Evaluation of Contrast Injection Site Effectiveness: Thoracic CT Angiography in Children With Hand Injection of IV Contrast Material

Transcription

1 Pediatric Imaging Original Research Schooler et al. Injection Sites for CTA in Children Pediatric Imaging Original Research Gary R. Schooler 1 David Zurakowski 2 Edward Y. Lee 1 Schooler GR, Zurakowski D, Lee EY Keywords: contrast injection, pediatric patients, thoracic CT angiography (CTA) DOI: /AJR Received March 7, 2014; accepted after revision May 10, Department of Radiology, Boston Children s Hospital and Harvard Medical School, 300 Longwood Ave, Boston, MA Address correspondence to E. Y. Lee (edward.lee@childrens.harvard.edu). 2 Department of Anesthesiology, Boston Children s Hospital and Harvard Medical School, Boston, MA. AJR 2015; 204: X/15/ American Roentgen Ray Society Evaluation of Contrast Injection Site Effectiveness: Thoracic CT Angiography in Children With Hand Injection of IV Contrast Material OBJECTIVE. The purpose of this study was to evaluate the effectiveness of various contrast injection sites when performing thoracic CT angiography (CTA) using hand injection of IV contrast material in infants and young children with a small IV catheter. MATERIALS AND METHODS. We used our hospital information system to retrospectively identify consecutive pediatric patients who underwent thoracic CTA with hand injection of contrast material from August 2012 to July The study indication for thoracic CTA was to evaluate the thoracic systemic arterial vasculature and pulmonary venous vasculature. Both qualitative and quantitative evaluation of thoracic CTA image quality was performed by two reviewers independently. Qualitative evaluation of thoracic CTA image quality was performed by visual assessment of the degree of contrast enhancement in the ROI on a 4-point scale. Quantitative evaluation was performed by measuring attenuation obtained with the ROI placed within the aorta at two locations (the level of the aortic arch and at the level of the carina) to evaluate the thoracic systemic arterial vasculature. For evaluation of the pulmonary venous system, attenuation measurements were obtained at the center of the left atrium. Six individual injection sites were identified: head, jugular vein, arm vein, hand vein, leg vein, and foot vein. Injection sites were categorized into three regional groups: head-neck region (head vein and jugular veins), upper extremity region (arm and hand veins), and lower extremity region (leg and foot veins). Comparisons of attenuation values between individual and regionally grouped contrast injection sites were determined using the F-test in ANOVA. RESULTS. The study cohort included 50 pediatric patients (29 boys and 21 girls; mean age, 8 months ± 1 year; range, 1 week to 5 years) who underwent a total of 50 thoracic CTA studies for evaluating the thoracic systemic arterial vasculature (n = 38; 76%) or pulmonary venous vasculature (n = 12; 34%). All 50 thoracic CTA studies were of diagnostic quality on the basis of qualitative evaluation (all 3). For quantitative evaluation with the threshold for a diagnostic thoracic CTA study defined as attenuation greater than 150 HU in the ROI, all 50 thoracic CTA studies were technically successful (aortic arch, 380 ± 150 HU; descending 392 ± 155 HU; and left atrium, 352 ± 90 HU). There were no significant differences in mean attenuation between individual injection sites (p > 0.20 for each comparison) or different regional groups (p > 0.50 for each comparison). CONCLUSION. Diagnostic quality thoracic CTA can be achieved with hand injection of IV contrast material in infants and young children with a small IV catheter, independent of the IV access site. T horacic CT angiography (CTA) is currently a frequently performed procedure in the pediatric population. CTA, which is a noninvasive imaging modality, can be used for various clinical indications, including evaluation of congenital and acquired intrathoracic vascular abnormalities such as vascular rings and sling, aortic coarctation, pulmonary arteriovenous malformation, pulmonary sequestration, pulmonary embolism, and postsurgical vascular graft and stent patency [1 13]. Thoracic CTA is faster and safer and associated with less ionizing radiation than conventional catheter-based angiography, once regarded as the reference standard for evaluating the thoracic vasculature. These benefits have further increased the routine use of thoracic CTA in pediatric patients in recent years. However, obtaining diagnostic quality thoracic CTA with optimal enhancement of vessels of interest often is still challenging, particularly in infants and young AJR:204, February

