The effects of water soluble contrast agents on the respiratory tract

The water soluble contrast agents Gastrografin (Sodium diatrizoate and meglumine diatrizoate, Schering, Berlin), Iopamiro 300 (Iopamidol, Schering, Berlin), and Dionosil Aqueous (propyliodone BP, Glaxo, England) were instilled into the tracheobronchial tree of rats in doses of either 0.1 ml and 0.25 ml. Rats being used as controls, underwent sham operations with the instillation of air instead of contrast agent. In all, 85 rats were used. All rats that had not already died from the effects of contrast agent were sacrificed 30 minutes after instillation. The relative effects of the contrast agents were measured by comparing: 1. survival time; 2. radiographic effects of the contrast agents on the lungs and; 3. pathological changes as estimated by post mortem lung section and microscopy. The least toxic agent was the one with the lowest osmotic activity, namely Aqueous Dionosil. It is therefore recommended that Aqueous Dionosil be used in preference to Gastrografin or Iopamidol for studies of the oesophagus whenever there is a danger of aspiration of contrast agent into the tracheobronchial tree.     

Experimental evaluation of various available contrast agents for use in the upper gastrointestinal tract in case of suspected leakage: effects on mediastinum

The tissue reaction of seven contrast agents--pure barium sulphate, Micropaque, Hytrast, Dionosil, Gastrografin, Amipaque and Hexabrix-was evaluated on the mediastinum of rats. This work was undertaken to define the most suitable and safe contrast agent for use in the upper gastrointestinal tract in cases where leakage outside the gut into the mediastinum, pleura or peritoneal cavity may be suspected and aspiration may be an accompanying risk. Keeping in mind the danger of aspiration, Hexabrix and Amipaque appear to be the safest contrast media for the mediastinum.     

In vitro evaluation of alternative oral contrast agents for MRI of the gastrointestinal tract

PURPOSE: In vitro evaluation of different materials as potential alternative oral contrast agents for small bowel MRI. MATERIALS AND METHODS: The T1 and T2 relaxation times of rose hip syrup, black currant extract, cocoa, iron-deferoxamine solution and a commonly used oral contrast material (1 mM Gd-DTPA) were determined in vitro at different concentrations on a 1.0 T clinical MR scanner. T1 values were obtained with an inversion prepared spoiled gradient echo sequence. T2 values were obtained using multiple echo sequences. Finally the materials were visualized on T1-, T2- and T2*-weighted MR images. RESULTS: The relaxation times of the undiluted rose hip syrup (T1=110+/-5 ms, T2=86+/-3 ms), black currant extract (T1=55+/-3 ms, T2=39+/-2 ms) and 5 mM iron-deferoxamine solution (T1=104+/-4 ms, T2=87+/-2 ms) were much shorter than for a 1mM Gd-DTPA solution (T1=180+/-8 ms, T2=168+/-5 ms). Dilution of black currant extract to 30% or a 3 mM iron-deferoxamine solution conducted to T1 relaxation times which are quite comparable to a 1 mM Gd-DTPA solution. Despite its much lower metal content an aqueous cocoa suspension (100 g/L) produced T2 relaxation times (T1=360+/-21 ms, T2=81+/-3 ms) more or less in the same range like the 5 mM iron-deferoxamine solution. Imaging of our in vitro model using clinical sequences allowed to anticipate the T1-, T2- and T2*-depiction of all used substances. Cocoa differed from all other materials with its low to moderate signal intensity on T1- and T2-weighted sequences. While all substances presented a linear 1/T1 and 1/T2 relationship towards concentration, rose hip syrup broke ranks with a disproportionately high increase of relaxation at higher concentrations. CONCLUSIONS: Rose hip syrup, black currant extract and iron-deferoxamine solution due to their positive T1 enhancement characteristics and drinkability appear to be valuable oral contrast agents for T1-weighted small bowel MRI. Cocoa with its differing relaxation and signal enhancement properties is a promising oral contrast agent but needs further clinical evaluation.     

