for renal enhancement patterns and presence of renal artery calcifications. The association between non-contrast CT findings and CIN development was examined by Fisher’s Exact Test.

RESULTS

CIN occurred in 11/106 (10.3%) procedures (Group A, n = 10). The renal enhancement pattern in patients who did not experience CIN (Group B, n = 74 with 95/106 procedures) was late excretory in 93/95 (98%) and early excretory (EE) in 2/95 (2%). However, in Group A, there was a significantly higher rate of EE pattern (6/11, 55%) compared to late excretory pattern (5/11) (P < 0.001). A significantly higher percentage of patients that developed CIN had renal artery calcifications (6/11 vs 20/95, 55% vs 21%, P = 0.02).

CONCLUSION

A hyperdense renal parenchyma relative to surrounding skeletal muscle (EE pattern) and presence of renal artery calcifications on immediate post-HAE non-contrast CT images in patients with low risk for CIN are independently associated with CIN development.

Mimics and Pitfalls in Renal Imaging

There are several potential pitfalls that radiologists face when interpreting images of the kidneys. Some result from image acquisition and can arise from the imaging equipment or imaging technique, whereas others are patient related. Another category of pitfalls relates to image interpretation. Some difficulties stem from methods to detect enhancement after contrast administration, whereas others are benign entities that can mimic a renal tumor. Finally, interpretation and diagnosis of fat-containing renal masses may be tricky due to the complexities discerning the pattern of fat within a mass and how that translates to an accurate diagnosis.

CT urography: how to optimize the technique

PURPOSE

Computed tomography urography (CTU) has emerged as the modality of choice for imaging the urinary tract within the past few decades. It is a powerful tool that enables detailed anatomic evaluation of the urinary tract in order to identify primary urothelial malignancies, benign urinary tract conditions, and associated abdominopelvic pathologies. As such, there have been extensive efforts to optimize CTU protocol.

METHODS

This article reviews the published literature on CTU protocol optimization, including contrast bolus timing, dose reduction, reconstruction algorithms, and ancillary practices.

CONCLUSION

There have been many advances in CTU techniques, which allow for imaging diagnosis of a wide spectrum of diseases while minimizing radiation dose and maximizing urinary tract distension and opacification.

Attenuation values of renal parenchyma in virtual noncontrast images acquired from multiphase renal dual-energy CT: Comparison with standard noncontrast CT

OBJECTIVES

To compare the renal parenchyma attenuation of virtual noncontrast (VNC) images derived from multiphase renal dual-energy computed tomography (DECT) with standard noncontrast (SNC) images, and to determine the optimum phase for VNC images.

MATERIALS AND METHODS

Twenty-nine men and 16 women (mean age, 61 ± 13 years; range, 37-89 years) underwent dynamic renal DECT (100/Sn140 kVp) were included in this institutional review board-approved retrospective study. There were four phases of the scan, which included noncontrast, corticomedullary (CMP), nephrographic (NP), and excretory phases (EP). The VNC images was generated from CMP, NP and EP. CT numbers of SNC images and VNC images of each phases were measured in the renal cortex and medulla. Mean standard deviation of subcutaneous fat was measured as image noise on SNC and VNC images. Radiation dose was recorded and potential radiation dose reduction was estimated. Results were tested for statistical significance using the unpaired t-test and agreement using Bland-Altman plot analysis.

RESULTS

The difference in mean attenuation between SNC and each phase of VNC images were ≤4 HU. The mean attenuation of renal cortex and medulla was 33.2 ± 4.4 HU, and 34.2 ± 4.8 HU in SNC, 33.6 ± 7.6 HU and 31.1 ± 8.3 HU in VNC of CMP, 34.8 ± 8.6 HU and 35.6 ± 8.5 HU in VNC of NP, 31.5 ± 7.6 HU and 32.4 ± 7.5 HU in VNC of EP. In VNC of CMP, the attenuation of the cortex was higher than the medulla (p < 0.05), and the attenuation of medulla was significant lower than that of SNC (p < 0.01). In VNC of NP, the attenuation of renal cortex was higher than SNC (p < 0.05). In VNC of EP, the attenuation of cortex and medulla were lower than SNC (p < 0.05), and inadequate iodine subtraction in collecting system was noted. Image noise was significantly greater in SNC (p < 0.001). Mean radiation dose reduction achievable by removing the SNC was 12.3% ± 0.9%.

