Low Contrast Agent Research Articles

Kidney Function: Glomerular Filtration Rate Measurement with MR Renography in Patients with Cirrhosis

To assess the accuracy of glomerular filtration rate (GFR) measurements obtained with low-contrast agent dose dynamic contrast material-enhanced magnetic resonance (MR) renography in patients with liver cirrhosis who underwent routine liver MR imaging, with urinary clearance of technetium 99m ((99m)Tc) pentetic acid (DTPA) as the reference standard. This HIPAA-compliant study was institutional review board approved. Written informed patient consent was obtained. Twenty patients with cirrhosis (14 men, six women; age range, 41-70 years; mean age, 54.6 years) who were scheduled for routine 1.5-T liver MR examinations to screen for hepatocellular carcinoma during a 6-month period were prospectively included. Five-minute MR renography with a 3-mL dose of gadoteridol was performed instead of a routine test-dose timing examination. The GFR was estimated at MR imaging with use of two kinetic models. In one model, only the signal intensities in the aorta and kidney parenchyma were considered, and in the other, renal cortical and medullary signal intensities were treated separately. The GFR was also calculated by using serum creatinine levels according to the Cockcroft-Gault and modification of diet in renal disease (MDRD) formulas. All patients underwent a (99m)Tc-DTPA urinary clearance examination on the same day to obtain a reference GFR measurement. The accuracies of all MR- and creatinine-based GFR estimations were compared by using Wilcoxon signed rank tests. The mean reference GFR, based on (99m)Tc-DTPA clearance, was 74.9 mL/min/1.73 m(2) ± 27.7 (standard deviation) (range, 10.3-120.7 mL/min/1.73 m(2)). With both kinetic models, 95% of MR-based GFRs were within 30% of the reference values, whereas only 40% and 60% of Cockcroft-Gault- and MDRD-based GFRs, respectively, were within this range. MR-based GFR estimates were significantly more accurate than creatinine level-based estimates (P < .001). GFR assessment with MR imaging, which outperformed the Cockcroft-Gault and MDRD formulas, adds less than 10 minutes of table time to a clinically indicated liver MR examination without ionizing radiation. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101338/-/DC1.

Use and efficacy of saline hydration and N-acetyl cysteine to prevent contrast-induced nephropathy in low-risk populations undergoing coronary artery angiography

Contrast-induced nephropathy (CIN) is most commonly defined as acute renal failure occurring within 48-72 h of exposure to an intravascular radiographic contrast medium that is not attributable to other causes. In the international literature, a 25% increase in serum creatinine levels or an increase in absolute values of 0.5 mg/dl from baseline has been suggested to define CIN. The reported incidence of CIN varies widely, ranging from 2 to 50%. This variability results from differences in the presence or absence of risk factors. With a retrospective analysis we evaluated the use of saline hydration plus N-acetyl cysteine (NAC) to prevent CIN in a low-risk population of patients undergoing coronary artery angiography compared with an historic low risk group not treated. From January 2009 to December 2009, 152 consecutive patients who underwent coronary artery angiography with a low osmolarity contrast agent were enrolled in our study, and compared with an historic control group consisting of 172 low-risk patients. Nephrotoxic drugs such as diuretics, ACE-I and ARBs were stopped at least 24 h before the procedure. Inclusion criteria to define low-risk population were the absence of: diabetes, age >65 years, or baseline creatinine >1.4 mg/dl. We have treated group A (152 patients, 47.3%) with a saline hydration (1 ml/kg/h) plus N-acetyl cysteine 600 mg 12 h before and 12 h after the procedure; group B (group control of 170 patients, 52.7%) were not treated. The overall incidence of CIN was 7.1% (23 patients). In particular, the incidence of CIN was 2.6% (4 patients) in the group A and 11.2% (19 patients) in the group B (p = 0.002). In the multivariate analysis, including risk factor such as age, hypertension, hypercholesterolemia, current smoking habit baseline creatinine level, contrast index and hydration, the last variable was the only one inversely correlated independently with the incidence of CIN (p = 0.001). In conclusion, intravenous hydration with saline and NAC is an effective and low cost tool in preventing CIN in patients undergoing coronary artery angiography, and, according to the current guidelines, should be used in all high-risk patients for CIN. Our results show that even in patients at low risk, hydration with saline 0.9% plus NAC is useful and significantly reduces the incidence of CIN.

