Vascular Contrast Enhancement Research Articles

Multi‐modality imaging characteristics of a surgically confirmed emphysematous torsion of papillary process of the caudate liver lobe and pneumoperitoneum in a dog

AbstractA 7‐year‐old, female, spayed dog presented with a 1‐week history of vomiting, diarrhoea and lethargy. Abdominal radiographs and ultrasound revealed bicavitary effusion, a large, gas‐cavitated, soft tissue mass in the region of the papillary process of the caudate lobe of the liver, with associated peritonitis and mild pneumoperitoneum. The location of the mass and gas cavitation were confirmed on computed tomography. The absence of vascular and parenchymal contrast enhancement and the distortion of the caudal vena cava was consistent with hilar torsion of the papillary process of the liver. The torsion was surgically confirmed and excised, and ischemic necrosis was histologically confirmed. The patient fully recovered following surgery.

Deep learning reconstruction allows for usage of contrast agent of lower concentration for coronary CTA than filtered back projection and hybrid iterative reconstruction.

The demand for homogeneous and higher vascular contrast enhancement is critical to provide an appropriate interpretation of abnormal vascular findings in coronary computed tomography angiography (CTA). To evaluate the effect of various contrast media concentrations (Iohexol-370, Iohexol-300, Iohexol-240) and image reconstructions (filtered back projection [FBP], hybrid iterative reconstruction [IR], and deep learning reconstruction [DLR]) on coronary CTA. A total of 63 patients referred for coronary CTA between July and October 2021 were enrolled in this prospective study, and they randomly received one of three contrast media. CTA images were reconstructed with FBP, hybrid IR, and DLR. The CT attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated for all three images. The images were subjectively evaluated by two radiologists in terms of overall image quality, artifacts, image noise, and vessel wall delineation on a 5-point Likert scale. The application of DLR resulted in significantly lower image noise; higher CT attenuation, SNR, and CNR; and better subjective analysis among the three different concentrations of contrast media groups (P < 0.001). There was no significant difference in the CT attenuation of the left ventricle (P = 0.089) and coronary arteries (P = 0.072) between hybrid IR at Iohexol-300 and DLR at Iohexol-240. Furthermore, application of DLR to the Iohexol-240 significantly improved SNR and CNR; it achieved higher subjective scores compared with hybrid IR at Iohexol-300 (P < 0.001). We suggest that using DLR with Iohexol-240 contrast media is preferable to hybrid IR with Iohexol-300 contrast media in coronary CTA.

MO226A NEW DIAGNOSTIC TOOL FOR CKD PATIENTS: CONTRAST-ENHANCED ULTRASONOGRAPHY. A SINGLE CENTER EXPERIENCE

Abstract Background and Aims Contrast-enhanced ultrasonography (CEUS) is a minimally invasive diagnostic tool available for diagnosing microvascular disturbances in tumors and many vascular pathologies. Unlike other radiological contrast agents, it is completely harmless for CKD patients and therefore it is used for the safe diagnosis of many diffuse or focal pathologies. Method We used CEUS examination in 50 CKD patients for the following pathologies: 10 atypical cysts, 15 liver focal lesions, 2 splenic focal lesions, 3 renal infarcts, 12 kidney focal lesions and 8 other organ involvements. Examination was made using a VOLUSON E8 machine (GE Medical System Kreztechnik GmbH Tiefenbach 15, Austria) with a 3.5 MHz convex array abdominal transducer. 2.4 ml of microbubble contrast-agent was administered intravenously and recording of the results were made for 3-5 minutes after injection. Results Depending on the organ vascular characteristics, contrast enhancement and/or wash-out were suggestive for the final diagnosis. In liver lesions there are three phases and in kidneys, spleen, gallbladder, adenopathies there are two vascular phases. We obtained a very good positive predictive value and sensitivity in detecting malignant lesions. Conclusion According to The EFSUMB Guidelines and Recommendations for the Clinical Practice of Contrast-Enhanced Ultrasound they are used both for hepatic and Non-Hepatic Applications. Being non-invasive and non-irradiating it could be the main diagnostic examination in CKD population in the future.

