Use of additives to contrast media to improve imaging in plain film and computed tomography urography

RATIONALE AND OBJECTIVES: To investigate the effects of additives to iodinated radiograph contrast agents on image quality in plain film and CT urography. MATERIALS AND METHODS: Urea (52 mg/mL), iloprost (10, 20, 50, and 100 ng/mL), nifedipine (0.02 mg/mL), papaverine (0.625 mg/mL) and sodium nitroprusside (0.05 microg/mL) were added to commercial iopromide (300 mg/mL) and iotrolan preparations (280 mg/mL) and plain film urograms were obtained at different time points after contrast injection in rabbits and dogs at iodine doses of 300 or 600 mg/kg body weight. The experiments were repeated in rabbits using CT imaging and iopromide or iotrolan plus urea (52 mg/mL) or iloprost (20 ng/mL) and iodine doses of 50 mg/kg body weight. RESULTS: Urea and iloprost at low concentrations (10 and 20 ng/mL) increased image quality both in plain film and in CT urography. Iloprost at high concentrations (50 and 100 ng/mL), nifedipine, papaverine and sodium nitroprusside decreased image quality. An increase in image quality was accompanied by faster renal elimination of the contrast agent. CONCLUSION: Image quality in plain film and CT urography might be improved by additives to the contrast medium. More data, particularly on dose-response relationships are needed.     

Contrast media-induced renal morphologic lesions during experimental hemorrhagic necrotizing pancreatitis.

RATIONALE AND OBJECTIVES. Contrast media-induced renal morphologic changes were studied in rats. Hemorrhagic pancreatitis was induced as a means of sensitizing the animals to the effects of contrast media. METHODS. The histologically verified hemorrhagic pancreatitis was induced in Wistar rats (n = 66) by injecting 6% sodium taurocholate into the pancreatic duct. After 2 hours, the animals received intravenously 1.0 or 3.0 g iodine/kg of high-osmolal osmolal diatrizoate, low-osmolal iopromide or iohexol, iso-osmolal iotrolan or 0.2 or 0.6 g/kg of high-osmolal magnetic resonance contrast agent, gadolinium-DTPA (Gd-DTPA). Control animals received physiologic saline. The kidneys were fixed by perfusion 2 hours later, and the morphologic changes were reviewed by two independent observers blinded to the injected agent. RESULTS. The smaller dose of iohexol and the larger dose of all the contrast media induced a statistically significant (P < .001 or .01) cytoplasmic vacuolization in the proximal convoluted tubule (PCT) cells. The nonionic, low- and iso-osmolal contrast media caused as much or even significantly more vacuolization than diatrizoate. CONCLUSIONS. Hemorrhagic pancreatitis potentiates the contrast media-induced renal morphologic changes, which depend on the type and dose of the injected contrast media.     

A new animal model for testing renal tolerance of contrast agents

RATIONALE AND OBJECTIVES: To develop a new animal model for the evaluation of the renal tolerance of contrast agent and its application to diatrizoate and iotrolan injections in comparison to saline and mannitol solution. MATERIALS AND METHODS: The nephrotoxic potential of intravenously injected contrast agents in Beagle dogs was determined from the effects on the pharmacokinetics of creatinine injected immediately after these agents in comparison with the kinetics of creatinine injected alone. The kinetic parameters evaluated included plasma half-life, volume of distribution, and clearance. In a series of studies, the experimental conditions were optimized in terms of creatinine dose and the effects of diatrizoate, iotrolan, saline, and mannitol solution on the pharmacokinetic parameters of creatinine were determined. RESULTS: Bolus injection of creatinine into dogs followed a dose-linear pharmacokinetic behavior with a terminal half-life of 90 minutes (10 mg/kg) and 108 minutes (20 mg/kg), respectively, and a clearance of 5 mL/min/kg. Injection of diatrizoate decreased the clearance and the half-life of creatinine significantly. A mannitol solution with the same osmolality as diatrizoate showed the same effect whereas physiological saline did not affect pharmacokinetic parameters of creatinine. The isotonic iotrolan was intermediate between saline and diatrizoate in its effects on creatinine clearance. CONCLUSION: The effect of contrast agents on pharmacokinetic parameters of creatinine injected immediately after the administration of the agents in dogs might be a useful model for the evaluation of renal tolerance. In a cross-over study, iotrolan was not statistically separable from diatrizoate.     