Epileptogenic effects of radiographic contrast agents: experimental study

Electrical activity in cells directly exposed to water-soluble radiographic contrast agents was investigated by intracellular recordings from neurons of the abdominal ganglia of Aplysia. Measurements of membrane resting potential, membrane conductance, synaptic and action potential configuration, and spontaneous electrical activity were performed. Test solutions included sodium diatrizoate, meglumine iothalamate, metrizamide, and control solutions. Solutions (100 and 200 mOsm) of these agents did not significantly alter resting membrane potential, membrane conductance, action potential frequency or configuration, or excitatory postsynaptic potentials. Inhibitory postsynaptic potentials were suppressed by contrast agents. These results suggest that contrast agents affect at least some neurons by disinhibition.     

口服不同对比剂对PET／CT胃肠道充盈及FDG摄取影响

目的 比较PET／CT显像前口服泛影葡胺、甘露醇和清水对胃肠道显示和脱氧葡萄糖（FDG）摄取的差异。方法将61例无胃肠道疾病行PET／CT显像的患者按随机数字法分成3组,组1（25例）显像前口服质量分数1％泛影葡胺1L;组2（20例）显像前口服质量分数2．5％甘露醇1L;组3（16例）显像前口服清水1L。患者注射18F—FDG（按体质量5．55MBq/kg）后50min应用二维（2D）模式进行PET／CT显像。由3位核医学科医师分别应用目测分析法将胃肠道充盈状态和FDG摄取情况分为4类：无、轻度、中度和重度。应用秩和检验、配对t检验对相关数据进行统计学分析。结果组2患者口服甘露醇前后血糖和血胰岛素水平差异无统计学意义。组2患者胃肠道充盈好于组1;除直肠外,其余部位充盈状态好于组3。组1患者胃、空肠、升结肠和横结肠充盈状态好于组3患者。组3患者胃、空肠和回肠FDG摄取程度高于组2患者（z=-3．192,-3．290,-3．290,P〈0．05）;空肠FDG摄取高于组1（z=-3．603,P〈0．05）,升结肠FDG摄取低于组1（z=-2．706,P〈0．05）,横结肠和降结肠FDG摄取均明显低于其他2组（Z=-3．503,-2．403,-4．223,-4．027,P〈0．05）,直肠FDG摄取明显低于组2（Z=-4．128,P〈0．01）。组1患者胃、空肠、回肠和升结肠最大CT值分别为（132±23）,（191±31）,（313±47）和（374±53）HU,差异有统计学意义（t=-7．088～-1．781,P〈0．01）。结论口服甘露醇作为增强剂胃肠道充盈好,FDG生理性摄取相对较低。     

Formulation of radiographically detectable gastrointestinal contrast agents for magnetic resonance imaging: effects of a barium sulfate additive on MR contrast agent effectiveness.

Complete and homogeneous distribution of gastrointestinal (GI) contrast media are important factors for their effective use in computed tomography as well as in magnetic resonance (MR) imaging. A radiographic method (using fluoroscopy or spot films) could be effective for monitoring intestinal filling with GI contrast agents for MR imaging (GICMR), but it would require the addition of a radiopaque agent to most GICMR. This study was conducted to determine the minimum amount of barium additive necessary to be radiographically visible and to evaluate whether this additive influences the signal characteristics of the GICMR. A variety of barium sulfate preparations (3-12% wt/vol) were tested in dogs to determine the minimum quantity needed to make the administered agent visible during fluoroscopy and on abdominal radiographs. Solutions of 10 different potential GI contrast agents (Gd-DTPA, ferric ammonium citrate, Mn-DPDP, chromium-EDTA, gadolinium-oxalate, ferrite particles, water, mineral oil, lipid emulsion, and methylcellulose) were prepared without ("nondoped") and with ("doped") the barium sulfate additive. MR images of the solutions in tubes were obtained at 0.38 T using 10 different spin-echo pulse sequences. Region of interest (ROI) measurements of contrast agent signal intensity (SI) were made. In addition, for the paramagnetic contrast media, the longitudinal and transverse relaxivity (R1 and R2) were measured. A 6% wt/vol suspension of barium was the smallest concentration yielding adequate radiopacity in the GI tract. Except for gadolinium-oxalate, there was no statistically significant difference in SI for doped and non-doped solutions with most pulse sequences used. In addition, the doped and nondoped solutions yielded R1 and R2 values which were comparable. We conclude that barium sulfate 6% wt/vol added to MR contrast agents produces a suspension with sufficient radiodensity to be viewed radiographically, and it does not cause significant alteration in the MR signal appearance of most GICMR. These formulations can be useful for achieving optimal filling of the gastrointestinal tract prior to MRI.     