Split-bolus single-pass CT for vascular complications in acute pancreatitis: assessment of radiation dose and multi-phasic contrast enhancement compared to single-bolus multi-pass CT

To assess vascular contrast enhancement and radiation dose of split-bolus single-pass computed tomography (CT) compared to single-bolus multi-pass CT for acquiring a multi-phasic study. Patients who underwent CT for acute pancreatitis were included retrospectively. Thirty consecutive patients scanned with a split-bolus protocol were compared to 30 consecutive patients scanned with a single-bolus protocol. Data were collected on attenuation measurements (aorta, portal vein and spleen) and images were assessed for subjective vascular enhancement quality and splenic homogeneity. Radiation dose was measured by dose-length product (DLP). There was no significant difference in the aortic (p=0.88) or portal vein (p=0.35) attenuation values between the two groups. The percentage of examinations reaching the target aortic and portal attenuation in the split-bolus group were 96.7% and 93.3%, and in the single-bolus group were 96.7% and 85.7%, respectively. The mean DLP was 492 mGy.cm for the single-bolus group and 940 mGy.cm for the split-bolus group (p < 0.0001). Subjective assessment revealed higher rates of splenic heterogeneity in the split-bolus group. In acute pancreatitis, split-bolus imaging can produce arterial and venous enhancement comparable to a multi-pass technique with a significant reduction in radiation dose. Loss of temporal resolution and increased splenic heterogeneity are the main disadvantages. The low prevalence of pseudoaneurysms favours the lower-dose imaging technique.

CT characteristics of primary splenic torsion in eight dogs.

Splenic torsion is a rare potentially life-threatening condition characterized by rotation of the spleen around the gastrosplenic and phrenosplenic ligaments leading to occlusion of venous drainage and arterial supply. This retrospective study describes the CT characteristics for dogs with surgically confirmed splenic torsion from 2013 to 2018 using the submissions to a large multinational teleradiology database. Eight dogs had the splenic torsion confirmed with surgery. Seven of eight cases had histology confirming congestion, hemorrhage, and necrosis, and one had concurrent myelolipoma infiltration. The CT characteristics included an enlarged (8/8), rounded (7/8), folded C-shaped spleen (8/8) with a difference of median parenchymal attenuation between pre- and postcontrast of +1.15 HU (Hounsfield units). Other common features included a mainly homogeneous parenchyma on pre- and post-contrast images (6/8), lack of subjective and objective vascular and parenchymal contrast enhancement (6/8) and free peritoneal fluid (6/8). A "whirl sign" was seen in the majority of cases (7/8) alongside a strongly hyperattenuating center (95-416HU) on the precontrast images (5/7), which has not been previously described in the veterinary literature. Gastric position was normal in all cases. More variable CT characteristics of the confirmed torsions were attributable to suspected partial torsion and myelolipomatous infiltration. Overall, primary splenic torsion confirmed with surgery showed consistent characteristics on CT.

An Optimized Test Bolus Contrast Injection Protocol for Consistent Coronary Artery Luminal Enhancement for Coronary CT Angiography

Consistent levels of coronary artery enhancement are essential for quantitative analysis of coronary artery plaque. We studied three contrast injection protocols for coronary CT angiography (CCTA) and compared mean attenuation level and consistency of vascular contrast enhancement. We hypothesized that test bolus adjusted protocols will have a superior consistency of coronary attenuation compared to a weight-based protocol. We prospectively evaluated a standard test bolus injection protocol (protocol 1, 32 subjects) and an optimized test bolus injection protocol (protocol 2, 59 subjects) in comparison to a body weight-based injection protocol (60 subjects). The test bolus was diluted contrast (20%-30% iopamidol 370 mixed with normal saline); peak aortic attenuation was measured and used to calculate a specific water/contrast mixture for the CCTA. The mean attenuation of the coronary lumen was measured on CCTA. Metrics of optimum arterial enhancement included the percentage of patients within a predetermined range for coronary attenuation (325-500 HU) and optimal timing with maximal ascending aortic attenuation. In addition, interpatient variation in coronary enhancement was quantified as percentage standard deviation of the attenuation. The mean attenuation of the coronary arteries was similar in all protocols (362, 364, and 375 HU for the weight-based, test bolus 1 and 2 protocols, respectively). The percentage standard deviations of the weight-based, test bolus 1 and 2 protocols for coronary attenuation were 25.3%, 27.1%, and 10.5%, respectively (p < 0.0001). Test optimized bolus protocol 2 yielded the highest percentage of scans within the preferred coronary attenuation range (88%, p = 0.002). In test bolus protocol 2, the contrast timing was optimal in 73% of cases compared to only 22% of cases in the body mass guided injection protocol (protocol 1, p < 0.0001). An optimized test bolus guided injection protocol resulted in a marked reduction in variation in coronary enhancement for CCTA compared to a body weight-based injection protocol.

