Radiological study to evaluate the spreading of two volumes (10 vs. 20ml) of radiological contrast in the block of cutaneous branches of intercostal nerves in medial axillary line (BRILMA) in a porcine experimental model

OBJECTIVE

Interfascial blocks of the thoracic wall are being developed as an alternative to central blocks in breast surgery. However, there are few studies that have evaluated the anatomical extension of the local anaesthetic. The objective of this study was to analyse, using fluoroscopy, the spreading of two volumes (10 vs. 20ml) of radiological contrast in the serratus-intercostal plane block in an experimental pig model.

MATERIAL AND METHODS

Ten Large-White breed pigs were selected to have a bilateral ultrasound serratus-intercostal plane block performed, with the administering of 10ml and 20ml of iopamidol in the right and left hemithorax, respectively. The spreading of contrast was analysed by fluoroscopy. The Spearman test correlation was used to evaluate the relationship between the administered volume and radiological spreading. A value of P<.05 was considered significant.

RESULTS

Twenty anaesthetic blocks were performed, being able to analyse 18 of them. The administration of 10ml of contrast was associated with a mean spreading of 2.28±0.31 (95% CI; 2.01-2.54) intercostal spaces, while the administration of 20ml showed a spreading of 3±0.25 (95% CI; 2.81-3.18) intercostal spaces. There was a significant correlation between the injected volume and the spreading of the contrast (Spearman correlation coefficient of 0.81; P=.0001).

CONCLUSION

The results showed a spreading of volume subject to the serratus-intercostal plane block, although not maintaining a 1:1 ratio. Doubling the volume increased the blocked segments by 31%. These findings, if corroborated in the clinical practice, would allow a more precise adjustment in the anaesthetic volume administered.

Internal jugular veins out flow in patients with multiple sclerosis:a catheter venography study

PURPOSE

To investigate an examiner-independent catheter venography protocol that could be used to reliably diagnose venous outflow abnormalities in patients with multiple sclerosis (MS) and chronic cerebrospinal venous insufficiency and to determine whether venous angioplasty is effective in the treatment of these abnormalities.

MATERIALS AND METHODS

A total of 313 patients with MS and 12 patients with end-stage renal disease underwent echo-color Doppler sonography and catheter venography of the internal jugular veins (IJVs) to evaluate contrast medium clearance time. In patients with venous outflow anomalies, balloon angioplasty of the IJVs was performed.

RESULTS

A contrast medium clearance time cutoff value of 4 seconds or less provided the maximal combination of sensitivity and specificity for the right IJV (sensitivity, 73.4%; specificity, 100%) and left IJV (sensitivity, 91.4%; specificity, 100%). IJVs with a clearance time between 4.1 and 6 seconds had moderate delayed flow (MDF), and IJVs with a clearance time longer than 6 seconds had severe delayed flow (SDF); 89% of patients showed MDF/SDF through at least one IJV, 79% showed MDF/SDF through both IJVs, and only 5% showed normal flow in both IJVs. Balloon angioplasty was immediately able to improve flow in at least one IJV in 69% of patients, but venous flow was normalized in both veins in only 37% of patients; SDF persisted after angioplasty in 32% of patients.

CONCLUSIONS

There is a high prevalence of abnormal delayed flow through IJVs in patients with MS. Venous angioplasty was effective in only a minority of patients with SDF.

Transplacental passage of the non-ionic contrast agent iopamidol in twins

Premature dizygotic twins, exposed in utero to iopamidol (Isovue-370®) 4 days prior to delivery, were born with abdominal radiopaque densities that made exclusion of necrotizing enterocolitis difficult when they developed abdominal distention and feeding intolerance. This is a unique case report of transplacental passage of iopamidol.

Comment on "Developing DCE-CT to quantify intra-tumor heterogeneity in breast tumors with differing angiogenic phenotype"

In our comment some essential issues concerning determination of arterial input function (AIF), cardiac and respiratory related motion artifacts, contrast agent application and compartmental model fitting done by Cao et al., 2009 are discussed.

Developing DCE-CT to quantify intra-tumor heterogeneity in breast tumors with differing angiogenic phenotype

The objective of this study is to evaluate the ability of dynamic contrast enhanced computed tomography (DCE-CT) to assess intratumor physiological heterogeneity in tumors with different angiogenic phenotypes. DCE-CT imaging was performed on athymic nude mice bearing xenograft wild type (MCF-7(neo)) and VEGF-transfected (MCF-7(VEGF)) tumors by using a clinical multislice CT, and compared to skeletal muscle. Parametrical maps of tumor physiology--perfusion (F), permeability-surface area (PS), fractional intravascular plasma (f(p)), and interstitial space (f(is))--were obtained by fitting the time-dependent contrast-enhanced curves to a two-compartmental kinetic model for each voxel (0.3 x 0.3 x 0.75 mm(3)). Mean physiological measurements were compared with (positron emission tomography (PET) imaging, and the spatial distribution of tumor vasculature was compared with histology. No statistically significant difference was found in mean physiological values of F, PS, and f(p) in MCF-7(neo) and muscle, while f(is) of MCF-7(neo) was a factor of two higher ( p < 0.04). MCF-7(neo) tumors also showed a radial heterogeneity with significant higher physiological values in periphery than those in middle and core regions ( p < 0.01 for all physiological parameters). MCF-7(VEGF) tumors demonstrated significant increases in all physiological parameters compared with MCF-7(neo) tumors, and a distinct saccular heterogeneous pattern compared with MCF-7(neo) and muscle. Both PET imaging and histological results showed good correlation with the above results for this same mouse model. No statistically significant difference was found in the mean perfusion and intravascular volume measured by PET imaging and DCE-CT. Increases in cross-sectional area of blood vessels ( p < 0.002) were observed in MCF-7(VEGF) tumors than MCF-7(neo), and their spatial distribution correlated well with the spatial distribution of f(p) obtained by DCE-CT. The results of this study demonstrated the feasibility of DCE-CT in quantification of spatial heterogeneity in tumor physiology in small animal models. Monitoring variations in the tumor environment using DCE-CT offers an in vivo tool for the evaluation and optimization of new therapeutic strategies.

Impact of right ventricular contrast attenuation on the accuracy of right ventricular function analysis at cardiac multi-detector-row CT

PURPOSE

To investigate the impact of right ventricle (RV) contrast attenuation on the accuracy of RV function analysis at cardiac CT performed for coronary imaging.

MATERIALS AND METHODS

We analyzed multi-phase cardiac dual-source CT studies of 40 consecutive patients (mean age 60.9+/-12.3 years; 13 women) with normal valve function. Function analyses of both the right and left ventricle (RV and LV) were performed using dedicated post processing software and stroke volumes (SV) were computed for each ventricle. The accuracy of the RV-SV measurements was determined based upon comparison to LV-SV measurement. The level of contrast attenuation of the RV was recorded at three separate regions of interest-below the pulmonary valve, mid-ventricular, and inferior RV. The accuracy of RV function assessment was correlated with the level of attenuation using regression analyses.

RESULTS

There was a statistically significant correlation between the accuracy of RV function assessment and the level of RV attenuation in the inferior RV (adjusted R(2)=73.1%, p<0.0001). When compared to LV-SV measurements, in studies with low RV attenuation (<175 HUs, n=19) the mean deviation of RV-SV from LV-SV was 29.0+/-10.8 ml (42.1+/-13.9%). In studies with high RV attenuation (> or =175 HUs, n=21) the mean deviation of RV-SV from LV-SV was significantly lower 6.9+/-10.5 ml (9.9+/-16.0%).

CONCLUSION

The accuracy of RV function analysis is dependent on the level of contrast medium attenuation achieved in the inferior RV. There should be at least intermediate attenuation (>175 HUs) to enable accurate functional analysis. At low attenuation levels RV function parameters are prone to underestimation.

