A decade ago, the introduction of the first spiral CT scanners began a revolution in CT technology that continues to this day. The increased speed of the new slip-ring scanners gradually increased the capabilities, resolution, and clinical efficacy of CT. The new capabilities provided by faster CT scanners led to the development of new studies, such as multiphase examinations and CT angiography. These developments have caused the clinical utilization of CT to skyrocket. Indications for CT continue to grow, and there is an increasing reliance on the modality for diagnosis and intervention.

Among the changes brought about by spiral CT technology is a re-examination of contrast-media dosing protocols. By taking advantage of the increased speed afforded by spiral CT scanners, many patient examinations can be performed quickly using a reduced dose of contrast agent. The use of a power injector for contrast media is now standard in part because it helps users take full advantage of shorter examination times to increase patient throughput. The combination of increased speed and potentially reduced contrast dose makes this technology very attractive. At the same time, increased financial pressures have resulted in staffing reductions and tighter controls on capital budgets. These factors contribute to increased workloads, and have necessitated improvements in efficiency.

In 1998, the introduction of multidetector CT (MDCT) scanners further increased examination speed. In fact, 16-detector scanners are now up to 100 times faster than first-generation spiral CT scanners.¹ The increased capabilities of MDCT scanners are used to shorten examination time, increase the data collected in the same amount of time, or some combination of the two. The busy CT department, however, needs more than a fast CT scanner. As scan times decrease, the time needed for CT-suite setup and cleanup and for patient preparation becomes a critical factor in departmental efficiency. For the CT technologist, multitasking is the norm; the technologist must keep the patient safe and comfortable, obtain important patient information, perform equipment checks, administer contrast, and lead the patient through the examination effectively.

Supplies used for manual filling of contrast media syringes: empty syringe cartridge, transfer tubing, transfer straw, contrast bottle, and hand-control syringe. Figure reprinted with permission from Applied Radiology. Enterline DS. Prefilled syringes: applications in CT imaging. Applied Radiology. 2001;30(suppl):1-14.

Approximately half of all CT examinations are performed using contrast agents. While brain CT and some pediatric studies may still be performed using a hand-injected bolus, the use of a power injector is now standard for almost all contrast-enhanced examinations. The technologist loads and operates the injector. Poor technique can lead to technologist injury or to contamination, misadministration, or the accidental injection of air.

Prefilled contrast media syringes simplify the tasks associated with contrast injection. Prefilled syringes have a set volume and concentration of contrast agent in a power injectorcompatible syringe. They are considerably easier to use than bottle-filled cartridges and reduce the possibility of contamination or misadministration. According to a recent survey commissioned by the American Society of Radiologic Technologists (ASRT), most CT technologists prefer prefilled syringes to bottle-filled cartridges, believing them to be safer and more efficient (12). Until now, however, the potential of prefilled syringes to improve efficiency has not been evaluated scientifically. For this reason, a multicenter time-and-motion analysis of the efficiency of using prefilled syringes was undertaken in 2002.

METHODS

Independent observers from a company specializing in time-and-motion evaluations monitored and recorded the time necessary to perform the steps of contrast-enhanced CT examinations. The four participating sites were Duke University Medical Center, Durham, NC; Massachusetts General HospitalWest Imaging, Waltham, Mass; MD Anderson Cancer Center, Houston; and Charleston Area Medical CenterGeneral Division, Charleston, W Va. None of these institutions had been using prefilled syringes prior to the study.

The contrast-enhanced CT examinations of 401 patients were studied. Of these 401 examinations, 206 were performed using prefilled syringes and 194 were performed using bottle-filled cartridges. In one instance, the contrast loading method was not recorded. The bottle-filled cartridge method involves tearing the seal off of a vial of contrast medium, drawing the contrast into a syringe compatible with a power injector, labeling the syringe according to departmental guidelines, and disposing of the used supplies. When using a prefilled syringe, the technologist selects the syringe, removes the rubber safety cap, and installs the syringe in the injector head. With both methods, care must be taken to expel any air before administering contrast to the patient.

In this study, time data points were recorded for total patient time in the room, scan setup time, total scan time, contrast loading time, contrast cleanup time, and room cleanup time.

Scan setup time was defined as the interval between the patient's entry of the room and the initiation of the CT scan. Activities typically performed during this time are patient positioning, establishment of intravenous (IV) access, and console setup. Scan time was measured from the initiation of the CT scan until the end of scanning. This phase included entering data, obtaining all preliminary and standard images, and reviewing the images. Contrast loading time was defined as the time needed to complete all elements of loading the power injector (getting contrast, loading the contrast into the injector, and purging air from the extension tubing). Contrast cleanup time was also monitored; this consisted of the time needed to remove the contrast cartridge and connection tubing and discard it, as well as to wipe the power injector when necessary. Room cleanup time was defined as the time used to escort the patient from the room, clean the room (including the table and scanner), and change the linens for the next patient.