Magnetic resonance angiography contrast enhancement and combined 3D visualization of cerebral vasculature and white matter pathways

Recently, in diffusion magnetic resonance imaging, the reconstruction and three-dimensional rendering of white matter pathways have been introduced to clinical routine protocols. In a number of clinical situations, for example the preoperative analysis of vascular pathologies, the assessment of spatial relations between vascular structures and nearby fiber pathways is of vital interest for treatment planning. In this paper, we present an approach to the integrated vessel and fiber visualization, based on a novel vascular contrast enhancement operator for Magnetic Resonance Angiography (MRA) datasets. We propose a 3D dynamic programming method, allowing contrast enhancement of vascular structures and suppression of partial voluming effects at vessel borders. This makes it easier to visualize vascular structures by realtime volume rendering with surface shading. In contrast to maximum intensity projection, the method provides better depth cues and allows for easier spatial orientation. The integration of tractography-generated fibers as streamlines or streamtubes with correct visibility computation is performed by a combined volume and geometry renderer. In situations where tractography fails to provide reliable results, we use a line integral convolution method to assess white matter structures. In this manner, the spatial relations of vessels to fiber structures can be depicted by three-dimensional visualizations. We evaluate our approach with clinical data from patients with arteriovenous malformations, stenoses, aneurysms, and from healthy volunteers.

Best Protocol for Combined Contrast-Enhanced Thoracic and Abdominal CT for Lung Cancer: A Single-Institution Randomized Crossover Clinical Trial.

The purpose of this study was to evaluate the superiority of either of two protocols for combined contrast-enhanced thoracic and abdominal CT of patients with lung cancer by comparing contrast enhancement, contrast-related artifacts, image quality, and radiation dose. In this randomized controlled crossover clinical trial, 77 patients who underwent 203 CT examinations were enrolled. All patients underwent at least two examinations performed with both protocols. Protocol A consisted of two acquisitions: one 35-second delayed CT acquisition for the chest followed by a 70-second delayed abdominal acquisition. Protocol B was a single 60-second delayed acquisition covering the chest and the abdomen. Attenuation and noise of the aorta, pulmonary artery, and liver were measured. Contrast-related artifacts, mediastinal lymph node visualization, liver enhancement, and noise were visually scored. Dose-length product was recorded. Statistical analysis was performed by t and chi-square tests and kappa statistics. Contrast-related artifacts were more severe at all evaluated levels, and visualization of lymph node regions was statistically significantly worse with protocol A. There were no differences in enhancement or noise score of the liver. Tumor delineation and pleural findings were better evaluated with delayed phase images. Dose-length product was significantly higher with protocol A (645.0 vs 521.5 mGy · cm; p < 0.0001). A single 60-second delayed acquisition for thoracic and abdominal contrast-enhanced CT is associated with less contrast artifact and affords better visualization of lymph nodes at a lower radiation dose while acceptable vascular and hepatic contrast enhancement is maintained.

Whole-Body High-Pitch CT Angiography: Strategies to Reduce Radiation Dose and Contrast Volume.

