Thin-section multidetector CT angiography of renal artery stents

Phantom Study of In-Stent Restenosis at High-Spatial-Resolution CT

Purpose To examine the diagnostic performance of high-spatial-resolution (HSR) CT with 0.25-mm section thickness for evaluating renal artery in-stent restenosis. Materials and Methods A 0.05-mm wire phantom and vessel phantoms with renal stents with in-stent stenotic sections of varying diameters were scanned with both an HSR CT scanner equipped with 160-section multi-detector rows (0.25-mm section thickness) and a conventional CT scanner. The wire phantom was used to analyze modulation transfer function (MTF). With the vessel phantoms, the error rates were calculated as the absolute difference between the measured diameters and true diameters divided by the true diameters at the narrowing sections. For qualitative evaluation, overall image quality and diagnostic accuracy for evaluating stenosis in three stages were assessed by two radiologists. Statistical analyses included the paired t test, Wilcoxon signed-rank test, and McNemar test. Results HSR CT achieved 24.3 line pairs per centimeter ± 0.5 (standard deviation) and 29.1 line pairs per centimeter ± 0.4 at 10% and 2% MTF, respectively; and conventional CT was 12.5 line pairs per centimeter ± 0.1 and 14.3 line pairs per centimeter ± 0.1 at 10% and 2% MTF, respectively. The mean error rate of the measured diameter at HSR CT (8.0% ± 5.8) was significantly lower than that at at conventional CT (16.9% ± 9.3; P < .001). Image quality at HSR CT was significantly better than that at conventional CT (P < .001), but HSR CT was not significantly superior to conventional CT in terms of diagnostic accuracy. Conclusion Compared with conventional CT, high-spatial-resolution CT achieved spatial resolutions of up to 29 line pairs per centimeter at 2% modulation transfer function and yielded improved measurement accuracy for the evaluation of in-stent restenosis in a phantom study of renal artery stents. Published under a CC BY 4.0 license.

Ischemic bowel syndromes

Atherosclerotic vascular disease involving the mesenteric arteries occurs frequently in the elderly population. Although the prevalence of ischemic bowel disease is difficult to determine, acute mesenteric ischemia (AMI) has been reported to cause in 1 in 1000 hospital admissions, whereas chronic mesenteric ischemia (CMI) is estimated to affect 1 in 100,000 individuals. Mesenteric ischemia generally manifests in its chronic form as postprandial abdominal pain resulting in significant weight loss, and in its acute form as an abrupt development of abdominal pain, lower gastrointestinal bleeding, and subsequent intestinal necrosis. This article discusses the cause, clinical manifestations, diagnosis, and management of AMI and CMI.

Congenital renal malrotation in ovarian cancer surgery: A case report

► We consider a case of laparoscopic aortic lymphadenectomy for an early ovarian cancer including a comprehensive surgical staging. ► The patient was found to have a congenital anatomic abnormality: a right renal malrotation with an accessory renal artery. ► We used a preoperative CT angiography study to diagnose such anatomical variations and to adequate the proper surgical technique.

CT angiography of the renal circulation

Although catheter angiography remains the accepted gold standard for imaging of the renal vascular system, rapid progress in cross-sectional imaging techniques has caused a paradigm shift in many diagnostic algorithms toward noninvasive techniques such as computed tomographic angiography (CTA). CTA's cross-sectional imaging techniques provide an opportunity for comprehensive renal investigation that would be impossible with angiography alone. While other competing noninvasive technologies such as ultrasound and magnetic resonance angiography can be used successfully in renal imaging, the benefits of CTA are substantial, including high spatial and temporal resolution, widespread availability, implantable device compatibility, and easy technical reproducibility. This article describes the technical considerations relevant to CTA of the renal vascular system, postprocessing algorithms for volumetric data, and numerous specific applications.