CONCLUSIONS

VNC images from multiphase renal DECT were similar to SNC images. Using the nephrographic phase can gives more comparable VNC images to SNC images in renal parenchyma than other phases.

The role of imaging in the management of cardiorenal syndrome

Imaging of the kidney and the heart can provide valuable information in the diagnosis and management of cardiorenal syndromes. Ultrasound- (US-) based imaging (echocardiogram and renal US) is an essential component in the initial diagnostic workup of CRS. Echocardiography provides information on the structure and function of heart, and renal ultrasound is useful in differentiating between acute and chronic kidney disease and excluding certain causes of acute kidney injury such as obstructive uropathy. In this paper we overview the basic concepts of echocardiogram and renal ultrasound and will discuss the clinical utility of these imaging techniques in the management of cardiorenal syndromes. We will also discuss the role of other imaging modalities currently in clinical use such as computerized tomography and magnetic resonance imaging as well as novel techniques such as contrast-enhanced ultrasound imaging.

Segmental enhancement inversion at biphasic multidetector CT: characteristic finding of small renal oncocytoma

PURPOSE

To retrospectively determine the usefulness of segmental enhancement inversion during the corticomedullary phase (CMP) and early excretory phase (EEP) of biphasic multidetector computed tomography (CT) in differentiating small renal oncocytoma from renal cell carcinoma (RCC).

MATERIALS AND METHODS

This retrospective study was institutional review board approved; informed consent was waived. Between January 2004 and December 2006, 98 patients with pathologically confirmed renal masses smaller than 4 cm (10 renal oncocytomas and 88 RCCs) were included in this study. Segmental enhancement inversion was defined as follows: In a mass with two segments showing different degrees of enhancement during CMP, the relatively highly enhanced segment became less enhanced during EEP, whereas the less-enhanced segment during CMP became highly enhanced during EEP. Two experienced radiologists retrospectively assessed the presence of segmental inversion in all masses and measured attenuation with consensus. The Fisher exact test was used to determine the significance of segmental enhancement inversion in differentiating small renal oncocytoma from RCC.

RESULTS

Eight of 10 renal oncocytomas and only one of 88 RCCs showed segmental inversion during CMP and EEP, which significantly differentiated small renal oncocytomas and RCCs (P < .0001). For differentiating oncocytoma from RCC, segmental inversion was found to have a sensitivity of 80% (eight of 10), a specificity of 99% (87 of 88), a positive predictive value of 89% (eight of nine), and a negative predictive value of 98% (87 of 89). The mean values of the attenuation differences shown by two segments during CMP and EEP were 62.75 HU +/- 36.96 (standard deviation) and -36.88 HU +/- 20.02, respectively.

CONCLUSION

Segmental enhancement inversion during CMP and EEP was found to be a characteristic enhancement pattern of small renal oncocytoma at biphasic multidetector CT and it may help in differentiating small oncocytoma from RCC.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/2522081180/DC1.

Integrated evaluation of hypertensive patients with cardiovascular magnetic resonance

BACKGROUND

Hypertension causes cardiac morbidity and premature mortality. Accurate evaluation to exclude potentially curable causes is important. Cardiovascular Magnetic Resonance and Magnetic Resonance Angiography (CMR/CE-MRA) provide an integrated approach to the assessment of hypertensive patients - a single study can identify certain secondary causes and assess left ventricular (LV) mass and function. The aim of this study was to prospectively evaluate the feasibility of CMR/CE-MRA to define LV dimensions and exclude some secondary causes in a selected group of hypertensives.

METHODS AND RESULTS

Fifty-three hypertensives (46+/-17 years, 18 females) were prospectively studied (early onset hypertension, n=17; drug resistant hypertension, n=23; hypertension with increased creatinine at baseline/after ACEi, n=12; hypertension with peripheral vessel disease, n=1). Study protocol included assessment of LV and aorta, imaging of adrenals and 3D CE-MRA of aorta and renal arteries. Significant abnormalities were found in 13 patients (25%) - renal artery stenosis (n=8), aortic coarctation (n=4), adrenal mass (n=1). Mean LV mass index was increased compared with matched controls. LV systolic dysfunction was found in 9 patients.