2 Schooler et al. children because only small IV catheters are available for contrast administration. A critical component in successful thoracic CTA in the pediatric patient is the effective delivery of IV contrast material, which affects the contrast enhancement of the vessel of interest. Diagnostic quality thoracic CTA in pediatric patients can be obtained when injecting contrast material from various peripheral IV access sites [14]. However, the previous study was performed using mechanical injection (i.e., power injection) of IV contrast material. In infants and young children with only small peripheral IV catheters, there is concern and reluctance among radiologists whether mechanical administration of IV contrast material is safe and whether hand injection of contrast material is effective for obtaining diagnostic quality thoracic CTA in this patient population. Unfortunately, there is currently a paucity of information regarding the effectiveness of various contrast injection sites for performing thoracic CTA with hand injection of IV contrast material in infants and young children. Such information, which can help determine the site of hand injection of IV contrast material for obtaining diagnostic quality thoracic CTA, would be clinically valuable. Therefore, the purpose of this study was to evaluate the effectiveness of various contrast injection sites when performing thoracic CTA using hand injection of IV contrast material in infants and young children with a small IV catheter. Materials and Methods Subjects The institutional review board approved the retrospective review of radiologic and clinical data for this study. The need to obtain patient consent was waived, but patient confidentiality was protected in accordance with HIPAA guidelines. We used our hospital information system to identify consecutive pediatric patients ( 18 years old) who underwent thoracic CTA with hand injection of contrast material from August 2012 to July The study indication for thoracic CTA was to evaluate the thoracic systemic arterial vasculature and pulmonary venous vasculature. For each patient, only the initial thoracic CTA examination was included for analysis. From these inclusion criteria, an initial study cohort of 51 patients was identified who underwent a total of 51 thoracic CTA examinations. One pediatric patient who underwent thoracic CTA for evaluation of systemic thoracic arterial vasculature using a large femoral line catheter (7 gauge) was excluded from the study. Therefore, the final study cohort consisted of 50 pediatric patients who underwent a total of 50 thoracic CTA studies. Among these 50 thoracic CTA studies, 38 (76%) were performed for evaluation of the systemic thoracic arterial vasculature and 12 (24%) were performed for evaluation of the pulmonary venous vasculature. CT Imaging Technique Sedation At our institution, the ability of the patient to cooperate for thoracic CTA is assessed in advance by a CT nurse and pediatric anesthesiologist. Children more than 4 years old (n = 1; 12%) were able to undergo thoracic CTA without sedation or general anesthesia, and the remaining 49 patients who were 4 years old or younger required adjuvant medication for sedation. IV contrast material All thoracic CTA examinations were performed using nonionic iodinated contrast material (iopamidol 370 mg I/mL, Isoview, Bracco Diagnostics) at a dose of 1.5 ml/kg (not to exceed 150 ml). All catheters were carefully inspected by a nurse who evaluated the integrity and patency by flushing the catheter with a saline solution and confirming blood return before contrast injection. The contrast material was hand injected by an experienced pediatric nurse who was trained to administer the contrast material at an approximate rate of 1 ml/s. The injection site was monitored closely at the time of injection to minimize the risk of contrast extravasation. The size of the IV catheter and IV access site for iodinated contrast injection were recorded at the time of the examination for each patient. After the completion of contrast injection and CT, all catheters were evaluated for evidence of complications, such as catheter rupture or contrast extravasation. Any complication related to hand injection of the contrast material was recorded. Thoracic CTA technique All of the thoracic CTA studies were performed using a 64-MDCT scanner (Sensation 64, Siemens Healthcare). Before acquisition of axial CT images, topographic images were obtained to determine the area of coverage, which extended from the thoracic inlet to the level of the diaphragm. The thoracic CTA study was performed in the supine position at end-inspiration. All thoracic CTA studies were performed with the following parameters: 0.6-mm collimation, weight-based low-dose kilovoltage and tube current, high-speed mode, and pitch equivalent of A slice thickness of 1.25 mm was used to reconstruct the dataset for review of the axial thoracic CTA images. The radiologist or CT technologist initiated acquisition of the thoracic CTA images when the contrast enhancement of 150 HU or greater was achieved using bolus-tracking monitoring with the ROI placed in the left ventricle. When an upper extremity IV access site was used, scanning was performed in an inferior to superior (diaphragm to apexes) direction, and when using a lower extremity IV access site, scanning was performed in a superior to inferior (apexes to diaphragm) direction to reduce streak artifact from the contrast bolus. Thoracic CTA Image Evaluation Two board-certified pediatric radiologists independently reviewed all thoracic CTA studies. Although both reviewers knew the thoracic CTA studies were performed for evaluation of thoracic vessels in children, they were blinded to all other clinical information, reports of thoracic CTA studies, and results of prior imaging studies. For CTA image quality assessment, both quantitative and qualitative evaluation