OC080: Assessment of embryonic and placental blood flow &amp; placental ultrastructure changed with contrast agent (SonoVueTM) in late pregnant rat

The study was to investigate the ability of the contrast pulse sequencing technology (CPS) and SonoVueTM (a new contrast agent) to delineate placental angioarchitecture and their influence on placental function, circulation and ultrastructure. sixty late pregnant Wistar rats (median weight, 300 g; range, 260 g to 330 g; median gestational age, 19 days) were selected and divided into three experimental groups, i.e. control group (n=20) injected with 2.0 ml/kg physiologic saline solution, high dose group (n=20) injected with 10 mg/ml SonoVueTM 2.0 ml/kg (Bracco S.p.A., Milan, Italy), and low dose group (n=20) injected with 0.01 mg/ml SonoVueTM 2.0 ml/kg. One of placentas was randomly selected for examination by contrast enhanced ultrasonography. Maternal and embryonic heart rate (HR) and resistance index (RI), pulsatility index (PI), and systolic-diastolic ratio (S/D) in the embryonic middle cerebral artery (MCA), umbilical artery (UA), and uterine artery (UTA) were measured before and after administration of contrast agent or physiologic saline solution. In each group, fifteen rats were cesarean to take the placenta immediately after exam, other five did after 12 hours of exam. The ultrastructural changes of the placenta were observed by electron microscope. Intravascular injection of SonoVueTM was capable of delineating the vascular architecture of the villous tree of rat. No enhancement was seen after saline solution injections. There were no significant changes of resistance index (RI), pulsatility index (PI), and systolic-diastolic ratio (S/D) in the embryonic middle cerebral artery, umbilical artery, and uterine artery after administration of contrast agent or physiologic saline solution. The maternal and embryonic heart rate significantly decreased. However, differences among three groups were not statistically significant; In low dose group, there were no obvious changes of helicine artery in rats's placenta taken immediately and after 12 hours of examination. In high dose group, taken immediately, the helicine artery wall were uneven, there are blood platelet aggregate and accrete around the thinningz; draw it after 12 hours, the vessel wall were thickening and swell, to be missing normal architecture of the blood vessel wall, the endothelial cell exfoliate in Lumen of blood vessel, we can also see apoptotic body in it. Contrast-enhanced ultrasonography limpidly presents the characteristics of perfusion of placenta in a rat model and does not affect the embryonic hemodynamic parameters. Low dose contrast agent does not impact ultrastructural changes of placent. High dose contrast agent can influence on ultrastructural of helicine artery wall.

P846, a new gadolinium based low diffusion magnetic resonance contrast agent, in characterizing occlusive infarcts, reperfused ischemic myocardium and reperfused infarcts in rats

