Injection rate threshold of triple-lumen central venous catheters: an in vitro study

RATIONALE AND OBJECTIVES

Computed tomographic angiography (CTA) requires the rapid injection of contrast media ideally through an 18-gauge intravenous line in the antecubital fossa. Patients with CVCs undergoing CTA, however, are typically injected at low rates for two reasons: the potential for catheter failure and because of the lack of manufacturer recommendations for high injection rates typically used during CTA. The purpose of the study is to measure the injection rate thresholds of CVC. The results suggest that CVC can be used at high injection rates that are now typically used with peripheral intravenous catheters during CTA.

MATERIALS AND METHODS

We used 16-cm-long catheters and 20-cm-long catheters in six groups (n = 5 for each catheter length). After the catheters were placed into a water bath, each group was injected at 5, 10, 15, 20, 25, and 30 ml/sec. New contrast, pressure tubing, and catheters were used for each test.

RESULTS

No catheter ruptures were encountered during the experiment, but there was one episode of power injector tubing rupture during the injection of a 16-cm catheter at an injection rate of 30 ml/sec.

CONCLUSION

No catheter failures were demonstrated in this study using injection rates well above those used in conventional CTA. Power injector tubing failure was demonstrated at an injection rate of 30 ml/sec, which generated mean pressures in the 16-cm catheters of 920 psi (tubing rating per manufacturer is 300 psi). This study demonstrated no catheter or injector tubing failure at injection rates of 5 to 25 ml/sec.

A novel approach to flexor hallucis longus tenography

OBJECTIVE

This article presents a technically simple and more accurate approach to flexor hallucis longus (FHL) tenography than any we found reported in the literature.

CONCLUSION

Tenography is used to evaluate and treat tenosynovitis. Standard FHL tenography protocol involves either direct percutaneous access of the FHL synovial sheath posterior to the medial malleolus or indirect filling of the FHL sheath from an injection of the flexor digitorum longus (FDL) tendon sheath, which often communicates with the FHL tendon sheath. However, with these methods, difficulty entering the FHL sheath may be encountered. We adapted our technique to access the FHL sheath as it courses below the sustentaculum talus. Our early experience with five cases using this technique reflects a 100% success rate with accurate needle placement within the FHL tendon sheath, thereby improving procedural efficiency.

Prospective comparison of helical CT of the abdomen and pelvis without and with oral contrast in assessing acute abdominal pain in adult Emergency Department patients

PURPOSE

This prospective study compares the agreement of nonenhanced helical computed tomography (NECT) with oral contrast-enhanced computed tomography (CECT) in Emergency Department (ED) patients presenting with acute abdominal pain.

MATERIALS AND METHODS

One hundred eighteen patients presenting to the ED with acute abdominal pain undergoing CT were enrolled over a 13-month period using convenience sampling. Exclusion criteria included acute trauma, pregnancy, unstable patients, and patients suspected of having urinary calculi. Patients were scanned helically using 5-mm collimation before and approximately 90 min after oral contrast administration. Both exams were prospectively interpreted by different attending radiologists in a blinded fashion using an explicit data sheet specifying the presence or absence of 28 parameters relating to various common diagnoses.

RESULTS

The 118 patients had a mean age of 49 years, a male: female ratio of 7:13, and a median height, weight, and BMI of 166 cm, 80 kg, and 29, respectively. The most common indications for the study included appendicitis (32%) and diverticular disease (12%). Pain maximally localized to the right lower quadrant in 37% and the left lower quadrant in 21%. There were 21 patients that had significant disagreement of interpretations between NECT and CECT resulting in a simple agreement of 79% (95% CI: 70-87%). For specific radiologic parameters, agreement ranged from 77 to 100%. A post hoc agreement analysis was subsequently performed by two radiologists and only five paired scans were identified as discordant between the NECT and CECT. For only one of these patients did both radiologists agree that there was a definite discordant result between the two studies. A final unblinded consensus review demonstrated that much of the disagreement between the interpretations was related to interobserver variation.

CONCLUSION

There is 79% simple agreement between NECT and CECT in diagnosing various causes of acute abdominal pain in adult ED patients. Post hoc analysis indicates that a significant portion of the discordance was attributable to interobserver variability. This data suggests that NECT should be considered in adult ED patients presenting with acute abdominal pain.

Virtual Cystoscopy by Intravesical Instillation of Dilute Contrast Medium: Preliminary Experience

PURPOSE

We determined whether virtual cystoscopy based on helical data sets can yield urinary capabilities similar to those achieved by fiber-optic cystoscopy.

MATERIALS AND METHODS

A total of 11 patients with ultrasound detected bladder tumors underwent pelvic CT as a single volumetric scan after preliminary bladder distention with saline mixed with contrast medium using a 6Fr infant feeding tube. Cystoscopy was simulated based on a 3-dimensional helical CT data set in real time. Source raw CT data for virtual cystoscopy were reconstructed and navigation was done in real time using surface rendering navigation software. These images and findings were then compared with conventional cystoscopy findings.

RESULTS

An attenuation gradient of 350 HU between the vesical mucosa and urine was noted. Two of the 14 tumors (11 patients) were missed and each was 0.7 cm. All tumors greater than 0.9 cm were detected. Overall sensitivity was 85.7%. There were no false-positive findings. There was good correlation with tumor location and size. The ureteral orifices and their relationship to the tumor were also well appreciated. Subtle mucosal changes on conventional cystoscopy were not delineated by virtual cystoscopy.

CONCLUSIONS

Our method of instilling dilute contrast medium in the bladder offers an excellent attenuation gradient. The overall sensitivity of tumor detection is better than that reported for intravenous contrast medium and pneumocystoscopy.

Power Injection of Microcatheters: An In Vitro Comparison

PURPOSE

To determine the tolerance of 0.021-inch and 0.027-inch microcatheters to power injection in an in vitro flow model.

MATERIALS AND METHODS

Twenty-four microcatheters (0.021-inch, n = 13; 0.027-inch, n = 11) were injected with iothalamate meglumine through a flow model with use of a power injector and high-pressure tubing. Catheters used included Rebar (0.021-inch, n = 4; 0.027-inch, n = 4), Transit (0.021-inch, n = 3; 0.027-inch, n = 3), Renegade (0.021-inch, n = 4; 0.027-inch, n = 4), and Renegade STC-18 (0.021-inch, n = 2) models. Through the 0.021-inch microcatheters, 5-second injections were performed at an initial rate of 0.7 mL/sec. Injection rates were increased by 0.5 mL/sec and the process was repeated until the pressure approached 1,000 psi or catheter breakage occurred. A similar process was repeated for the 0.027-inch catheters starting at a rate of 3.4 mL/sec.