Initial Experience with a Novel Low-Dose Micro-CT System

PURPOSE

Investigation of the hardware and image characteristics of a novel micro-CT system and evaluation of its potential to image animals and tissue samples.

MATERIALS AND METHODS

The scanner was characterized by phantom studies regarding image homogeneity, CT number stability, soft-tissue contrast, spatial resolution and X-ray dose. The phantoms used were specially designed to evaluate the imaging of mice and rats. Scans of hearts with coronary stents were performed and the tissue morphology and vascularization of tumor-bearing rodents were studied with dynamic contrast-enhanced (DCE) CT.

RESULTS

The CT numbers of the acrylic phantoms were reproducible with a 4 HU deviation. The inter-pixel deviation was low but depended on the scan mode. The correlation coefficient between CT number and iodine concentration (0 - 6000 HU) was 0.99. Single wires, lumen and endo-luminal plaques of heart stents were distinguishable. The density-time courses were reliably recorded and made it possible to distinguish the tumor and muscle tissue in DCE micro-CT scans

CONCLUSION

The novel micro-CT scanner is suitable for studying tissue densities and contrast agent kinetics.

Usefulness of saline pushing in reduction of contrast material dose in abdominal CT: evaluation of time–density curve for the aorta, portal vein and liver

The effects of saline pushing after contrast material injection were investigated as well as the possibility for this technique to reduce contrast material doses in liver CT examinations. 52 patients were divided randomly into three groups: 100 ml of contrast material (300 mg I ml(-1)) only (A; n = 19), 100 ml of contrast material pushed with 50 ml of saline solution (B; n = 17), and 85 ml of contrast material pushed with 50 ml of saline solution (C; n = 16). Single-level images were obtained at the level of the main portal vein after the initiation of contrast material injection. There were no significant differences in the mean peak enhancement values (PE) and the mean time to peak enhancement values (TPE) of the aorta between the three groups. The mean PE of the portal vein in group B increased 21 HU over that in group A (p<0.05), and there was no significant difference between groups A and C. The mean PE of the liver in group B increased 7 HU over that in group A (p<0.05), and there was no significant difference between groups A and C. The mean TPE of the portal vein was shorter by 4 s (p<0.05), and that of the liver was shorter by 5 s (p<0.05) in group C compared with those in group A. In conclusion, saline pushing increases the enhancement values of the portal vein and liver, and allows a contrast material dose reduction of 15 ml without decreasing hepatic and vascular enhancement at adequate scan timing.

Prediction of aortic peak enhancement in monophasic contrast injection protocols at multidetector CT: phantom and patient studies

PURPOSE

The aim of this study was to investigate whether it is possible to predict aortic peak enhancement (APE) from the contrast dose and injection rate.

MATERIALS AND METHODS

We first undertook an experimental study using a flow phantom that simulates the human circulation. We delivered 90-150 ml of iomeprol-350 at various injection rates and measured the APE values of the simulated aorta. In our clinical study we randomized 20 patients into four groups. In groups A, B, and C the iodine dose per kilogram of body weight (BW) ranged from 450 to 600 mg, and the injection duration was fixed at 30 s; group D received 450 mg/kg over 25 s. We then measured APE in all patients at the whole aorta, averaged the three highest values, and took the result as APE.

RESULTS

In the phantom study, the decision coefficient for the best-fit equation obtained by multiple regression analysis of the relation between the iodine dose and injection rate and the simulated APE was high (0.93). In the patient study, the predicted APE values almost corresponded with the averaged APE values when we applied the fitness equation.

CONCLUSION

Using our fitness equation, APE on contrast-enhanced computed tomography can be predicted from the iodine dose and the contrast injection rate per patient weight.

High iodine concentration contrast material for noninvasive multislice computed tomography coronary angiography: iopromide 370 versus iomeprol 400

OBJECTIVE

The objective of this study was to compare intracoronary attenuation on 16-row multislice computed tomography (16-MSCT) coronary angiography using 2 contrast materials (CM) with high iodine concentration.

MATERIAL AND METHODS

Forty consecutive patients (29 male, 11 female; mean age, 61+/-11 years) with suspected coronary artery disease were randomized to 2 groups to receive 100 mL of either iopromide 370 (group 1: Ultravist 370, 370 mg iodine/mL; Schering AG, Berlin, Germany) or iomeprol 400 (group 2: Iomeron 400, 400 mg iodine/mL; Bracco Imaging SpA, Milan, Italy). Both CM were administered at a rate of 4 mL/s. All patients underwent 16-MSCT coronary angiography (Sensation 16; Siemens, Germany) with collimation 16 x 0.75 mm and rotation time 375 ms. The attenuation in Hounsfield units (HU) achieved after each CM was determined at regions of interest (ROIs) placed at the origin of coronary arteries and on the ascending aorta, descending aorta, and pulmonary artery. Differences in mean attenuation in the coronary arteries and on the ascending aorta, descending aorta, and pulmonary artery were evaluated using Student t test.

RESULTS

The mean attenuation achieved at each anatomic site was consistently greater after iomeprol 400 than after iopromide 370. At the origin of coronary arteries, the mean attenuation after iomeprol 400 (340+/-53 HU) was greater (P<0.05) than that after iopromide 370 (313+/- 42 HU). Similar findings were noted for the mean attenuation in the ascending aorta, descending aorta, and pulmonary artery.

CONCLUSION

The intravenous administration of iomeprol 400 provides higher attenuation of the coronary arteries and of the great arteries of the thorax as compared with iopromide 370 using the same injection parameters.

Optimal Delay Time for the Hepatic Parenchymal Enhancement at the Multidetector CT Examination

The objective of this study was to determine the optimal scan delay time after hepatic parenchymal enhancement using a 16-channel multidetector row helical CT (MDCT) scanner. Two hundred fifty-five consecutive patients underwent biphasic CT scans using a 16-channel MDCT. In group A (n = 125), two hepatic venous phase scans (HVP1 and HVP2) were obtained at 40 and 60 seconds, after 100-HU threshold time (T100HU) in the abdominal aorta. In group B (n = 130), HVP1 and HVP2 scans were obtained 50 and 70 seconds after T100HU. Both groups were divided into subgroups that were given different contrast media. Groups A1 and B1 received a contrast medium of 300 mgI/mL; groups A2 and B2 received a contrast medium of 370 mgI/mL. Each patient was injected with contrast medium at a dose of 2 mL/kg at a rate adjusted to the patient's body weight with a constant injection duration of 47 seconds. The attenuation values (HU) for the liver, portal vein, hepatic vein, and aorta were measured. The average HU was compared between the groups. Hepatic enhancement in the images obtained at 50 and 60 seconds after T100HU was greater (P < 0.05) than in images obtained at 40 and 70 seconds. These results were obtained with both contrast media. A few patients showed greater enhancement at a 40 seconds or 70 seconds. Hepatic enhancement was significantly greater in all scans using a contrast medium dose of 370 mgI/mL compared with the 300-mgI/mL dose (P < 0.05). Independent of the concentration of contrast medium, scan delays of 50 to 60 seconds after T100HU may provide optimal hepatic enhancement.

Prolonged survival of Fischer rats bearing F98 glioma after iodine-enhanced synchrotron stereotactic radiotherapy

PURPOSE

Heavy-atom-enhanced synchrotron stereotactic radiotherapy (SSR) is a treatment that involves selective accumulation of high-Z elements in tumors followed by stereotactic irradiation with X-rays from a synchrotron source. The purpose of this study was to determine whether the efficacy of iodine-enhanced SSR could be further improved in the F98 rodent glioma model, by using a concomitant injection of an iodinated contrast agent and a transient blood-brain barrier opener (mannitol) during irradiation.