This study has two objectives: (1) to compare the kinetics of low diffusion P846 with Gd-DOTA using inversion recovery echo planar (IR-EPI) magnetic resonance (MR) imaging and (2) to determine the potential of P846 in defining myocardial viability in hearts subjected to various injuries using T1-weighted spin echo (T1-SE). Rats were subjected to (1) occlusive infarcts (n = 16), (2) reperfused ischemic injuries (n = 8) or (3) reperfused infarcts (n = 16). A dose of 0.05 mmol/kg P846 was compared to 0.1 mmol/kg Gd-DOTA. IR-EPI and T1-SE images were obtained during 60 min. T(1), DeltaR(1) and DeltaR(1) ratio were measured on IR-EPI. Infarct extents were evaluated on T1-SE and compared with histochemical staining. Blood DeltaR(1) was higher at 5 min after P846 (6.36 +/- 0.32 s(-1)) than after Gd-DOTA (1.30 +/- 0.14 s(-1); P < 0.001). With P846, occlusive infarcts appeared as a hypoenhanced region surrounded by a hyperenhanced rim that lasted for 60 min. The increase in the DeltaR(1) ratio value was slower after P846 than with Gd-DOTA in the reperfused infarcts, suggesting low diffusion/convection of P846. Gd-DOTA homogenously enhanced both occlusive and reperfused infarcts at 30 min. P846 provides better contrast and extended discrimination between occlusive and reperfused infarcts compared with Gd-DOTA. The gadolinium dose could be reduced with P846.

Incorporating contrast agent diffusion into the analysis of DCE‐MRI data

Standard two-compartment pharmacokinetic models that describe the dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) time course of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) concentration in a tissue do not account for the passive diffusion of contrast agent (CA) from a well-perfused to a less vascularized region. Even when the arterial input function (AIF) is perfectly known, the standard Tofts model returns inaccurate values of K(trans) (mean absolute relative difference [ARD] of 43%) from realistic simulated data where a well-defined delineation exists between a well-perfused and a poorly vascularized region. This contribution proposes a diffusion-perfusion (DP) model in which diffusion of a low molecular weight CA is incorporated in the standard two-compartment Tofts model. The proposed DP model reliably retrieved the values of K(trans) and v(e) (mean ARD of 16% and 17%, respectively) from simulated data. On mouse adenocarcinoma xenograft data showing evidence of CA diffusion, the standard model returned unphysical values of v(e) in the tumor core whereas the proposed DP model found values that were in the physical range (0 < v(e) < 1) throughout the tissue. In addition, K(trans) distributions from the DP model more closely corresponded to the observed sharp delineation between highly and poorly perfused areas observed in the mouse tumors.

Correcting saturation effects of the arterial input function in dynamic susceptibility contrast-enhanced MRI — a Monte Carlo simulation

To prevent systematic errors in quantitative brain perfusion studies using dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI), a reliable determination of the arterial input function (AIF) is essential. We propose a novel algorithm for correcting distortions of the AIF caused by saturation of the peak amplitude and discuss its relevance for longitudinal studies. The algorithm is based on the assumption that the AIF can be separated into a reliable part at low contrast agent concentrations and an unreliable part at high concentrations. This unreliable part is reconstructed, applying a theoretical framework based on a transport-diffusion theory and using the bolus-shape in the tissue. A validation of the correction scheme is tested by a Monte Carlo simulation. The input of the simulation was a wide range of perfusion, and the main aim was to compare this input to the determined perfusion parameters. Another input of the simulation was an AIF template derived from in vivo measurements. The distortions of this template was modeled via a Rician distribution for image intensities. As for a real DSC-MRI experiment, the simulation returned the AIF and the tracer concentration-dependent signal in the tissue. The novel correction scheme was tested by deriving perfusion parameters from the simulated data for the corrected and the uncorrected case. For this analysis, a common truncated singular value decomposition approach was applied. We find that the saturation effect caused by Rician-distributed noise leads to an overestimation of regional cerebral blood flow and regional cerebral blood volume, as compared to the input parameter. The aberration can be amplified by a decreasing signal-to-noise ratio (SNR) or an increasing tracer concentration. We also find that the overestimation can be successfully eliminated by the proposed saturation-correction scheme. In summary, the correction scheme will allow DSC-MRI to be expanded towards higher tracer concentrations and lower SNR and will help to increase the measurement to measurement reproducibility for longitudinal studies.