RESULTS

The 0.021-inch catheters were injected 303 times and the 0.027-inch catheters were injected 210 times. Three catheter failures occurred, with all breaks occurring at pressures greater than manufacturer recommendations. The 0.027-inch catheters as a group tolerated significantly higher injection rates than the 0.021-inch catheters. Of the 0.021-inch catheters, the STC-18 also provided superior maximum flow and volume compared with the Renegade catheter. The Rebar catheter tolerated significantly lower maximum injection rates and volumes than the other 0.027-inch catheters.

CONCLUSIONS

The majority of microcatheters can be power-injected in vitro at pressures far greater than manufacturer recommendations. When fractures occur, they are near the hub of the catheter. Significantly greater rates of injection are possible through 0.027-inch catheters.

Peak contrast enhancement in CT and MR angiography: when does it occur and why? Pharmacokinetic study in a porcine model

PURPOSE

To investigate pharmacokinetic and physiologic factors that determine the time to peak intravenous contrast medium enhancement in computed tomographic (CT) and magnetic resonance (MR) angiography in the porcine mid-abdominal aorta.

MATERIALS AND METHODS

Four pigs were imaged repeatedly in seven to eight sets: For each set, 20 dynamic CT scans were obtained at a fixed aortic level after intravenous injection of contrast medium. From a physiologically based compartment model, aortic contrast enhancement curves were generated by varying contrast medium injection duration from 1 to 40 seconds. Contrast enhancement curves and times to peak aortic enhancement from the experiment and model were compared. Time to peak aortic enhancement obtained from the injection with the shortest duration was considered the time to peak test bolus contrast enhancement. Mathematic and pharmacokinetic analyses were performed to investigate factors that determine peak enhancement.

RESULTS

Empiric and compartmental model times to peak aortic enhancement were in good agreement. Time to peak aortic enhancement corresponded to the weighted sum of injection duration and time to peak test bolus enhancement. With increasing injection duration, the relative contribution of injection duration to peak aortic enhancement time increased. When injection duration was longer than time to peak test bolus enhancement, time to peak aortic enhancement increased linearly with injection duration and occurred shortly after completion of injection. However, when injection duration was shorter than time to peak test bolus enhancement, time to peak aortic enhancement was determined predominantly by time to peak test bolus enhancement and only gradually increased with injection duration.

CONCLUSION

Time to peak aortic enhancement is determined by the relative contributions of injection duration and contrast medium traveling time and may well be explained by contrast medium volumetric inflow and recirculation physiology.

Comparative cytotoxicity of low-osmolar nonionic and high-osmolar ionic contrast media to dog gallbladder epithelial cells

BACKGROUND

Most studies of the adverse effects of x-ray contrast media used in ERCP have focused on post-ERCP pancreatitis. However, the biliary epithelial cells are also exposed to contrast media during ERCP and acute cholangitis is also a serious complication of ERCP. The present study compared the cytotoxicity with gallbladder epithelial cells of ionic and nonionic contrast agents.

METHODS

A high-osmolar ionic contrast agent (meglumine ioxithalamate) and a low-osmolar nonionic contrast agent (iopromide) were tested. Monolayer cell cultures of dog gallbladder epithelial cells were used. The cells were exposed to the 2 contrast agents with increasing iodine concentration and osmolality for 2 days. Cell number, S-phase fraction, aneuploidy, and supernatant LDH activities were measured each day.

RESULTS

Cell growth was more severely inhibited by ioxithalamate than iopromide (p < 0.05) and strongly dependent on the osmolality of contrast agent. The cytostatic effect estimated by S-phase fraction was more pronounced for ioxithalamate. Chromosomal damage determined by aneuploidy was more frequently detected with ioxithalamate.

CONCLUSIONS

High-osmolar ionic contrast media are more cytotoxic than low-osmolar nonionic contrast media to gallbladder epithelial cells. Animal and clinical studies are needed to estimate the clinical implications of these findings.

Multiphasic injection method for uniform prolonged vascular enhancement at CT angiography: pharmacokinetic analysis and experimental porcine model

PURPOSE

To determine if multiphasic injection provides uniform, prolonged vascular contrast medium enhancement at computed tomographic (CT) angiography.

MATERIALS AND METHODS

With a computer-based, compartmental model of the cardiovascular system, theoretic analysis was performed to estimate an injection algorithm for uniform, prolonged vascular enhancement. For algorithm validation, four pigs were scanned after intravenous injection of 50 or 70 mL of contrast medium (282 mg of iodine per milliliter). Uni-, bi-, and multiphasic injection schemes were tested. In most cases, the initial injection rate was 2 mL/sec. In each CT study, 27 dynamic images were acquired every 2 seconds at a fixed mid-abdominal aortic level. Time-enhancement curves were calculated. Injection duration, peak aortic enhancement, and enhancement uniformity (duration of enhancement achieved within 90% of the peak [90% DCE]) were evaluated.

RESULTS

Theoretic and experimental results agreed well. Compared with uniphasic injection, biphasic injection resulted in more prolonged enhancement but generated two enhancement peaks with a valley between, and multiphasic injection yielded more uniform and prolonged enhancement. With 50- and 70-mL multiphasic injections, respectively, injection duration increased by 32% and 51%, peak enhancement decreased by 19% and 18%, and 90% DCE increased by 81% and 94%.

CONCLUSION

Uniform, prolonged vascular enhancement, which is desirable for CT angiography and essential for steady-state quantification of blood volume in organs, can be achieved with multiphasic injection.

Experimental study of mortality and morbidity of contrast media and standardized fecal dose in the peritoneal cavity

BACKGROUND

The use of radiographic contrast media in the setting of possible bowel ischemia and potential perforation is known to be associated with increased clinical risk. However, there is a lack of controlled studies using a standard native fecal load to define and compare the intrinsic mortality and morbidity among options of contrast media currently available to the radiologist. We have compared the mortality and gross and histopathologic morbidity of a standard intraperitoneal native fecal dose in the guinea pig, using barium, two iodinated media, saline and air.