脑血氧饱和度的近红外光谱测量技术及其在超重条件下的应用

目的：用近红外光谱技术对加速度作用后(超重条件下)的大鼠进行脑血氧饱和度(％SaO2)的无损监测。方法：制作头部不同程度缺血缺氧模型，抽血测量其血氧饱和度，并计算出与正常组之间的差值。同时测定出在850nm和760nm波长处缺血缺氧模型的光谱吸收强度，计算出与正常组之间的差值，并绘制出两者之间的关系曲线。根据关系曲线，通过用近红外光谱仪监测高 Gz和推拉动作后的光谱吸收强度，计算出与0 Gz组差值，推测出加速度作用后脑血氧饱和度。结果：由关系曲线推测出加速度作用后，大鼠脑血氧饱和度降低；推拉动作后，脑血氧饱和度降低更为明显。结论：根据关系曲线，用近红外光谱技术可以无损监测脑血氧饱和度的变化。     

Enhancement of the relative uptake of 18F-FDG in mouse fibrosarcoma by rolipram

The effect of rolipram, a selective phosphodiesterase type 4 inhibitor, on the uptake of 18F-fluorodeoxyglucose (18F-FDG) in tumor tissue was examined in mice transplanted with NFSa fibrosarcoma. The uptake indexes of 18F-FDG in the heart, skeletal muscle and brain remarkably decreased after treatment with 3 mg/kg of rolipram (heart: 13%, skeletal muscle: 14%, brain: 31%), but fibrosarcoma tissue showed only a 50% reduction in the uptake index of 18F-FDG. The tumor/muscle ratio of radioactivity 30 min after 18F-FDG injection was consequently enhanced from 1.9 to 6.5 by rolipram. This indicates the possible use of rolipram to enhance the sensitivity of tumor detection, as well as characterization of tumors in 18F-FDG PET.     

A micropuncture assessment of the effects of contrast media of different osmolality

The pathophysiology of radiographic contrast media-induced acute renal failure is unclear. Different causes are suggested, including hypertonicity, charged molecules, and toxicity of the media. This study deals with hemodynamic changes after injection of contrast media of high osmolarity iohexol, and metrizoate. Proximal tubular free-flow and stop-flow pressure (Psf), (the latter a marker of glomerular capillary pressure) were measured before, during, and afer injection of contrast media into the renal artery, compared with saline injection, in both normal rats and rats with ureteral obstruction (UO). Urine and electrolyte excretion also were examined. Metrizoate caused an initial decrease in Psf, from 37 to 20 mm Hg, followed by an increase to 81 mm Hg, and the value remained high for 10 minutes. During UO, the elevation of Psf was prolonged. Iohexol injection had a less marked effect. The change in glomerular capillary pressure may be dependent on the osmolarity of the contrast agent.     

Accuracy and safety of carbon dioxide inferior vena cavography.

