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1
Division of Pediatric Radiology, Department of Radiology, McGovern-Davison
Children's Health Center, Rm. 1905, Duke University Health System, Box 3808,
Erwin Rd., Durham, NC 27710.
2
Division of Emergency Medicine, Departments of Surgery and Pediatrics, Duke
University Health System, Durham, NC 27710.
Received July 3, 2001;
accepted after revision September 14, 2001.
Presented at the annual meeting of the American Roentgen Ray Society,
Seattle, WA, April—May 2001.
Abstract
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MATERIALS AND METHODS. Multidetector CT examinations were set up using either a conventional or a color-coded format for a period of 6 weeks each. Variations (errors) from protocol parameters (including tube current, detector configuration, table speed, and IV contrast media dose) were tabulated. Qualitative assessment consisted of a survey of CT technologists (n = 20) for preference in six areas related to ease of use and clarity of the formats.
RESULTS. There were 44 CT examinations (n = 30 infants and children) in the conventional group and 55 CT examinations (n = 31 infants and children) in the color-coded protocol format group. Overall, the number of errors was significantly less in the color-coded group (p < 0.01), with a significantly lower error percentage in individual parameters affecting radiation dose, including tube current, detector configuration, and table speed (p < 0.05). In all areas, the color-coded format was preferred over the conventional format (p < 0.0003).
CONCLUSION. Color-coded CT formatting is an extension of a clinical color-coded system. This system provides an easy, expeditious, consistent, and preferable format for general pediatric body CT protocols. Most importantly, the color-coded system can reduce variations (errors) in the radiology department.
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One potential result of inappropriate CT parameters is unnecessary radiation dose. Recently, concern was raised about the risk for radiation-induced malignancy after CT [4]. At the same time, guidelines were provided for size-based adjustments in pediatric examination parameters [5, 6]. Although these guidelines are an important step toward the goal of reducing excessive radiation in children, another goal should be to provide a format in which these guidelines can be easily, consistently, and accurately followed. This would minimize the potential for errors in performing CT examinations. Reduction of medical error is an important contemporary topic in medicine [7] and should be applicable to radiology. To our knowledge, no data exist evaluating the effect of the format for CT protocols (or guidelines), variations (or errors) between protocols, and actual examination parameters.
One system that has been shown to reduce medical errors is the Broselow-Luten pediatric color-coded system. This system uses a color assignment based on the length or weight of a child [8, 9]. The appropriate support equipment (such as endotracheal tube size), correct medication doses, and IV fluid volumes are predetermined for each color zone. This method has been shown to substantially reduce the error rate in the emergency stabilization of infants and children in which care (i.e., range of sizes) can also be complicated (Frush KS et al., presented at the Emergency Medical Services for Children National Forum on Enhancing Pediatric Patient Safety, January 2001). Based on this success and the fact that the concept of color-coding is potentially applicable across a wide range of children's health care, we decided to evaluate this system for routine body CT in infants and children.
The objectives of this investigation were to compare our conventional weight-based body multidetector CT scanning protocol format with a color-coded format for the type and frequency of variations from the actual CT examination and technologist preference.
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The conventional format, modeled after existing size-based chart formats for pediatric helical CT [5, 10, 11], consisted of our routine weight-based instructions for scanning of the general chest, chest and abdomen, or abdomen (Tables 1 and 2).
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The color-coded format was created on the basis of ongoing evaluation of a
color-coded system in the emergency department at our institution. This
system, the Broselow-Luten pediatric system, has been previously described in
more detail [9]. Basically,
infants and children are assigned to a color zone based on size (weight or
length). The color zones were established using anatomic and physiologic
parameters for resuscitation and support apparatus, medications, and IV fluids
and therefore do not correspond to equal increments of weight, such as 10 kg
used in the conventional weight-based format
[5]. For CT, we modified the
color-coded system by adding a ninth weight category of black (40.5-55 kg)
because this weight group is not included in the established Broselow-Luten
pediatric system. For each child over 55 kg (
120 lbs), our adult protocols
for body CT were performed; these children were not included in the
investigation, irrespective of age. An example of a color-coded format for a
child weighing 22.5-31.4 kg (orange) is found in
Table 3.
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Two 6-week study periods were compared. The first period consisted of CT examinations performed using the conventional format, which had been in place for several months. Subsequently, the color-coded format was implemented on a 6-week trial basis. As part of our Ct practice, regular meetings are held with the technologists to discuss any problems with pediatric CT. The only difference in the meeting content before implementation of the color-coded format was a statement that the format for examination parameters would change, but that the CT examination parameters themselves and the weight-based principle would be similar for any given weight. Conventional and color-coded formats were not entered into the scanner software but were entered individually for each infant or child on the basis of weight.
All protocols were for a multidetector scanner (LightSpeed QX/i; General Electric Medical Systems, Milwaukee, WI). This scanner had been in use at our institution for pediatric CT for over 18 months before the format modification. The CT technology personnel remained unchanged during this period. The range of CT examination experience was from 1 to 20 years (mean, 7.5 years).