Detection of pharyngeal perforation: comparison of aqueous and barium-containing contrast agents

OBJECTIVE: We sought to assess the value of aqueous and barium-containing contrast agents in the detection of pharyngeal perforation. SUBJECTS AND METHODS: Visual and objective in vitro comparisons of an iodinated aqueous contrast agent, a 50% weight/volume barium suspension, and a 100% weight/volume barium suspension were performed. Moreover, to exclude pharyngeal perforation after surgery, we prospectively examined 109 patients by pharyngography, using the aqueous contrast agent and the 100% weight/volume barium suspension. All patients with a pharyngeal perforation were followed up clinically to exclude complications due to barium application. RESULTS: As opposed to the 100% weight/volume barium suspension, in vitro comparison between the aqueous contrast agent and the 50% weight/volume barium suspension yielded no substantial differences. Seventeen perforations could be detected with the aqueous contrast agent. Although 10 of 17 perforations could be slightly better visualized with the 100% weight/volume barium suspension, two perforations were missed with this agent. Five perforations were equally well detected with both. CONCLUSION: Because of a higher radiopacity, 100% weight/volume barium suspensions may more sharply delineate perforations. However, in contrast to aqueous contrast media, narrow pharyngeal perforations can be missed. Thus, the use of a 100% weight/volume barium suspension does not improve the detection of pharyngeal perforation.     

The radioprotective effects of vasopressin on the gastrointestinal tract of mice.

Three-hundred Balb/C mice were used to assess the effect of vasopressin on the response of the gastrointestinal tract to irradiation. Median lethal doses were determined for control and vasopressin treated animals in which the whole abdomen was irradiated. There was a significant difference in LD50/6 (882 +/- 27 for controls vs. 1051 +/- 23 for vasopressin-treated animals). In addition studies demonstrated a significant difference in the survival rate of jejunal crypts at 800 and 1,000 rads.     

Experimental evaluation of various available contrast agents for use in the gastrointestinal tract in case of suspected leakage. Effects on peritoneum

The effects of seven contrast agents were studied on the peritoneum of rats in order to find the most suitable and safe contrast agent in cases where leakage might be expected from the gastrointestinal tract into the peritoneal cavity. Hexabrix appeared to give the least tissue reaction, with Amipaque and Gastrografin in second place (but not significantly different statistically).     

Experimental evaluation of various available contrast agents for use in the gastrointestinal tract in case of suspected leakage. Effects on pleura

Intrapleural injections of seven contrast agents were carried out in experimental rats in order to find a safe contrast agent to use in the radiological examination of the upper gastrointestinal tract in cases where leakage outside the upper gastrointestinal tract into the pleural space could be suspected, particularly post-operatively. The contrast agent in such cases could enter the mediastinum, pleura, peritoneum or lungs and bronchi. Hexabrix (May and Baker) and Gastrografin (Schering AG) produced the least tissue reaction in the pleura. Due to the potential risk of aspiration in such cases Gastrografin is not suitable as it is known to produce significant reaction in the lungs and may even prove to be fatal. Hexabrix, therefore, appears to be the safest contrast agent where leakage into the pleural space may be suspected.     