METHODS AND MATERIALS

Fourteen days after intracerebral inoculations of F98 cells, the rats were irradiated with 50-keV X-rays while receiving an infusion of hyperosmotic mannitol with iodine, either intravenously or via the carotid (9 to 15 rats per group, 117 rats total).

RESULTS

For doses<or=15 Gy, the intracarotid infusion of mannitol and iodine improved the rats' survival compared with intravenous injection or irradiation alone. The percentage-increased life spans (ILS) were 91%, 116%, and 169% without iodine, after infusion of iodine and mannitol intravenously, and intracarotid, respectively (15 Gy). At 25 Gy, the rats irradiated without iodine had the longest survival (ILS=607%), but no additional benefit was obtained with iodine and mannitol.

CONCLUSIONS

Iodine-enhanced SSR is significantly improved with concomitant intracarotid infusion of iodine and mannitol for radiation doses<or=15 Gy.

Solitary Pulmonary Nodule: Characterization with Combined Wash-in and Washout Features at Dynamic Multi–Detector Row CT

PURPOSE

To prospectively assess the accuracy of combined wash-in and washout characteristics at dynamic contrast material-enhanced multi-detector row computed tomography (CT) in distinguishing benign from malignant solitary pulmonary nodules.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. The study included 107 patients (62 men, 45 women; mean age, 55 years; range, 22-81 years) with a solitary pulmonary nodule. After unenhanced CT (2.5-mm collimation) scans were obtained, dynamic CT was performed by using a helical technique (series of images obtained throughout the nodule, with 2.5-mm collimation, at 30, 60, 90, and 120 seconds and 4, 5, 9, 12, and 15 minutes) after intravenous injection of contrast medium (120 mL). Tissue diagnosis was made in 70 nodules, and follow-up images showed benignancy in the remaining 37 (no change in size, n = 32; decrease in size, n = 5). CT findings were analyzed in terms of wash-in and washout of contrast medium. Sensitivity, specificity, and accuracy for malignant nodules were calculated by considering both the wash-in and washout characteristics at dynamic CT.

RESULTS

There were 49 malignant and 58 benign nodules. When diagnostic criteria for malignancy of both wash-in of 25 HU or greater and washout of 5-31 HU were applied, sensitivity, specificity, and accuracy for malignancy were 94% (46 of 49 nodules), 90% (52 of 58 nodules), and 92% (98 of 107 nodules), respectively. Of 58 benign nodules, 27 showed less than 25 HU wash-in, 14 showed persistent contrast enhancement without washout and with wash-in of 25 HU or greater, and 11 showed washout greater than 31 HU and wash-in of 25 HU or greater.

CONCLUSION

Evaluation of solitary pulmonary nodules by analyzing combined wash-in and washout characteristics at dynamic contrast-enhanced multi-detector row CT showed 92% accuracy for distinguishing benign nodules from malignant nodules.

High-Concentration Contrast Media in Multiphasic Abdominal Multidetector-Row Computed Tomography

OBJECTIVE

The purpose of this study was to assess the influence of the iodine flow rate on parenchymal and vascular enhancement during multiphasic abdominal multidetector-row computed tomography (MDCT).

METHODS

Fifteen patients underwent MDCT at an iodine flow rate of 1.2 g/s as well as 1.6 g/s (group A, protocols 1 and 2), and 90 patients underwent MDCT at an iodine flow rate of 1.2 g/s (group B) or 1.6 g/s (group C). Measurements were performed for all groups in the liver, spleen, pancreas, portal vein, inferior vena cava, and abdominal aorta.

RESULTS

Aortal and pancreatic enhancement during the arterial phase was significantly higher with the higher iodine flow rate. The mean difference in aortal enhancement was 60 Hounsfield units (HU) between protocols 1 and 2 of group A, and the mean difference was 70 HU between groups B and C. The mean difference in pancreatic enhancement was 10 HU between protocols 1 and 2 of group A and 17 HU between groups B and C. During the portal and hepatic venous phases, no significant difference in enhancement was observed.

CONCLUSION

A high iodine flow rate in multiphasic abdominal MDCT improves enhancement of the aorta and the pancreas during the arterial phase but does not influence later phases.

Quantification of Intravenously Administered Contrast Medium Transit through the Peripheral Arteries: Implications for CT Angiography

PURPOSE

To prospectively determine the range of aortopopliteal bolus transit times in patients with moderate-to-severe peripheral arterial occlusive disease (PAOD) as a guideline for developing injection strategies for computed tomographic (CT) angiography of peripheral arteries.

MATERIALS AND METHODS

The study protocol was approved by the local ethics board, and informed consent was obtained. Twenty patients with PAOD referred for CT angiography of the lower extremities were categorized into two groups, Fontaine stage IIb (group 1) and stage III or IV (group 2), and demographic information was collected. In all patients, a 16-mL test bolus was injected intravenously, and single-level dynamic acquisitions were obtained at the level of the abdominal aorta. After injection of a second 16-mL test bolus, dynamic acquisitions were obtained at the level of the knee (popliteal arteries). Aortopopliteal bolus transit times were calculated by subtracting the time to peak enhancement in the popliteal arteries from that in the aorta. Aortopopliteal transit speeds also were derived. Transit times and speeds were compared graphically between clinical stage groups. The time required for the contrast medium to enhance the entire peripheral arterial tree in patients with PAOD was estimated by using linear extrapolation.

RESULTS

Sixteen men and four women with a mean age of 69 years (range, 49-86 years) were included. Twelve patients were included in group 1, and eight patients, in group 2. Aortopopliteal bolus transit times ranged from 4 to 24 seconds (median, 8 seconds) in all subjects, which corresponded to bolus transit speeds of 177 and 29 mm/sec, respectively. Wide overlap of transit times and transit speeds was observed between clinical stage groups. The estimated time needed for the bolus to enhance the entire peripheral arterial tree was 6-39 seconds.

CONCLUSION

Aortopopliteal bolus transit times differ widely among patients and may be substantially delayed in all patients with PAOD. Empirical injection protocols should include an injection duration of 35 seconds or more, as well as an increased scanning delay, with table speeds of more than 30 mm/sec.

Quantitative colorectal cancer perfusion measurement using dynamic contrast-enhanced multidetector-row computed tomography: effect of acquisition time and implications for protocols

OBJECTIVE

To determine the effect of acquisition time on quantitative colorectal cancer perfusion measurement.

METHODS

Dynamic contrast-enhanced computed tomography (CT) was performed prospectively in 10 patients with histologically proven colorectal cancer using 4-detector row CT (Lightspeed Plus; GE Healthcare Technologies, Waukesha, WI). Tumor blood flow, blood volume, mean transit time, and permeability were assessed for 3 acquisition times (45, 65, and 130 seconds). Mean values for all 4 perfusion parameters for each acquisition time were compared using the paired t test.

RESULTS

Significant differences in permeability values were noted between acquisitions of 45 seconds and 65 and 130 seconds, respectively (P=0.02, P=0.007). There was no significant difference for values of blood volume, blood flow, and mean transit time between any of the acquisition times.

CONCLUSIONS

Scan acquisitions of 45 seconds are too short for reliable permeability measurement in the abdomen. Longer acquisition times are required.

Real-time in vivo imaging of the convective distribution of a low-molecular-weight tracer

Object. Convection-enhanced delivery (CED) is increasingly used to distribute therapeutic agents to locations in the central nervous system. The optimal application of convective distribution of various agents requires the development of imaging tracers to monitor CED in vivo in real time. The authors examined the safety and utility of an iodine-based low-molecular-weight surrogate tracer for computerized tomography (CT) scanning during CED.