The purpose of this study was to assess the noninferiority of dual-source high-pitch CT angiography (CTA) performed with high-concentration (iopamidol 370) low-volume (60 mL) iodinated contrast material at low voltage (100 kVp) in comparison with dual-source high-pitch CTA with standard-of-care low-concentration (iopamidol 300) standard-volume (75 mL) iodinated contrast material at high voltage (120 kVp) to determine whether use of the high-concentration low-volume method would afford a reduction in radiation dose and contrast volume without negatively affecting vascular opacification. This study had three arms. A phantom was used to assess vascular contrast enhancement at different iodine and saline solution dilutions with iopamidol 300 or 370 to compare lower-iodination (iopamidol 300) high-voltage (120 kVp) high-pitch (120 kVp, 250 mAs) imaging with higher-iodination (iopamidol 370) low-voltage (100 kVp) high-pitch (100 kVp, 100-240 mAs) acquisition. Metal-oxide-semiconductor field-effect transistors were placed in an anthropomorphic phantom to extract organ-based radiation profiles, and ANOVA was performed. The study prospectively enrolled 150 patients: 50 patients received 75 mL iopamidol 300, and image acquisition was performed at 120 kVp and 250 mAs; 50 patients received 75 mL iopamidol 370, and acquisition was performed at 100 kVp and 240 mAs; and 50 patients received 60 mL iopamidol, and acquisition was performed at 370 at 100 kVp and 240 mAs. Vascular signal-to-noise ratio was evaluated at 18 anatomic locations. Longitudinal signal-to-noise ratio was used to assess homogeneity of contrast enhancement. Size-specific dose estimates were calculated. Statistical analyses were performed by ANOVA. Noninferiority of high-concentration (iopamidol 370) low-voltage (100 kVp) high-pitch acquisitions compared with low-concentration (iopamidol 300) high-voltage (120 kVp) high-pitch acquisition was achieved at 170 mAs in vitro. Radiation assessment showed significant decreases in radiation dose for the 100-kVp 240-mAs protocol (p < 0.0001). Noninferior vascular contrast (p > 0.280) and luminal homogeneity (p > 0.191) were found for all high-pitch protocols. Significantly decreased radiation dose was observed for the two groups that received 60 and 75 mL of iopamidol 370 at 100 kVp and 240 mAs (p < 0.0001). Dual-source high-pitch CTA with high-concentration (iopamidol 370) low-volume (60 mL) iodinated contrast medium and low-voltage acquisition (100 kVp) is noninferior to dual-source high-pitch CTA with low-concentration (iopamidol 300) standard-volume (75 mL) iodinated contrast material at high voltage (120 kVp) and affords simultaneous reduction in radiation dose and contrast volume without negatively affecting vascular contrast enhancement.

A Proposed Computed Tomography Contrast Agent Using Carboxybetaine Zwitterionic Tantalum Oxide Nanoparticles

