Injectable Ovalbumin-Based Composite Implant for Photothermal Tumor Therapy.

Polymeric hydrogels with three-dimensional network structures have found tremendous applications in biomedicine. Herein, we report the synthesis of a multifunctional implant based on ovalbumin (OVA) as a carrier capable of synergistically delivering a photothermal transducing agent (polydopamine, PDA) to tumors. The formation of PDA was achieved by utilizing the basicity of OVA, whereas the formation of the hydrogel implant was achieved through the in vitro/in vivo near-infrared (NIR) laser-induced hyperthermia of PDA. The as-prepared PDA@OVA implant exhibits high photothermal conversion efficiency (38.7 %). Once implanted in vivo, the OVA-based implant shows great versatility in the treatment of malignant tumors. Furthermore, a chemotherapeutic (doxorubicin, DOX) and a contrast agent (iohexol), dispersed in the OVA solution in advance, can also be firmly entrapped in the hydrogel along with the hydrogel formation. It is anticipated that the multifunctional OVA-based implant, not showing any obvious toxicity to healthy tissue, could be a promising system for synergistic cancer treatment.

Increased image quality and reduced radiation dose and contrast media volume: a holistic approach to intracranial CTA.

AIM: To investigate the dose-length product (DLP) during intracranial computed tomography angiography (CTA) using a patient-specific contrast formula. MATERIALS AND METHODS: Intracranial CTA was performed on 120 patients using 64-channel CT. Patients were subjected in equal numbers to one of two acquisitions/contrast medium protocols. Protocol A, consisted of 80 ml contrast medium and protocol B, involved a novel contrast medium formula. In each protocol, contrast medium and saline were injected at a flow rate of 4.5 ml/s. The DLP and contrast volume (CV) were measured between each protocol and the data obtained were compared using two-tailed independent t-test. RESULTS: Mean arterial vessel attenuation was up to 56% (p<0.01) higher using protocol B compared with A. In the venous system, the mean vessel attenuation was significantly lower in protocol B than A with a maximum reduction of 93% (p<0.001). The mean CV was significantly lower in protocol B (53±10 ml) compared to A (80±1 ml, p<0.001). The scan time was equal in each protocol (B, 4.22±1.2 seconds; A, 4.01±1.3 seconds). A significant reduction in mean DLP was demonstrated in protocol B (3.99±0.22 mSv) compared to A (4.74±0.22 mSv; p=0.02). CONCLUSION: A significant reduction in CV and DLP during intracranial CTA can be achieved when employing a patient-specific contrast medium formula.

Carbon Dioxide as Contrast Medium to Guide Endovascular Aortic Aneurysm Repair.

BACKGROUND: Iodine contrast medium (ICM) is considered to be gold standard in endovascular procedures, but its nephrotoxicity and hypersensitivity limit the widespread use. Carbon dioxide (CO2) is considered as an alternative for endovascular procedures in patients with contraindication to ICM. However, no studies have compared the outcomes of endovascular aneurysm repair (EVAR) performed with ICM or CO2 among patients with no contraindication to ICM. METHODS: From May 2012 to April 2014, 36 patients with abdominal aortic aneurysms underwent EVAR in a prospective, randomized, and controlled study. Patients were randomized into 2 groups, CO2 or ICM group. RESULTS: We were able to perform the proposed procedures in all patients in this study. There were no conversions to open surgery and no CO2-related complications. Endovascular material costs, duration of surgery, and time of fluoroscopy were similar between groups, and the cost of the contrast media was smaller in the CO2 group than in the ICM group. Among CO2 group procedures, 62.5% of the patients needed ICM complementary use. CONCLUSIONS: The use of CO2 as a contrast medium for EVAR is an alternative in patients with no restriction for ICM, with similar outcomes when compared to ICM, regarding duration of surgery, duration of fluoroscopy, and endovascular material costs. Using CO2, there were no changes in creatinine clearance and no risk of hypersensitivity reactions; moreover, there was a reduction in contrast-related costs for EVAR procedures. However, in our study, additional use of ICM to visualize the internal iliac artery was needed in most procedures.

Local delivery of paclitaxel in the treatment of peripheral arterial disease.