PURPOSE: The purpose of this study was to assess the accuracy of carbon dioxide compared to iodinated contrast material for determining inferior vena cava (IVC) diameter prior to filter placement, and to assess the safety of CO2 when used for this purpose. PATIENTS AND METHODS: Consecutive patients undergoing inferior vena cavography prior to filter placement were prospectively evaluated with use of both CO2 and iodinated contrast material. The diameter of the IVC was measured and compared in the same four locations in each patient for both agents. The diameter was corrected for magnification and pin-cushion distortion. The ability of CO2 to correctly classify IVC diameter as < or =28 mm or >28 mm, based on the IVC diameter with iodinated contrast material, was determined. A consensus panel assessed renal vein visualization with CO2 and iodinated contrast material. Blood pressure and arterial oxygen saturation were measured immediately before and after CO2 injection. RESULTS: Among 30 patients, there was no significant difference in the measured diameter of the IVC with CO2 versus iodinated contrast material after correction for magnification and pin-cushion distortion. One of 30 patients (3.3%) in this study was misclassified as having an IVC < or =28 mm with CO2 when, in fact, the IVC diameter was >28 mm based on iodinated contrast material. This could be clinically significant for certain IVC filters. Forty-seven percent of renal veins identified on contrast venography were identified by CO2 vena cavography. There was no significant difference in the blood pressure or oxygen saturation values measured before and after CO2 injection. However, one patient with pulmonary artery hypertension did experience transient, symptomatic hypotension after CO2 injection. CONCLUSIONS: In most patients, CO2 vena cavography accurately evaluated IVC diameter prior to filter placement. In 3.3% of patients, the discrepancy in measurements between CO2 and iodinated contrast material could be clinically significant, depending on the type of filter placed. CO2 was less accurate than iodinated contrast material in identifying renal veins. Although CO2 vena cavography is safe in the majority of patients, it should be used with caution in patients with pulmonary hypertension.     

Monitoring tissue oxygen availability with near infrared spectroscopy (NIRS) in health and disease

Near infrared spectroscopy (NIRS) is becoming a widely used research instrument to measure tissue oxygen (O2) status non-invasively. Continuous-wave spectrometers are the most commonly used devices, which provide semi-quantitative changes in oxygenated and deoxygenated hemoglobin in small blood vessels (arterioles, capillaries and venules). Refinement of NIRS hardware and the algorithms used to deconvolute the light absorption signal have improved the resolution and validity of cytochrome oxidase measurements. NIRS has been applied to measure oxygenation in a variety of tissues including muscle, brain and connective tissue, and more recently it has been used in the clinical setting to assess circulatory and metabolic abnormalities. Quantitative measures of blood flow are also possible using NIRS and a light-absorbing tracer, which can be applied to evaluate circulatory responses to exercise along with the assessment of tissue O2 saturation. The venular O2 saturation can be estimated with NIRS by applying venous occlusion and measuring changes in oxygenated vs. total hemoglobin. These various measurements provide the opportunity to evaluate several important metabolic and circulatory patterns in very localized regions of tissue and may be fruitful in the study of occupational syndromes and a variety of diseases.     

Validation of in Vivo MR Measurement of Oxygen Saturation after Resuscitation with a Hemoglobin-Based Oxygen Carrier in a Rabbit Model

RATIONALE AND OBJECTIVES: The authors tested whether noninvasive magnetic resonance (MR) oximetry is accurate in the in vivo measurement of oxygen saturation in a stroma-free, hemoglobin-based oxygen carrier (HBOC). MATERIALS AND METHODS: A central venous catheter was placed in the inferior vena cava (IVC) of 10 New Zealand white rabbits (weight range, 2.5-3.2 kg). Each rabbit underwent removal of 20% of blood volume followed by resuscitation with 10 mL/kg of bovine HBOC-200. Oxygen saturation of the blood mixture was measured in vivo at the IVC with MR oximetry, with separate in vitro calibration for each animal. Blood drawn from the IVC was measured with ex vivo oximetry, which was used as the standard of reference. The in vivo and ex vivo measurements were compared. RESULTS: There was no significant difference (P > .1) between measurements obtained with MR oximetry and ex vivo oximetry. The results with in vivo MR oximetry demonstrated excellent correlation with those from ex vivo oximetry (r = 0.99) over a wide range of physiologic oxygen saturation values (16.7%-74.9%) in venous blood. CONCLUSION: Noninvasive in vivo MR measurement of oxygen saturation is valid for whole blood mixed with stroma-free hemoglobin. Therefore, MR oximetry may be clinically useful for assessing the oxygenation status in patients resuscitated with a HBOC.     

Artificial oxygen carriers--the new doping threat in endurance sport?