The aim of this study was to produce and evaluate a proposed computed tomography (CT) contrast agent based on carboxybetaine zwitterionic (CZ)-coated soluble tantalum oxide (TaO) nanoparticles (NPs). We chose tantalum to provide superior imaging performance compared with current iodine-based clinical CT contrast agents. We developed the CZ coating to provide biological and physical performance similar to that of current iodinated contrast agents. In addition, the aim of this study was to evaluate the imaging, biological, and physicochemical performance of this proposed contrast agent compared with clinically used iodinated agents. We evaluated CT imaging performance of our CZ-TaO NPs compared with that of an iodinated agent in live rats, imaged centrally located within a tissue-equivalent plastic phantom that simulated a large patient. To evaluate vascular contrast enhancement, we scanned the rats' great vessels at high temporal resolution during and after contrast agent injection. We performed several in vivo CZ-TaO NP studies in healthy rats to evaluate tolerability. These studies included injecting the agent at the anticipated clinical dose (ACD) and at 3 times and 6 times the ACD, followed by longitudinal hematology to assess impact to blood cells and organ function (from 4 hours to 1 week). Kidney histological analysis was performed 48 hours after injection at 3 times the ACD. We measured the elimination half-life of CZ-TaO NPs from blood, and we monitored acute kidney injury biomarkers with a kidney injury assay using urine collected from 4 hours to 1 week. We measured tantalum retention in individual organs and in the whole carcass 48 hours after injection at ACD. Carboxybetaine zwitterionic TaO NPs were synthesized and analyzed in detail. We used multidimensional nuclear magnetic resonance to determine surface functionality of the NPs. We measured NP size and solution properties (osmolality and viscosity) of the agent over a range of tantalum concentrations, including the high concentrations required for standard clinical CT imaging. Computed tomography imaging studies demonstrated image contrast improvement of approximately 40% to 50% using CZ-TaO NPs compared with an iodinated agent injected at the same mass concentration. Blood and organ analyses showed no adverse effects after injection in healthy naive rats at 3 times the ACD. Retention of tantalum at 48 hours after injection was less than 2% of the injected dose in the whole carcass, which very closely matched the reported retention of existing commercial iodine-based contrast agents. Urine analysis of sensitive markers for acute kidney injury showed no responses at 1 week after injection at 3 times the ACD; however, a moderate response in the neutrophil gelatinase-associated lipocalin biomarker was measured at 24 and 48 hours. Compared with other TaO NPs reported in the literature, CZ-TaO NPs had relatively low osmolality and viscosity at concentrations greater than 200 mg Ta/mL and were similar in these physical properties to dimeric iodine-based contrast agents. We found that a CZ-TaO NP-based contrast agent is potentially viable for general-purpose clinical CT imaging. Our results suggest that such an agent can be formulated with clinically viable physicochemical properties, can be biologically safe and cleared rapidly in urine, and can provide substantially improved image contrast at CT compared with current iodinated agents.

Frequency Selective Non-Linear Blending to Improve Image Quality in Liver CT.

Purpose: To evaluate the effects of a new frequency selective non-linear blending (NLB) algorithm on the contrast resolution of liver CT with low intravascular concentration of iodine contrast. Materials and Methods: Our local ethics committee approved this retrospective study. The informed consent requirement was waived. CT exams of 25patients (60 % female, mean age: 65 ± 16 years of age) with late phase CT scans of the liver were included as a model for poor intrahepatic vascular contrast enhancement. Optimal post-processing settings to enhance the contrast of hepatic vesselswere determined. Outcome variables included signal-to-noise (SNR) and contrast-to-noise ratios (CNR) of hepatic vessels and SNR of liver parenchyma of standard and post-processed images. Image quality was quantified by two independent readers using Likert scales. Results: The post-processing settings for the visualization of hepatic vasculature were optimal at a center of 115HU, delta of 25HU, and slope of 5. Image noise was statistically indifferent between standard and post-processed images. The CNR between the hepatic vasculature (HV) and liver parenchyma could be significantly increased for liver veins (CNRStandard 1.62 ± 1.10, CNRNLB 3.6 ± 2.94, p = 0.0002) and portal veins (CNRStandard 1.31 ± 0.85, CNRNLB 2.42 ± 3.03, p = 0.046). The SNR of liver parenchyma was significantly higher on post-processed images (SNRNLB 11.26 ± 3.16, SNRStandard 8.85 ± 2.27, p = 0.008). The overall image quality and depiction of HV were significantly higher on post-processed images (NLBDHV: 4 [3 - 4.75], StandardDHV: 2 [1.3 - 2.5], p = < 0.0001; NLBIQ: 4 [4 - 4], StandardIQ: 2[2 - 3], p = < 0.0001). Conclusion: The use of a frequency selective non-linear blending algorithm increases the contrast resolution of liver CT and can improve the visibility of the hepatic vasculature in the setting of a low contrast ratio between vessels and the parenchyma. Key Points: • Using the new frequency selective non-linear blending algorithm is feasible in contrast-enhanced liver CT.• Optimal post-processing settings make it possible to significantly increase the contrast resolution of liver CT without affecting image noise.• Especially in low contrast CT images, the novel algorithm is capable of significantly increasing image quality. Citation Format: • Bongers MN, Bier G, Kloth C et al. Frequency Selective Non-Linear Blending to Improve Image Quality in Liver CT. Fortschr Röntgenstr 2016; 188: 1163 - 1168.