CONCLUSIONS

CMR/CE-MRA provides comprehensive evaluation of hypertensive patients and could allow for a unique integrated approach with assessment of LV dimensions as well as detection of some secondary causes.

Multi-detector row CT of the kidney: Optimizing scan delays for bolus tracking techniques of arterial, corticomedullary, and nephrographic phases

PURPOSE

To determine optimal scan delays for renal arterial-, corticomedullary-, and nephrographic-phase imaging with multi-detector row computed tomography (MDCT) of the kidney using a bolus-tracking technique.

METHODS AND MATERIALS

One hundred and twenty-eight patients underwent three-phase CT scan of the kidney with eight-row MDCT after receiving 2 mL/kg of 300 mgI/mL contrast medium at 4 mL/s. Patients were prospectively randomized into three groups with different scan delays for the three scan phases (arterial, corticomedullary, and nephrographic) after bolus-tracking triggered at 50 HU of aortic contrast enhancement: group 1 (5, 20, 45 s); group 2 (10, 25, 50s); and group 3 (15, 30, 55 s). Mean CT values (HU) of the abdominal aorta, renal artery, renal vein, renal cortex, and renal medulla were measured; increases in CT values pre- to post-contrast were assessed as contrast enhancement. Renal artery-to-vein and renal cortex-to-medulla contrast differences were also assessed. Qualitative analysis was also performed.

RESULTS

Mean renal artery enhancement was 240-288 HU at 5-15s after the trigger and peaked at 10s (P<.001). Mean renal cortical enhancement was 195-217 HU at 10-30s and peaked at 25s (P<.01). Contrast enhancement in the renal medulla increased gradually and reached mean 145 HU at 55 s. Cortex-to-medulla contrast difference was high (110-140 HU) at 5-30s and decreased below 30 HU at 45 s after the trigger. Renal artery-to-vein contrast difference was high (121-125 HU) at 5-10s. Qualitative results correlated well with quantitative results.

CONCLUSION

For the injection protocol used in this study, optimal scan delays after the bolus-tracking trigger were 5-10 s for renal arterial, 15-25 s for corticomedullary, and 50-55 s for nephrographic phases.

Diagnosis of Medullary Sponge Kidney by Computed Tomographic Urography

The diagnosis of medullary sponge kidney traditionally was established by means of intravenous pyelography. Beginning in the mid-1990s, intravenous pyelography rapidly was supplanted by computed axial tomography as the preferred imaging study for evaluating patients with renal stone disease. Conventional computed tomographic imaging has not been satisfactory for diagnosing medullary sponge kidney. The introduction of multidetector-row computed tomography in 1999 allowed radiologists to acquire images composed of elements allowing the creation of high-resolution 3-dimensional displays. Computed tomographic urography is an imaging technique that provides both cross-sectional displays and images of the contrast-filled renal collecting systems, ureters, and urinary bladder that are the equivalent of intravenous pyelography. We report a case of medullary sponge kidney diagnosed by means of 3-dimensional multidetector-row computed tomographic urography.

Evaluation of Renal Transplant Donors with 16-Section Multidetector CT Angiography: Comparison of Contrast Media with Low and High Iodine Concentrations

PURPOSE

To compare the degree of contrast enhancement, image quality, and accuracy of renal computed tomographic (CT) angiography performed with a 16-detector row CT unit and equal iodine doses of low- and high-iodine-concentration contrast medium in the evaluation of renal transplant donors.

MATERIALS AND METHODS

Eighty donors scheduled to undergo renal CT angiography with 16-detector row CT were administered nonionic contrast media with two iodine concentrations. The first group (group A, n=40) received a contrast medium with 300 mg of iodine per milliliter, and the second group (group B, n=40) received a contrast medium with 370 mg of iodine per milliliter. An equal iodine dose of 550 mg per kilogram body weight was given to both groups. Contrast enhancement was quantified by measuring attenuation in the abdominal aorta and in both renal arteries. Subjective assessment of contrast enhancement, quality of reformatted images, and visualization of branch order of renal arteries were rated with a 5-point scale. The number of renal arteries and veins seen at CT was correlated with the results at surgery.