AG-013736, a novel inhibitor of VEGF receptor tyrosine kinases, inhibits breast cancer growth and decreases vascular permeability as detected by dynamic contrast-enhanced magnetic resonance imaging

Dynamic contrast-enhanced MRI (DCE-MRI) was used to noninvasively evaluate the effects of AG-03736, a novel inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases, on tumor microvasculature in a breast cancer model. First, a dose response study was undertaken to determine the responsiveness of the BT474 human breast cancer xenograft to AG-013736. Then, DCE-MRI was used to study the effects of a 7-day treatment regimen on tumor growth and microvasculature. Two DCE-MRI protocols were evaluated: (1) a high molecular weight (MW) contrast agent (albumin-(GdDTPA)(30)) with pharmacokinetic analysis of the contrast uptake curve and (2) a low MW contrast agent (GdDTPA) with a clinically utilized empirical parametric analysis of the contrast uptake curve, the signal enhancement ratio (SER). AG-013736 significantly inhibited growth of breast tumors in vivo at all doses studied (10-100 mg/kg) and disrupted tumor microvasculature as assessed by DCE-MRI. Tumor endothelial transfer constant (K(ps)) measured with albumin-(GdDTPA)(30) decreased from 0.034+/-0.005 to 0.003+/-0.001 ml min(-1) 100 ml(-1) tissue (P<.0022) posttreatment. No treatment-related change in tumor fractional plasma volume (fPV) was detected. Similarly, in the group of mice studied with GdDTPA DCE-MRI, AG-013736-induced decreases in tumor SER measures were observed. Additionally, our data suggest that 3D MRI-based volume measurements are more sensitive than caliper measurements for detecting small changes in tumor volume. Histological staining revealed decreases in tumor cellularity and microvessel density with treatment. These data demonstrate that both high and low MW DCE-MRI protocols can detect AG-013736-induced changes in tumor microvasculature. Furthermore, the correlative relationship between microvasculature changes and tumor growth inhibition supports DCE-MRI methods as a biomarker of VEGF receptor target inhibition with potential clinical utility.

Evaluation of Engineered Meniscal Cartilage Constructs Based on Different Scaffold Geometries Using Magnetic Resonance Imaging and Spectroscopy

Magnetic resonance imaging (MRI) and spectroscopy (MRS) were used to evaluate the properties different scaffold geometries for the production of bioartificial meniscal cartilage constructs. Engineered were generated in perfusion bioreactors from mature sheep meniscal fibrochondrocytes,scaffolds cut from a knitted polyethylene therephtalate (PET) fabric, with a distribution of fibers, 50 microm pores and a density of 45 mg/cm(3) (NF scaffolds), and from two versions of this fabric, which included larger pore sizes (1500 x 500 microm(2)) and densities of (sIV scaffolds) and 83 mg/cm(3) (sV scaffolds). MRI methods were used to determine the permeability the constructs to a low molecular weight MR contrast agent and to measure the macroscopic of medium through and around the constructs. These parameters were correlated with measurements of cell growth and cellular energetics. Cell-free sIV scaffolds were 2- and 5-more porous to flow than the empty sV and NF scaffolds, respectively. These scaffolds, after days of cell growth, were also more permeable to an MR contrast agent. sIV scaffolds yielded(n = 9) with higher cellularities (41 +/- 1%) compared with NF (32 +/- 1%, p < 0.0001) and sV (30 +/- 1%, p < 0.0001) and, when normalized to cell numbers, demonstrated proportionally levels of nucleoside triphosphates (NTP), indicating increased cell viability. Scaffold geometry a marked effect on the properties of engineered meniscal cartilage. MRI and MRS are powerful techniques that can be used to optimize the design of engineered meniscal cartilage and that could be used subsequently to evaluate clinical outcome postimplantation.