Semiautomated MIP Images Created Directly on 16-Section Multidetector CT Console for Evaluation of Living Renal Donors

Institutional Review Board approval was obtained and informed consent was waived for this HIPAA-compliant study. The aim of this study was to retrospectively compare the accuracy of semiautomated maximum intensity projection (MIP) images created at a 16-section multidetector CT console with three-dimensional (3D)-workstation-generated images for the definition of renal donor anatomy, with intraoperative findings as a reference standard. In examining 40 renal donors (21 men and 19 women; age range, 24-56 years; mean age, 40.4 years), the sensitivity and accuracy for mapping donor anatomy by two readers were greater than 95%, interobserver agreement was excellent (kappa = 0.89-1.00). The 95% confidence interval for sensitivity was also calculated. Simple MIPs compared well with 3D-workstation images. MIPs from a predesigned protocol on the scanner console were generated more quickly than similar images from 3D workstations; postprocessing demands (eg, for renal donors) can be quickly fulfilled at the scanner console itself. The average time to generate simple MIPs at the console was 3.4 minutes (range, 1.7-4.4 minutes), and 22.3 minutes (range, 15-30 minutes) to create images at the 3D workstation.

Multidetector CT Angiography in the Follow-Up of Patients Treated with Renal Artery Stents: Value of Different Reformation Techniques Compared with Axial Source Images

PURPOSE

To evaluate the role of 4 different reformation techniques in comparison with axial images from multidetector computed tomographic angiography (MDCTA) in the follow-up of renal artery stents.

METHODS

Data on 40 patients (20 men; mean age 65 years) who underwent MDCTA as part of their routine follow-up after successful primary stenting of a main renal artery were retrospectively analyzed. Multiplanar reformation (MPR), curved planar reformation (CPR), volume rendering threshold (VRT), and virtual angioscopy (VA) were reviewed by 2 independent observers who were blinded to the results of the axial source images, which served as the gold standard. The stenosis degree was scored as I = 0%, II <50%, III = 51%-75%, IV = 76%-99%, or V = occlusion; a stenosis >50% was considered hemodynamically significant.

RESULTS

Five hemodynamically significant stenoses were identified on axial images. The correlation with axial images was perfect for both observers using MPR and CPR (kappa = 1 for each observer); corresponding results were kappa = 0.69 and kappa = 0.64 for VRT and kappa = 0.88 and kappa = 0.83 for VA, respectively. The interobserver correlations were excellent for all reformation techniques (kappa = 0.95 to 1).

CONCLUSION

Compared to axial images, MPR and CPR correlated perfectly with axial images; VA performed surprisingly well, while VRT was affected by artifacts and consequently showed inferior results.

Quantitative assessment of in-stent dimensions: a comparison of 64 and 16 detector multislice computed tomography to intravascular ultrasound

OBJECTIVES

To determine the utility of multislice computed tomography (MSCT) technology to evaluate coronary stent luminal diameter.

BACKGROUND

Stent metal induced "blooming" artifact makes quantitative coronary angiography by MSCT difficult. There is a paucity of data on the efficacy of using 64 and 16 detector MSCT in evaluating coronary stents.

METHODS

We evaluated four commercially available bare metal and polymer coated drug eluting stents using 64 and 16 detector MSCT for the following: (1) Strut density in Hounsfield's Units (Hu) using a 2 mm MIP; (2) In-stent luminal diameter (ISLD) measured by MSCT compared to intravascular ultrasound (IVUS).

RESULTS

Increased strut thickness did not correlate with greater strut density as measured in Hu (R(2) = 0.05, P = 0.29). The ISLD by 16 MSCT vs. IVUS is: Vision 1.63 +/- 0.58 mm vs. 2.8 +/- 0.0; Cypher 1.80 +/- 0.00 vs. 2.9 +/- 0.0; Taxus 1.87 +/- 0.58 vs. 2.9 +/- 0.0; Liberté 1.80 +/- 0.10 vs. 3.0 +/- 0.1 (P < 0.01). ISLD determined by 64 MSCT vs. IVUS is: Vision 1.73 +/- 0.06 mm vs. 2.8 +/- 0.0; Cypher 1.87 +/- 0.12 vs. 2.9 +/- 0.0; Taxus 1.77 +/- 0.06 vs. 2.9 +/- 0.0; Liberté 1.80 +/- 0.10 vs. 3.0 +/- 0.1 (P < 0.01).

CONCLUSIONS

When compared to IVUS measurements, MSCT results in a significant, underestimation of ISLD. This consistent underestimation (even with 64 MSCT) limits the applicability of CT angiography to quantify in-stent restenosis.