The project was approved by the institutional review boards of each of the four participating centers. Since the study did not affect the care provided to patients, no patient consent process was deemed necessary. Participating technologists completed a form indicating their consent to be monitored, as well as a short opinion survey on prefilled syringes. Time-and-motion data were recorded only by objective, trained monitors using stopwatches. The monitors observed the actions of the technologists from a distance, in an unobtrusive manner. Data were recorded for each of the activities described. Type of examination; patient-location category (inpatient, outpatient, or emergency department); contrast medium concentration; contrast volume; and injection rate were also recorded.

This study was designed to have a 95% confidence interval. Time-and-motion data from individual observations were entered into a database, tabulated, and summarized. Mean time intervals were calculated for each of the periods described. Differences in the mean time intervals recorded using the two contrast methods were compared using an independent two-tailed unpaired t test, with statistical significance determined as P<.05.

Efficiency gains for various study components were expressed as a percentage of the mean time recorded using bottle-filled cartridges. For example, the prefilled syringe contrast loading time efficiency was derived as the result of bottle-filled cartridge contrast loading time minus prefilled syringe contrast loading time divided by bottle-filled cartridge contrast loading time.

RESULTS

Distribution of contrast methods by site is found in Table 1. At MD Anderson Cancer Center, most examinations were performed using prefilled syringes; at Duke University Medical Center, approximately two thirds of examinations were conducted using bottle-filled cartridges. The distribution of examination types is found in Table 2. Most examinations monitored were performed in outpatient settings. Of all examinations monitored, 89% were outpatient, 8% were for inpatient, and 3% were performed in the emergency department.

The most frequently monitored examination was CT of the abdomen and pelvis or abdomen, which accounted for 38% of examinations monitored, followed by CT of the chest, abdomen, and pelvis (23%) and CT of the chest (18%). The type and concentration of contrast used was recorded in 400 of 401 examinations. The contrast agent most often used in the study was iopamidol, used in 289 procedures, followed by iohexol (63 procedures), ioversol (41 procedures), and iopromide (8 procedures). Most studies (73%) were performed using a contrast-medium concentration of 300 mg I/ml; the remaining examinations were performed using concentrations of 320, 350, or 370 mg I/ml. The prefilled syringes used in this study contained iopamidol in all cases but one. The mean volume of contrast administered in this evaluation was 130 ml (range: 30 to 200 ml). Contrast media were administrated at a mean rate of 2.5 ml per second (range: 0.5 to 5 ml per second). Differences between the two methods in terms of mean contrast volume (129 ml for prefilled syringes and 132 ml for bottle-filled cartridges) or mean injection rate (2.43 ml per second for prefilled syringes and 2.57 ml per second for bottle-filled cartridges) were not statistically significant.

In 14 cases, data were excluded from the final analysis of time efficiency. Five of these cases represent a single missing data point. In eight cases, excessive time (defined as a value of greater than twice the mean value) passed while the patient waited in the room for an IV to be restarted or for patient transport. In these cases, the time value was considered an outlier, and the entire examination was excluded from the efficiency analyses. In one case, an intervention was performed (after initial scanning) that took substantially more than twice the mean scan time. Of the remaining 387 examinations, 202 were performed with prefilled syringes and 185 with bottle-filled cartridges.

The mean times measured for the various parts of the CT examination are shown in Table 3. Statistically significant improvements in mean times were noted when technologists used prefilled syringes for the following study components: contrast loading time, room setup, disposal of supplies/injector cleanup, and overall patient time in the room.

As expected, prefilled syringes showed the greatest time savings over bottle-filled cartridges for those activities most closely dependent on the contrast method used, such as contrast loading time and disposal of supplies/injector cleanup. Overall, recorded examination times in the prefilled syringe group were approximately 9% shorter than those in the bottle-filled cartridge group, but how much of this improvement is attributable to the contrast method is unclear. One explanation for the improved overall examination time in the prefilled syringe group is the slightly increased proportion of inpatient examinations performed using bottle-filled cartridges.

(1) (Load time BFC - Load time PFS)/Load time BFC (2) (Injector clean time BFC - Injector clean time PFS)/Injector clean time BFC (3) (Setup time BFC - Setup time PFS)/Setup time BFC (4) (Load time BFC - Load time PFS) + (Injector clean time BFC - Injector clean time PFS)/Patient time in room BFC

The calculated efficiency improvements for prefilled syringes for contrast loading, setup time, and overall patient time in the room (expressed as a percentage of bottle-filled cartridge time) are shown in Table 4. As expected, the greatest gain in efficiency came from the contrast loading time. Overall setup time and overall patient time, which are measures progressively less sensitive to factors related to contrast administration, show smaller efficiency gains overall. Taken together, contrast-related activities account for 8.8% of total patient time in the room. Therefore, the theoretical maximum increase possible in overall study efficiency was less than 9%. In this study, we demonstrated a 3% increase in overall efficiency due to the use of prefilled syringes, a finding consistent with a 33% decrease in injector loading time.