MRI monitoring of Avastin™ antiangiogenesis therapy using B22956/1, a new blood pool contrast agent, in an experimental model of human cancer

To evaluate the diagnostic and prognostic potential of a new protein-binding contrast medium, B22956/1, for quantitatively characterizing tumor microvessels by MRI and monitoring response to antiangiogenic therapy. Dynamic contrast-enhanced MRI (DCE-MRI) was performed in an experimental cancer model with the use of the novel protein-binding agent B22956/1, a low molecular contrast agent (ProHance), and a macromolecular contrast medium, albumin-(Gd-DTPA). MDA-MB-435, a human cancer cell line, was implanted in 22 athymic rats. Animals were assigned randomly to a control (saline) or drug-treated (Avastin) group. MRI was performed at baseline and after nine days of treatment. The transendothelial permeability (KPS) and the fractional blood volume (fBV) were estimated from the kinetic analysis of dynamic MR data using a two-compartment model. Tumor growth was also measured from volumetric MRI. Tumors grew more slowly, although not significantly (P=0.07), in the drug-treated group. The KPS determined for B22956/1 decreased significantly in the drug-treated group compared to baseline (P <0.05), and progressed significantly in the control group. However, no significant changes were resolved with the use of ProHance or albumin-(Gd-DTPA). With the use of appropriate contrast media, the therapeutic effects of an anti-VEGF antibody on tumor microvessels can be monitored by dynamic MRI. The dynamic range of permeability to B22956/1, and the sensitivity to change of this parameter suggest a potential application in the clinical setting.

Water exchange and inflow affect the accuracy of T1-GRE blood volume measurements: implications for the evaluation of tumor angiogenesis.

The goal of this study was to determine the degree to which vascular water exchange and blood flowing into an imaging slice affect the accuracy of blood volume measurements of brain and tumor tissue when using intravascular T(1) contrast agents. The study was performed using 2D and 3D gradient-echo imaging sequences, since these are two of the most commonly used MRI methods used to evaluate tissue blood volume fraction. Computer simulations were performed and measurements made in a rat 9L gliosarcoma brain tumor model. The computer simulations demonstrate that, with either water exchange or inflow effects alone, the dependence on the physiologic and imaging parameters can be well characterized and therefore potentially offset. In the exchange only case, the parametric dependence of 3D simulations suggest that the best accuracy is achieved with high flip angles, short TR, and low blood contrast agent concentrations. However, for a 2D GRE sequence which is influenced by both water exchange and inflow, the simulations predict that the error trend as a function of the imaging and physiologic parameters is unpredictable and therefore difficult to compensate. With both 2D and 3D GRE the measured blood volume data in rat brain and tumor tissue demonstrate tissue-specific trends, which reflect differences in the considered physiologic parameters. The experimental data strongly support the computer simulations and also indicate that minimization of the physiological effects by proper selection of imaging parameters, contrast concentration, and volume calculation methods is crucial for accurate assessment of absolute blood volume fraction.

Transplacental passage of iohexol

We describe the appearance of an iodinated, low molecular weight radiographic contrast agent, iohexol, in the intestines of twin neonates after administration to a pregnant mother during angiography. Nonionic contrast agents cross the human placenta and enter the fetus in significant concentrations and in this case facilitated identification of an omphalomesenteric duct cyst in one twin.

Effect of NC100150 injection on the (1)H NMR linewidth of human whole blood ex vivo: dependency on blood oxygen tension.

The linewidth of the (1)H NMR signal (7.05 T) of human whole blood titrated with a superparamagnetic contrast agent (NC100150 injection) was evaluated at different blood oxygen tensions. In deoxygenated blood and low contrast agent concentrations, NC100150 injection caused a decrease in linewidth. After reaching a minimum, the linewidth increased as the concentration of NC100150 injection increased. At the concentration corresponding to the minimum linewidth, the magnetization of the extracellular space containing the NC100150 injection was equal to that of the paramagnetic (deoxygenated hemoglobin) intracellular space. The minimum linewidth is therefore consistent with a complete elimination of the local microscopic susceptibility effect, the major cause of linebroadening. Additionally, phantom studies were performed at 1.5 T, confirming that the contrast enhancement of NC100150 injection in blood is dependent on oxygen tension. The data suggest that NC100150 injection may be useful in differentiating vessels with varying relative oxygen tensions.