MATERIALS AND METHODS

The study was performed on adult Hartley guinea pigs. A standard native fecal solution with a colony count of 10(8) aerobes and 2 x 10(7) anaerobes was prepared, and the LD50 of intraperitoneal injection of the solution was determined. The standard solution at the LD50 dose was then used to compare the mortality and morbidity when commercial barium sulfate (18% w/v), Conray 30 (iothalamate meglumine 30%), 1:1 dilution of Conray 30 with sterile water, termed Conray "15" (iothalamate meglumine 15%), saline and air, were added to the intraperitoneal injection of the fecal solution in five groups of 20 animals each. Mortality and acute (96 h) and chronic (30 days) gross and histopathology were assessed and graded according to a standard system and analyzed statistically.

RESULTS

Barium was significantly more deleterious than the dilute water-soluble iodinated media, saline and air. Mortality occurred within 24 h in the barium group and within the initial 48 h in all groups as follows: barium 19/20 (95%); Conray 30 16/20 (80%); Conray "15" 7/20 (35%); saline 0; air 0. Acute gross and histopathology showed extensive grade 4 lesions in 19/19 barium animals; less severe lesions were present in a lesser percentage of the animals in the other four groups. Entirely chronic lesions were present only in the single surviving barium animal and were non-significant (< 400 microns) or absent in the other four groups.

CONCLUSIONS

In our study, barium incurred the most significant deleterious short and long-term effects in the setting of fecal peritonitis. Dilute water-soluble media offer a much greater margin of safety. Saline under sonographic guidance is less deleterious than any of the positive radiographic contrast media. However, in our study, air was the safest contrast medium in the setting of peritoneal soiling.

Hepatic CT enhancement: effect of the rate and volume of contrast medium injection in an animal model

BACKGROUND

To evaluate the relative effect of rate of injection and volume of contrast medium on aortic, portal, and hepatic enhancement during computed tomography (CT).

METHODS

Thirty-eight nonincremental CT examinations were performed in three mini-pigs by using a combination of three different volumes (1.5, 2, and 3 mL/kg) and five different rates (1.5, 3, 4.5, 6, and 7.5 mL/s) of contrast material injection. Time-density enhancement curves of the aorta, portal vein, and liver were plotted over time for each rate of injection, each volume of contrast, and each volume-rate combination. In addition, aortic, portal, and liver peak enhancements, time-to-peak enhancements, optimal scanning intervals, and contrast enhancement indices were calculated for each volume-rate combination.

RESULTS

Higher rates of injection increased peak aortic enhancement but had no effect on peak portal or hepatic enhancement. This result may be explained by the dilution of the bolus of contrast medium in the splanchnic circulation. When the results of a 6-mL/s injection of 1.5 mL/kg of contrast material were compared with a 3-mL/s injection of 2 mL/kg, maximum aortic enhancement increased by 32%, whereas maximum liver enhancement decreased by 35%.

CONCLUSION

An increase in the rate of contrast injection results in an increase of peak aortic enhancement even when the total iodine load is decreased. However, an increase of the rate of contrast injection does not increase maximum liver enhancement, which is related to the total iodine dose injected. Therefore, one cannot compensate a decrease in the iodine load by an increase in injection rate in contrast-enhanced CT of the liver.

Assessment of a bolus-tracking technique in helical renal CT to optimize nephrographic phase imaging

PURPOSE

To evaluate a bolus-tracking technique in helical computed tomography (CT) for identifying the onset of the nephrographic phase and to determine the effect of varying the volume and injection rate of contrast material on nephrographic phase onset.

MATERIALS AND METHODS

Seventy-five patients underwent bolus tracking of contrast material followed by helical renal CT. In 50 patients, 150 mL of 60% iodinated contrast material (iohexol or iothalamate meglumine) was injected at either 2 mL/sec (25 patients [group 1]) or 3 mL/sec (25 patients [group 2]). In 25 patients who had previously undergone nephrectomy, 100 mL of 60% iodinated contrast material was injected at 3 mL/sec (group 3). Nephrographic phase onset was determined by visually assessing the transition to a homogeneous nephrogram during a monitoring scan series starting 40 seconds after injection.

RESULTS

Nephrographic phase onset ranged from 60 to 136 seconds (mean, 89 seconds +/- 17 [+/- SD]). Statistically significant differences in mean onset times were observed among groups 1 (103 seconds +/- 12), 2 (91 seconds +/- 16), and 3 (75 seconds +/- 9) (P < .001). Multiple regression analysis showed patient age, contrast material volume, and injection rate to be independent predictors of nephrographic phase onset. Contrast material volume, patient age, and patient weight were independent predictors of the degree of renal enhancement.

CONCLUSION

Nephrographic phase onset is highly dependent on methods of contrast material administration and patient characteristics.

Effect of contrast medium dose and image acquisition timing on ureteral opacification in the normal dog as assessed by computed tomography

Computed tomography (CT) excretory urography was performed in five adult female dogs after intravenous injection of a bolus of four different doses of water-soluble iodinated contrast medium (100, 200, 400, and 800 mgI/kg). CT images centered over the urinary bladder were performed before injection and 1, 3, 5, 7, 9, 11, 15, 20, 25, 30, 40, 50, and 60 minutes after injection. Opacification of both ureters was evaluated by measuring maximum CT number of individual ureters at each time. Time opacification curves were generated for each dose. Best opacification of the ureters was obtained with 400 and 800 mgI/kg, with a constant peak at 3 minutes and durable opacification for 1 hour. Insufficient opacification was obtained with lower dose of 100 and 200 mgI/kg.

Diagnosis of fatty infiltration of the liver on contrast enhanced CT: limitations of liver-minus-spleen attenuation difference measurements

BACKGROUND

We investigated whether liver-minus-spleen (L-S) attenuation differences can accurately diagnose fatty infiltration of the liver on contrast-enhanced computed tomography (CT).

METHODS

A group of 78 patients administered a fast injection (90-s duration) of 150 mL 60% ionic contrast was compared with 81 patients given a slow injection (152.5 s). The presence or absence of fatty infiltration of the liver was diagnosed by noncontrast CT.