CT angiography for pulmonary embolism detection: the effect of breathing on pulmonary artery enhancement using a 64-row detector system

Computed tomography pulmonary angiography (CTPA) is used most often in routine clinical practice for the assessment of a suspected pulmonary embolism. The diagnostic accuracy relies on sufficient contrast enhancement. To evaluate whether image acquisition during shallow breathing can improve the image quality in patients with insufficient contrast enhancement during breath-hold examinations. A total of 2786 CT pulmonary angiographies, acquired on a 64-row CT during deep-inspiration breath-hold, were reviewed. Twenty-four examinations were considered non-diagnostic due to poor contrast enhancement in the pulmonary arteries (PA), although they showed preserved vascular enhancement of the superior vena cava (SVC) and the ascending aorta (AO). Eleven flawed CTPA examinations, including severe breathing artifacts and incorrect triggering were excluded. In 13 of the remaining patients, the examination was repeated during shallow breathing. Vascular contrast enhancement was compared between both scans by measuring the relative enhancement within the SVC, the main PA, and the AO. Image quality was scored by two, clinically experienced radiologists. The values are given as median and [25th;75th] quartile. There was a significant difference in the CT values for the PA between the repeated scans (P = 0.0002, Wilcoxon test), and with the CTPA in deep-inspiration showing a median enhancement of 97 HU (59-173), compared with 303 HU (239-385) in the CTPA acquired during free breathing. The differences for both the AO (P = 0.54) and the SVC (P = 0.78) were not significant. Scoring for the attenuation quality rose significantly (P = 0.0002) and no severe motion artifacts were detected on either scans. If there is insufficient pulmonary artery enhancement during CTPA, attenuation of the pulmonary arteries can be improved by acquisition during shallow breathing and is without significant loss of the overall diagnostic image quality.

An unusual case of sclerosing angiomatoid nodular transformation: radiological and histopathological analyses

Sclerosing angiomatoid nodular transformation (SANT) is a rare benign primary vascular lesion of the spleen. Its etiology is still debated. Radiological characteristics are less known, although there are some reports regarding histopathological features ofSANT. A 21-year-old male patient was admitted to our hospital with fatigue, weight loss, and abdominal pain for 4 months. Physical examination, complete blood count, andbiochemical parameters were unremarkable. Dynamic contrast-enhanced computed tomography (CT) of the abdomen was performed. A heterogeneous well-defined hyperdense nodular lesion 3 cm in diameter was detected during the arterial phase. The detected lesion was seen as isodense with the spleen parenchyma during the portal venous and late venous phases. Magnetic resonance imaging (MRI) showed an isointense-hypointense nodular lesion on T1- and T2-weighted images. Intraabdominal LAM or splenomegaly was not detected. Microscopically, it was composed of angiomatoid nodules separated by central stellate fibrous stroma and fibrous septa. The contrast enhancement pattern was described as centrally hypovascular, radially progressive centripetal vascular contrast enhancement, called a spoke-wheel pattern in previously reported cases. We present CT and MRI findings and their correlation with histopathological findings of a case of unusual symptomatic SANT.

Poly(ethylene glycol)-poly(ε-caprolactone) Iodinated Nanocapsules as Contrast Agents for X-ray Imaging

Synthesis and formulation of iodinated PCL-mPEG nanocapsules as new original blood pool contrast agents for computed tomography. PCL-mPEG was synthesized and formulated following the emulsion-solvent diffusion process, in the form of iodinated nanocapsules. Physico-chemical characterization of such nano-materials was performed by DLS and transmission electron microscopy. A stability study of the nanocapsules suspension was followed-up to 3 month. Blood biocompatibility was performed. Finally, the nanocapsules suspension radiopacity was evaluated in vitro then in vivo in mice as micro-CT contrast agent. In this study, the iodine concentration in nanocapsules suspension was about 70 mgI/mL. Besides, these nanocarriers appeared non-toxic, and stable in suspension. In vivo, i.v. administration of 10 μL/g of mouse body weight of theses nano-particles induced a vascular contrast enhancement of 168 HU and a half-life in blood of 4.2 +/- 0.5 h. Elimination route of these particles appears mainly performed by the liver, without sequestration in spleen and lymph nodes confirming their stealth properties. This study proposes the first example of iodinated biodegradable polymeric blood pool contrast agent, able to induce an exploitable contrast enhancement. The main advantage of polymeric system compared to lipid ones, lies in their stability and handling, e.g. towards drying for storage.