Oral administration of a low-cost negative contrast agent: a three-year experience in routine practice.

A low cost, well tolerated, and effective gastrointestinal contrast agent is needed for abdominal MRI. The authors tested, in vitro and in routine practice, a mixture of 192 g of barium sulfate (Micropaque HD oral, Guerbet, France) diluted in 500 ml of gastric antacid (Maalox, Rohrer, Fort Washington, PA). Its T1 and T2 relaxation times were 324 and 14 msec, respectively (.2 T). This contrast agent was used in routine practice in 789 patients (.5 T). It had a low signal intensity in 86% and 82% of the cases on T1- and T2-weighted sequences, respectively. No side effect due to magnetic susceptibility was seen, even with gradient-echo sequences. The dilution of barium sulfate in gastric antacid, instead of water, causes a low signal intensity on all sequences for a low barium sulfate concentration (38% w/v). This product is an effective and low cost contrast agent in routine practice.

703-3 Second Harmonic Mode Imaging Improves Contrast Agent [SHU 508-A] Visualization in an In Vitro Model

Non invasive myocardial contrast echocardiography requires an ultrasoundimaging mode capable of detecting small amounts of a crossing lungs contrastagent (CA) which reach the cardiac muscle. At present, commercialB-Mode imaging can not visualize CA in myocardium after intravenous injectionand transpulmonary passage. Second harmonic Mode imaging (SHM) uses resonance properties of microbubbles to produce a gray scale imageof CA. We tested an prototype ultrasound machine (Acuson) using SHM to detect CA SHU 508-A (Schering AG, Berlin) flow in an in vitro model at variousconcentrations, For each CA injection, videointensity in arbitrary Units(VU), in SHM and B-Mode was assessed:SHU 508-Ainjected volume (ml)VUB-ModeVUSHMVU% increase0.1251932680.253151670.55369301.06987262.082102244.010011515SHM vs. B-Mode p &lt; 0.0001 SHM vs. B-Mode p &lt; 0.0001 SHM is more sensitive than B-mode in detecting SHU 508-A, particularly at lower CA concentrations. SHM has a potential for the evaluation of low CA concentration in clinical setting and therefore in myocardial perfusion studies after CA intravenous injection.

Low density contrast in upper abdominal computed tomography

We describe the use of a fat-based low density oral contrast agent in computed tomography (CT) of the upper abdomen. It has a CT number of -71 Hounsfield units (HU) and allows excellent visualization of the bowel wall and adjacent structures as well as reducing the artefacts seen with iodinated high density contrast.

Effects of new intravascular contrast agents on [Ca2+]i transients and contraction in cultured ventricular myocytes

We examined the effects of four kinds of intravascular contrast agents (amidtrizoic acid, iohexol, iopamidol, and ioxaglic acid) on [Ca2+]i transients (indo-1 fluorescence) and cell contraction (video motion analyzer), using cultured chick embryo ventricular myocytes. Exposure of ventricular myocytes to amidtrizoic acid (a conventional contrast agent) reduced the [Ca2+]i transients and the sensitivity of the contractile elements to [Ca2+]i. Ioxaglic acid (a low osmotic contrast agent) also reduced the [Ca2+]i transients, but did not significantly change the sensitivity of the contractile elements to [Ca2+]i. Neither iohexol nor iopamidol (nonionic contrast agents) reduced the [Ca2+]i transients, but both significantly decreased the sensitivity of the contractile elements to [Ca2+]i. A marked negative inotropic effect of amidtrizoic acid was caused by both calcium binding and hypertonicity. The less marked depression of contractility produced by ioxaglic acid is possibly the result of calcium binding, but is not caused by hypertonicity. The negative inotropism produced by nonionic contrast agents (iohexol and iopamidol) was due to hypertonicity, but not due to alterations in the [Ca2+]i transients. Exposure of ventricular myocytes to nonionic contrast agents (iohexol and iopamidol) slowed decay in the [Ca2+]i transients with increased end-diastolic [Ca2+]i. After washing out the nonionic contrast agents, these parameters returned to control levels. On the other hand, exposure to amidtrizoic acid decreased end-diastolic [Ca2+]i without changing decay time in the [Ca2+]i transients. After washing out amidtrizoic acid, there was a prolongation of half decay time in [Ca2+]i transients with a significant increase in end-diastolic [Ca2+]i and cell position. Diastolic dysfunction just after washout of amidtrizoic acid was possibly caused by an increase in [Na+]i due to sodium influx during exposure to the contrast agent.