BACKGROUND: Despite advancements from balloon angioplasty to drug-eluting stents, primary patency rates after endovascular revascularization of peripheral artery disease have remained inferior compared to surgery. Endovascular revascularization has been limited by restenosis and mechanical stent failure. Thus, there is increased research into other nonstent-based local drug delivery modalities, which can provide an active drug to inhibit restenosis focally and avoid the risk of systemic adverse effects. METHODS: This review will summarize the unique properties of paclitaxel and studies on paclitaxel local delivery for the treatment of peripheral artery disease. A MEDLINE search for relevant peer-reviewed scientific literature published in English was conducted. Search terms included but were not limited to paclitaxel pharmacodynamics, paclitaxel local drug delivery, and drug eluting balloons, with a focus on the use of paclitaxel in the context of coronary and peripheral vascular disease. RESULTS: The primary search produced 182 results of which 51 papers were relevant. Of the 51 relevant papers, 27 were original research papers and 24 were either review papers, commentary or opinion papers. CONCLUSIONS: Paclitaxel has several chemical properties, which make it ideal for local drug delivery including its hydrophobicity, ability to concentrate into the arterial intima layer and prolonged effect on cells even after brief exposure periods. Local delivery of paclitaxel via injection catheters, balloon catheters and coated balloons has shown encouraging results in terms of efficacy and safety in small-scale animal and clinical studies. Additional preclinical and clinical studies are needed to determine the long-term efficacy and safety of these treatments in humans.

Lack of functional patency of the lamina terminalis after fenestration following clipping of anterior circulation aneurysms.

OBJECT: Fenestration of the lamina terminalis (FLT) during aneurysm surgery for subarachnoid hemorrhage can, in theory, improve CSF circulation from the lateral and third ventricles to the cortical subarachnoid space, which may, in turn, decrease the incidence of hydrocephalus and vasospasm. However, the actual effects of FLT on CSF circulation have been difficult to determine, due to confounding factors. In addition, it is unclear whether the lamina terminalis remains functionally patent when the brain resumes its normal position. The goal of this study was to assess the functional patency of the fenestrated lamina terminalis in patients who underwent surgery for ruptured aneurysms. METHODS: This prospective study included 15 patients who underwent surgical clipping of ruptured anterior circulation aneurysms, with FLT performed during surgery. On postoperative Day 1, the external ventricular drain of each patient was closed, and 1 ml of Omnipaque 300, an iodine based contrast agent, was injected intraventricularly, accompanied by cranial maneuvering designed to position the contrast agent adjacent to the lamina terminalis. Three to 5 minutes after cranial maneuvering, the flow of contrast agent into the basal cisterns was assessed with CT imaging. Flow was verified by an increase in Hounsfield units in a prespecified "region of interest" within the basal cisterns on the CT scan. This procedure was performed using a standardized protocol designed in consultation with the Department of Radiology and approved by the institutional review board. One patient who underwent endoscopic third ventriculostomy was recruited as a positive control to validate the technique, and 1 patient who underwent aneurysm clipping but not FLT was recruited as a negative control. RESULTS: Seventeen patients consented to study participation. In the 15 patients who underwent aneurysm clipping and FLT, and the negative control patient who underwent aneurysm clipping but not FLT, the contrast agent followed the normal ventricular pathway from the lateral ventricles into the fourth ventricle, and did not appear in the basal cisterns. In the positive control patient, the contrast agent robustly and immediately filled the basal cisterns. CONCLUSIONS: Fenestration of the lamina terminalis did not result in functional patency of the lamina terminalis when performed as part of surgical clipping for ruptured aneurysms.

Visualisation of the rectoanal inhibitory reflex with a modified contrast enema in children with suspected Hirschsprung disease.

BACKGROUND: Patients with Hirschsprung disease lack the normal rectoanal inhibitory reflex, which can be studied with anorectal manometry or US. OBJECTIVE: To see whether the rectoanal inhibitory reflex could be visualised with a modified contrast enema, thereby increasing the diagnostic accuracy of the contrast enema and reducing the number of rectal biopsies. MATERIALS AND METHODS: Fifty-nine boys and 42 girls (median age, 12 months) with suspected Hirschsprung disease were examined with a modified contrast enema, supplemented with two injections of cold, water-soluble contrast medium, to induce the reflex. Two paediatric radiologists evaluated the anonymised examinations in consensus. The contrast enema findings were correlated with the results of rectal biopsy or clinical follow-up. RESULTS: Five boys and one girl (median age, 7.5 days) were diagnosed with Hirschsprung disease. The negative predictive value of the rectoanal inhibitory reflex was 100%. A contrast enema with signs of Hirschsprung disease in combination with an absent rectoanal inhibitory reflex had the specificity of 98% and sensitivity of 100% for Hirschsprung disease. CONCLUSION: The modified contrast enema improves the radiological diagnosis of Hirschsprung disease. By demonstrating the rectoanal inhibitory reflex in children without Hirschsprung disease, we can reduce the proportion of unnecessary rectal biopsies.