Urine Attenuation Ratio: A New CT Indicator of Renal Artery Stenosis

OBJECTIVE

The purpose of our study was to evaluate the value of a ratio of the attenuation measurements of urine in each kidney (hereafter referred to as the urine CT attenuation ratio) in the detection and lateralization of significant renal artery stenosis (RAS).

SUBJECTS AND METHODS

In 33 patients with suspected renovascular hypertension and 43 normotensive patients, 5-mm-thick transverse CT scans of the kidney area were obtained 4 min after helical CT angiography (CTA). The attenuation of urine in each kidney was measured, and its ratio was calculated. All 76 patients underwent intraarterial digital subtraction angiography within 2 days after the CT examination. The results of angiography were correlated with the urine attenuation ratio of both kidneys.

RESULTS

Twenty-six patients showed significant RAS: unilaterally in 20 and bilaterally in six patients. Two patients showed moderate stenosis of renal arteries. The other patients with essential hypertension (n = 5) or normal blood pressure (n = 43) showed normal renal arteries. The CT attenuation of urine in each kidney was measured and its ratio calculated in all patients except four patients with unilateral RAS. The urine CT attenuation ratio in 22 patients with significant RAS ranged from 1.11 to 4.76 (mean, 2.07). The two patients with moderate RAS showed ratios of 1.83 and 1.23. The others (n = 48) had a urine CT attenuation ratio that ranged from 1.00 to 1.54 (mean, 1.07). The difference of the ratio between the RAS group and the normal group was statistically significant (p < 0.01). The mean urine CT attenuation ratio was 2.18 in patients with unilateral RAS (n = 16) and 1.75 in patients with bilateral RAS (n = 6). The difference of the ratio between the two groups was not statistically significant (p = 0.16). At a cutoff value of 1.22, the sensitivity, specificity, positive predictive value, and negative predictive value of the urine CT attenuation ratio in the diagnosis of significant RAS were 95%, 96%, 91%, and 98%, respectively.

CONCLUSION

The urine CT attenuation ratio is a simple and reliable indicator with which to detect and lateralize significant RAS and is a useful adjunct to helical CTA.

Endovascular therapy for chronic mesenteric ischemia

OBJECTIVES

We sought to describe the outcomes of a consecutive series of patients with chronic mesenteric ischemia (CMI) who were treated with percutaneous stent revascularization.

BACKGROUND

Historically, the treatment for CMI has been surgical revascularization. However, surgery carries a significant procedural complication rate and mortality.

METHODS

Fifty-nine consecutive patients with CMI underwent stent placement in 79 stenotic (>70%) mesenteric arteries. All patients had clinical follow-up and 90% had anatomical follow-up with angiography (computed tomography or conventional) or ultrasound at > or =6 months after the procedure.

RESULTS

Procedural success was obtained in 96% (76 of 79 arteries) and symptom relief occurred in 88% (50 patients). At a mean follow-up of 38 +/- 15 months (range, 6 to 112 months), 79% of the patients remained alive, and 17% (n = 10) experienced a recurrence of symptoms. Angiography or ultrasound obtained at 14+/- 5 months after the procedure demonstrated a restenosis rate of 29% (n = 20). All patients with recurrent symptoms had angiographic in-stent restenosis and were successfully revascularized percutaneously.

CONCLUSIONS

Percutaneous stent placement for the treatment of CMI can be performed with a high procedural success and a low complication rate. The long-term freedom from symptoms and vascular patency are comparable with surgical results. The inherent lower procedural morbidity and mortality makes the endovascular approach the preferred revascularization technique for these patients.

IV Contrast Selection for MDCT: Current Thoughts and Practice

OBJECTIVE

The purpose of this article is to review studies evaluating how contrast concentration affects MDCT of the body and to report IV contrast infusion protocols from MDCT angiography and MDCT of abdominal tumors.

CONCLUSION

Higher concentrations (350 mg I/mL or greater) may improve visualization of small abdominal arteries. However, preliminary data comparing 300 mg I/mL to higher concentrations for MDCT of hypervascular hepatocellular carcinoma and pancreatic cancer have shown that higher concentrations may not increase tumor conspicuity.