Evaluation of the Safety and Efficacy of Gadoteridol Injection (a low osmolal magnetic resonance contrast agent): Clinical Trials Report

Evaluation of the Safety and Efficacy of Gadoteridol Injection (a low osmolal magnetic resonance contrast agent): Clinical Trials Report

10% low density corn-oil emulsion oral contrast agent for abdominal computed tomography

10% low density corn-oil emulsion oral contrast agent for abdominal computed tomography

Hemodynamic changes induced by cardiac angiography with ioxaglate: Comparison with diatrizoate

The hemodynamic and electrocardiographic changes induced by left ventriculography and coronary arteriography with ioxaglate (a new low osmolality angiographic contrast agent) were characterized and compared with the changes induced by a commercial formulation of the commonly used angiographic contrast agent, diatrizoate (Renografin-76). Left ventriculography and coronary arteriography were performed in 25 patients utilizing ioxaglate and in another 25 patients utilizing diatrizoate. Both agents increased left ventricular end-diastolic pressure and decreased arteriovenous oxygen difference after left ventriculography, but the magnitude of the increase caused by ioxaglate was significantly less than that caused by diatrizoate (changes in left ventricular end-diastolic pressure was 5.3 +/- 1.3 mm Hg with ioxaglate and 9.5 +/- 1.5 mm Hg with diatrizoate [p less than 0.02] ). Change in arteriovenous oxygen difference was -0.33 +/- 0.19 ml/100 ml with ioxaglate and -0.85 +/- 0.13 ml/100 ml with diatrizoate (p less than 0.05). Both agents were well tolerated when used for coronary arteriography with no adverse events occurring in either group. Ioxaglate is a well tolerated cardiac angiographic contrast agent that produces less hemodynamic disturbance than diatrizoate. Accordingly, it may be particularly well suited to use in patients with impaired left ventricular function.

High kVp vs. low kVp for T-tube and operative cholangiography.

Based on several considerations, high kVp and high contrast agent concentration should produce better-quality operative and T-tube cholangiograms than the currently recommended low kVp and low contrast agent concentration. To test this theory, two kinds of studies were performed. In a laboratory phantom, the influence of kVp and contrast agent concentration on detectability of different size phantom stones was evaluated. High kVp and high contrast agent concentration (110 kVp, 38% iodine) were also compared with low kVp and low contrast agent concentration (75 kVp, 15% iodine) in 62 patients undergoing operative or T-tube cholangiography. Almost all phantom stones were well shown with all kVps and iodine concentrations. As the kVp was raised there was a mild decrease in stone detectability but this decrease was partially corrected by raising the iodine concentration. Overall stone detectability with high kVp and high contrast agent concentration technique was better than or similar to the currently recommended low kVp and low contrast agent concentration technique. Evaluation of the direct cholangiograms by five radiologists revealed that the high kVp, high contrast agent concentration studies were superior or similar to the low kVp and low contrast agent concentration radiographs in 70% of the cases. Based on these results high kVp (100-110) and a high contrast agent concentration (38%) are recommended for direct cholangiography.