Magnetic Resonance Assessment of Peritoneal Carcinomatosis: Is There a True Benefit From Diffusion-Weighted Imaging?

PURPOSE: To assess the added value of diffusion weighted imaging (DWI) with intermediate (500 s/mm2) and high (1000 s/mm2) b values when combined to conventional contrast-enhanced magnetic resonance imaging (MRI) in identifying peritoneal neoplastic involvement. METHODS: Twenty-four patients with peritoneal carcinomatosis from gastrointestinal or gynecological tumors were retrospectively evaluated. All patients underwent peritonectomy with hyperthermic intraoperative chemotherapy and 1.5 T MRI including DWI with 500 s/mm2 and 1000 s/mm2 b values within 1 month from surgery. Images were independently reviewed by 2 radiologists with different experience in abdominal MRI in 3 separate reading sessions, the first including conventional MR images alone (T2-weighted, T1-weighted pre- and post gadolinium injection), the second conventional MRI and DWI with a b value of 500 s/mm2 (b 500-DWI), and the third conventional MRI and DWI with a b value of 1000 s/mm2 (b 1000-DWI). Apparent diffusion coefficient maps were included in the DWI analyses. Peritoneal dissemination was assessed in 9 anatomical sites, including right and left subphrenic space, paracolic gutters, small bowel mesentery, greater omentum, gastric-bowel serosa, free peritoneal surfaces, rectosigmoid-colon mesentery, and pelvis. The presence or absence of peritoneal dissemination for each patient and for each site was scored using a 5-point confidence scale. Sensitivity, specificity, and area under the curve (AUC) for identifying per-site peritoneal implants were calculated for each reader at each reading session. Interobserver agreement was evaluated using kappa statistics. RESULTS: For both readers, the sensitivity and AUC values resulting from combined interpretation of conventional MRI and DWI (both b500-DWI and b1000-DWI) were significantly higher than those of conventional MRI alone (P < 0.001). The added value of DWI was greater for the less experienced reader (sensitivity 0.55, specificity 0.73, AUC 0.64 on conventional MRI; sensitivity 0.75, specificity 0.72, AUC 0.74 on b500-DWI; sensitivity 0.87, specificity 0.72, AUC 0.80 on b1000-DWI) than for the more experienced reader (sensitivity 0.63, specificity 0.75, AUC 0.70 on conventional MRI; sensitivity 0.76, specificity 0.77, AUC 0.77 on b500-DWI; sensitivity 0.85, specificity 0.72, AUC 0.79 on b1000-DWI), although the differences between the 2 observers were not statistically significant. Interobserver agreement resulted to be fair (κ = 0.30) when dealing with conventional MRI alone. The addition of b500-DWI and b1000-DWI to conventional MRI allowed to reach a substantial agreement (κ = 0.75). CONCLUSIONS: The combined interpretation of high b value DWI and conventional MRI provides increased sensitivity and diagnostic performance in detection of peritoneal carcinomatosis in oncologic patients.

Ultra-low dose CT colonography with automatic tube current modulation and sinogram-affirmed iterative reconstruction: Effects on radiation exposure and image quality.

OBJECTIVE: To assess the radiation dose and image quality of ultra-low dose (ULD)-CT colonography (CTC) obtained with the combined use of automatic tube current (mAs) modulation with a quality reference mAs of 25 and sinogram-affirmed iterative reconstruction (SAFIRE), compared to low-dose (LD) CTC acquired with a quality reference mAs of 55 and reconstructed with filtered back projection (FBP). METHODS: Eighty-two patients underwent ULD-CTC acquisition in prone position and LD-CTC acquisition in supine position. Both ULD-CTC and LD-CTC protocols were compared in terms of radiation dose [weighted volume computed tomography dose index (CTDIvol ) and effective dose], image noise, image quality, and polyp detection. RESULTS: The mean effective dose of ULD-CTC was significantly lower than that of LD-CTC (0.98 and 2.69 mSv respectively, P < 0.0001) with an overall dose reduction of 63.2%. Image noise was comparable between ULD-CTC and LD-CTC (28.6 and 29.8 respectively, P = 0.09). There was no relevant difference when comparing image quality scores and polyp detection for both 2D and 3D images. CONCLUSION: ULD-CTC allows to significantly reduce the radiation dose without meaningful image quality degradation compared to LD-CTC.