Spectral optimization of chest CT angiography with reduced iodine load: experience in 80 patients evaluated with dual-source, dual-energy CT.

PURPOSE: To determine the energy levels that provide optimal imaging of thoracic circulation at dual-energy computed tomographic (CT) angiography with reduced iodine load in comparison with a standard technique. MATERIALS AND METHODS: The institutional review board approved the study with waiver of patient consent. Eighty patients underwent a dual-source, dual-energy CT examination after administration of low-concentration contrast material (170 mg of iodine per milliliter), and eight series of images were reconstructed, including the original polychromatic images at 80 and 140 kV and six series of virtual monochromatic spectral images at 50, 60, 70, 80, 90, and 100 keV. For each vascular compartment, the energy level that provided optimal evaluation on virtual monochromatic spectral images was determined, and these series were compared with the polychromatic dual-energy images and with standard chest CT images that were used as controls. Comparisons between groups were performed by using the paired Student t test for continuous variables and the McNemar test for categorical variables. Comparisons between dual-energy and standard CT images were performed by using the unpaired Student t test for continuous variables and the χ(2) test for categorical variables. RESULTS: For the aorta, pulmonary arteries, and veins, the reconstruction at 60 keV provided adequate attenuation without marked beam-hardening artifacts in 90% of patients, with the highest contrast-to-noise and signal-to-noise ratios, the lowest level of subjective noise, and no significant differences with images at 80 kV (mean energy, 54 keV). For the superior vena cava and brachiocephalic veins, the reconstructions at 100 keV enabled artifact-free analysis of the perivascular anatomic zone without a significant difference with images at 140 kV (mean energy, 92 keV). Compared with standard CT images acquired after administration of a 35% iodinated contrast agent, there was a statistically significant reduction in the frequency of artifacts around systemic veins at 100 keV (P < .001) and similar overall image quality for central vessels at 60 keV (P > .05). CONCLUSION: An optimal analysis of thoracic circulation can be achieved on virtual monochromatic spectral images at 60 keV and 100 keV and on the original polychromatic images at 80 kV and 140 kV. SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120195/-/DC1.

Embolisation of bone metastases from renal cancer.

PURPOSE: This study was done to evaluate embolisation for palliative and/or adjuvant treatment of bone metastases from renal cell carcinoma and discuss the clinical and imaging results. MATERIALS AND METHODS: We retrospectively studied 107 patients with bone metastases from renal cell carcinoma treated from December 2002 to January 2011 with 163 embolisations using N-2-butyl cyanoacrylate (NBCA). Mean tumour diameter before embolisation was 8.8 cm and mean follow-up 4 years. Clinical and imaging effects of treatment were evaluated at follow-up examinations with a pain score scale, analgesic use, hypoattenuating areas, tumour size and ossification. RESULTS: A clinical response was achieved in 157 (96%) and no response in six embolisations of sacroiliac metastases. Mean duration of clinical response was 10 (range 1-12) months. Hypoattenuating areas resembling tumour necrosis were observed in all patients. Variable ossification appeared in 41 patients. Mean maximal tumour diameter after embolisation was 4.0 cm. One patient had intraprocedural tear of the left L3 artery and iliopsoas haemorrhage and was treated with occlusion of the bleeding vessel with NBCA. All patients had variable ischaemic pain that recovered completely within 2-4 days. Postembolisation syndrome was diagnosed after 15 embolisations (9.2%). Transient paraesthesias in the lower extremities were observed after 25 embolisations (25%) of pelvis and sacrum metastatic lesions. CONCLUSIONS: Embolisation with NBCA is recommended as primary or palliative treatment of bone metastases from renal cell carcinoma. Strict adherence to the principles of transcatheter embolisation is important to avoid complications.

In vivo differentiation of complementary contrast media at dual-energy CT.