Computed Tomography Angiography of Carotid Stent. Comparison of Various Self-expandable Stent in a Phantom Model

SUMMARY

We evaluated Computed Tomography Angiography (CTA) of four different self-expandable stents in phantom model. Three stents ware made of nitinol and one was made of cobaltbased alloy. Each stent placed in plastic injector, filled with diluted iodinated contrast material, and placed on a plastic case filled with saline. CTA was performed on a four-detector CT scanner (detector collimation, 0.5mm: helical pitch 3.5). Axial and longitudinal reconstructions of CT imaging were compared with the instent attenuation. Three nitinol stents showed few artifact, and cobalt-based alloy stent was appeared artificial narrowing. In conclusion, CTA is useful for follow-up examination after carotid artery stenting (CAS) as a less invasive evaluation method.

Observations from multidetector CT imaging of different types of renal artery stents

PURPOSE

To present an optimized protocol for acquisition and reconstruction of multidetector computed tomographic angiographic (CTA) images of the stents most commonly used in renal arteries.

TECHNIQUE

CTA was performed on a 16-detector row CT scanner using 0.75-mm collimation. Multiplanar reformatted images perpendicular to the stents and 2-dimensional curved reformatted images were displayed. Two different view windows ("vascular" and "stent") were used, each adapted to the stent density, the vascular wall density, and the aortic enhancement. Five different types of stainless steel balloon-expandable stents were examined; all caused discernable artifacts. These artifacts became more prominent as the stent density increased, becoming most significant when 2 stents were positioned one inside the other. The "stent" window allowed better appreciation of the stent shape and its position compared to the aortic wall and ostial calcifications. The "vascular" window afforded a better view of the vascular lumen, in addition to visualizing the stent in several planes.

CONCLUSIONS

Multidetector CTA using dedicated acquisition and reconstruction protocols is capable of visualizing the vascular lumen of different types of renal stents while avoiding metallic artifacts.

Virtual endoscopy in renal artery stenosis: an innovative approach for diagnosis and follow-up

PURPOSE

We investigated the utility of virtual endoscopy (VE) as a diagnostic and follow-up tool in patients with renal artery stenosis, especially as a means of defining vascular patency.

PATIENTS AND METHODS

We performed VE in 24 patients with ostial atherosclerotic renal artery stenosis and correlated the results with those of conventional angiography. The patients were treated successfully by placement of metal stents and conventional catheter angiography and VE for patency assessment 6 and 12 months after stent insertion.

RESULTS

In all patients, the stenotic segment was identified, and VE findings were concordant with those of angiography. The average degree of stenosis was estimated to be 70% +/- 20% when angiography was used and 62% +/- 15% when VE was used. After metal stent insertion, the 12-month patency rate was 83.3% (20 patients). Angiography and VE findings remained concordant during the follow-up period, but VE provided more information beyond the stenotic segment, allowing examination of the arterial lumen both cephalad and caudal to the point of obstruction.

CONCLUSION

Virtual endoscopy provided a more dynamic, direct, minimally invasive approach that was equal to or better than angiography for both the verification of the vascular stenosis and the evaluation of the arterial lumen.

Contrast-Enhanced MR Angiography at 1.5 T After Implantation of Platinum Stents: In Vitro and In Vivo Comparison with Conventional Stent Designs

OBJECTIVE

The objective of our study was to evaluate the in vitro and in vivo 3D contrast-enhanced MR angiography characteristics of a new platinum-based balloon-expandable stent system and compare this system with a variety of competing metallic stents.

MATERIALS AND METHODS

All experiments were performed on 1.5-T scanners. In vitro experiments were performed using 10 stents implanted into a custom-built phantom. Different orientations of the stents along the magnetic field and multiple flip angles were examined. In addition, 19 patients underwent contrast-enhanced MR angiography after the implantation of 36 stents, including four patients with six platinum stents. Angiographic correlation was available for all 19 patients, and luminal patency and stent-induced artifacts were assessed quantitatively.

RESULTS

Of the tested balloon-expandable stents, only the platinum-based stents created artifact causing luminal narrowing of 30% or less. All other balloon-expandable stents induced larger artifacts that resulted in higher degrees of narrowing. Thus, if patent, the platinum-based stents allow significant in-stent stenosis to be ruled out reliably. Selected nitinol- or tantalum-based self-expandable stents also are suitable in this regard.