Maximal oxygen uptake is the major performance limiting factor in endurance sports. Sophisticated training methods have been developed to increase this variable. On the other hand, attempts have been made to improve maximal oxygen uptake by artificial means: blood doping and the misuse of recombinant human erythropoietin have beneficial effects on aerobic exercise capacity. Both methods have been banned by international sporting federations. A new class of substances might represent the next step of fraudulent improvement of the maximal oxygen uptake: artificial oxygen carriers, such as solutions based on recombinant, bovine or human hemoglobin and perfluorocarbon-emulsions have been shown to improve oxygen delivery to the muscle. Hemoglobin-based solutions improve aerobic exercise capacity in animal and human testing. Both substances have potentially lethal side effects including renal toxicity, increased systemic and pulmonary blood pressure and impairment of the immune system. Hemoglobin-based carriers can be detected in drug testing with routine laboratory tests based on the detection of free hemoglobin. Perfluorocarbon is not metabolized by the body and exhaled through the lung and can be measured with chromatography. No screening for these substances in drug tests has been performed so far. International sporting federations should be aware of this new, emerging doping threat.     

Three-dimensional rotational angiography of transplanted renal arteries: influence of an extended angle of rotation on beam-hardening artifacts

PURPOSE: To investigate whether three-dimensional rotational angiography (3D-RA) of the transplant renal artery performed with an extended angle of rotation can reduce beam-hardening artifacts in 3D reconstructed images without image quality being lost or side effects to the transplanted kidney being increased. MATERIAL AND METHODS: 3D-RA with a C-arm rotation of 180 degrees was performed consecutively in 12 renal transplanted patients with suspicion of renal artery stenosis. A 1.7-mm balloon occlusion catheter was placed using the crossover technique and this was compared to a protocol with 160 degrees rotation and a traditional 1.4-mm catheter in 10 patients. The occurrence of beam-hardening artifacts was registered and the effects of the reduced contrast load on image quality and of arterial occlusion on renal function were assessed. RESULTS: The extended angle of rotation, from 160 degrees to 180 degrees, reduced the beam-hardening artifacts. Artifacts were observed in 4/11 patients (36%) in the study group and in all 10 (100%) of the controls. There was no statistical difference regarding image quality between the two protocols. Renal function was equally affected in both protocols. CONCLUSION: 3D-RA with an extended C-arm rotation reduced the beam-hardening artifacts. Image quality was not reduced despite the reduced contrast medium load. The different protocols had no effect on patient outcome.     

Cardiovascular effects of polymethylmethacrylate use in percutaneous vertebroplasty

BACKGROUND AND PURPOSE: Previous investigators have described an association between polymethylmethacrylate (PMMA) use in hip arthroplasty and cardiovascular derangement. Our purpose was to evaluate the effects of PMMA injection on patient vital signs during percutaneous vertebroplasty. METHODS: We retrospectively reviewed patient charts at our institution to gather blood pressure, heart rate, and arterial oxygen saturation data for the following time points: before, during, 5 minutes after, and 10 minutes after PMMA injection during percutaneous vertebroplasty. These data were obtained for 142 injections (78 patients), and preinjection vital signs were compared with vital signs during and after PMMA injection. Multivariable regression modeling was used to ascertain the effects of cardiopulmonary comorbidities on vital signs. RESULTS: Mean arterial blood pressure and heart rate during, 5 minutes after, and 10 minutes after PMMA injection were not significantly different from their respective preprocedure values (P =.19-.92). Values for oxygen saturation during PMMA injection and 5 minutes thereafter were not significantly different from preprocedure values (P =.80 and.89, respectively). Oxygen saturation was significantly lower at 10 minutes after injection than before injection (P =.007), although the mean difference was negligible (0.6%). CONCLUSION: We find no generalized association between PMMA injection during percutaneous vertebroplasty and systemic cardiovascular derangement.     