PURPOSE: To evaluate the feasibility of using a commercially available clinical dual-energy computed tomographic (CT) scanner to differentiate the in vivo enhancement due to two simultaneously administered contrast media with complementary x-ray attenuation ratios. MATERIALS AND METHODS: Approval from the institutional animal care and use committee was obtained, and National Institutes of Health guidelines for the care and use of laboratory animals were observed. Dual-energy CT was performed in a set of iodine and tungsten solution phantoms and in a rabbit in which iodinated intravenous and bismuth subsalicylate oral contrast media were administered. In addition, a second rabbit was studied after intravenous administration of iodinated and tungsten cluster contrast media. Images were processed to produce virtual monochromatic images that simulated the appearance of conventional single-energy scans, as well as material decomposition images that separate the attenuation due to each contrast medium. RESULTS: Clear separation of each of the contrast media pairs was seen in the phantom and in both in vivo animal models. Separation of bowel lumen from vascular contrast medium allowed visualization of bowel wall enhancement that was obscured by intraluminal bowel contrast medium on conventional CT scans. Separation of two vascular contrast media in different vascular phases enabled acquisition of a perfectly coregistered CT angiogram and venous phase-enhanced CT scan simultaneously in a single examination. CONCLUSION: Commercially available clinical dual-energy CT scanners can help differentiate the enhancement of selected pairs of complementary contrast media in vivo.

Locoregional chemoembolic delivery: prediction with transcatheter intraarterial perfusion MRI.

OBJECTIVE: To our knowledge there is currently no quantitative preprocedural method for predicting the distribution and selectivity of delivery of chemoembolic material during trans-arterial chemoembolization. Transcatheter intraarterial perfusion MRI has been developed as a method of quantifying hepatic arterial perfusion. The purpose of this study was to investigate whether findings at transcatheter intraarterial perfusion MRI before chemoembolization can be used to predict uptake of the chemoembolic material delivered during chemoembolization. SUBJECTS AND METHODS: We compared quantitative prechemoembolization transcatheter intraarterial perfusion MRI parameters with analogous postchemoembolization CT chemoembolic distribution parameters and analyzed correlation using the Pearson correlation coefficient. These MRI and CT parameters included volume of distribution (a metric for volumetric liver perfusion or therapeutic agent delivery) and chemoembolic delivery selectivity factor (a ratio of volume-normalized tumor to background signal intensity that indicates the selectivity of chemoembolic delivery). RESULTS: Twenty-four hepatocellular carcinomas were targeted in 18 patients (14 men, four women; mean age, 66 years), and segmental or lobar chemoembolization with intraprocedural transcatheter intraarterial perfusion MRI was successful in all 18. Transcatheter intraarterial perfusion MRI and CT volume of distribution did not differ significantly (MRI, 233 cm(3); CT, 235 cm(3); p = 0.857). Transcatheter intraarterial perfusion MRI selectivity factor was an underestimate of CT selectivity factor (MRI, 0.20; CT, 0.25; p = 0.005). Prechemoembolization transcatheter intraarterial perfusion MRI and postchemoembolization CT volume of distribution (r = 0.93; p < 0.001) and selectivity factor (r = 0.95; p < 0.001) showed significant correlation. CONCLUSION: Tumor perfusion measured with transcatheter intraarterial perfusion MRI is predictive of uptake of chemoembolic material before delivery. This MRI technique may have utility as a method of quantifying delivery of the therapeutic agent during chemoembolization and, potentially, other liver-directed locoregional therapies.

Assessment of the tissue diffusion of anesthetic agent following administration of a low palmar nerve block in horses.