Monte Carlo modeling of light–tissue interactions in narrow band imaging

Light-tissue interactions that influence vascular contrast enhancement in narrow band imaging (NBI) have not been the subject of extensive theoretical study. In order to elucidate relevant mechanisms in a systematic and quantitative manner we have developed and validated a Monte Carlo model of NBI and used it to study the effect of device and tissue parameters, specifically, imaging wavelength (415 versus 540 nm) and vessel diameter and depth. Simulations provided quantitative predictions of contrast-including up to 125% improvement in small, superficial vessel contrast for 415 over 540 nm. Our findings indicated that absorption rather than scattering-the mechanism often cited in prior studies-was the dominant factor behind spectral variations in vessel depth-selectivity. Narrow-band images of a tissue-simulating phantom showed good agreement in terms of trends and quantitative values. Numerical modeling represents a powerful tool for elucidating the factors that affect the performance of spectral imaging approaches such as NBI.

Reduced contrast medium in abdominal aorta CTA using a multiphasic injection technique

PurposeThe purpose of this study was to determine if with a multiphasic injection technique the administered amount of contrast medium for abdominal computerized tomographic angiography (CTA) can be decreased, whilst improving CT image quality. Materials and methodsIn 30 patients a multiphasic injection method was compared to the standard uniphasic contrast medium injection protocol. Fifteen patients underwent abdominal CTA with a standard uniphasic injection protocol (protocol I) receiving 100mL of a non-ionic radiopaque contrast agent (Ioversol). The second group of 15 patients underwent CTA with a multiphasic injection protocol (protocol II) receiving a total of 89mL Ioversol. Vascular contrast enhancement and difference in enhancement uniformity were assessed quantitatively and image quality was assessed by three independent radiologists. ResultsQuantitative assessment of the vascular contrast enhancement showed that there was no significant difference in enhancement uniformity for patients between the protocols. The image quality was rated as being good to excellent in 81.8% and 88.0% of the scans, for protocol I and protocol II, respectively. However these differences were not statistically significant. ConclusionBy using a multiphasic injection technique with CTA of the abdominal aorta a reduction of 11 percent of contrast medium can be realized. Enhancement patterns are quantitatively as well as qualitatively comparable to the standard contrast medium injection protocol.

High concentration (400 mgI/mL) versus low concentration (320 mgI/mL) iodinated contrast media in multi detector computed tomography of the liver: A randomized, single centre, non-inferiority study

ObjectivesTo compare vascular and parenchymal contrast enhancement in multidetector computed tomography of the liver using two contrast media with different iodine concentration (Iodixanol 320mgI/mL and Iomeprol 400mgI/mL) and similar viscosity, using fixed total iodine volume (40gI) and iodine delivery rate (1.6gI/s). Methods110 patients were prospectively randomized into two groups. Group A received 125mL of Iodixanol 320 and group B 100mL of Iomeprol 400.Attenuation values were measured at the level of the aorta, portal vein and liver parenchyma on unenhanced, arterial, portal and equilibrium phases. A non inferiority test was performed on the differences between the two groups. An independent reader evaluated image quality. ResultsThe equivalence of the two CM was demonstrated in all measurements. Higher, but not statistically significant, attenuation values were obtained with Iomeprol 400 in the aorta during the arterial phase (305.3HU versus 288.4HU; P=0.32) and with Iodixanol 320 in the liver parenchyma, during both portal (59.8HU versus 65.5HU; P=0.78) and equilibrium (40.4HU versus 41.8HU; P=0.55) phases. ConclusionsIodixanol 320 and Iomeprol 400 injected at the same iodine delivery rate (1.6gI/s) and total iodine load (40gI) did not provide statistically significant differences in liver parenchymal and vascular contrast enhancement.