Sources of absorption and scattering contrast for near-infrared optical mammography

RATIONALE AND OBJECTIVES: Near-infrared (NIR) diffuse optical spectroscopy and imaging may enhance existing technologies for breast cancer screening, diagnosis, and treatment. NIR techniques are based on sensitive, quantitative measurements of functional contrast between healthy and diseased tissue. In this study, the authors quantified the origins of this contrast in healthy breasts. MATERIALS AND METHODS: A seven-wavelength frequency-domain photon migration probe was used to perform noninvasive NIR measurements in the breasts of 28 healthy women, both pre- and postmenopausal, aged 18-64 years. A diffusive model of light transport quantified oxygenated and deoxygenated hemoglobin, water, and lipid by their absorption signatures. Changes in the measured light-scattering spectra were quantified by means of a "scatter power" parameter. RESULTS: Substantial quantitative differences were observed in both absorption and scattering spectra of breast as a function of subject age. These physiologic changes were consistent with long-term hormone-dependent transformations that occur in breast. Instrument response was not adversely affected by subject age or menopausal status. CONCLUSION: These measurements provide new insight into endogenous optical absorption and scattering contrast mechanisms and have important implications for the development of optical mammography. NIR spectroscopy yields quantitative functional information that cannot be obtained with other noninvasive radiologic techniques.     

Renal effects of CO2 and iodinated contrast media in patients undergoing renovascular intervention: a prospective, randomized study

PURPOSE: CO2 gas has been proposed for use instead of iodinated contrast media in angiographic examinations in patients at risk of developing renal failure from contrast media. The influence of intraarterial injection of CO2 with small added amounts of ioxaglate (200 mgI/mL) or ioxaglate alone on renal function in patients with suspected renal artery stenosis was studied in a prospective, randomized study. MATERIALS AND METHODS: One hundred twenty-three patients underwent renovascular intervention (n = 83) and/or renal angiography (n = 40) for suspected renal artery stenosis. Patients with a serum creatinine concentration less than 200 micromol/L (n = 82) were randomized prospectively to receive CO2 with small added amounts of ioxaglate (n = 37) or only ioxaglate (n = 45). Patients with serum creatinine levels greater than 200 micromol/L (n = 41) were not randomized and initially received CO2. Serum creatinine concentrations were measured within 1 day before and 1 day, 2 days, and 2-3 weeks after the procedure. RESULTS: The amount of injected CO2 did not relate to an increase in serum creatinine level. In the randomized groups, and also when the whole patient sample was considered, the amount of injected iodine was significantly correlated (P = .011) with an increase in serum creatinine level and a decrease in estimated creatinine clearance after 2 days. Among the randomized patients, one in the CO2 group and three in the ioxaglate group had a more than 25% increase in serum creatinine level within the first 2 days after the intervention. CONCLUSION: The risk of impairment of renal function is lower after injection of CO2 with small amounts of added ioxaglate compared with injection of a larger amount of ioxaglate alone. The larger the amount of administered iodinated contrast medium, the greater the risk of development of renal failure.     

A near-infrared spectrophotometric method for studying brain O2 sufficiency in man during +Gz acceleration

A technique for the noninvasive monitoring of cerebral oxygen status was evaluated on volunteer subjects on the USAF School of Aerospace Medicine centrifuge. By using multiwavelength near-infrared spectrophotometry, the instrumentation measured changes in the quantities of reduced and oxygenated hemoglobin (and their sum, an indicator of cerebral blood volume), and the quantity of oxidized cytochrome c oxidase within the forebrain. Tests used acceleration of up to 9 G with onset rates from 0.1 to 5.0 G.s-1, anti-G suits and straining maneuvers, and hyperoxic and hypoxic breathing mixtures. In general, +Gz acceleration produced a fall in blood volume within the cerebral microcirculation with a relative increase in the content of reduced hemoglobin and a tendency towards reduction of cytochrome c oxidase. These findings are discussed in relation to accepted changes in arterial blood pressure, cerebral blood flow, and arterial oxygen saturation caused by acceleration exposure.     