OBJECTIVE: To investigate tissue diffusion of anesthetic agent following administration of low palmar nerve blocks (LPBs) in horses. DESIGN: Randomized clinical trial. ANIMALS: 12 adult horses. PROCEDURES: In 9 horses, mepivacaine hydrochloride-iohexol (50:50 dilution) injections were administered bilaterally (2 or 4 mL/site) to affect the medial and lateral palmar and palmar metacarpal nerves (4 sites). Lateral radiographic views of both metacarpal regions were obtained before and at 5, 15, 30, 60, 90, and 120 minutes after block administration; proximal and distal extents of contrast medium (and presumably anesthetic agent) diffusion from palmar and palmar metacarpal injection sites were measured and summed to determine total diffusion. Methylene blue solution was injected in forelimbs of 3 other horses that were subsequently euthanized to determine the potential route of anesthetic agent diffusion to the proximal suspensory ligament region. RESULTS: Mean extents of proximal and total contrast medium diffusion were 4.0 and 6.6 cm, respectively, for the palmar metacarpal nerves and 4.3 and 7.1 cm, respectively, for the palmar nerves. Subtle proximal diffusion secondary to lymphatic drainage was evident in 17 of the 18 limbs. Contrast medium was detected in the metacarpophalangeal joint or within the digital flexor tendon sheath in 8 and 7 limbs, respectively. In the cadaver limbs, methylene blue solution did not extend to the proximal suspensory ligament region. CONCLUSIONS AND CLINICAL RELEVANCE: In horses, LPBs resulted in minimal proximal diffusion of anesthetic agent from the injection sites. Limbs should be aseptically prepared prior to LPB administration because inadvertent intrasynovial injection may occur.

Vascular effects of paclitaxel following drug-eluting balloon angioplasty in a porcine coronary model: the importance of excipients.

AIMS: The vascular effects of drug- eluting balloon (DEB) deployment in the absence of coronary stents have not been characterised. This study evaluated potential vascular effects of paclitaxel-coated angioplasty balloons using different excipients in the absence of additional stents. METHODS AND RESULTS: A total 45 porcine arteries were treated with paclitaxel-coated DEBs using four different excipients (all 3.0 µg/mm2): A) iopromide (n=9), B) ATEC excipient (n=8), C) BTHC excipient (n=10), D) lecithine excipient (n=10). Uncoated bare angioplasty balloons served as controls (n=8). Histology, histomorphometry, and quantitative angiography analysis were performed 28 days following intervention. Tissue concentrations of paclitaxel were measured in selected animals using BTHC excipient (n=39 arteries) and reached maximum concentrations of 165 ng/mg 30 min after delivery in coronary target tissue. There were no differences in efficacy endpoints using histomorphology or quantitative angiography between groups. In contrast, however, treatment with DEBs using BTHC excipient or iopromide was associated with increased fibrin deposition and inflammation indicating delayed vascular healing. DEBs using lecithin excipient or uncoated angioplasty balloons did not induce any comparable vascular effects. CONCLUSIONS: Effective excipients are necessary to accomplish successful balloon facilitated paclitaxel delivery, which is associated with delayed vascular healing as a sign of successful drug transfer. The potential of DEBs to diminish restenosis following angioplasty may be insufficient in the absence of additional stents.

Neonatal thyroid function: effect of a single exposure to iodinated contrast medium in utero.

PURPOSE: To evaluate the effect of in utero exposure to a single dose of water-soluble intravenous iodinated contrast medium on thyroid function at birth. MATERIALS AND METHODS: This study was approved by the institutional review board, with waiver of consent, and was HIPAA compliant. Maternal and newborn records were retrospectively reviewed. All pregnant women who underwent multidetector pulmonary computed tomographic angiography because they were suspected of having pulmonary embolism between 2004 and 2008 and newborns resulting from the index pregnancy were included. In all examinations, iohexol was used as the contrast agent. Dose and amount of contrast agent and gestational age at the time of administration of the contrast agent were collected, and thyroxine (T(4)) and thyroid-stimulating hormone (TSH) levels were measured at birth. A total of 344 maternal and 343 newborn records were reviewed. A descriptive analysis was performed, and means, standard deviations, and confidence intervals were reported. RESULTS: Mean gestational age at the time of administration of the contrast material was 27.8 weeks +/- 7.4. The mean dose of total iodine administered was 45,000 mg/L +/- 7321. All newborns had a normal T(4) level at birth; only one newborn had a transiently abnormal TSH level at birth, which normalized at day 6 of life. This newborn was born to a mother who had many drug exposures during pregnancy. CONCLUSION: A single, high-dose in utero exposure to water-soluble, low-osmolar, iodinated intravenous products, such as iohexol, is unlikely to have a clinically important effect on thyroid function at birth.

Transcatheter intraarterial perfusion: MR monitoring of chemoembolization for hepatocellular carcinoma--feasibility of initial clinical translation.