RESULTS

The L-S attenuation differences varied significantly, depending on both injection rate and timing of measurements. For the fast-injection group, the optimal L-S threshold for diagnosing fatty infiltration ranged from -43 to -33 Hounsfield units (HU) for early (79 s) and late measurements (106 s), respectively. For the slow-injection group, the optimal threshold ranged from -31 to -25 HU (80 and 112 s, respectively). In addition, sensitivity was not very high (range = 0.54-0.71) for either injection protocol at any measurement time because of significant overlap of L-S values between normal and fatty infiltration patients. Moderate and severe fatty infiltration were more reliably diagnosed than mild fatty infiltration by this method.

CONCLUSIONS

Contrast injection rate and timing of measurements significantly influence the optimal L-S threshold for diagnosing fatty liver. This limits the clinical usefulness of such measurements.

Imaging of the rotator cuff: an arthrographic pitfall

We present a case where MRI and arthrography of the shoulder reports provided seemingly conflicting data. The subsequent findings at arthroscopy revealed a potential pitfall in arthrographic interpretation.

Ionic versus nonionic contrast media: a prospective study of the effect of rapid bolus injection on nausea and anaphylactoid reactions

PURPOSE

The purpose of our study was to evaluate the effect of bolus infusion of contrast medium (ionic versus nonionic) on the incidence of nausea and anaphylactoid reactions.

METHOD

We prospectively studied 1,827 patients who had bolus enhanced body CT scans and divided them into four groups: 725 patients received higher osmolality contrast medium (HOCM) at the slower bolus rate of 1-2.5 ml/s (SLOW-HOCM group); 650 patients were in the FAST-HOCM group and received the same ionic contrast medium at 4-5 ml/s; 250 patients received lower osmolality contrast medium (LOCM) at 1-2.5 ml/s, forming the SLOW-LOCM group; and 202 patients in the FAST-LOCM group got the same nonionic agent at 4-5 ml/s.

RESULTS

We found no significant difference in the rate of nausea among the first three groups: SLOW-HOCM (3.9%), FAST-HOCM (4.9%), and SLOW-LOCM (3.2%). A statistically significant lower incidence of nausea (0.5%) was found in the FAST-LOCM group. Anaphylactoid reactions were significantly more common in both groups who received HOCM (8.3 and 9.1%) compared with the groups who received LOCM (2.0 and 2.5%).

CONCLUSION

The bolus injection of warmed ionic contrast medium at a rate of 1-2.5 ml/s causes no significant increase in nausea compared with similar infusion rates of nonionic agents. For CT protocols that require infusion rates of 4-5 ml/s, the use of a nonionic agent is associated with a significantly reduced prevalence of nausea. The prevalence of anaphylactoid reactions is not affected by the rate of injection.

Chronic traumatic pseudoaneurysm of right subclavian artery

A right subclavian artery pseudoaneurysm caused by blunt trauma is described. CT and digital subtraction angiography helped us to establish a correct diagnosis. Radiologic features of subclavian artery aneurysms and relevant literature are briefly discussed.

Frequency and effects of extravasation of ionic and nonionic CT contrast media during rapid bolus injection

PURPOSE

To determine the frequency and clinical effects of extravasation related to rapid bolus infusion of ionic and nonionic contrast media.

MATERIALS AND METHODS

Records of 5,106 computed tomographic studies in adult patients who underwent mechanical bolus injection of contrast medium through a plastic cannula in an upper extremity were retrospectively reviewed.

RESULTS

Mean infusion rate was 2.8 mL/sec (range, 1-5 mL/sec). Extravasation occurred in 48 (0.9%) patients, including in four of 928 patients who received the median injection rate (2.5 mL/sec). Injection rate was not correlated with frequency or amount of extravasation. Average age and use of ionic versus nonionic contrast medium were identical in patients with and in those without extravasation. There was no sex difference. Thirty-one patients had extravasation of ionic contrast medium; nine of these had extravasation of at least 50 mL. Seventeen patients had extravasation of nonionic contrast medium; seven of these had extravasation of at least 50 mL. Hyaluronidase infiltration was often used as treatment for larger extravasations (in 10 patients each with extravasation of ionic or nonionic medium). No patient required surgical intervention, and none had severe or permanent long-term effects.

CONCLUSION

The frequency of extravasation of contrast medium after mechanical bolus injection is higher than that reported for hand-injection or drip-infusion techniques, but there is no correlation between injection rate and extravasation frequency.

Aortic and hepatic peak enhancement at CT: effect of contrast medium injection rate--pharmacokinetic analysis and experimental porcine model

PURPOSE

To investigate the effect of injection rate of contrast medium on aortic and hepatic peak enhancement at computed tomography.

MATERIALS AND METHODS

Early pharmacokinetics of contrast enhancement was analyzed theoretically and simulated with a compartment model. Contrast enhancement curves were generated from the model at different injection rates (0.5-10.0 mL/sec). Time-enhancement curves were measured. The effect of contrast medium injection rate on the time and magnitude of peak enhancement was evaluated and validated empirically in pigs.

RESULTS

Theoretic predictions and experimental results were in good agreement. Time to aortic peak enhancement was the sum of injection duration and bolus transfer time of contrast medium from the injection site to the aorta. Time to hepatic peak enhancement was the sum of injection duration and time to equilibrium. The magnitude of peak enhancement increased with the injection rate, but the increase was different in the aorta and liver.

CONCLUSION

Use of injection rates above 2 mL/sec did not substantially increase hepatic peak enhancement but helped increase the magnitude of arterial enhancement and temporal separation of arterial and venous phases of enhancement for dual-phase spiral CT.

Development of a nonisotopic capillary electrophoresis-based method for measuring glomerular filtration rate

The conditions for quantitative measurement of nonisotopic iothalamate meglumine (Conray) in urine and plasma by capillary zone electrophoresis (CE) have been developed. The impetus for developing this methodology was to replace the traditional [125I]iothalamate glomerular filtration rate (GFR) marker assay, a routine tool in the measurement of kidney function. This new approach for measuring kidney function is attractive since it avoids the cost of administration of radioisotopic compounds to patients, as well as the cost associated with purchase and disposal of isotopic compounds and contaminated samples. The concentration of iothalamate in urine and plasma determined by CE can be used directly to calculate GFR. The GFR in patients injected with [125I]iothalamate and nonisotopic iothalamate simultaneously showed an excellent correlation (0.998) with between-day coefficient of variation of 2.30% and a recovery of 102% and 98%, respectively, when added to urine and plasma. Interference from drugs and other urinary compounds is eliminated with this method. Collectively, this study has shown that CE is a cost-effective alternative to the current methodology for measuring GFR.