Whole body diffusion for metastatic disease assessment in neuroendocrine carcinomas: comparison with OctreoScan® in two cases

Neuroendocrine tumor (NET) patients must be adequately staged in order to improve a multidisciplinary approach and optimal management for metastatic disease. Currently available imaging studies include somatostatin receptor scintigraphy, like OctreoScan®, computed tomography (CT), scans and magnetic resonance imaging (MRI), which analyze vascular concentration and intravenous contrast enhancement for anatomic tumor localization. However, these techniques require high degree of expertise for interpretation and are limited by their availability, cost, reproducibility, and follow-up imaging comparisons. NETs significantly reduce water diffusion as compared to normal tissue. Diffusion-weighted imaging (DWI) in MRI has an advantageous contrast difference: the tumor is represented with high signal over a black normal surrounding background. The whole-body diffusion (WBD) technique has been suggested to be a useful test for detecting metastasis from various anatomic sites. In this article we report the use of DWI in MRI and WBD in two cases of metastatic pulmonary NET staging in comparison with OctreoScan® in order to illustrate the potential advantage of DWI and WBD in staging NETs.

High-Dose Antiangiogenic Therapy for Glioblastoma: Less May Be More?

Targeting angiogenesis in glioblastoma rapidly reduces vascular permeability and contrast enhancement on MRI and prolongs progression-free survival. The long-term efficacy of bevacizumab and other antiangiogenic agents is limited, however, because of the rapid development of resistance. Alternative dosing approaches may be one mechanism of prolonging therapeutic efficacy.

FLAIR, T1 contrast enhancement, MR perfusion, and FDG PET following hypofractionated stereotactic radiotherapy (HFSRT), bevacizumab (BEV), and temozolomide (TMZ) for glioblastoma (GBM).

2048 Background: In GBM, VEGF inhibition decreases vascular permeability and MRI contrast enhancement (CE), which may or may not reflect meaningful anti-tumor activity. We sought to evaluate the relationships between different imaging modalities and anti-tumor activity in a prospective phase II trial of BEV, TMZ and HFSRT in GBM. Methods: Newly diagnosed GBM pts (N=40) received HFSRT with concomitant/ adjuvant BEV and TMZ. All pts underwent dynamic susceptibility contrast MR perfusion (DSC) at baseline, after HFSRT and every 2m. An FDG-PET scan was done at cycle 6. McDonald and RANO response criteria were applied. Results: DSC showed early/progressive decreases in relative cerebral blood volume (rCBV): baseline mean rCBV: 2.77; 6 weeks: 1.65 (p=0.014); 2m: 1.07 (p<0.001); 4m: 0.98 (p<0.001). Conversely, the extent of FLAIR hypersignal progressively increased (mean diameter product: 953, 1165, 1145, 1384 at 6 wks, 2m, 4m and 6m). Response rates per McDonald vs RANO were: complete response (27 vs 10%), partial (63 vs 63%), stable disease (3% vs 20%), progression (7 vs 7%). Because progressive FLAIR occurred within the RT port, time to radiographic progression per McDonald and RANO were identical: median 13m. Residual hypermetabolism seen at the 6m PET (N=6/31) predicted poor survival (p<0.001). Three pts with progressive FLAIR but not CE underwent re-resection; two had true PD and one had mainly radionecrosis. Conclusions: As treatment failure was mostly local, RANO criteria did not shorten time to progression compared to McDonald. DSC depicted early changes in rCBV linked to VEGF modulation, validating DSC as a reliable tool to evaluate anti-VEGF properties of new drugs in vivo. However, VEGF modulation was not predictive of durable anti-tumor activity. A positive PET at 6m predicted poor survival, indicating treatment failure even if other imaging modalities suggested otherwise. However, tumor progression may still be present despite negative PET and DSC, particularly in the setting of increasing non-enhancing FLAIR within the RT port. New imaging tools and improved response criteria are needed to guide management of these pts.