Performance of diffusion-weighted magnetic resonance imaging at 3.0T for early assessment of tumor response in locally advanced rectal cancer treated with preoperative chemoradiation therapy.

PURPOSE: The purpose of the article is to determine whether changes in apparent diffusion coefficient (ADC) values of locally advanced rectal cancer (LARC) obtained 2 weeks after the beginning of chemoradiation therapy (CRT) allow to predict treatment response and whether correlate with tumor histopathologic response. METHODS: Forty-three patients receiving CRT for LARC and 3.0T magnetic resonance imaging with diffusion-weighted sequences before treatment, 2 weeks during, and 8 weeks post the completion of CRT were included. ADC values were calculated at each time point and percentage of ADC changes at 2 weeks (ΔADC during) and 8 weeks (ΔADC post) were assessed. Data were correlated to surgical results and histopathologic tumor regression grade (TRG), according to Mandard's classification. ADC values and ΔADCs of complete responders (CR; TRG1) and non-complete responders (non-CR; TRG 2-5) were compared. Receiver-operating characteristic curve (ROC) analysis was used to assess diagnostic accuracy of ΔADC for differentiating CR from non-CR. The correlation with TRG was investigated using Spearman's rank test. RESULTS: ΔADC during and ΔADC post were significantly higher in CR (33.9% and 57%, respectively) compared to non-CR (13.5% and 2.2%, respectively) group (p = 0.006 and p < 0.001, respectively). ROC analysis revealed the following diagnostic performances: ΔADC during: AUC 0.78 (0.08), p = 0.004, cut-off 20.6% (sensitivity 75% and specificity 76.5%); ΔADC post: AUC 0.94 (0.04), p ≤ 0.001, cut-off 22% (sensitivity 95% and specificity 82.4%). Significant moderate and good negative correlation was found between ΔADC during and ΔADC post and TRG (r = - 0.418, p = 0.007; r = - 694, p ≤ 0.001, respectively). CONCLUSION: ΔADC at 2 weeks after the beginning of CRT is a reliable tool to early assess treatment response.

Molecular, Cellular and Pharmaceutical Aspects of Bone Grafting Materials and Membranes During Maxillary Sinus-lift Procedures. Part 1: A General Overview.

Sinus augmentation procedure has been demonstrated to be a highly predictable treatment in posterior maxilla atrophy. All the surgical interventions in the maxillary region require deep knowledge of anatomy and possible anatomical variations. In this article, pre-operative and post- operative assessments of sinus cavity as well as novel approaches to deepen our knowledge of the behavior of bone substitute materials are described. The awareness of the patient's morphologic conditions enables exact planning of invasive surgery and aids to avoid complications. Pre- operative radiologic evaluation of the region before sinus lift is advisable both for a planning of the sinus augmentation and for selection and alignment of the optimum placement of implants. On the orthopantomography it is possible to measure the vertical dimension of graft, but not the volume and 3D changes. Cone-beam computed tomography (CBCT) has become the "gold standard" to plan a comprehensive implant treatment and to achieve a post-operative assessment. A computer-aided design/computer-aided manufacturing (CAD/CAM) technique is proposed to produce custom-made block grafts for sinus lift procedure, and a customized cutting guide to accurately place the lateral wall and ease membrane elevation. This procedure allows to reduce intervention time, to precisely adapt the scaffold, to reduce risk of complications and to improve operation quality. Recently, a novel approach has been used to deepen our knowledge of the behavior of BSBs: by means of synchrotron micro-tomography (SCT). It is a 3-D analyzing method, suitable to examine the dynamic and spatial arrangement of regenerative phenomena in complex anatomical structures such as bone, where tissues with several morphologies (alveolar process, unmineralized extracellular matrix, regenerated vessels, etc.) compete to achieve the final goal of bone regeneration.

Molecular, Cellular and Pharmaceutical Aspects of Bone Grafting Materials and Membranes During Maxillary Sinus-lift Procedures. Part 2: Detailed Characteristics of the Materials.