CONCLUSION

Of the tested devices, platinum-based stents are the only type of currently available balloon-expandable stent that creates 30% or less artifact-induced apparent stenosis and thus are suitable for MR angiography.

Multidetector-row CT angiography of the aorta and visceral arteries

Within recent years, technical developments of multidetector-row CT (MDCT) have dramatically changed the application of CT angiography in the assessment of abdominal vascular pathologies. The simultaneous acquisition of multiple thin collimated slices in combination with enhanced gantry rotation speed offers thin slice coverage of extended volumes without any loss in spatial resolution. Using 4 detector-row CT scanners, the scan volume still has to be restricted and focused on dedicated abdominal vessel territories in order to provide high spatial resolution (1-2 mm), while 16 detector-row technology now enables full abdominal coverage from the diaphragm to the groin with full spatial resolution. Therefore, comprehensive CT angiography of the abdomen can be performed without the necessity of focusing on any vascular territory. This technique enables the evaluation of the whole arterial visceral vasculature (e.g., hepatic vessels, mesenteric vessels, renal arteries) and the aortic-iliac axis in a single data acquisition.

Multidetector CT angiography with perfusion analysis in the surveillance of renal artery stents

PURPOSE

To evaluate 4 perfusion parameters obtained by multidetector computed tomographic angiography (CTA) in the follow-up of patients after renal artery stenting.

METHODS

Thirty-three consecutive patients (20 women; mean age 64.3+/-10.7 years) with renal artery stents were included in this prospective pilot trial. CTA was performed in 21 patients on a 4-row scanner and in 12 patients on a 16-row scanner. Volume maximum intensity projections and curved planar reconstructions were used for morphological analysis. The initial contrast test bolus was used for perfusion imaging by placing 2 additional regions of interest in the cortex of each kidney. The maximum relative attenuation values (Hounsfield units [HU max]), the time-to-peak values, an attenuation ratio, and a time-to-peak ratio for each side were calculated.

RESULTS

Over a mean follow-up of 3.4+/-1.7 years, restenosis was detected in 4 (12.1%) of the 33 stents; in all 66 main renal arteries, 5 (7.5%) significant flow obstructions were detected. Interobserver agreement for all morphological parameters was excellent (kappa>0.8). Mean relative HU max for the cortical region of stented arteries was 63.7+/-29.7 (mean HU ratio 0.37+/-0.12); the mean TTP max was 32.9+/-7.4 seconds (mean ratio 0.76+/-0.10). None of the perfusion parameters differed significantly between patients with and without significant flow obstructions (p>0.05).

CONCLUSIONS

Despite the excellent morphological information provided by multidetector CTA in the follow-up of renal stents, this modality does not provide hemodynamic information. Unfortunately, none of the evaluated perfusion parameters added any useful information in the follow-up after renal artery stenting.

Basics of computed tomography angiography of the lower extremity vessels

Complete noninvasive, angiographic evaluation of the abdominal aorta and lower extremity vessels using the latest generation of multidetector row computed tomography (CT) scanners can now be accomplished in a single scan lasting less than a minute. The high spatial resolution of these new scanners and their more efficient use of contrast permit accurate depiction of disease in the smaller tibial and pedal vessels, as well as the larger diameter iliac and femoral arteries; nevertheless, many challenges and obstacles remain to its more widespread acceptance. Foremost among these, is the difficulty in accurately reconstructing the smaller leg and pedal vessels from individual CT slices, a process that must to a very great extent be done manually, and the potential nephrotoxicity of iodinated contrast material. Future advances in imaging software that could more fully automate accurate three-dimensional reconstructions of the lower extremity vasculature, and detector technology to allow for even finer resolution of the vasculature will further enhance an already powerful and clinically useful tool.

CT and MR Imaging of Nitinol Stents with Radiopaque Distal Markers

PURPOSE

To evaluate imaging characteristics and artifacts of a nitinol stent with distal tantalum markers with computed tomography (CT) angiography and magnetic resonance (MR) angiography.

MATERIALS AND METHODS

A vascular phantom was built to simulate in-stent restenosis. A nitinol stent with tantalum markers (Luminexx stent) was evaluated with CT angiography in different orientations relative to the z-axis and with MR angiography in different positions relative to both B0 and the readout gradient. Stenosis measurements were compared with conventional digital subtraction angiography for both modalities. In-stent signal intensity obtained with different flip angles was assessed in two nitinol stents with distal markers (Luminexx stent and SMART stent) and one without markers (Memotherm-FLEXX stent).