In-line pressures generated in small-bore central venous catheters during power injection of CT contrast media

PURPOSE

To determine in-line pressures generated in small-bore central venous catheters during power injection of computed tomographic (CT) contrast media.

MATERIALS AND METHODS

Five 3.0-7.0-F central venous catheters for pediatric patients were tested at full and half lengths in vitro. In-line pressures were measured during power injection of three contrast media. Rates of injection were increased in steps from 0.1 to 5.0 mL/sec or until a peak pressure of 100 psi (700 kPa) was achieved. The maximum tolerated flow rate was determined with reference to the manufacturer's suggested operating pressure limit for each catheter.

RESULTS

At full length, the maximum tolerated flow rates were as follows: 2-3 mL/sec for the large lumen and 1-1.4 mL/sec for the small lumen of the 7.0-F double-lumen catheter; 0.2-0.4 and 0.8-1.2 mL/sec for the 3.0- and 4.0-F peripherally inserted central catheters, respectively; 0.7-1.2 mL/sec for the 6.6-F catheter; and only 0.2 mL/sec for the 4.2-F catheter, which ruptured during testing at higher flow rates.

CONCLUSION

Flow rates were documented at which certain small-bore central venous catheters should tolerate power injection of CT contrast media with peak pressures remaining below the manufacturer's recommended operating pressure limits. These data may serve as a guide for clinical use.

Power injection of intravenous contrast material through central venous catheters for CT: in vitro evaluation

PURPOSE

To determine the feasibility of use of a power injector to deliver contrast material through central venous catheters for computed tomographic (CT) examinations.

MATERIALS AND METHODS

Ioversol 240 and iothalamate meglumine 43% were separately injected through three 9.6-F Hickman catheters and three 10.0-F Leonard catheters with a power injector in an in vitro study. Flow rates of 1.0, 1.5, 2.0, and 2.5 mL/sec were tested. Peak pressures were mechanically recorded from two sites. A 95% prediction interval was calculated for each peak pressure, and the upper limits at the prediction interval were evaluated to determine if it was less than the recommended limit of 25 psi (175 kPa).

RESULTS

Contrast medium, flow rate, and catheter type each statistically significantly affected the measured peak pressures (P = .0001). For each flow rate tested, the upper limits of the prediction interval for the peak pressure at the connection between the coiled tubing and the catheter were below the manufacturer's specified peak pressure.

CONCLUSION

In vitro analysis demonstrates that power injection of intravenous contrast medium through central venous catheters does not exceed the pressure limits of these catheters at the flow rates tested. In vivo testing to evaluate the safety and efficacy of power injection through central venous catheters is necessary.

Multiphasic renal CT: comparison of renal mass enhancement during the corticomedullary and nephrographic phases

PURPOSE

To evaluate thin-section computed tomography (CT) performed during the corticomedullary and nephrographic phases of contrast material enhancement in the characterization of renal masses.

MATERIALS AND METHODS

A prospective study of 30 patients was undertaken with CT to characterize 31 "indeterminate" renal masses. In all patients, 5-mm-thick, contiguous, high-tube-current (320-340-mA) scans were obtained through the kidneys before (axial mode), during (helical mode, 25-second delay, corticomedullary-phase images), and after (axial mode, 120-second delay, nephrographic-phase images) administration of a 117-second biphasic injection of intravenous contrast material.

RESULTS

Eight of 16 neoplasms measured less than 20 HU on CT scans obtained without contrast material enhancement; measurements of two of these corresponded to "cyst attenuation" during the corticomedullary phase. Enhancement of 10 HU or greater was demonstrated in 11 neoplasms during the corticomedullary phase and in all neoplasms in the nephrographic phase. No enhancement was seen in 15 radiologically benign cysts. Both renal neoplasms and normal renal cortex demonstrated significantly greater enhancement in the nephrographic phase compared with that in the corticomedullary phase (P = .0002 and P < .0001, respectively).

CONCLUSION

Enhancement of renal neoplasms is time dependent and may not be evident in hypovascular tumors analyzed during the early corticomedullary phase. Reliance on absolute CT attenuation measurements, without use of internal standards as controls, may lead to misdiagnosis of neoplasms as cysts.

Evaluation of selective wrist arthrography of contralateral asymptomatic wrists for symmetric ligamentous defects

OBJECTIVE

The objective of this investigation was to study the role of selective wrist arthrography of the asymptomatic wrists of patients with unilateral wrist pain and the efficacy of three-compartment and selective-compartment injections of contrast medium into the asymptomatic wrist in demonstrating symmetric and asymmetric intercarpal ligament and triangular fibrocartilage communicating defects.

SUBJECTS AND METHODS

Wrist arthrography with bilateral three-compartment injections was performed for 62 patients with unilateral wrist pain. The numbers of bilateral intercarpal ligament and triangular fibrocartilage communicating defects were recorded. The results obtained with three-compartment injections in each wrist of these patients were compared with those obtained with single-compartment injections.

RESULTS

Bilateral three-compartment injections identified 110 communicating defects (59 in the symptomatic and 51 in the asymptomatic wrists). Midcarpal injections showed all 36 scapholunate and lunatotriquetral ligament defects that were also shown by three-compartment injections in asymptomatic wrists. However, only 26 (72%) of these 36 ligament defects were shown by radiocarpal injections. No single-compartment injection showed all triangular fibrocartilage defects that were shown by three-compartment injections. Ten bilateral symmetric triangular fibrocartilage communicating defects were shown by three-compartment injections. All 10 triangular fibrocartilage communicating defects in asymptomatic wrists were shown by radiocarpal injections. However, only five of the 10 triangular fibrocartilage communicating defects in asymptomatic wrists were shown by injection of the distal radioulnar joints.

CONCLUSION

Selective midcarpal injection of an asymptomatic wrist showed all matching defects in that wrist when only intercarpal ligament defects were found in the symptomatic wrist. Similarly, selective radiocarpal injection of an asymptomatic wrist showed all matching defects of the triangular fibrocartilage in that wrist. In either situation, routine injection of all three compartments of the asymptomatic wrist should not be necessary.

Effect of rate of contrast medium injection on hepatic enhancement at CT

PURPOSE

To determine the effect of the rate of contrast medium injection on liver enhancement at computed tomography (CT).