Various grafts or combination of bone substitute materials have been used in sinus lift procedures. Currently, ongoing developments in several disciplines, from molecular biology and chemistry to computer science and engineering, have contributed to the understanding of biological processes leading to bone healing after the use of bone substitute materials (BSBs) and therefore of the behavior of BSBs. The understanding of the properties of each graft enables individual treatment concepts and therefore allows shift from a simple replacement material to the modern concept of an individually created composite biomaterial. Indeed, the choice of the best BSB still remains crucial for success in maxillary sinus augmentation procedures. The present article provides an overview of most of the materials currently available for sinus lift, with a specific focus on their histological, molecular, cellular and pharmaceutical aspects.

The role of diffusion-weighted imaging in the detection of hepatic metastases from colorectal cancer: A comparison with unenhanced and Gd-EOB-DTPA enhanced MRI.

OBJECTIVES: To compare the role of DWI vs. gadoxetic-acid-disodium enhanced MRI in the detection of colorectal hepatic metastases. METHODS: Fifty-four patients with 115 hepatic metastases were included in this retrospective study, approved by the Ethical Board. All patients underwent intraoperative-ultrasound and surgical resection within two weeks after MRI. Images were grouped in 4 sets, which were analyzed by two radiologists in different sessions: unenhanced T1-T2w (set A), set A plus DWI (set B), set A plus gadoxetic-acid-disodium (set C), set A plus DWI plus gadoxetic-acid-disodium (set D). For each set, metastases presence/size/site was reported. Interobserver agreement and statistical significance were assessed by Cohen's kappa and Mc-Nemar's test, respectively. RESULTS: Readers' agreement was always very good (k>0.80). Mean sensitivity values were 84.3/92.1/95.6/97.3% for set A/B/C/D, respectively. Mean specificity, positive predicted, negative predicted, and accuracy values strongly and progressively increased in the various set too: from 62.5% (set A) to 85.0% as for specificity, from 92.8% to 97.3% as for positive predicted value, from 41.0% to 85.1% as for negative predicted value, and from 81.1% to 95.5% as for accuracy. For each reader from set A to D, the number of false negatives progressively decreases. CONCLUSIONS: For both readers, DWI improved all statistical parameters in the unenhanced examinations, as for nodules either smaller or greater than 1cm, while in the EOB-enhanced examinations DWI prevalently increased specificity/negative predictive value.

CT findings in acute peritonitis: a pattern-based approach.

Many inflammatory and infectious entities may acutely affect the peritoneum causing a thickening of its layers. Unfortunately, several acute peritoneal diseases can have overlapping features, both clinically and at imaging. Therefore, the awareness of the clinical context, although useful, may be sometimes insufficient to identify the underlying cause. This article provides a specific computed tomography-based approach including morphologic characteristics of peritoneal thickening (e.g., smooth, irregular, or nodular) and ancillary findings to narrow the differential diagnosis of acute peritonitis.

Developing a decision-making model based on an interdisciplinary oncological care group for the management of colorectal cancer.

AIM: To report our experience on implementation and preliminary results of a decision-making model based on the recommendations of an Interdisciplinary Oncological Care Group developed for the management of colorectal cancer. PATIENTS AND METHODS: The multidisciplinary team identified a reference guideline using appraisal of guidelines for research and evaluation (AGREE) tool based on a sequential assessment of the guideline quality. Thereafter, internal guidelines with diagnostic and therapeutic management for early, locally advanced and metastatic colonic and rectal cancer were drafted; organizational aspects, responsibility matrices, protocol actions for each area of specialty involved and indicators for performing audits were also defined. RESULTS: The National Institute for Health and Care Excellence (NICE) UK guideline was the reference for drafting the internal guideline document; from February to November 2013, 125 patients with colorectal cancer were discussed by and taken under the care of the Interdisciplinary Oncological Care Group. The first audit performed in December 2013 revealed optimal adherence to the internal guideline, mainly in terms of uniformity and accuracy of perioperative staging, coordination and timing of multi-modal therapies. To date, all patients under observation are within the diagnostic and therapeutic course, no patient came out from the multidisciplinary "path" and only in 14% of cases have the first recommendations proposed been changed. The selected indicators appear effective and reliable, while at the moment, it is not yet possible to assess the impact of the multidisciplinary team on clinical outcome. CONCLUSION: Although having a short observation period, our model seems capable of determining optimal uniformity of diagnostic and therapeutic management, to a high degree of patient satisfaction. A longer observation period is necessary in order to confirm these observations and for assessing the impact on clinical outcome.