Methods. Various volumes (total volume range 90–150 µ1) of iopamidol (MW 777 D) were delivered to the cerebral white matter of four primates (Macaca mulatta) by using CED. The distribution of this imaging tracer was determined by in vivo real-time and postinfusion CT scanning (≤ 5 days after infusion [one animal]) as well as by quantitative autoradiography (14C-sucrose [all animals] and 14C-dextran [one animal]), and compared with a mathematical model. Clinical observation (≤ 5 months) and histopathological analyses were used to evaluate the safety and toxicity of the tracer delivery.

Real-time CT scanning of the tracer during infusion revealed a clearly definable region of perfusion. The volume of distribution (Vd) increased linearly (r2 = 0.97) with an increasing volume of infusion (Vi). The overall Vd/Vi ratio was 4.1 ± 0.7 (mean ± standard deviation) and the distribution of infusate was homogeneous. Quantitative autoradiography confirmed the accuracy of the imaged distribution for a small (sucrose, MW 359 D) and a large (dextran, MW 70 kD) molecule. The distribution of the infusate was identifiable up to 72 hours after infusion. There was no clinical or histopathological evidence of toxicity in any animal.

Conclusions. Real-time in vivo CT scanning of CED of iopamidol appears to be safe, feasible, and suitable for monitoring convective delivery of drugs with certain features and low infusion volumes.

Role of vasa vasorum in transendothelial solute transport in the coronary vessel wall: a study with cryostatic micro-CT

Using cryostatic microscopic computed tomography (micro-CT), we sought to determine the role of coronary vasa vasorum (VV) in transendothelial solute transport in arteries with normal and increased permeability due to high plasma cholesterol levels. In 6-mo-old pigs on a normal (n=23) and 2% high cholesterol (HC) diet (n=8), 2-cm segments of the proximal left anterior descending coronary arteries were removed in vivo after a selective injection of X-ray contrast solution. Harvesting of the specimens occurred at 0, 15, 25, 35, or 45 s after completion of the contrast injection. Specimens were snap frozen and scanned in our cryostatic micro-CT. The spatial distribution of contrast in the coronary artery wall was quantified using the CT images. Right coronary arteries were infused with Microfil to determine VV density (VV/mm2) and the cumulative lumen surface area (mm2/mm3). Transendothelial diffusion of contrast into the coronary vessel wall is a dynamic process starting at both the subintima and the adventitia. The subintimal opacification moves as a wave toward the adventitia, whereas the adventitial wave resolves. The coronary vessel wall in animals on a HC diet shows higher opacification than in normal coronary arteries without an increase of VV total luminal surface area. The loss of endothelial integrity in hypercholesterolemia significantly alters VV solute washin to, and washout from, the coronary artery wall.

Simultaneous hemodialysis during coronary angiography fails to prevent radiocontrast-induced nephropathy in chronic renal failure

BACKGROUND

Radiocontrast medium- (RM) associated nephrotoxicity continues to be a common cause of acute renal failure and may lead in patients with pre-existing chronic renal insufficiency even to end-stage renal failure requiring chronic dialysis. Since extracorporeal removal of RM after RM administration has been shown to be effective but does not prevent radiocontrast-induced nephropathy, the effect of a simultaneous dialysis during RM administration on renal function is not clear.

METHODS

In a prospective, randomized and controlled trial, we studied the effect of a 4-hour online dialysis during RM (iomeprol) application in patients with advanced chronic renal failure (serum creatinine > or = 3 mg/dl) undergoing coronary angiography. All patients received hydration with saline before and after standardized coronary angiography and were randomized to receive a simultaneous high-flux hemodialysis (7 patients, HD group) or to control group (10 patients). 24-hour creatinine clearance (CrCl) was measured in all patients before, 1 week and 8 weeks after coronary angiography. The clinical follow-up comprised 8 weeks after RM application. RM plasma levels were measured in both groups 15, 30, 60 minutes, 2, 4, 12, 24, 48 and 72 hours after application by high-pressure liquid chromatography.

RESULTS

At baseline, CrCl (19 +/- 10 vs 17 +/- 7 ml/min), percentage of diabetics (57 vs 70%) and dose of RM (77 +/- 27 vs 86 +/- 21 ml) were similar in both groups. Pharmacokinetics: Total clearance of iomeprol was significantly higher (54 +/- 15 vs 20 +/- 12 ml/min, p < 0.001) and the area under curve (AUC) was significantly lower (23 +/- 10 g x h/l vs 94 +/- 57 g x h/l, p < 0.001) in the HD group compared to control group. RM peak plasma levels 15 min after application were not different in both groups (3.0 +/- 1.1 vs 4.2 +/- 1.7 mmol/l, NS), however, significantly lower 60 min (1.6 +/- 0.4 vs 3.7 +/- 1.5 mmol/l, p < 0.01) and 240 min (0.7 +/- 0.3 vs 2.3 +/- 0.7 p < 0.001) after angiography.

CLINICAL RESULTS

CrCl showed no difference 1 week (24 +/- 11 vs 19 +/- 9 ml/min, ns) and 8 weeks (24 +/- 5 vs 20 +/- 9 ml/min, NS) after angiography from baseline or between the groups. In each group, 2 patients developed end-stage renal disease and requested permanent dialysis during the 8-week follow-up.

CONCLUSION

Simultaneous dialysis reduces AUC of iomeprol significantly, however, does not influence plasma peak concentration after angiography. Renal function and incidence of end-stage renal failure were not influenced by online-dialysis.

Evaluation of Kidney Function in Patients with Acute Renal Failure Using High-Performance Liquid Chromatography: A Case Report

Accurate measurement of glomerular function rate (GFR) in the setting of acute renal failure is difficult to achieve with current clinical methods, such as measuring plasma creatinine concentration and 24-hour urine creatinine clearance. High-performance liquid chromatography was used to measure GFR directly in a critically ill patient with acute renal failure. This approach involved evaluating the elimination kinetics of nonionic contrast material administered intravenously for radiologic imaging. It required no additional patient exposure to radiographic contrast media and enabled caregivers to determine kidney function accurately in the presence of worsening clinical status and delayed changes in plasma creatinine. This and other methods for more accurate measurement of GFR in patients with acute renal failure may provide the foundation for clinical studies that assess the severity and management of acute renal failure.

[Feasibility and optimization of the combined injection of contrast medium and normal saline with a single-syringe CT injection system]

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.

Conditions of iodine contrast transfer from lumbosacral CSF to blood

PURPOSE

To determine conditions which influence transfer of iopamidol from lumbosacral cerebrospinal fluid (CSF) to blood.

METHODS

Iopamidol transfer was measured in 32 patients over 180 min after radiculography and compared with patient variables.

RESULTS

Iopamidol transfer began early in 12 patients, more slowly in 13 patients, and was not detected during sample period in 7 patients. Transfer of sequential samples correlated highly with each other (r>0.8). Transfer was more pronounced in patients with prominent nerve root sleeves on radiculogram (p=0.006, t test), and correlated inversely with body weight (r=-0.4258), and with albumin CSF/serum quotient (r=-0.4702).

CONCLUSION

Early iopamidol transfer probably indicates transfer through spinal arachnoid villi and granulations with CSF bulk flow. Prominent nerve root sleeves may facilitate access to transfer sites. No transfer during sample period suggests no such spinal transfer, possibly due to sparse access to or presence of spinal transfer sites. Inverse correlation of transfer with body weight may reflect influence of body weight on retroperitoneal venous pressure, which regulates outflow of CSF and of compounds dissolved in it. Awareness of wide interindividual transfer variation and steady intraindividual transfer may help to specify dosage and effect expectation of intrathecal drug therapy.