To compare the two formats, both the objective and subjective assessments were made at the end of the 12-week period. For the objective measure, any variation of the actual CT examination parameters from the protocol parameters was recorded. This information was obtained through a data sheet and the filmed CT examination. For each CT examination performed at our institution, a data sheet is filled out that includes information on examination indications (categorized as trauma, cancer, inflammatory, or other) and IV contrast material, including amount, method of injection (manual or power injection), rate (if power injector is used), and delay from the end of contrast administration to the beginning of scanning. In addition, if chest and abdominal CT were both to be performed on the same patient, the chest scan was always obtained after the abdominal scan. Finally, filming parameters, including window and level, and filming format (e.g., 12 images on one sheet) were also recorded. Although the amount of oral contrast material for scanning of the abdomen is indicated on both formats, it was not possible to document how much was ingested. Therefore, this was not part of the comparison. A total of 12 parameters were tabulated for each CT examination (Table 4).
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A subjective comparison of both formats was also made. At the conclusion of the investigation, all 20 technologists were given the same questionnaire (Appendix 1). This questionnaire consisted of a 6-point preference scale for several categories comparing the two formats and also asked for any additional comments regarding strengths or weaknesses of the two formats.
For statistical analyses, age, weight, CT indication, and tube current, comparisons were performed using two-group t tests. Variation (error) analyses were performed using Fisher's exact test. Qualitative variables on the questionnaire for the two groups were compared using the sign test.
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A total of 44 CT examinations were performed in the conventional format group; 22 of these were chest examinations and 22 were abdominal examinations. In the color-coded format group, 55 total CT scans consisted of 28 chest and 27 abdominal examinations.
Although it appears that the number of CT examinations was small for a busy university-based practice over a 3-month period, not all children undergoing a CT examination were included in the study. We have five CT scanners that can be used for pediatric CT, only two of which are multidetector scanners. In addition, some of the children required CT using parameters other than those in the general protocols in either the conventional or color-coded format. For example, a dual-phase renal examination or a high-resolution CT of the chest would require a protocol different than the general body protocols. These examinations were excluded. If specific modifications were intentionally made to the protocol that differed from the general protocols, these examinations were also not included. Protocols are approved or modified for each individual pediatric CT examination either by a pediatric radiologist or by a radiology resident.
Table 4 compares the two groups with respect to a number of variations divided into three technical categories. These technical categories consisted of examination parameters (including tube current, kilovoltage, detector configuration, and table speed), IV contrast material (including amount and rate of administration, examination delay, and CT sequence in which the chest scan was obtained after the abdominal scan), and display (including algorithm, window and level for requested algorithms, and images per sheet).
A total of 48 variations were found with the conventional format, yielding a variation frequency of 9% (44 examinations x 12 parameters tabulated per examination = 528 total technical parameters that were monitored). The color-coded format, however, resulted in only a 3% frequency of variation (22 variations in 55 examinations x 12 = 660 total technical parameters that were monitored), one third of that of the conventional format. Overall, there was a significantly greater number of CT examinations with one or more variations in the conventional versus color-coded format groups (p < 0.002), as well as the total error occurrence between the groups (p < 0.01). Group comparisons for individual types of variations, placed in the three technical categories, are also found in Table 4. In the category of examination parameters, a significantly greater occurrence of variations (p < 0.05) was found using the conventional format for tube current, detector configuration, and table speed. When variations were encountered in these categories, the amount of resulting radiation was always greater (e.g., higher tube current or slower table speed than indicated on the protocol). Of note, there was no significant difference between the two groups in the magnitude of difference for tube current. The mean variation for tube current was +8.9 mA for the conventional group and +7.0 mA for the color-coded group.
An analysis of the results of the technologist questionnaire indicated a marked preference for the color-coded format over the conventional format (p < 0.0003). No technologist indicated a strong preference for the conventional format. Only one technologist preferred the conventional format and only in one of five categories. The average of the 20 ratings for all five categories fell between preference and strong preference for the color-coded format (mean response value was 3.2 on a scale of 4.0) (Appendix 1). This was statistically significant for all six responses (p < 0.003). Fifteen of 20 technologists wrote positive comments about the color-coded format, and comments from 13 (87%) indicated that the color-coded system was easier to use or to understand. There were only two positive comments for the standard format, and these related to a single page for the conventional format versus several pages for the color-coded format. Seven (78%) of nine negative comments about the conventional format also dealt primarily with a more confusing or less easy-to-follow system.