A tumour score with multidetector spiral CT for venous infiltration in pancreatic cancer: influence on borderline resectable.

PURPOSE: A tumour score for venous invasion in patients with pancreatic adenocarcinoma was evaluated by means of computed tomography (CT), in order to improve the assessment of medical treatment and clinical outcome with special attention to borderline resectable disease. MATERIALS AND METHODS: Fifty-six consecutive patients who underwent curative surgical resection for pancreatic cancer were analysed. On the basis of CT criteria, tumour involvement of the portal vein (PV) and superior mesenteric vein (SMV) was graded according to an adapted 4-point scale: score 1, definite absence of invasion; score 2, probable absence of invasion; score 3, probable presence of invasion; score 4, definite presence of invasion. Correlations between the venous infiltration scores and the patients' clinical features were also evaluated. RESULTS: After radiological evaluation of PV and SMV grades of infiltration, 21/56 (37 %) and 37/56 (66 %) patients, respectively, were found to have borderline resectable disease. The 4-point scale achieved a sensitivity of 80 %, a specificity of 96 % and an accuracy of 93 % in the evaluation of the PV, and a sensitivity of 100 %, a specificity of 94 % and an accuracy of 95 % in the evaluation of the SMV. Analysis of the distribution of clinical characteristics by PV and SMV infiltration showed that both scores correlated with the presence of distal metastasis (p = 0.016 and p = 0.028, respectively), and resection margins status (p = 0.015 and p = 0.006, respectively). CONCLUSIONS: This adapted tumour score is reliable for assessing venous invasion and might improve preoperative staging in patients with borderline resectable pancreatic cancer.

Focal liver lesion classification and characterization in noncirrhotic liver: a prospective comparison of diffusion-weighted magnetic resonance-related parameters.

PURPOSE: The objective of this study was to prospectively verify if diffusion-weighted magnetic resonance (DwMR)-related parameters such as perfusion fraction (f) and slow diffusion coefficient (D), according to Le Bihan theory, are more effective than apparent diffusion coefficient (ADC) for classification and characterization of the more frequent focal liver lesions (FLLs) in noncirrhotic liver. METHODS: Sixty-seven patients underwent standard liver magnetic resonance imaging (MRI) and free-breath multi-b DwMR study. Two regions of interest were defined by 2 observers, including 1 FLL for each patient (21 hemangiomas, 21 focal nodular hyperplasias, 25 metastases) and part of surrounding parenchyma, respectively. For every FLL, D, f, and ADC were estimated both as absolute value and as ratio between FLL and surrounding parenchyma by fitting the reduced equation of the bicompartmental model to experimental data; t test, analysis of variance, and receiver operating characteristic analysis were performed. RESULTS: t Test showed significant differences in ADClesion, f lesion, D lesion, ADCratio, and D ratio values between benign and malignant FLLs, more pronounced for ADClesion (P < 0.0009) and ADCratio (P = 0.001). Applying cutoff values of 1.55 × 10 mm/s (ADClesion) and 0.89 (ADCratio), the DwMR study presented sensitivities and specificities, respectively, of 84% and 80% (for ADClesion), 72% and 80% (ADCratio). CONCLUSIONS: Apparent diffusion coefficient (by fitting procedures) better performs than do D and f in FLL classification, especially when its values are less than 1.30 or greater than 2.00 × 10 mm/s.

Obscure and occult gastrointestinal bleeding: comparison of different imaging modalities.