[Method of injection of contrast medium for brain perfusion CT]

Perfusion computed tomography (CT) has great value for detecting stroke and evaluating blood flow in the brain. With perfusion CT, it is possible to obtain two absolute values, cerebral blood flow (CBF) (ml/min/100g) and cerebral blood volume (CBV) (%). In using this examination, the main problem is the method of iodine injection. The maximum slope of time-attenuation curve in organs must be reached before the peak enhancement time of the sagittal sinus. To solve this problem, we used a new method in which total injection volume is 30ml, and the rate of injection is 9ml/sec. The data acquisition time is one second for each scan, and the time interval is one second, for 20 scans in total. With this method, we can obtain reliable information on blood flow in the damaged brain. The most common examination used for the detection of brain blood flow is single-phased dynamic CT with Xe inhalation. However, the Xe inhalant examination is difficult to use in the routine clinical setting. Perfusion CT will be more useful for the detection of brain blood flow.

Pharmacokinetics and safety of iomeprol in healthy volunteers and in patients with renal impairment or end-stage renal disease requiring hemodialysis

RATIONALE AND OBJECTIVES

To present the results of two studies conducted to evaluate the pharmacokinetics and safety of iomeprol in healthy volunteers and in patients with various degrees of renal impairment.

METHODS

In these two open-label, single-dose, phase I studies, a 50-mL dose of iomeprol 400 was administered intravenously to a total of 30 subjects of either sex. In study 1, six healthy volunteers with normal renal function, six patients with mild renal failure, six patients with moderate renal failure, and four patients with severe renal failure were enrolled. In study 2, eight patients with end-stage renal disease requiring hemodialysis were enrolled. Safety was determined by predose and postdose (up to 10 days) measurement of vital signs, hematology, blood chemistry, urinalysis, electrocardiogram, physical examinations, and the incidence of adverse events. Pharmacokinetics was determined by measuring iomeprol levels in plasma, urine, feces, and dialysate samples, by using a validated high-performance liquid chromatography assay, up to 7 days after administration.

RESULTS

The plasma concentration of iomeprol declined biexponentially in both healthy subjects and patients. As expected, mean body and renal clearances decreased progressively with increasing renal impairment, with a significant correlation with the glomerular filtration rate. The elimination half-life increased progressively with increasing renal impairment. The extraction efficiency of dialyser was estimated as approximately 40%, and dialysis clearance of iomeprol was approximately 1.26 mL. min-1. kg-1 (80.6 mL/min), slightly less than the body clearance previously observed in healthy subjects. It appears that dialysis is almost as efficient as renal function in healthy subjects in the removal of iomeprol. After a single dialysis session, approximately 58% of the dose was recovered in dialysate. Mild to moderate adverse events were reported by 17 of 30 subjects; none was clinically meaningful. One serious adverse event, unrelated to iomeprol, was reported. No clinically meaningful findings were noted for other safety parameters.

CONCLUSIONS

Iomeprol was almost completely eliminated both in patients with renal impairment and in patients receiving dialysis. No dose adjustment appears to be necessary either in patients with renal impairment or with end-stage renal disease requiring hemodialysis. In this risk population, iomeprol 400 was safe and well tolerated.

Postinfarctional remodeling: increased dye intensity in the myocardial risk area after angioplasty of infarct-related coronary artery is associated with reduction of ventricular volumes

OBJECTIVES

We sought to evaluate if angiographic dye videointensity of the risk area during percutaneous transluminal coronary angioplasty (PTCA) of the infarct-related artery (IRA) relates to remodeling.

BACKGROUND

Poor reflow after myocardial infarction (MI) predicts worse ventricular remodeling.

METHODS

Fifty-three patients with a first anterior MI and isolated disease of the left anterior descending (LAD), who underwent "primary" (n = 14), "rescue" (n = 7) or "late" (after 10 +/- 4 days, n = 32) PTCA, were retrospectively selected. In 10 patients prospectively collected, we assessed Doppler flow velocities and Doppler flow reserve (DFR), relating them to the videointensity technique. Coronary stenosis and TIMI flow were determined, and echocardiographic volumes (end-diastolic and end-systolic volume indexes) and regional asynergy were computed before hospital discharge (baseline) and at six months. Assuming higher peak videointensity reflects greater myocardial blood volume, a 1- to 5-point (poor-optimal) perfusion scale was devised.

RESULTS

The correlation of Doppler peak velocity and DFR with videointensity was significant (r = 0.58, p = 0.007 and r = 0.71, p < 0.001, respectively). Patients were subdivided into group A (increased videointensity post-PTCA > or = 1.5 points, n = 29) and group B (unchanged videointensity, n = 24). Analysis of variance showed a time-group interaction for end-diastolic volume index (-4.6 +/- 23% vs. +22 +/- 22%, p = 0.003) and end-systolic volume index (-3.05 +/- 11.1% vs. +4.1 +/- 12.5%, p = 0.027). There was no interaction for changes in LAD stenosis (p = 0.39) and TIMI flow after PTCA (p = 0.27), or regional asynergy at six months (p = 0.31).

CONCLUSIONS

Angiographic dye videointensity in the risk area correlates with Doppler peak velocity and DFR, and its increase after PTCA of IRA has a limiting effect on ventricular volumes, independent of coronary stenosis resolution, changes in Thrombolysis In Myocardial Infarction (TIMI) flow or extent of regional asynergy.

Clinical experience with iomeprol in myelography and myelo-CT: clinical pharmacology and double-blind comparisons with iopamidol, iohexol, and iotrolan

RATIONALE AND OBJECTIVES

To evaluate iomeprol, a new nonionic iodinated contrast medium, as a contrast agent for myelography and to compare it with iopamidol, iohexol, and iotrolan.

METHODS

An extensive clinical program was conducted on more than 600 patients to assess iomeprol's pharmacokinetics, tolerability, safety, and efficacy after intrathecal injection.

RESULTS

Pharmacokinetics study results showed that after intrathecal administration iomeprol is completely absorbed from the cerebrospinal fluid compartment; once absorbed into the systemic circulation, it is rapidly excreted, unmetabolized, by glomerular filtration. Dose-finding studies showed that the opacification produced by iomeprol depends on the injected dose. Although a dose-dependent increase in efficacy was observed, no differences in neurotolerability and safety were detected between the doses tested. Doses of iomeprol greater than 3 g I did not cause a greater incidence of adverse events and produced significantly better contrast efficacy. Comparative clinical trials showed that iomeprol and iopamidol, iohexol, and iotrolan always provided adequate opacification of the subarachnoid space, both in conventional myelography and myelo-CT, with adequate delineation of normal structures and pathologic processes. No serious adverse events occurred up to a total dose of 4.5 g I. No differences between the agents with regard to tolerance, adverse events, and effects on vital signs, physical examination, and neurologic examination were observed.

CONCLUSIONS

Iomeprol is safe and effective and can be recommended for myelography and myelo-CT.