RESULTS

Stenosis detection was not possible with CT angiography when the stent was perpendicular to the z-axis because of streak-like artifacts induced by tantalum markers. Stenosis evaluation with multiplanar reformation was accurate when the stent was in parallel and oblique orientations relative to the table axis. With MR angiography, metallic artifacts were mostly related to the stent orientation with B0, whereas orientation of the readout gradient had little influence. The mean error (overestimation) for stenosis measurements varied between 0.1% and 7.4% for CT imaging in parallel and oblique positions and 3.6% and 9.5% for MR imaging. Higher flip angles did not improve signal intensity inside the three stents tested.

CONCLUSION

CT and MR angiography can be used for evaluating the patency of stents with distal markers that are parallel or oblique relative to the table axis (iliac, carotid, or femoral stents). MR angiography is preferred if the stent is perpendicular to the table axis (renal stent).

Quand, comment et pourquoi réaliser une exploration des artères rénales ?

The objectives of this course are both: to describe acquisition, injection and reconstruction parameters of volumic images for renal arteries examination and specific signs; to discuss the role of the different images in the diagnosis and in the therapeutic management. Ultrasound is one of the best imaging for the analysis of renal arteries in the detection of stenosis even if the sensitivity is less (around 85%)compared to CT Angiography (95%) and MR Angiography (90%). Because of this advantage and of 3D evaluation, CTA and MRA are sometimes in the first line for renal artery evaluation and can assess morphology before angioplasty. Renal scintigraphy with Captopril test and renin dosage are only used for small kidney evaluation. Arteriogram is systematically followed by angioplasty if possible. With the new endovascular materials, complications decrease (less than 5% with a major reduction in cholesterol emboli) and indications of endoprosthesis increase (71% of stenting with half of it in direct stenting technique). This course will give practical tools for imaging acquisition, specifically 3D imaging, for indications and management of lesion in accordance to symptoms and morphology.

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

Multi-detector row helical computed tomography (CT) offers considerable advantages in evaluation of the urinary tract. It has the potential to become the single imaging modality used for comprehensive evaluation and treatment planning of most conditions affecting the kidneys and urinary tract, making conventional diagnostic techniques such as intravenous urography and angiography nearly obsolete. This article illustrates important selected applications of multidetector CT in the evaluation of benign conditions of the kidneys and upper urinary tract, including evaluation of the renal arterial and venous anatomy in preparation for surgery, diagnosis of renal artery stenosis and aneurysms, assessment of the renal veins, imaging of inflammatory and infectious renal diseases and evaluation of selected benign pathologic processes of the urinary tract.

Long-term follow-up after renal artery stenting

BACKGROUND

Renal artery stenosis may cause secondary arterial hypertension and lead to end-stage renal disease. Percutaneous transluminal angioplasty with stent implantation (PTRAS) allows effective and consistent treatment with a high technical success rate. The present trial focuses on the morphological and clinical results as assessed at a long-term follow-up (FU) visit. The main goals were assessment of the restenosis rate and evaluation of arterial hypertension and renal function.

PATIENTS AND METHODS

40 patients who had undergone successful stenting of a main renal artery were prospectively enrolled. At the FU visit, all patients underwent a risk-factor assessment, evaluation of arterial blood pressure and serum creatinine, and multi-detector computed tomography angiography (CTA).

RESULTS

Median FU was 3.3 years. Hyperlipidemia was present in 67.5% of the patients, current cigarette smoking in 35% and diabetes mellitus in 15%. All patients still suffered from arterial hypertension but, compared with the pre-interventional situation, arterial hypertension was improved in 37.5%. Serum creatinine was increased in 25% of patients, mean creatinine level was 1.3 +/- 0.4 mg/dl. Hemodynamically relevant restenosis was detected by observer 1 in five patients and by observer 2 in six patients, giving restenosis rates of 12.5% and 15%, respectively, after the median FU period. Both observers detected three additional relevant stenoses in the contralateral main renal arteries.