MATERIALS AND METHODS

Forty-five patients who underwent a follow-up CT examination of the liver were included in five different groups according to the compared rates of contrast material delivery: group A, 2 versus 3 mL/sec; group B, 2 versus 4.5 mL/sec; group C, 3 versus 4.5 mL/sec; group D, 3 versus 6 mL/sec; and group E, 4.5 versus 6 mL/sec.

RESULTS

Time to peak enhancement was shorter for the faster rates of injection. In each group, maximum enhancement was nearly identical for the paired examinations (group A, 57 vs 58 HU; group B, 48 vs 47 HU; group C, 55 vs 58 HU; group D, 55 vs 54 HU; group E, 62 vs 61 HU, respectively). Mean enhancement in each group was similar when calculated at 3-second intervals.

CONCLUSION

Higher rates of injection shorten the time to peak liver enhancement but have no effect on maximum liver enhancement.

Helical CT of the liver: value of an early hepatic arterial phase

PURPOSE

To prospectively evaluate a dual-phase helical acquisition in computed tomography (CT) of the liver.

MATERIALS AND METHODS

Two helical CT acquisitions were performed in 103 patients: hepatic arterial phase (HAP) 15 seconds after injection of 2 mL/kg contrast material at a rate of 6 mL/sec and the portal venous phase (PVP) 90 seconds after injection. Detection of focal liver lesions, vascular anatomic features, and perfusion abnormalities were assessed by two reviewers. Liver enhancement was also calculated on every section.

RESULTS

Of 119 detected focal liver lesions, nine were seen during HAP only and 40 during PVP only. According to a 0-3 score, visualization of the arterial anatomic landmarks was better during HAP (P < .0001). Five right replaced and two left replaced hepatic arteries were visualized only during HAP. Parenchymal perfusion abnormalities were found in 32 patients during HAP and in four patients during PVP.

CONCLUSION

A dual-phase acquisition depicted 8% additional focal liver lesions and outlined the entire vasculature of the liver.

[Effects of viscosity, cannula size and temperature in mechanical contrast media administration in CT and magnetic resonance tomography]

PURPOSE

Mechanical contrast media application is used to improve image quality and allow better quantitative assessment of the contrast media kinetics for CT as well as MRI. The pressure within the i.v. line system must be known to enable safe and quantitatively exact application.

MATERIAL AND METHODS

Experimental setup to analyse the inline pressure, the storage volume as well as the exactness of delivery within the i.v. line system was prepared. Representative contrast media Ultravist 300, Ultravist 370, Magnevist and Conray 60 as well as 0.9% NaCl were measured with ten different flow rates from 0.1 ml/sec to 5.0 ml/sec using the six most common i.v. cannula sizes (22G-14G).

RESULTS

System pressures between 38-60 psi (maximum allowed system pressure = 60 psi) are commonly obtained with standard sizes of i.v. cannulas, such as an 18 G cannula and flow rates > or = 2.5 ml/sec using Ultravist 300 (viscosity 13 mPa.s at 20 degrees C). Higher system pressures (> 25 psi) produce an exponential increase of the storage volume within the i.v. line system. The additional storage volume within the i.v. line tubing (d = 2.9 mm, 76 shore) is at 60 psi and 20 degrees C 5 ml/m, and at 37 degrees C 11 ml/m in addition to the volume of the tubing of 7 ml/m.

CONCLUSION

Based on the measured data, both the minimum and the recommended sizes of the i.v. cannulas in respect of flow rate and viscosity of the used contrast media were compiled for system pressures at < or = 60 psi as well as < or = 38 psi.

A role for nitric oxide in X-ray contrast material toxicity

RATIONALE AND OBJECTIVES

We assessed the role that nitric oxide (NO) plays in contrast media (CM) toxicity, using 100% lethal dose (LD100) studies in hyperimmune Brown Norway (BN) rats.

METHODS

Ninety-two BN rats and 41 Sprague-Dawley (SD) rats underwent CM LD100 tail vein injections with methylglucamine iothalamate or sodium iothalamate to the point of cessation of respiration. Methylglucamine hydrochloride also was injected. The injections were accompanied by L-arginine (L-Arg) or D-arginine (D-Arg) analogues or by an H1 blocker. L-Arg analogues inhibit NO formation, and D-Arg analogues do not.

RESULTS

An L-Arg analogue, but not a D-Arg analogue, increased the tolerance of BN rats (p < .005) for methylglucamine iothalamate but not for sodium iothalamate. The L-Arg analogue also protected BN rats against methylglucamine chloride injections (p < .002). H1 blockade protected BN rats against methylglucamine iothalamate (p < .0005) and methylglucamine chloride (p < .005) injections. None of these measures altered the CM tolerance of SD rats. In SD rats, injections of either methylglucamine iothalamate or sodium iothalamate along with a D-Arg analogue or normal saline were better tolerated than similar injections in BN rats (p < .01 and .002 for methylglucamine iothalamate and sodium iothalamate, respectively). In SD rats but not BN rats, sodium iothalamate was better tolerated than was methylglucamine iothalamate (p < .0005).

CONCLUSION

NO appears to play a significant role in BN rats LD100 CM toxicity and has been implicated by others in the blood pressure fall characterizing some forms of antigen-induced anaphylaxis [1, 2]. The results of the current study and the literature suggest that methylglucamine-modulated release of histamine from mast cells may underlie the NO production.

[Adverse reactions to contrast media for intravenous use. A comparison between ionic and nonionic media]

The purpose of this study was to show that the nonionic contrast media of low osmolarity are better tolerated than ionic media of high osmolarity, which to date are most frequently used in the authors hospital. We found that adverse reaction occurred in 80% of the group in which nonionic contrast medium was used. The authors conclude that nonionic, low osmolarity contrast media significantly reduce the frequency of adverse reactions and increase their safe use.

Oral contrast is not necessary in the evaluation of blunt abdominal trauma by computed tomography

The administration of oral contrast (OC) is widely recommended for computed tomography (CT) of the abdomen in patients with blunt trauma. The purpose of this study was to determine whether routine abdominal CT scans performed without OC were associated with diagnostic error in patients with blunt trauma. Four hundred ninety-two patients were identified from our Trauma Registry who had CT scans for the evaluation of blunt abdominal trauma between January 1988 and December 1991. Seventy-six percent (372) of the CT scans were interpreted as negative, and 24% (120) were considered positive. OC was used in 8 (1.6%) of 492 patients. Only 1 of 372 patients whose initial non-OC--enhanced scan was negative subsequently required surgery. There were 5 bowel injuries among the 42 patients who underwent an abdominal operation; in none would the use of OC have ensured the preoperative diagnosis. We found that the omission of OC did not represent a disadvantage to patients with blunt trauma undergoing a routine abdominal CT scan. Potential time delays and the hazards associated with the use of OC were minimized.