Iomeprol: a review of its use as a contrast medium

Iomeprol is a nonionic, monomeric iodinated contrast medium. Unlike the older ionic agents, iomeprol has low chemotoxicity, osmolality and viscosity and high water solubility. Compared with other nonionic contrast media, the osmolality and viscosity are lower and the water solubility is reported to be higher with iomeprol. Most radiographs (about 67 to 100%) obtained with iomeprol (containing 150 to 400 mg/ml of iodine) were of good or excellent quality in noncomparative and comparative trials recruiting 40 to 6127 patients undergoing various radiographic procedures. As expected, the diagnostic efficacy of iomeprol did not differ significantly from that of other nonionic agents (iopamidol, iopromide, iohexol and iotrolan). Iomeprol (containing 150 to 400 mg/ml of iodine) was well tolerated in clinical trials. Most adverse events were transient and of mild to moderate intensity and were similar to those observed with other contrast media. The overall incidence of adverse events ranged from 3 to 49.7% and mainly included localised pain (< or =6%) and heat sensations (8 to 45%), taste disturbances (3 to 27%) and various pseudoallergic reactions (< or =20% for each type of event). The incidence of heat or pain and taste disturbances with iomeprol was similar to that observed with iopromide and iopamidol. Pain (but not heat sensations) was reported significantly less frequently and taste disturbances reported significantly more frequently with iomeprol than with iohexol in a comparative trial. Pseudoallergic reactions (such as nausea, vomiting, skin reactions, dizziness, headache) were significantly less common with iomeprol than with ioxaglate and occurred at a similar frequency to that with iopromide and iopamidol. Cardiovascular events were rarely observed with iomeprol. Currently available iomeprol solutions contain a range of iodine concentrations (150 to 400 mg/ml) and are approved for a wide variety of diagnostic procedures. Iomeprol solutions are chemically stable which negates the need for chelating agents. Formulations of this agent are therefore the first not to contain edetic acid (EDTA).

CONCLUSIONS

Iomeprol shows equivalent diagnostic efficacy, and a similar adverse event profile, to that of other nonionic contrast media. The availability of a range of iodine concentrations enables iomeprol to be used in a variety of diagnostic procedures. Iomeprol, like others in its class, is suitable for use in diagnostic imaging.

Helical CT of the liver with computer-assisted bolus-tracking technology: scan delay of arterial phase scanning and effect of flow rates

PURPOSE

The purpose of this work was to assess the scan delay and the effect of flow rates on arterial phase scanning of hepatic CT.

METHOD

One hundred twenty patients suspected of having hepatocellular carcinoma were examined by three-phase helical CT using computer-assisted bolus-tracking technology. We set the region of interest (ROI) in the abdominal aorta at the level of the celiac artery as a baseline. The triggering threshold was set at 100 HU. A volume of 100 ml of iomeprol (350 mg of I/ml) was administered at 2, 2.5, or 3 ml/s i.v.

RESULTS

In all cases, helical CT scanning began after reaching the ROI threshold. Then, portal venous phase scanning was initiated 50 s after arterial phase initiation. The mean delay time from the initiation of contrast agent administration to the beginning of arterial phase scanning was 29.2 +/- 3.8 s (mean +/- SD, range 22-39 s). A faster injection rate significantly shortened the scan delay (p < 0.01). In portal venous phase scanning, calculated areas under the hepatic enhancement curves were almost equal among different injection rates.

CONCLUSION

The computer-assisted bolus-tracking technology is a useful method for determining an individual scan delay of arterial phase CT.

Albumin permeability in isolated glomeruli in incipient experimental diabetes mellitus

AIMS/HYPOTHESIS

The pre-clinical phase of diabetic nephropathy is characterised by increased glomerular filtration rate and episodes of microalbuminuria. The cause of the microalbuminuria has been variably ascribed to alterations of the size or charge selective barriers of the glomerulus or both or as a consequence of the haemodynamic changes. Our aim was to investigate very early albumin permeability alterations in isolated glomeruli which were not subject to perfusion pressure.

METHODS

Isolated glomeruli were studied from 120 male Wistar rats, divided into three groups: streptozotocin-treated, streptozotocin-treated with insulin pellet implants, and controls. From each group ten animals were killed at 7, 14, 28, and 56 days after induction. Study variables included blood pressure, proteinuria, iopamidol clearance, albumin permeability and glomerular area. Subsequently, albumin permeability, proteinuria, and iopamidol clearance were determined in an additional group of 40 diabetic animals studied at 24, 72, 96, and 120 h after induction.

RESULTS

Albumin permeability increased steadily from induction in streptozotocin-treated animals, reaching a plateau at approximately 120 h. Glomerular filtration rate was shown to increase significantly at approximately 7 days and proteinuria correlated with it. Glomerular hypertrophy was observed both in streptozotocin-treated animals and in streptozotocin-treated rats with insulin pellet implants. Strict blood glucose control delayed the appearance of the permeability defect in isolated glomeruli and inhibited the increase in glomerular filtration in intact animals. It did not prevent glomerular hypertrophy.

CONCLUSION/INTERPRETATION

An albumin permeability defect exists early in isolated non-perfused glomeruli from streptozotocin-treated rats and seems to be independent of glomerular filtration rate alterations.

Safety and pharmacokinetics of a new liposomal liver-specific contrast agent for CT: results of clinical testing in nonpatient volunteers

RATIONALE AND OBJECTIVES

To evaluate the safety and pharmacokinetics of BR21, a liposome-encapsulated iomeprol formulation, in nonpatient volunteers.

METHODS

This was a single-blind, placebo-controlled, ascending dose study in 30 adult, male nonpatient volunteers, randomized to receive a single intravenous bolus (2 mL/s) of BR21 (0.5, 1.0, 1.5, 2.0, and 2.5 mL/kg, four volunteers per dose level) or matched volumes of placebo (0.9% saline, 10 volunteers). The safety controls performed consisted of preand postdose complete physical examinations, measurement of vital signs, electrocardiographic controls, clinical laboratory investigations (hematology, serum chemistry, and urinalysis), and monitoring of adverse events. The safety controls and monitoring of subjects for adverse events continued up to 7 days after the dose. For pharmacokinetic analysis, the determination of total iomeprol content was performed by a high-performance liquid chromatography assay procedure in blood, urine, and fecal samples collected before the dose and serially after the dose, up to 120 hours.

RESULTS

No serious adverse events occurred throughout the study. All nonserious adverse events were minor and mild in intensity and rapidly resolved without treatment. No difference in the incidence of adverse events was observed among the various doses of BR21 and between BR21 and placebo. There were no clinically significant changes in vital signs, electrocardiographic parameters, or clinical laboratory findings. Iomeprol blood level decay can be described by a three-exponential function, consistent with a distribution phase (range, t1/2 0.12-0.21 hours), a fast elimination phase (range, t1/2 1.2-1.5 hours), and a slow elimination phase from a deep compartment (range, t1/2 3.3-4.5 hours). There was an apparent linearity in the relation between the area under the curve and the dose. Urinary elimination of unchanged iomeprol accounted for 89% to 90% of injected dose within 24 hours.

CONCLUSIONS

BR21 appeared to be safe and well tolerated in nonpatient subjects. Its pharmacokinetic profile was compatible with nonspecific distribution into the extracellular fluid space and specific distribution into a deep compartment.

Elimination of iomeprol in patients undergoing continuous ambulatory peritoneal dialysis

OBJECTIVE

To examine the elimination of iomeprol, its safety in clinical use, and its peritoneal permeability in continuous ambulatory peritoneal dialysis (CAPD) patients with variable degrees of residual renal function (RRF).

DESIGN

A nonrandomized comparison study.

SETTING

Hospitalized patients in CAPD unit of Chikuho and University Hospitals.

PARTICIPANTS

Fourteen patients treated by CAPD and 6 by hemodialysis (HD).

INTERVENTIONS

Total dialysate, blood, and 24-hour urine collections were obtained for 4 consecutive days after the administration of iomeprol. A peritoneal equilibration test was performed just before and after the administration of iomeprol.

MEASUREMENTS

Iomeprol (iodine) concentration was measured. Residual renal function was estimated as the mean of renal creatinine and urea clearances. Dialysate-to-plasma ratios (D/P) of creatinine and iomeprol were also determined.