CONCLUSIONS

PTRAS gives excellent morphological long-term results. However, the clinical long-term outcome regarding arterial hypertension and renal function is only moderate.

The origin of right inferior phrenic artery on multidetector row helical CT

The origin of the right inferior phrenic artery (RIPA) was assessed in 216 patients using arterial-phase, contrast-enhanced multidetector row helical computed tomography (CT) and that of 26 patients was confirmed by angiography. One hundred and eighty patients showed the origin of the RIPA in aorta, the celiac artery, the right renal artery or the left gastric artery on CT. The sensitivity of CT was 92%. Multidetector row helical CT provides valuable anatomical information for angiographer.

Multidetector CT angiography for preoperative evaluation of living laparoscopic kidney donors

OBJECTIVE

The purpose of this study was to determine the accuracy of multidetector CT (MDCT) angiography as the primary imaging technique in the evaluation of living kidney donors.

SUBJECTS AND METHODS

Seventy-four consecutive living kidney donors (30 men, 44 women; mean age, 41.7 years) who underwent MDCT were evaluated. CT examination was performed with 120 mL of IV contrast material at an injection rate of 3 mL/sec and a pitch of 6. In every case, arterial and venous phase volumetric data sets were acquired at 25 and 55 sec, respectively. Scans were reconstructed at 1-mm intervals for three-dimensional (3D) imaging using a volume-rendering technique. Axial CT images and 3D CT angiography were evaluated prospectively by one reviewer and retrospectively by two reviewers who had no knowledge of surgical results. Surgical correlation for the location of primary and accessory renal arteries, early branching of the renal arteries, and renal vein anomalies was made.

RESULTS

Seventy-two subjects underwent left nephrectomy, and two subjects underwent right nephrectomy because supernumerary left renal arteries were detected on preoperative CT angiography. Eighteen supernumerary renal arteries (two arteries to 16 kidneys and three arteries to one kidney) to 74 kidneys underwent nephrectomy. CT and surgical findings agreed in 93% of subjects (the average of three reviewers; range, 89-97%). Two small accessory renal arteries were missed by all three reviewers. Those arteries were diminutive and were thought to be insignificant by the surgeons. Early branching of the renal arteries was shown in 14 arteries, and CT and surgical findings agreed in 96% (the average of three reviewers; range, 93-97%). Renal vein anomalies were present in eight subjects, and CT and surgical findings agreed in 99% of the cases (range, 96-100%).

CONCLUSION

MDCT angiography is highly accurate for detecting vascular anomalies and providing anatomic information for laparoscopic living donor nephrectomy.

Volume-rendered multidetector CT angiography: noninvasive follow-up of patients treated with renal artery stents

OBJECTIVE

The purpose of our study was to evaluate the role of multidetector CT (MDCT) angiography with volume rendering for estimating the patency of renal artery stents.

SUBJECTS AND METHODS

In 16 patients, 16 renal artery stents were evaluated with MDCT renal angiography and digital subtraction angiography (DSA). CT data were evaluated using multiplanar volume reformations and the volume-rendering algorithm with three different volume-rendered parameter settings (low-to-high, high-to-low, and high-low-high opacity transfer functions: VR(LH), VR(HL), and VR(VE), respectively). Targeted images of each stent were rendered in paraaxial and paracoronal planes and were interactively interpreted. The overall restenosis severity was measured on postprocessed paraaxial and paracoronal images and compared with that obtained on DSA using linear regression analysis. Image quality and lumen delineation on rendered images were also compared using Wilcoxon's signed rank test.

RESULTS

Eight restenoses were identified on DSA. Correlations between restenosis severity measured with DSA and those measured with MDCT were significant (p < 0.001). Volume rendering with VR(HL) allowed the best correlation with DSA (reviewer 1, r(2) = 0.86; reviewer 2, r(2) = 0.94) and was significantly better than multiplanar volume reformations (p = 0.028). Overall image quality was high with all rendering techniques and with no significant differences (p > 0.59, for all comparisons). Stent lumen was well delineated with volume-rendering modalities; however, VR(HL) was significantly better than VR(LH) (p = 0.033).

CONCLUSION

Volume-rendered MDCT angiography enabled high-quality three-dimensional reproducible evaluation of the patency of implanted renal artery stents. Volume rendering with VR(HL) achieved the best performance.