Noninvasive CT determination of arterial blood concentration of meglumine iothalamate

A quantity that often must be determined in physiological imaging studies is the blood concentration of the tracer over time. This is usually performed by direct arterial or venous blood sampling. We studied the relationship between the concentration of meglumine iothalamate in arterial blood and values determined from voxels containing large blood vessels in a series of CT images at the same location over time. After correction for volume averaging based on a single venous blood sample, there was an excellent correlation between the two blood curves. Differences between the curves were shown to be inconsequential by a simulation of transcapillary transport determinations. We thus conclude that determination of plasma concentration from CT images is a reliable technique for CT transcapillary transport studies.

Peritoneal carcinomatosis: preoperative CT with intraperitoneal contrast material

Thirty-five abdominal computed tomographic (CT) scans of 27 patients with peritoneal metastases from a mucin-producing tumor of the appendix, colon, small bowel, or ovary were retrospectively reviewed. Fifteen scans were obtained of 15 patients after CT with intraperitoneal infusion of contrast material (IP), and 20 scans were obtained of 16 patients with CT without IP. Subsequent exploratory laparotomy revealed that all 27 patients had multi-focal spread of peritoneal metastases. The sensitivity of CTIP and CT without IP for detection of peritoneal metastases at all sites of involvement was 61% and 59%, respectively. For CTIP, the highest sensitivity was in the right subphrenic space (88%), splenic hilum (86%), and left subphrenic space (83%). For CT without IP, the highest sensitivity was noted in the splenic hilum (100%), left subphrenic space (75%), and left paracolic gutter (75%). CTIP and CT without IP had low sensitivity for detection of disease in the greater omentum (50% each) and small-bowel mesentery (38% and 59%, respectively), two areas that had the highest frequency of metastases.

Radiocontrast increases plasma and urinary endothelin

Recent studies indicate that endothelin (ET), a potent endogenous systemic and renal vasoconstrictor peptide, may mediate decreases in GFR in models of acute renal dysfunction. Moreover, in an animal model of radiocontrast-induced nephropathy (RCIN), it was recently demonstrated that early renal hemodynamic responses to radiocontrast are attenuated by intra-arterial atrial natriuretic factor (ANF), which prevents subsequent RCIN. The studies presented here were therefore designed to determine whether i.v. infusion of radiocontrast produces increases in endogenous plasma and urinary ET and whether these responses are modulated by intra-arterial ANF in an animal model of RCIN. In these studies, dogs with pacing-induced heart failure received i.v. radiocontrast in the presence and absence of an intra-aortic infusion of ANF. Significant increases in both plasma and urinary ET were observed during and after radiocontrast. Although coadministration of ANF did not prevent increases in plasma and urinary ET, ANF preserved renal function acutely in this model of RCIN by increasing GFR above baseline levels.

Selective injection of contrast media: inflammatory effects on rabbit fallopian tubes

The inflammatory effects of fallopian tube catheterization and selective injection of seven contrast agents (ethiodized oil, diatrizoate meglumine 52%, diatrizoate meglumine 66%, iothalamate meglumine 60%, iopamidol, ioxitol, and ioxaglate) were evaluated in 88 rabbits. The contrast agent used was randomly selected and selectively injected after unilateral catheterization; the contralateral side was used for control. Pathologic inspection of right and left uteri with attached fallopian tubes and ovaries was done without knowledge of side of catheterization or duration of time since catheterization. The degree and location of inflammation were noted. Inflammation disappeared by 4 days in five of seven contrast agents. Iothalamate meglumine 60% and iopamidol required 2 weeks for disappearance of inflammation. Essentially no inflammation was associated at any time with ioxaglate. These findings suggest that all of these contrast agents would be clinically acceptable for direct injection into the human fallopian tube.

Irresectable hepatoma treated by intrahepatic iodized oil doxorubicin hydrochloride: initial results

In this study we describe the investigation and treatment of 14 patients with primary hepatocellular carcinoma. Patients were treated with intra-arterial infusion of iodized oil and doxorubicin hydrochloride. Five of these patients were alive after 1 year. Twelve patients showed a fall in alpha-fetoprotein, and in seven of these patients, the fall in alpha-fetoprotein was greater than 50%.

Comparison of nonionic and ionic contrast agents in the rabbit lung

The objective of this study was to determine the short- and long-term radiographic, physiologic and histologic changes elicited in the lung of rabbits following the aspiration of commonly used radiographic contrast agents. All agents used, including nonionic agents, caused radiographically evident pulmonary edema which cleared by 24 hours. The contrast materials with higher osmolality, viscosity, and iodine content elicited the greatest physiologic and pathologic changes. No differences were found between an ionic and a nonionic agent with similar viscosities and iodine content, despite a lower osmolality in the nonionic agent. No contrast agent is innocuous when introduced into the lung.

CT cystography in the evaluation of bladder trauma

At our trauma center we have replaced plain film cystography with CT cystography to evaluate trauma patients with hematuria sent for emergent CT of the abdomen and pelvis. Ten cases of ruptured bladders evaluated by CT are tabulated, and characteristic images are presented.