Patients with persistent, recurrent, or intermittent bleeding from the gastrointestinal (GI) tract for which no definite cause has been identified by initial esophagogastroduodenoscopy, colonoscopy, or conventional radiologic evaluation are considered to have an obscure GI bleeding (OGIB). The diagnosis and management of patients with OGIB is challenging, often requiring extensive and expensive workups. The main objective is the identification of the etiology and site of bleeding, which should be as rapidly accomplished as possible, in order to establish the most appropriate therapy. The introduction of capsule endoscopy and double balloon enteroscopy and the recent improvements in CT and MRI techniques have revolutionized the approach to patients with OGIB, allowing the visualization of the entire GI tract, particularly the small bowel, until now considered as the "dark continent" . In this article we review and compare the radiologic and endoscopic examinations currently used in occult and OGIB, focusing on diagnostic patterns, pitfalls, strengths, weaknesses, and value in patients' management.

The role of hepatocyte-specific staining in liver pathology.

The advantages of MRI in the investigation of liver disease are well documented. Recent developments, including fast scanning technique and new MRI contrast agents, enable improved detection and characterization of focal liver lesions. Therefore, a definitive diagnosis can be made avoiding invasive procedures, such as liver biopsy. In this article, a special emphasis is placed on the clinical use of combined perfusional and hepatocyte-selective MRI contrast agents, which allow us to obtain morphologic and vascular information, owing to the dynamic study, as well as functional information, owing to the hepatocyte-selective phase of enhancement. Different clinical scenarios are considered in order to highlight the proper use of the hepatocyte phase to noninvasively characterize and detect different focal liver lesions.

A prospective evaluation of iron deficiency anemia in the GI endoscopy setting: role of standard endoscopy, videocapsule endoscopy, and CT-enteroclysis.

BACKGROUND: Iron deficiency anemia (IDA) is a frequently encountered condition in clinical practice. After conventional endoscopy, the cause of anemia remains unknown in up to 40% of patients. OBJECTIVE: To evaluate prospectively the diagnostic efficacy of a systematic endoscopic approach to IDA and to compare the diagnostic yield of videocapsule endoscopy (VCE) and CT-enteroclysis in endoscopy-negative patients. DESIGN: Consecutive patients with IDA were enrolled prospectively. SETTING: Open-access endoscopy within an academic hospital. PATIENTS: This study involved 189 patients with IDA, including 98 women and 91 men; mean (±standard deviation) age 68 years±16.6 years. INTERVENTION: Patients with IDA underwent gastroscopy and colonoscopy plus ileoscopy. Endoscopy-negative patients were further blindly evaluated by both CT-enteroclysis and VCE. MAIN OUTCOME MEASUREMENTS: Diagnostic yield of conventional endoscopy; diagnostic yield of VCE versus CT-enteroclysis. RESULTS: Endoscopy results were positive in 144 of 189 patients (76.2%). CT-enteroclysis and VCE allowed a diagnosis in 37 of 45 endoscopy-negative patients (82.2%). Overall, VCE was superior to CT-enteroclysis (77.8% vs 22.2%; P<.001), in particular when flat lesions were found. LIMITATIONS: Single-center study. CONCLUSION: A systematic approach to IDA, which includes standard endoscopy, VCE, and CT-enteroclysis allows an overall diagnostic rate of 95.7%; however, CT-enteroclysis should be limited to cases of nondiagnostic VCE.

Enhancement of liver parenchyma after injection of hepatocyte-specific MRI contrast media: a comparison of gadoxetic acid and gadobenate dimeglumine.

PURPOSE: To compare enhancement of liver parenchyma in MR imaging after injection of hepatocyte-specific contrast media. MATERIALS AND METHODS: Patients (n = 295) with known/suspected focal liver lesions randomly received 0.025 mmol gadoxetic acid/kg body weight or 0.05 mmol gadobenate dimeglumine/kg body weight by means of bolus injection. MR imaging was performed before and immediately after injection, and in the delayed phase at approved time points (20 min after injection of gadoxetic acid and 40 min after injection of gadobenate dimeglumine). The relative liver enhancement for the overall population and a cirrhotic subgroup was compared in T1-weighted GRE sequences. An independent radiologist performed signal intensity measurements. Enhancement ratios were compared using confidence intervals (CIs). RESULTS: The relative liver enhancement in the overall population was superior with gadoxetic acid (57.24%) versus gadobenate dimeglumine (32.77%) in the delayed-imaging phase. The enhancement ratio between the contrast media was statistically significant at 1.75 (95% CI: 1.46-2.13). In the delayed phase, the enhancement of cirrhotic liver with gadoxetic acid (57.00%) was comparable to that in the overall population. Enhancement with gadobenate dimeglumine was inferior in cirrhotic liver parenchyma (26.85%). CONCLUSION: In the delayed, hepatocyte-specific phase, liver enhancement after injection of gadoxetic acid was superior to that obtained with gadobenate dimeglumine.