RESULTS

The mean enhancement values in group B were significantly greater (P<.001) than those in group A. The mean HU (+/-standard deviation) in groups A and B were 298+/-76 and 344+/-75, respectively, in the aorta, 284+/-74 and 331+/-71 in the right renal artery, and 285+/-72 and 329+/-73 in the left renal artery. The mean enhancement, image quality, and branch orders visualized were rated better in group B than in group A (P<.01). The accuracies for correctly identifying renal arteries and veins, respectively, were 91% and 95% for group A and 96% and 96% for group B.

CONCLUSION

Renal donor CT angiography with a contrast medium of 370 mg of iodine per milliliter provides greater enhancement and image quality compared with a contrast medium of 300 mg of iodine per milliliter. The diagnostic accuracies were similar.

Multidetector computed tomography urography (MDCTU) for diagnosing urothelial malignancy

Multidetector computed tomography (MDCT) is well established for the detection of stones and renal masses, but more recently MDCT urography (MDCTU) is becoming widely used for examination of the entire urinary tract aimed specifically for diagnosing urothelial lesions. Evidence is rapidly accumulating to support the use of MDCTU in this manner. Familiarity with the MDCTU signs of urothelial malignancy is a prerequisite for optimum radiological practice. This article provides a review of the appearances of transitional cell cancer in the upper urinary tract and bladder.

Volume changes of experimental carotid sidewall aneurysms due to embolization with liquid embolic agents: a multidetector CT angiography study

Iodine-containing polyvinyl alcohol polymer (I-PVAL) is a novel precipitating liquid embolic that allows for artifact-free evaluation of CT angiography (CTA). As accurate aneurysm volumetry can be performed with multidetector CTA, we determined volumes of experimental aneurysms before, immediately after, and 4 weeks after embolization of 14 porcine experimental carotid sidewall aneurysms with this liquid embolic. An automated three-dimensional software measurement tool was used for volumetric analysis of volume-rendering CTA data. Furthermore, intra-aneurysmal pressure changes during liquid embolization were measured in four silicone aneurysms and potential polymer volume changes within 4 weeks were assessed in vitro. Liquid embolic injection was performed during temporary balloon occlusion of the aneurysm neck, resulting in a mean occlusion rate of 98.3%. Aneurysms enlarged significantly during embolization by 61.1 +/- 28.9%, whereas a significant shrinkage of 5.6 +/- 2.7% was observed within the follow-up period. Histologic analysis revealed an inflammatory foreign body reaction with partial polymer degradation. In silicone aneurysm models, intra-aneurysmal pressure remained unchanged during liquid embolic injection, whereas balloon inflation resulted in a mean pressure increase of 31.2 +/- 0.7%. No polymer shrinkage was observed in vitro. The aneurysm enlargement noted was presumably due to pressure elevation after balloon inflation, which resulted in dilatation of the weak venous wall of the newly constructed aneurysm--another shortcoming of this experimental aneurysm model. The volume decrease after 4 weeks expressed partial polymer degradation.

Evaluation of Living Renal Donors: Accuracy of Three-dimensional 16-Section CT

PURPOSE

To retrospectively assess the sensitivity and specificity of three-dimensional (3D) 16-section computed tomography (CT) in the evaluation of vessels, pelvicalyceal system, and ureters in living renal donors, with surgical findings as the reference standard.

MATERIALS AND METHODS

This was a HIPAA-compliant study. Institutional review board approval was obtained for the review of subjects' medical records and data analysis, with waiver of informed consent. Forty-six renal donors (18 men, 28 women; mean age, 42 years) were examined with 16-section CT. Two blinded reviewers independently studied renal vascular and urographic anatomy of each donor CT scans by fist using 3D images alone, then transverse images alone, and finally transverse and 3D data set. Image quality, degree of diagnostic confidence, and time used for review were recorded. Sensitivity and specificity were calculated.