Effect of hyperosmotic blood-brain barrier disruption on transcapillary transport in canine brain tumors

Whether hyperosmotic blood-brain barrier (BBB) disruption is a technique that can be used to increase permeability of brain-tumor capillaries and thereby transiently increase drug delivery to the brain tumor is controversial. Nine virally induced brain tumors were studied in seven dogs, before and after hyperosmotic BBB disruption with 1.4 osmolar mannitol. Each dog was studied with computerized tomography (CT) after administration of the water-soluble tracer meglumine iothalamate. Each study lasted 30 minutes. A baseline CT scan and 35 to 40 additional CT scans were obtained to provide a time-related measurement of the amount of meglumine iothalamate in tissue (Am(t], and 30 plasma samples were collected to provide the time-related measurement of meglumine iothalamate in plasma (Cp(t]. The data were analyzed by three different methods: 1) a two-compartment model and nonlinear curve fitting were used to calculate K1 (blood-to-tissue or influx constant), k2 (tissue-to-blood or efflux constant), and Vp (plasma vascular space); 2) K1 values were calculated with a two-compartment model, assuming no efflux, at the time point for each CT scan; and 3) a "tissue advantage ratio" was calculated that expressed the ratio of tissue uptake of meglumine iothalamate at each time point, comparing values before and after BBB disruption. Regardless of which method of data analysis was used, there was a marked and significant increase in transcapillary transport of meglumine iothalamate to tumor-free brain regions, while there was only a small, transient, and insignificant increase to the brain tumors. Although there were often marked increases in delivery to cortex in the same hemisphere as the tumors, there was no significant increase to brain immediately surrounding the tumors, perhaps due to altered circulatory dynamics in this region. These data raise serious questions as to the wisdom of using this technique to increase drug delivery to brain tumors in patients and strongly support the continued study of this technique in experimental brain tumors before it is used in patients.

Nonsurgical fallopian tube recanalization for treatment of infertility

Fluoroscopic transcervical fallopian tube recanalization was performed in 100 consecutive patients with infertility and proximal tubal obstruction documented with hysterosalpingography. In 86 patients, the procedure enabled at least one tube to be opened. Twenty-six intrauterine pregnancies resulted from the successful recanalization. A well-defined subset of 20 patients were evaluated to better define the treatment effect of fallopian tube recanalization. All 20 had bilateral proximal tubal obstruction without other tubal disease, and all had been recommended for tubal microsurgery or in vitro fertilization. Recanalization of one or both tubes was successful in 19 of these women (95%). Nine patients conceived (47%) without receiving any other therapy, and the average time from procedure to conception was 4 months. All pregnancies were intrauterine. Eight of the 10 patients who did not conceive underwent follow-up hysterosalpingography an average of 6 months following the procedure; four (50%) demonstrated reocclusion of both tubes. The authors conclude that nonsurgical fallopian tube recanalization is an effective treatment for infertility caused by proximal tubal obstruction.

Muscular and CNS effects of carotid artery administration of contrast media in rabbits

Facial muscle twitching during intracarotid injections of nonionic contrast media has been observed in rabbits. To investigate the cause of this reaction, cortical EEG and facial EMG recordings were made from rabbits receiving selective internal and external carotid artery injections of control solutions (normal saline, mannitol), an ionic contrast medium (meglumine iothalamate), and three nonionic contrast media (iohexol, iopromide, and iotrolan). Internal carotid artery injections with all contrast media, both ionic and nonionic, produced ipsilateral EEG changes in 24 of 28 animals; however, ipsilateral EMG changes and visible twitching were observed only in animals injected with nonionic contrast media. Internal carotid artery injections with control ionic and nonionic solutions (physiological saline and mannitol, respectively) produced no EEG changes in any animals. Mannitol produced only ipsilateral EMG changes and visible twitching in most animals. The severity of the reaction to mannitol was generally less than that to the nonionic contrast media, and this difference was statistically significant when comparing mannitol with iohexol and iotrolan but not with iopromide. External carotid artery injections with nonionic solutions (contrast media and mannitol) produced significantly more severe ipsilateral EMG changes and visible twitching than were recorded with the internal carotid artery injections. Ionic solutions (contrast media and saline) had no effect. EEG changes were not observed after external carotid artery injection of any solution, with the exception of two of the seven animals injected with iotrolan. Angiography demonstrated retrograde filling of the external carotid arterial system from internal carotid artery injection via functioning orbital anastamoses. In contrast, internal carotid arterial vessels were not seen angiographically after external carotid artery injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Incompatibility of contrast agents with intravascular medications. Work in progress

In vitro and in vivo precipitation of iodinated contrast agents when ioxaglate and papaverine are given together has been reported. To verify these reports and to investigate other medications not previously tested, the authors analyzed mixtures of contrast agents and medications in vitro with a light spectrophotometer and observed them for visible precipitates for up to 120 minutes. Previously reported incompatibilities between ionic or low-osmolality contrast media and medications were verified, and several new incompatibilities were discovered. No incompatibilities were found when the drugs tested were mixed with the new nonionic contrast media.

[Electronystagmographic evaluation of changes in vestibular reactions after administration of diverse substances into cerebral ventricles]

Vestibulo-oculomotor reflexes (nystagmus) were recorded by the method of electronystagmography in 33 neurosurgical patients before and after ventriculography. Cerebral ventricles were examined using water soluble compounds (conray, dimeriks, amipaque) in 18 patients or water soluble compounds combined with majodil emulsion in 15 patients. Ventriculography by means of water soluble compounds led to insignificant changes in nystagmic parameters while that by means of X-ray contrasting mixtures caused a frequent and noticeable enhancement of stem vestibular reactions as related to all nystagmic parameters and a significant increase of vestibulo-autonomic reactions.

Intra-arterial digital subtraction angiography in the evaluation of peripheral vascular trauma

The role of intra-arterial digital subtraction angiography (IADSA) in the evaluation of extremity trauma has not been clearly established. Several potential advantages would make IADSA a preferable study to conventional angiography (CA). This retrospective study analyzed 104 major peripheral arteries with suspected injury. Multiplane IADSA studies were compared with conventional angiography of the same vessel in 97 patients. The arteriograms were evaluated by a physician and a radiologist in a double-blinded fashion. IADSA correlated well with CA. Similar findings comparing both studies were noted in 101 of 104 angiograms (97%) (p less than 0.001) in review by the radiologist and in 100 of 104 (96%) (p less than 0.001) by the surgeon. Only one injury confirmed at surgery was not seen on IADSA; this study was read as equivocal by both examiners. These data confirm that IADSA is a reliable and reasonable study for the evaluation of patients with suspected peripheral arterial injury.

[Dose and time dependency of "CT clearance"]

The contrast medium dose used in CT renal function analysis corresponds to about 1 ml/kg body weight at a measurement interval of 5 or 10 minutes. In the present study the dependence of "CT clearance" on dosage and time was examined in 12 healthy subjects. The amount of clearance was directly proportional to the employed contrast medium dose and to the length of the measurement interval. On account of the superior signal-to-noise ratio, the higher dose (1 ml/kg body weight) will continue to be preferred in future. The measurement interval can be limited to 10 minutes.