The effects of incremental brightness and contrast adjustments on radiographic data: a quantitative study

OBJECTIVES: To determine the border level of brightness and contrast changes in order to prevent the loss of originality of the quantitative data on digital dental radiographs. METHODS: After measuring the baseline mean grey values (MGVs) of a fixed region of interest on the alveolar bone and an aluminium step wedge, incremental brightness and contrast adjustments were performed on a digital periapical radiograph. The distribution of the data was analysed to investigate the significance of the changes on radiodensitometric data after incremental increase of brightness and contrast. RESULTS: The original MGVs were easily retrieved after brightness adjustments; however, the contrast increase led to more complicated density changes. The originality of the data was saved up to 50 units of contrast increase, but further than this limit, significant radiodensitometric changes occurred. CONCLUSIONS: Contrast adjustments should be performed cautiously when making quantitative analyses on the digital radiographs.     

Neurotoxic effects of water-soluble contrast agents on rat hippocampus

Electrical activity in cells directly exposed to water-soluble radiographic contrast agents was investigated by intracellular and extracellular recordings from neurons in in vitro rat hippocampus slices. Measurements included extracellular field potentials, intracellular resting membrane potential and membrane conductance, postsynaptic events, action potential configurations and spontaneous electrical activity. The neurons were exposed to test solutions of an ionic contrast agent, sodium diatrizoate, and a nonionic contrast agent, metrizamide, as well as control solutions. The ionic contrast agent produces bursts of action potentials having epileptogenic characteristics which is temporally followed by a depression of all electrical activity. The nonionic contrast agent produces minimal convulsive-like electrical bursts, but does produce a consistent depression of transmembrane electrical potentials, though in a lesser degree than the ionic contrast agents. The excitatory electrical events appear to be related to large depolarizing post-synaptic events while the later electrical depression is at least partially due to hyperpolarization. The depressing effects may be related to the hyperosmolality of the test solutions; however, no excitatory changes are related to hyperosmolality. These results provide the initial data on the neurotoxicity of water-soluble contrast agents at the intraneuronal level.     

Experimental evaluation of various available contrast agents for use in the upper gastrointestinal tract in case of suspected leakage. Effects on lungs

The reactions of seven contrast agents--pure barium sulphate, Micropaque, Gastrografin, Dionosil, Hytrast, Amipaque and Hexabrix--on the bronchi and lungs of rats were studied. This work was undertaken to find a safe gastrointestinal contrast agent for use in post-operative patients where aspiration may be an accompanying risk. Amipaque and Hexabrix produced no significant histological reaction in the lungs and would, therefore, appear to be suitable for use in such cases.     

The non-ionic dimers: a new class of contrast agents

Non-ionic dimers are a new class of iodinated radiological contrast agents. Some physico-chemical and pharmacological properties of three representative compounds are presented. Non-ionic dimers are iso-osmolar with plasma at all iodine concentrations unless diluted with saline and in terms of chemotoxicity they appear to be closely comparable with the established non-ionic monomeric agents. It is shown that the data lend support to the theory that it is the degree of steric hindrance of the hydrophobic iodine atoms by side-chains which determines this chemotoxicity. Areas in which agents of this type may find applications are indicated.     

Three new low-osmolality contrast agents: a comparative study of patient discomfort

Relative patient discomfort resulting from carotid injections of three new low-osmolality contrast agents was assessed in 78 patients. Omnipaque-300 (iohexol), Isovue-300 (iopamidol), and hexabrix (ioxaglate) were sequentially injected into both common carotid arteries of each patient. Patients were asked to rank the relative intensities of the three injections on each side. Mean patient rankings revealed that Hexabrix was preferred most often, Omnipaque-300 next, and Isovue-300 the least. The differences are statistically significant. We conclude that while patients usually tolerated all intracarotid low-osmolality contrast agents rather well, the agent preferred most often was Hexabrix.