RESULTS

In all CAPD patients, plasma iomeprol clearance was markedly slow, with a biological half-life (T1/2) of over 32 hours. However, no patients suffered from any adverse effects, and over 80% of plasma iomeprol was eliminated during the 4-hour HD. The plasma iomeprol elimination rate was significantly higher from 4 hours after the iomeprol administration in CAPD patients with RRF [mean estimated creatinine clearance (CCr) 3.8 mL/min, n = 7] compared to the remaining patients (mean estimated CCr 0.6 mL/min, n = 7); however, T1/2 in patients with RRF was over 24 hours. D/P creatinine was significantly correlated with D/P iomeprol, and peritoneal iomeprol permeability may depend on an individual's peritoneal solute transport properties.

CONCLUSIONS

A prolonged elimination rate of iomeprol was documented in our CAPD patients both with and without RRF. A HD procedure or intensive peritoneal dialysis just after the use of iomeprol may be advisable to promptly remove circulating iomeprol.

Iodine absorption in patients undergoing ERCP compared with coronary angiography

BACKGROUND

Systemic absorption of iodinated contrast material occurs during endoscopic retrograde cholangiopancreatography (ERCP), the clinical significance of which has not yet been determined.

METHODS

Urinary iodine excretion was measured before and after coronary angiography (n = 20) and ERCP (n = 12). Thyroid hormone levels were determined before iodine load and after 6 and 24 weeks.

RESULTS

Before coronary angiography, iodine excretion was 101 +/- 38.3 micromol/mol creatinine and increased to 865. 10(5) +/- 721. 10(5) micromol/mol on the next day (p </= 0.001). After 6 weeks, it was still elevated (167 +/- 88.8 micromol/mol, p < 0.01). Before ERCP, iodine excretion was 115 +/- 60.3 micromol/mol and reached a peak of 5.3. 10(5) +/- 4.9. 10(5) micromol/mol (p < 0.001). Six weeks later, it had returned to baseline. Two patients in the coronary angiography group but none in the ERCP group had suppressed thyrotropin after 6 weeks.

CONCLUSIONS

The systemic iodine load during ERCP is approximately 0.6% of the iodine load during coronary angiography. Therefore routine measurement of thyroid hormones before ERCP is not recommended.

Time dependence of iopamidol and iodixanol in arthrography of the knee

PURPOSE

The safety and diagnostic efficacy of iodixanol (Visipaque) 270 mg I/ml was compared to that of iopamidol (Iopamiron) 300 mg I/ml in knee arthrography.

MATERIAL AND METHODS

This trial was a bi-center double-blind trial including 128 patients (iodixanol/iopamidol 64/64 patients). Efficacy was evaluated by blinded grading of the diagnostic quality of the p.a. images taken 0, 12 and 25 min after contrast administration by the examining radiologist and later at a consensus evaluation by two experienced skeletal radiologists. Adverse events were recorded.

RESULTS

No patient experienced any adverse event. The proportion of better images at both 12 and 25 min after injection was higher in the iodixanol group compared to the iopamidol group both by the examining radiologist and at the consensus evaluation.

CONCLUSION

In the knee joint iodixanol is a safe contrast medium. The contrast effect of iodixanol lasted longer than that of iopamidol, which can be important when performing arthrography, especially CT arthrography, where the time between puncture and examination can be prolonged.

Contrast medium-removing effect of hemofiltration and hemodiafiltration

The contrast medium-removing effect of hemofiltration (HF) and hemodiafiltration (HDF) was experimentally investigated using a bovine blood tank model. HF and HDF were performed at a blood flow rate of 100 ml/min with a polysulfone hemofilter (PS filter-CF; membrane area: 0.7 m2). Two hundred milliliters of iomeprol (300 mgI/ml) was administered by a single injection into 4 liters of bovine blood. The blood half-lives of iomeprol were 1.0 hr for the high flow rate HDF group [replacement fluid flow rate (QF): 10 ml/min and dialysate flow rate (QD): 40 ml/min], 1.8 hr for the HDF group (QF: 10 ml/min and QD: 10 ml/min), and 3.8 hr for the HF group (QF: 10 ml/min). The mean clearance rates were 39.7 ml/min for the high flow rate HDF group, 21.4 ml/min for the HDF group, and 12.0 ml/min for the HF group. Iomeprol was mostly excreted in the waste fluid. It is concluded that HDF can remove contrast media more effectively than HF.

Effect of acute renal failure on the distribution of iomeprol, a nonionic contrast agent, to cerebrospinal fluid in rats

The effect of acute renal failure on the pharmacokinetics concerning the cerebrospinal fluid (CSF) distribution of iomeprol, a nonionic contrast agent, was studied. The concentrations of iomeprol in the plasma and CSF were measured after intravenous (i.v.) administration at the dose of 50 or 500 mg/kg body weight. The time courses of plasma and CSF concentration were linear within the dose studied. Influx and efflux clearances estimated by simultaneous fitting were 4.6 x 10(-5) ml/min and 8.8 x 10(-4) ml/min, respectively, which suggested that the distribution of iomeprol to CSF low and linear. The distribution volume at steady state was 300-500 ml/kg, suggesting that iomeprol was readily distributed to the extracellular space but hardly distributed to the intercellular space. Total body clearance (9-13 ml/min/kg) indicated that iomeprol was mainly excreted by glomerular filtration. In the rat with acute renal failure induced by ligating the binary ureters, the concentration of iomeprol in CSF after i.v. administration of 500 mg/kg dose was much higher than that in the intact rat according to the delay of elimination from plasma (CLtot = 0.07 ml/min/kg). However, the time course of iomeprol concentration in CSF was predictable using the values of the influx clearance to CSF and the efflux clearance from CSF determined by intact rats. In conclusion, renal failure is one risk factor for central nervous system toxicity because of decreased total body clearance, while acute renal failure may not affect the transport of iomeprol to CSF.

Elimination of iomeprol by hemodialysis

Iomeprol is commercially a relatively new type of contrast medium. There have been no reports concerning its dialysability and safety when administered to patients with end-stage renal failure undergoing regular therapeutic hemodialysis (HD). One hundred milliliters of iomeprol (350 mgl/ml) was injected intravenously at computed tomography in 10 patients suffering from chronic renal failure. HD was then performed within 30 min after the start of iomeprol injection. The duration of HD was 4 h and blood samples were taken at 15, 30 min, 1, 2 and 4 h after its start. Mean dialysance of urea was 176.0-182.9 ml/min, compared to 131.4-133.3 ml/min for iomeprol. Elimination rate of iomeprol was 821.4 +/- 4.6% 4 h after the start of HD. Two of the 10 patients had side effects. One of them complained of a heat sensation and the other of sneezing and rash. As 4-h HD effectively removed iomeprol from the body and there were no severe side effects, it is concluded that iomeprol is suitable for HD patients.

Renal cortical retention of contrast medium after angiography as assessed by delayed CT: a multivariate analysis

Renal cortical retention (RCR) of contrast medium discovered by delayed X-ray examination is sometimes reported in patients with problems in the urinary system. However, we frequently found RCR even in patients with normal renal function. Therefore, we examined the incidence and factors involved in RCR by delayed computed tomography (CT) 12-24 hours after angiography in 168 patients. RCR was found in 80 of 168 cases (48%). Ioxaglate (60%) and iohexol (60%) showed higher incidences of RCR than diatrizoate (37%) and iopamidol (37%). Multivariate logistic regression analysis was performed to determine the predisposing factors of RCR. Dose of administered contrast medium by body weight (p = 0.004), age (p = 0.009), sex (p = 0.013), type of contrast medium (p = 0.003), serum albumin (p = 0.011), and serum creatinine (p = 0.002) were identified as significant and independent predisposing factors of RCR. We suggest that RCR is not a rare phenomenon if delayed CT is carried out.

Brain penetration of intrathecal iomeprol in dogs

PURPOSE

Iomeprol, a new nonionic iodinated compound for intravascular use, is being evaluated as a myelographic contrast agent because of its low neurotoxicity. This study aimed to assess the degree of brain penetration of iomeprol after intrathecal administration.