PURPOSE: To prospectively test the hypothesis that intraprocedural transcatheter intraarterial perfusion (TRIP) magnetic resonance (MR) imaging can be used to successfully measure reductions in perfusion to the targeted hepatocellular carcinoma (HCC) and the adjacent surrounding liver tissue during MR-interventional radiology (IR)-monitored transcatheter arterial chemoembolization (TACE). MATERIALS AND METHODS: This HIPAA-compliant prospective study was approved by the institutional review board. An MR-IR unit was used to perform TACE in 10 patients with HCC (seven male, three female; eight younger than 69 years, two older than 69 years). Intraprocedural reductions in tumor perfusion before and after TACE were monitored with TRIP MR imaging. Time-signal intensity curves were derived, and semiquantitative spatially resolved area under the time-signal intensity curve maps of tumor perfusion before and after TACE were produced. Mean perfusion values before and after TACE for liver tumors and adjacent liver tissue were compared by using a mixed-model analysis, with alpha = .05. RESULTS: Perfusion reductions were measured successfully with TRIP MR imaging in 18 separate tumors during 13 treatment sessions. Perfusion maps showed significant perfusion reductions for tumors (P < .013) but not for adjacent nontumorous liver tissue (P = .21). For tumors, the mean perfusion value was 193 arbitrary units (AU) +/- 223 (standard deviation) before TACE and 45.3 AU +/- 91.9 after TACE, with a mean reduction in baseline perfusion of 74.6% +/- 24.8. For adjacent liver tissue, the mean perfusion value was 124 AU +/- 93.5 before TACE and 93.2 AU +/- 72.3 after TACE, with a mean reduction in baseline perfusion of 24.2% +/- 14.5. CONCLUSION: TRIP MR imaging can be used to detect intraprocedural changes in perfusion to HCC and surrounding liver parenchyma during MR-IR-monitored TACE.

Influence of needle position on lumbar segmental nerve root block selectivity.

BACKGROUND AND OBJECTIVES: In patients with chronic low back pain radiating to the leg, segmental nerve root blocks (SNRBs) are performed to predict surgical outcome and identify the putative symptomatic spinal nerve. Epidural spread may lead to false interpretation, affecting clinical decision making. Systematic fluoroscopic analysis of epidural local anesthetic spread and its relationship to needle tip location has not been published to date. Study aims include assessment of epidural local anesthetic spread and its relationship to needle position during fluoroscopy-assisted blocks. METHODS: Patients scheduled for L4, L5, and S1 blocks were included in this prospective observational study. Under fluoroscopy and electrostimulation, they received 0.5 mL of a mixture containing lidocaine 5 mg and iohexol 75 mg. X-rays with needle tip and contrast were scored for no epidural spread (grade 0), local spread epidurally (grade 1), or to adjacent nerve roots (grade 2). RESULTS: Sixty-five patients were analyzed for epidural spread, 62 for needle position. Grade 1 epidural spread occurred in 47% of L4 and 28% of L5 blocks and grade 2 spread in 3 blocks (5%; L5 n = 1, S1 n = 2). For lumbar blocks, the needle was most frequently found in the lateral upper half of the intervertebral foramen. Epidural spread occurred more frequently with medial needle positions (P = .06). CONCLUSION: The findings suggest (P = .06) that the risk of grade 1 and 2 lumbar epidural spread, which results in decreased SNRB selectivity, is greater with medial needle positions in the intervertebral foramen. The variability in anatomic position of the dorsal root ganglion necessitates electrostimulation to guide SNRB in addition to fluoroscopy.

[Feasibility and optimization of the combined injection of contrast medium and normal saline with a single-syringe CT injection system]. / Durchführbarkeit und Optimierung einer kombinierten Kontrastmittel- und Kochsalzinjektion mit einem CT-Einzelinjektorsystem.