Effect of clinical history in focal liver lesion detection and classification on 4-detector row computed tomography and gadoxetic acid enhanced MR imaging in oncologic patients.

PURPOSE: To determine the influence of clinical data on reader diagnostic accuracy in focal liver lesion (FLL) detection and classification. MATERIALS AND METHODS: Eighty-seven oncologic patients with FLLs underwent contrast-enhanced multidetector-row computed tomography (MDCT) and gadoxetic acid-enhanced magnetic resonance imaging (MRI). Two independent readers reviewed images for FLL detection and classification as benign or malignant without knowledge and after provision of clinical information. The sensitivity, specificity, diagnostic accuracy, and Az values were calculated using intraoperative ultrasound and pathologic findings as standard of reference. RESULTS: The awareness of clinical data significantly improved the accuracy (p = 0.02 for both readers) and Az values (p = 0.03 for reader 1 and p = 0.04 for reader 2) of MDCT for the detection of lesions with a diameter of 1 cm or less. When considering MRI, the provision of clinical data produced an improvement of accuracy and Az values for both readers, although differences were not significant.For MDCT lesion classification, the awareness of clinical data produced a decrease of accuracy (p = 0.03 for both readers) and Az values (p = 0.07 for reader 1 and p = 0.06 for reader 2) because of an associated increase in false-positive findings. When considering MRI, the provision of clinical data produced an improvement of accuracy and Az values for both readers, although differences were not significant. CONCLUSIONS: For detecting and classifying FLLs in oncologic patients, the knowledge of clinical data does not significantly change diagnostic accuracy and reader performance when using MRI, whereas, when considering MDCT, it improves the detection rate but produces an increase of false-positive findings for diagnosis of malignancy.

Resovist enhanced MR imaging of the liver: does quantitative assessment help in focal lesion classification and characterization?

PURPOSE: To improve characterization of focal liver lesions by a prospective quantitative analysis of percentage signal intensity change, in dynamic and late phases after slow (0.5 mL/s) Resovist administration. MATERIALS AND METHODS: Seventy-three patients were submitted on clinical indication to MR examination with Resovist. Signal intensity of 92 detected focal lesions (5-80 mm) were measured with regions of interest and normalized to paravertebral muscle in arterial, portal, equilibrium and T1/T2 late phases, by two observers in conference. Five values of percentage variations per patient were obtained and statistically evaluated. RESULTS: The enhancement obtained on dynamic study is more suitable in hemangiomas and focal nodular hyperplasias than in adenomas and hepatocellular carcinomas. To discriminate benign versus malignant lesions on late-phase-T2-weighted images, a cutoff = -26%, allowed sensitivity and specificity values of 97.4% and 97.7%, respectively. Area under the receiver operating characteristic (ROC) curve was 0.99. To differentiate hemangioma versus all other focal liver lesions, on late-phase-T1-weighted images, a cutoff = +40% permitted sensitivity and specificity values of 90.5% and 98.0%, respectively. Area under the ROC curve was 0.98. CONCLUSION: Late phase quantitative evaluation after slow Resovist administration, allows to differentiate malignant from benign hepatic masses and hemangiomas from all the others focal liver lesions, on T2-/T1-weighted acquisitions, respectively. J

Four-detector row computed tomographic angiography in the evaluation of infrarenal aorta and peripheral arterial occlusive disease: influence of contrast medium concentration.