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This issue of error in the clinical medical care of children is as important in radiology as in other specialties in medicine. It has recently been shown that CT parameters with single-slice CT are not always adjusted for children, resulting in inappropriate radiation exposure [2]. The risks of radiation dose have recently been emphasized [4] with increasing public awareness and concern [13]. Radiologists and other radiology personnel have the responsibility to minimize this risk in children [6]. Although the lack of adjustments is arguably due to a lack of published guidelines [6], there are limited recommendations for the general reduction of radiation dose in pediatric single-detector body CT [14,15,16,17]. Even if guidelines are part of the scanning practice, it is also important to assess the ease in implementing these guidelines, which we have focused on as the protocol format. To our knowledge, this is the first investigation to look at both the variation between protocol parameters and the actual examination parameters and to evaluate a format that potentially reduces the number of variations.
For these reasons, we adapted the color-coded system, which was already in use in pediatric emergency care, to CT examinations. This color-coded format for pediatric CT protocols, when compared with a conventional system, resulted in less variation (or error) in examination performance and, importantly, was overwhelmingly preferred by CT technologists.
There are several possible explanations for this reduction in error. First, the color-coded format presents each weight category on a separate sheet, rather than in a single table as does the conventional format. It is reasonable to assume that breaking down the conventional format table into individual weight divisions on separate pages would have resulted in a similar variation level. However, the limited CT guidelines that exist for children are in tabular formats [5, 10, 11], and this was the standard against which we were comparing the color-coded format. It is also possible that the technologists were more careful when manually entering CT parameters because the color-coded system was a new and less familiar format. However, the technologists' responses on the survey overwhelmingly indicated the color-coded system was easier to use and made more sense. We believe that this was a major reason, rather than familiarity, for less variation with the color-coded system.
An argument can be made to simply preprogram a weight-based set of protocols in the scanner and not to enter scan parameters for each CT examination. This is now the case based on our results, but we first wanted to compare the two formats for setting up individual CT examinations. We had several reasons for using this approach. Even with preprogrammed protocols, there can be a need for a hard copy protocol source such as a book. For example, in an environment in which adults are also examined by CT, the number of protocols for body CT (including research protocols) can be extensive, with frequent modifications. At our institution, we have over 150 CT protocols for infants, children, and adults; and these protocols change frequently. The resources available to continually update these parameters on a scanner console can be limited, and reference to a protocol book for many CT examinations is more practical. The protocols on the CT scanner may need to be routinely checked and adjusted for accuracy against a standard such as a protocol book. Furthermore, not all parameters, such as IV and oral contrast material amount, can be entered on the console. These parameters are also important for easy, consistent, and accurate CT performance and are part of written formats. Finally, and perhaps most importantly, there is an increasing emphasis on the need to adjust CT examination parameters in children on the basis of the size of the child [4, 5, 11]. Although important, these adjustments will also amplify the number of protocols for pediatric scanning. For example, a single liver protocol may be used for adult scanning, but adjustments based on weight for children may increase the number of protocols by a factor of 10 [5].
Our study has several limitations. First, these formats were only tested on a single type of CT scanner. However, it is conceivable that the same types of complexities and potential for variations would be found on multidetector scanners from other manufacturers and similar color-coded formats developed for this equipment. Also, these protocol parameters are institutional, but they are ones that we have found to provide diagnostic images. Preferences and parameters would likely vary between institutions or practices. However, it was the format of these protocols that was tested, not the protocols themselves. Individualized modifications within the color-coded CT system could easily be made. Finally, although there were significant differences overall in the number of variations between the protocol parameters and the actual examination parameters comparing color-coded and conventional formats, we did not determine the potential risks with either examination quality or patient health (e.g., radiation dose) resulting from these variations. For example, given the small mean increase in tube current when variation occurred, a substantial increase in long-term risk is unlikely [4]. It is unclear why errors in tube current were usually greater than protocol. This may be because the technologists were also performing CT examinations on single-slice CT scanners where, because of different signal-to-noise ratios, the tube currents used were generally higher. There can be a slight increase in radiation exposure using a narrow detector configuration or slower table speed than requested; again, a direct link between this and adverse effects (i.e., cancer) is unproven. Nevertheless, it is incumbent on radiology personnel to do everything possible to adjust parameters to minimize radiation exposure in children. Finally, our evaluation of formats deals only with general protocols. However, specialized protocols such as dualphase scanning or high-resolution studies for the chest could also be easily color-coded.
A final and especially relevant justification for use of this color-coded system is that the system is expanding into other children's services at our institution, as well as other institutions. A single format obviates the need to depend on diverse and potentially confusing coding (color or other) formats for children across medical care, with potential for introducing more errors.
There are other important applications for this CT color-coded system, including musculoskeletal and central nervous system examinations, and for a more comprehensive system of weight-based care in the CT suite, including sedative medications, steroid premedication, resuscitation drugs, and IV fluids. This information could also include the weight-based normal vital signs that are critical in assessment and management in pediatric emergency care in the CT suite but are likely unfamiliar to most radiologists.
We conclude that the color-coded format for multidetector helical CT protocols for body scanning in children is one system that provides a simple and preferable method of scanning that results in close adherence to CT protocols, minimizing variations that can result in additional radiation dose to infants and children. This system is now in routine use in our department.
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