Preclinical findings with iotrolan: a short review

Iotrolan is a non-ionic hexa-iodinated dimeric contrast agent suitable for Ct enhancement, angiography, urography and the opacofocation of body cavities. It is more hydrophilic than any other X-ray contrast agent and is sweet to tast. Iotrolan 280 is isotnoc to blood and its pharmacokinetics are almost identical to other urographic contrast agents. The experiments reported in this review show very little protein binding, enzyme inhibition or injury to membranes of human erythrocytes, rat mast cells or cultured human enfothelial cells. Osmotically induced side effects, such as vascular pain, endothelial damage, disturbance of the blood-brain barner, vaso-contruction and hemodilution are greatly reduced or absent. In various studies in rats and dogs, the mechanical and electrical function of the heart and myocardial perfusion remained almost unaffected. In rats, renal tolerance of iotrolan was superior to that of a non-ionic monomer when the contrast agents were-infused into the renal arteries. The renal tolerance after intravenous injection depends on the anomal species and experimental conditions, with favorable results in most cases. The intravenous, LD 50 is very high and seems to be restricted more by physical overload of the animals tahn b osmotic or chemotoxic effects. Due to reduced osmotic diultion the contrast efficacy is slightly better than higher osmolality agents.     

Influence of Pretreatment Polarographically Measured Oxygenation Levels in Spontaneous Canine Tumors Treated with Radiation Therapy

BACKGROUND AND PURPOSE: The level of hypoxia in primary tumors has been described to influence response to treatment. The aim of the present study was to investigate the impact of pretreatment oxygen level measurements in spontaneous canine tumors on treatment outcome. MATERIALS AND METHODS: Data of pretreatment tumor oxygenation status and local tumor response after primary radiation therapy in a group of spontaneously occurring tumors in dogs (n=52) was collected. Radiation therapy was given with curative (14-17x3-3.5 Gy) or palliative intent (3x8 Gy or 4-5x6 Gy). Progression-free interval and overall survival were correlated to polarographically measured tumor oxygenation status. RESULTS: In the curatively irradiated group, tumors with median pO2 values相似文献   

Effects of hematocrit and oxygen saturation level on blood spin-lattice relaxation.

In the present study blood T(1) was determined as a function of hematocrit and oxygen saturation. T(1) showed a significant linear dependency on both of these parameters. In addition, oxygen dissolved in blood plasma in hyperoxygenated blood resulted in relaxation enhancement, comparable in size to that due to the change in oxygenation state of hemoglobin. As blood T(1) is a key factor for quantification of flow with arterial spin labeling methods, the influence of T(1) variation in the physiological range of hematocrit and oxygen saturation to flow determination is discussed.     

Use of transcranial cerebral oximetry to monitor regional cerebral oxygen saturation during neuroendovascular procedures.

Using transcranial cerebral oximetry, we monitored 30 patients who underwent cerebral angiography by the femoral route. Transcranial cerebral oximetry is a noninvasive technique of regional cerebral oxygen saturation measurement that uses near-infrared spectroscopy to differentiate oxyhemoglobin from reduced hemoglobin. Needle puncture, catheterization, and contrast media injection produced no significant peak changes in saturation from baseline. Acute and persistent decreases in oxygen saturation were associated with vascular complications and were detected before development of clinical symptoms. Greater changes in saturation were observed during several neuroendovascular procedures, indicating the development of complications, signaling a need to stop further endovascular manipulation.     

Mechanical Thrombectomy of Iliocaval Thrombosis Using a Protective Expandable Sheath

We report a case of successful percutaneous treatment of a subacute ilio-caval venous thrombosis in a 64-year-old female patient by using a novel combination of a rotatory fragmentation device (percutaneous thrombectomy device: PTD) and large wire basket (temporary Günther basket filter) under temporary caval filter protection using an expandable sheath. Because the patient had multiple myeloma with increased risk for contrast media-induced renal failure, the therapeutic angiographic procedure was performed without iodinated contrast medium. Non-contrast-enhanced MR venography (high-resolution True FISP) confirmed the effective thrombus removal by the percutaneous mechanical thrombectomy procedure.