*One week = 5 full days and one half day of CT operation **One year = 5 full days and one half day of CT operation for 52 weeks (#)Days here = 9-hour scanning days (@)Days here = 14-hour scanning days

The total mean time savings in the prefilled syringe group attributable to the contrast method selected was 39 seconds. The potential effect of a time savings of 39 seconds per study is modeled in Table 5 for a variety of clinical settings. It is assumed that 50% of all examinations are contrast enhanced. It is further assumed that a noncontrast examination requires approximately 60% as much time as a contrast examination, since noncontrast examinations do not require IV access or contrast preparation time and tend to have shorter scan durations.

DISCUSSION

Radiologic technologists are in short supply. There is a 15.3% hospital job-vacancy rate for imaging technologists, surpassing the rate for the more publicized nursing shortage, as reported in a study by the American Hospital Association.² A shortage of technologists is reported in 71% of hospitals, resulting in a market where the most experienced technologists often go to the highest bidders. Therefore, improving salaries, benefits, and work conditions has become essential to staff retention. This means that CT departments must place a higher value on job satisfaction and favorable work conditions for technologists.

The recent introduction of prefilled contrast-media syringes compatible with a specific power injector potentially allows for more rapid loading and cleanup of the injector. In addition, prefilled syringes minimize the risk of contrast spilling on the technologist, contamination of the contrast through lapses in sterile technique during filling, and misadministration of contrast due to mislabeling. Significant air bubbles can be generated by rapid aspiration of contrast from a bottle, so prefilled syringes minimize the risk of air-bubble injection. There is also a decreased potential risk of breakage, since prefilled syringes are plastic, but bottles of contrast are glass. Prefilled syringes are also more compliant with new medication standards proposed by the Joint Commission on Accreditation of Healthcare Organizations³ stating that, to ensure safe and accurate dispensing of medications, all medications must be appropriately and safely labeled using a standardized method. The standards further state that medications are to be dispensed in the most ready-to-administer form possible to minimize opportunities for error.³ Prefilled syringes fulfill these criteria much better than hand-filled syringes. Frequently, bottle-filled cartridges or syringes filled with contrast are not fully labeled. The potential advantages of prefilled syringes have been discussed at length.⁴

The impressive gain in efficiency shown by this study may actually underestimate the efficiency gains possible through use of prefilled syringes. The participating centers were not using prefilled syringes prior to the study, and only 2 of 29 technologists monitored for the study had extensive experience using prefilled syringes; in effect, the participating centers were at the bottom of the learning curve. It is likely that greater efficiency could be realized at centers that have already incorporated prefilled syringes into their departmental routines.

This study has some limitations. The overall time-and-motion data are very sensitive to issues not related to contrast administration. In fact, only 8.8% of total examination time was at all related to contrast preparation, injection, or cleanup. A further limitation was that the patient populations from the participating centers were not balanced in terms of patient source (inpatient, outpatient, or emergency department) or contrast method used. Since the data collected in this study are heavily skewed toward outpatient examinations, the study findings are most relevant for the outpatient setting. Contrast examinations, however, are more common in this group of patients. However, contrast examinations are more common in this group of patients.

CONCLUSION

In this study, contrast loading times decreased 33% when prefilled syringes were used. In addition, room setup efficiency increased 10% and overall examination efficiency increased 3%. These findings suggest that the use of prefilled syringes can potentially increase CT department throughput while improving technologists' satisfaction levels. As actual scanning times continue to decrease, the time spent administering contrast will become an increasingly large part of overall examination time, making efficiency differences between prefilled syringes and bottle-filled cartridges even more pronounced. Modeling the data obtained in this study shows that a facility could save from 4 to 8 days per year per scanner by converting to prefilled-syringe use, depending on workloads and scheduling efficiency. If the time saved by using prefilled syringes is used to perform additional examinations, the revenue generated might offset or exceed the incremental cost of converting to prefilled contrast-media syringes.

The study reported here was funded, in part, by an educational grant from Bracco Diagnostics Inc. Data collection for the time and motion study was managed by Dale Ewalt, VP, Collaborative Group, Hunt Valley, Md.

David S. Enterline, MD, is assistant professor of radiology, Duke University Medical Center, Durham, NC.

References:

1. Rubin GD. Techniques for performing multidetector-row computed tomography angiography. Techniques in Vascular and Interventional Radiology. 2001;4:2-14.
2. AHA Commission on Workforce for Hospitals and Health Systems. In Our Hands: How Hospital Leaders Can Build a Thriving Workforce. Chicago: American Hospital Association; 2002.
3. Joint Commission on Accreditation of Healthcare Organizations. Compre-hensive accreditation manual for hospitals: proposed revisions to medication use standards. Sections TX.3.9 and TX.3.10. Available at: http://www.jcaho.org. Accessed January 17, 2003.
4. Enterline DS. Prefilled syringes: applications in CT imaging. Applied Radiology. 2001;30(suppl):1-14.