PURPOSE: To optimize the technique of injecting contrast medium followed by saline flush with a single-syringe CT injection system. MATERIALS AND METHODS: A CT injection system with a single syringe was filled with 100 ml of contrast medium (Iopromide 300 or Iomeprol 400) and 50 ml of normal saline solution. The following variables were evaluated: filling sequence, filling rate, syringe position during filling, ejection rate and delay before ejection. In consecutive portions of 10 ml, the whole volume was continuously ejected into test tubes that were subjected to CT densitometry on these test tubes. Each experiment was performed three times. RESULTS: Filling the syringe first with saline solution and subsequently with contrast medium resulted in no substantial mixing, whereas filling in the reverse order caused noticeable mixing of both solutions. Manual filling at a rate < or = 1 ml/s gave the best results. At faster filling rates (4 ml/s, 10 ml/s), substantial mixing of contrast agent and saline solution was observed. The separation of the two liquids was optimal when the syringe nozzle was pointed downward. Ejection rate (3 ml/s, 4 ml/s) and time delay between filling and ejection (0 min, 10 min) did not influence the distribution of density. The maximum iodine concentration using this approach was 235 mg/ml for Iopromide 300 and 327 mg/ml for Iomeprol 400. This indicates a reduction of the maximum iodine concentration of up to 28 % even when using the optimal technique for controlling mixing of both liquids. CONCLUSION: Manual filling of the CT injection syringe with saline solution followed by contrast media with the syringe nozzle pointed downward provides the best separation between contrast medium and normal saline solution but reduces the maximum iodine concentration by up to 28 %. For examinations requiring a high iodine concentration, such as CT-angiography, an iodine concentration of 400 mg/ml should be selected for the combined injection of contrast medium and normal saline solution with a single-syringe CT injection system.

Measurement of glomerular filtration rate by low-dose iopromide plasma clearance.

PURPOSE: Glomerular filtration rate (GFR) can be measured by iopromide plasma clearance. As an injection of 120 ml nonionic contrast medium is expensive and especially in patients with nephropathy potentially nephrotoxic, we investigated whether iopromide plasma clearance could be measured using a tenth of that dose as 'low-dose' clearance. MATERIAL AND METHODS: Fifty adult patients scheduled for CT were recruited. Iopromide 300 mg I/ml was used for GFR measurement. Prior to CT, low-dose clearance was measured by injecting 12 ml iopromide per 75 kg b.w. At 3, 4 and 5 h after injection, plasma samples were obtained and the iodine concentration was measured by X-ray fluorescence analysis. Immediately after the last blood sample, CT was again performed following injection of 120 ml iopromide per 75 kg b.w. A further 3 plasma samples were then obtained 3, 4, and 5 h after CT and used for the determination of high-dose clearance. RESULTS: Low-dose clearance ranged from 20 ml/min to 141 ml/min (mean 78.3 ml/min). High-dose and low-dose clearance correlated excellently, with clearance (high-dose) = 1.4 + 0.994 clearance (low-dose); the correlation coefficient was r = 0.944, the standard deviation SDxy= 9.3 ml/min. CONCLUSION: Plasma clearance of iopromide is dose-independent on use of iodine amounts of 3.6 g and 36 g I/75 kg b.w. The GFR can be determined by high-dose and low-dose iopromide plasma clearance with identical accuracy.

Evaluation of gadobutrol in a rabbit model as a new lanthanide contrast agent for computed tomography.

RATIONALE AND OBJECTIVES: The efficacy of the neutral lanthanide contrast agent gadobutrol was compared to that of the iodinated contrast agent iopromide in rabbits. METHODS: The computed tomography (CT) attenuation of increasing concentrations of gadolinium (Gd) (gadobutrol) and iodine (I) (iopromide) was measured in Hounsfield units (HU) in aqueous solution at 80, 120, and 137 kV. The peak enhancement (net increase in CT attenuation compared with baseline) and the time-enhancement product in the aorta and in the renal parenchyma of the outer and inner cortex were measured in rabbits over a 5-minute period after the animals were given single intravenous injections of 0.7, 1.0, and 1.5 mmol Gd/kg of gadobutrol and 1.0 and 2.4 mmol I/kg of iopromide. RESULTS: In vitro, the CT attenuation of gadolinium was 40% higher than that of iodine at equivalent mass concentrations (120 kV). The mean peak enhancements in the aorta after the injections of 0.7, 1.0, and 1.5 mmol Gd/kg and 1.0 and 2.4 mmol I/kg were 216, 313, 591, 224, and 498 HU, respectively. In addition, a 30-second injection of the high dose of gadobutrol resulted in an attenuation profile that was suitable for a three-dimensional reconstruction of the aorta and the renal vasculature. CONCLUSIONS: Because of the higher CT attenuation of gadolinium compared with that of iodine, the neutral macrocyclic chelate gadobutrol is a more effective contrast agent than iopromide for CT at lower doses of the imaging atom.