MATERIAL AND METHODS

Brain penetration in dogs was investigated by CT and compared with that of iopamidol, iohexol, and ioversol, currently used as myelographic contrast media (CM). Nervous tissue density was determined in different brain structures by recording Hounsfield values.

RESULTS

The experiments revealed that CM diffused from the cisternae into the parenchyma, reaching a maximum at 5-24 h after injection. The density of the examined brain regions was still higher than the preinjection levels 24 h later. No differences in brain penetration were observed among the CM investigated.

CONCLUSION

The study has shown that iomeprol penetrates into the brain to the same extent as the most widely used myelographic CM.

Effects of iodinated contrast agents in MR imaging

PURPOSE

To investigate the effects of iodinated contrast agents in MRI.

MATERIAL AND METHODS

Twenty patients were examined with MRI immediately, 8 and 24 h after lumbar myelography. Signal intensities and calculated T1- and T2-relaxation times of different iodinated contrast agents, a dilution row of iopamidol, and a mixture of CSF and iotrolan were compared with physiological saline solution using different T1- and T2-weighted sequences. 1H-spectroscopy was performed with several solutions containing iodine or other substances.

RESULTS

A fluid-fluid level of the CSF existed in the lumbar dural sac in all patients immediately after lumbar myelography with a non-ionic iodinated contrast agent. Increased signal intensity on T1-weighted and decreased signal intensity on T2-weighted sequences was found for all contrast agents, as well as for the dilution row, compared with physiological saline solution. The structure of the side chains of the contrast agents is responsible for the T1- and T2-shortening effect.

CONCLUSION

It is important to be aware of the effect of iodinated contrast agents in MRI. To avoid misinterpretation of atypical findings, MRI of the spine should not be performed earlier than 24 h after myelography.

[Experimental study of flow rates in microcatheters using various kinds of contrast materials: comparison of imaging capability by iodine delivery rates]

In order to establish the optimal injection technique for abdominal digital subtraction angiography (DSA), flow rate measurement was performed under various combinations of all the currently available iodinated contrast materials with two types of coaxial microcatheters. In vitro study was done utilizing a plastic model of the abdominal aorta with the tip of the catheter positioned at the presumed proper hepatic artery. A total of 20ml of contrast material was injected by a pressure injector at a rate of 3 ml/sec at 300 or 600 psi, and actual flow volume was measured. Imaging capability was evaluated by calculating iodine delivery rates (IDRs). IDRs were highest in iopamidol 300 mgI/ml and iomeperol 300 mgI/ml, nonionic monomeric contrast materials of medium concentration. The results suggest that the best quality DSA images with injection to the proper hepatic artery using a coaxial microcatheter can be obtained with nonionic monomeric contrast materials of medium concentration.

Preclinical safety assessment of iomeprol for injection as contrast medium for myelography

A series of pharmaco-toxicological investigations were carried out in animals in order to assess the neurotolerance of iomeprol, a new nonionic iodinated contrast medium. After intrathecal administration iomeprol was completely eliminated from the cerebrospinal fluid, rapidly cleared from the plasma and excreted unchanged through the kidneys. When administrated intrathecally, iomeprol did not significantly alter the behavioural functions or the physiological activities of the brain. Unlike other contrast media, iomeprol was devoid of any epileptogenic activity. The acute neurotoxicity of iomeprol was comparable with that of iopamidol, but less than that of iohexol, iotrolan and iodixanol. Iomeprol was well tolerated in both rats and dogs following weekly intrathecal administrations for four weeks of doses up to three times higher than those foreseen for clinical use. High neurotolerance in animals and favourable physico-chemical characteristics make iomeprol particularly suitable as a contrast medium for both myelography and cerebral ventriculography.

Pharmacokinetics and tissue distribution of iomeprol in animals

The pharmacokinetics of iomeprol, a new triiodinated nonionic radiographic contrast agent, has been studied in rats, rabbits and dogs. Following intravenous administration, iomeprol did not bind measurably to plasma proteins and was rapidly excreted in unchanged form, mostly through the kidneys. The compound was rapidly distributed to the plasma and thence to the extracellular spaces. Iomeprol did not accumulate in specific organs or tissues except for those involved in its elimination, i.e. the kidneys and the liver. However, 24 h after administration, less than 1% of the injected dose remained in the tissues. The overall profile was very similar to the published profiles of other radiographic contrast agents used in uroangiography.

Effect of steroids on iopamidol blood-brain transfer constant and plasma volume in brain tumors measured with X-ray computed tomography

Tumor blood-brain transfer constant of iopamidol (K) and plasma volume (Vp) were measured in 10 patients with primary brain tumors before and after 7 days of dexamethasone treatment (4 x 4 mg per oral per day) using X-ray computed tomography. Both K and Vp decreased significantly after dexamethasone treatment with p < 0.01 and 0.09 respectively according to one-tail paired t-test. The mean percentage decrease in K and Vp was 32% and 10% respectively. Functional images of the two parameters before and after treatment were generated and showed clearly the effect of steroids on the reduction of K in brain tumors. In contrast, when before and after treatment contrast enhanced CT scans were compared, no difference was observed in the enhancement in 8 out of 10 cases. The result obtained support the conclusion that: (1) corticosteroids reduce the blood-brain permeability to small hydrophilic molecules; (2) the X-ray computed tomography method we have developed can be used to measure the K and Vp response of brain tumors to steroid therapy; and, (3) ordinary contrast enhanced CT scans at one fixed time or multiple times after contrast injection are not sensitive in detecting the reduction of K due to steroids.

[Experimental study on vascular permeability and hemodynamics of nonionic dimeric contrast media (Iotrolan): a comparison to nonionic monomer on dynamic CT and angiography]

The difference of vascular permeability and hemodynamics between Iotrolan and Iopamidol was experimentally studied on dynamic CT and angiography. A hemodialyzer with 60 A pores were applied as a phantom of a target organ with capillaries and extravascular space. Dynamic CT scans and DSA of the phantom were performed with injection of each contrast medium and time-density curves obtained from several regions of interest were compared. The dynamic CT scans performed at 40 seconds after the completion of injection, showed that Iopamidol was mostly distributed at the site of inlet, while Iotrolan was mostly at the center of the phantom. Time-density curves on DSA with Iotrolan revealed lower and shorter peak density and time than did Iopamidol. In conclusion, Iotrolan has lower permeability than that of Iopamidol because of its larger molecular size. Iotrolan has slower flow through catheters and capillaries than that of Iopamidol because of its higher viscosity. One should be aware the difference between the two contrast media and be careful to the analysis of time-density curves of dynamic CT and DSA.

Effects of diatrizoate and iopamidol on spermatogenesis

RATIONALE AND OBJECTIVES

The biological effects of iodinated contrast media were examined by using spermatogenesis in mouse testis as the experimental model.

METHODS

Spermhead survival and abnormality assays were used as the biological end points. Diatrizoate meglumine/diatrizoate sodium and iopamidol were administered intravenously at equal rates and concentrations. Testicular uptake and clearance of these contrast agents were examined by high-performance liquid chromatography techniques. Appropriate mannitol solutions were employed as osmolality controls.

RESULTS

Intravenous administration of the contrast agent or its respective mannitol control resulted in approximately a 30% decrease in spermhead count. A dose-related experiment with mannitol demonstrated that the spermhead count decreased rapidly until 600 mOsm/kg was reached, beyond which this decrease was minimal. Clearance of both contrast media was complete in approximately 4 hours. No significant increase in the induction of spermhead abnormalities was observed.

CONCLUSION

Osmotic substances, such as iodinated contrast agents, affect the process of spermatogenesis.