RESULTS

For 3D images, transverse images, and transverse in conjunction with 3D data sets, the respective sensitivity and specificity of CT in evaluation of accessory arteries by reviewer 1 were 100% and 100%, 89% and 100%, and 100% and 100%, and those by reviewer 2 were 89% and 97%, 89% and 100%, and 89% and 100%; the respective sensitivity and specificity in evaluation of venous anomalies by reviewer 1 were 100% and 98%, 100% and 98%, and 100% and 98%, and those by reviewer 2 were 100% and 98%, 100% and 95%, and 100% and 98%. For focused comprehensive assessment of renal donors with 3D scans alone, a reviewer on average (average of reviewers 1 and 2) used 2.4 minutes per scan, demonstrated full confidence in 93%, and rated the quality as excellent in 76%.

CONCLUSION

For focused assessment of renal vascular and urographic anatomy, review of 3D data set alone provides high sensitivity and specificity with regard to findings seen at surgery.

Applications of Computed Tomography in Renal Imaging

There have been huge advances in CT technology since its introduction more than 30 years ago. Modern, multislice CT scanners are fast and produce truly volumetric data, allowing it to be reconstructed in almost any plane. In this article, we explore the impact of these developments on the use of CT in imaging of the renal tract. Whilst it may take the radiologist longer to review and process the increased amount of data that is produced, diagnostic accuracy is unquestionably improved and new and exciting challenges are presented to the radiologist as he learns to manipulate and interpret the data in a way that he has never done before.

Multidetector CT urography: comparison of two different scanning protocols for improved visualization of the urinary tract

The goal of this study was to evaluate different CT scanning protocols on the depiction of the urinary tract by multidetector CT. The authors retrospectively reviewed 55 consecutive patients who underwent CT scanograms. Two groups of patients were included: renal donors (n=29) and hematuria patients (n=26). For the renal donor protocol, 120 mL of iodinated contrast was injected and a CT scanogram was obtained after a 5-minute delay. For the hematuria CT urography protocol, 100 mL of contrast was followed by a 250 mL normal saline drip and CT scanograms acquired after an 8-minute delay. Urinary tracts from both imaging protocols were then divided into four segments and evaluated by consensus reading of two experienced radiologists rated on a scale of 0 to 2. Complete visualization of the renal pelvis and the proximal, middle, and distal ureter for the renal donor protocol was noted to be 86%, 57%, 45%, and 52% and for that of the CT urography protocol to be 75%, 65%, 40%, and 44%, respectively. Comparing scanograms of the renal donor protocol and the CT urography protocol, there was no statistically significant difference in the depiction of renal pelvis or the proximal, middle or distal ureteral region (P=0.1625, 0.3226, 0.8636, and 0.6145, respectively). The study demonstrates that there is no significant difference between the CT urography protocol and the renal donor protocol in the depiction of the urinary tract.

Volume Determination of Intracranial Aneurysms Using 16-Row Multislice Computed Tomography Angiography

OBJECTIVE

To assess multislice computed tomography (CT) angiography for volume determination of intracranial aneurysms.

METHODS

Submillimetric 16-row multislice CT angiography was performed with optimized scan parameters on precision spheres and a soft carotid artery model harboring 3 aneurysms connected to a pulsatile circuit. The CT angiography images were produced using optimized techniques for axial, multiplanar reformation, maximum intensity projection, surface-shaded display, and volume-rendered images. Measurements were made with electronic precision calipers by segmentation according to the method of Cavalieri and by the use of automated volumetric analysis software.

RESULTS

Segmentation resulted in precise and accurate volume estimates of aneurysms, but small volumes were underestimated and evaluation time was long (36:44 minutes). Automated volume evaluation from volume-rendered reconstructions also resulted in low measurement error, although the evaluation process was significantly faster (3:25 minutes; P < 0.0001).

CONCLUSIONS

The use of an automated volume analysis tool on volume-rendered reconstructions is recommended for time-efficient volume assessment of intracranial aneurysms.

Renal Multidector Row CT

Multidetector row CT is the most recent advance in CT technology. An increased number of detector rows and more powerful x-ray tubes result in faster scanning time, increased volume coverage, and improved spatial and temporal resolution. MDCT technology allows superior image quality, decreased examination time, and the ability to perform complex multiphase vascular and three-dimensional examinations.