PURPOSE: To prospectively compare the diagnostic accuracy and quality of vascular enhancement of 2 contrast agents with different iodine concentrations in 4-detector row computed tomographic angiography of abdominal aorta and lower-extremity arteries. MATERIALS AND METHODS: Forty consecutive patients with peripheral arterial occlusive disease referred for conventional angiography (digital subtraction angiography [DSA]) of the lower extremity were prospectively enrolled in the study and underwent multidetector row computed tomographic angiography (CTA) receiving either 90 mL of iomeprol 400 (Iomeron 400, group A; Bracco Imaging S.p.A., Milan, Italy) or 120 mL of iomeprol 300 (Iomeron 300, group B; Bracco Imaging). Resultant images, both axial, maximum intensity projection, multiplanar reformatted, and volume-rendered 3-dimensional images, were independently evaluated by 2 clinically competent and experienced blinded radiologists for the presence of stenotic and occluded arterial segments using DSA as the standard of reference. Computed tomographic images were also evaluated quantitatively for maximum arterial and venous enhancement, and qualitatively for vascular opacification, venous overlap, and diagnostic efficacy. Quantitative and qualitative results of the 2 study agent groups were statistically compared. Both contrast media were evaluated for safety and tolerability. RESULTS: From 760 segments, 722 arterial segments were effectively evaluated in the comparative analysis of CTA and DSA. In the evaluation of significant stenoses (>70%) and occluded segments, multidetector row CTA obtained a sensitivity, specificity, and accuracy of 97.1%, 96%, and 96.3%, and 98.9%, 100%, and 99%, respectively. Iomeprol 400 demonstrated an increased arterial enhancement in aortoiliac and femoral districts in comparison to iomeprol 300 (mean increase in opacification, 37.3 Hounsfield units) and a significant better qualitative assessment in the aortoiliac segments without an increase in venous opacification or the presence of venous overlap. No significant differences were found for sensitivity and specificity for the diagnosis of significant stenoses (>70%) and occluded segments. Both agents were well tolerated, and no adverse events were recorded. CONCLUSIONS: The use of a small volume of a high-concentration contrast material yielded higher arterial enhancement from the abdominal aorta down to the femoral arteries with absent or minimal venous overlap and without significant differences in diagnostic ability.

Multidetector-row computed tomography angiography in abdominal aortic aneurysm treated with endovascular repair: evaluation of optimal timing of delayed phase imaging for the detection of low-flow endoleaks.

PURPOSE: To evaluate the optimal timing of delayed phase imaging for detecting low-flow endoleaks. MATERIALS AND METHODS: Fifty-eight patients with unruptured abdominal aortic aneurysm treated with endovascular repair underwent 1- and 6-month follow-up multidetector row computed tomography (CT) performed during unenhanced, arterial, and delayed phase. At 6-month follow-up, delayed phase imaging, focused on stent graft, was performed with a delay of 60 (early delayed enhanced phase) and 300 seconds (late delayed enhanced phase) after intravenous injection of 120 mL of iodinated nonionic contrast medium (iomeprol 300 mgI/mL, Iomeron), at a flow rate of 3 mL/s via an antecubital vein, with a detector-row configuration of 4 x 1-mm, a 1.25-mm slice width, and a pitch of 6. Six-month follow-up CT images were independently evaluated by 2 readers during 2 different reading sessions: sets A (unenhanced, arterial, and early delayed phase images) and B (unenhanced, arterial, and late delayed phase images). Sensitivity and diagnostic accuracy of both reading sessions were compared. The standard of reference was represented by the combined evaluation of 1- and 6-month CT scans. RESULTS: At standard of reference, 24 of 58 patients had an endoleak classified as type 1 in 2 cases, type 2 in 21 cases, and type 3 in the last 1 case. Seven of 21 type 2 endoleaks were classified as low-flow endoleaks. Set A reading session, including early delayed enhanced phase, allowed the detection of 19 of 24 endoleaks (5 false-negative cases represented by low-flow endoleaks), whereas all endoleaks were detected during set B reading session, including late delayed enhanced phase. Differences between sets A and B in terms of sensitivity and diagnostic accuracy were statistically significant (P < 0.05). CONCLUSIONS: For optimal multidetector CT detection of low-flow endoleaks in patients who underwent endovascular repair, delayed phase should be acquired 300 seconds after injection of contrast medium.