of image quality was performed. Qualitative evaluation of thoracic CTA image quality Qualitative evaluation of thoracic CTA image quality was performed by visual assessment of the degree of contrast enhancement in the ROI. The reviewers independently scored each thoracic CTA study on a 4-point scale that was based on the degree of contrast enhancement as follows: 1, unacceptable (nonvisualization of contrast material); 2, suboptimal (minimal contrast opacification); 3, good (sufficient contrast opacification); and 4, excellent (optimal contrast opacification). For cases in which there was a discrepancy between the two reviewers observations, the reviewers reevaluated the cases together and reached a final decision by consensus in a third review session. Diagnostic quality was considered to be achieved when the score was 3 or higher. Quantitative evaluation of thoracic CTA image quality Quantitative evaluation of thoracic CTA image quality was performed by assessing the degree of opacification of the vessels or cardiac chamber of interest with mean attenuation measurements performed on our PACS workstation (Synapse, Fujifilm Medical Systems). Thoracic CTA images were evaluated in the axial plane in standard soft-tissue (level, HU; width, HU) windows. Measurements were obtained and recorded by two board-certified pediatric radiologists by placing an ROI within the vessel of interest that was equal to one half the diameter of the vessel and positioned centrally within the lumen of the vessel (at the level of the midaortic arch and at the level of the carina) for thoracic CTA studies performed for evaluation of the systemic thoracic arterial vasculature, a method based on previously reported CT angiography quality criteria [15, 16]. A similar meth- 424 AJR:204, February 2015

3 Injection Sites for CTA in Children od of mean attenuation measurement was used for evaluation of the thoracic CTA studies performed for evaluation of the pulmonary venous vasculature by placing an ROI one half the diameter of the left atrium centrally within the chamber. The thoracic CTA studies were considered to have diagnostic opacification of the vessels or cardiac chamber of interest when the measured mean attenuation value was 150 HU or greater [15, 17]. Statistical Analysis Age, sex, and descriptive statistics were reported. To ascertain image quality of thoracic CTA on the basis of hand injection of IV contrast material, attenuation values for the aortic arch, descending thoracic aorta, and left atrium were compared among six injection sites and three regional groups by ANOVA and summarized by means and standard deviations. Statistical analysis was performed using SPSS Statistics, version 21.0 (IBM). Two-tailed p values less than 0.05 were considered statistically significant [18]. Results Patient Population Our study population consisted of 50 pediatric patients, 29 boys (57%) and 21 girls (43%) with a mean age (± SD) of 8 months ± 1 year, (range, 1 week to 5 years). All 50 thoracic CTA studies were performed without complications. Location of IV Catheters Six IV access sites for contrast injection were identified: head (n = 1, 2%), jugular vein (n = 3, 6%), arm vein (n = 11, 22%), hand vein (n = 16, 32%), leg vein (n = 1, 2%), and foot vein (n = 18, 36%). When injection sites were categorized into three regional groups, there were four (8%) in the head-neck region (head and jugular veins), 27 (54%) in the upper extremity region (arm and hand veins), and 19 (38%) in the lower extremity region (leg and foot veins). Size of IV Catheters The pediatric patients included in our study underwent thoracic CTA studies with an indwelling catheter size of 22 gauge (n = 16, 32%) or 24 gauge (n = 34, 68%). Contrast Enhancement The results of the subjective (qualitative assessment) and the objective (quantitative assessment) of thoracic CTA image quality will be presented next. Qualitative assessment The two reviewers qualitative assessments were in agreement in 48 (96%) of 50 thoracic CTA studies. For the remaining two thoracic CTA studies with initial disagreement, the two reviewers were able to reach a consensus. All 50 thoracic CTA studies were technically successful, showing good (grade 3, n = 7, 14%) or excellent (grade 4, n = 43, 86%) contrast enhancement in the ROI on visual qualitative assessment by two independent reviewers (Fig. 1). No thoracic CTA study showed poor or limited degree of contrast enhancement. Quantitative assessment All 50 thoracic CTA studies were technically successful on the basis of quantitative assessment. The overall mean attenuation and SD for all injection sites was aortic arch, 380 ± 150 HU; descending 392 ± 155 HU; and left atrium, 352 ± 90 HU. Individual IV access sites The mean attenuation and SD measurements at individual IV access sites were as follows: head vein aortic arch: 511 HU, descending thoracic aorta at the level of the carina, 546 HU; jugular vein aortic arch, 261 HU, descending thoracic aorta at the level of the carina, 266 HU, and left atrium 344 HU ± 62 SD; arm vein aortic arch, 447 ± 217 HU, descending thoracic aorta at the level of the carina, 464 ± 219 HU, and left atrium: 370 ± 23 HU; hand vein aortic arch, 366 ± 120 HU, descending thoracic aorta at the level of the carina, 377 ± 127 HU, left atrium, 399 ± 173 HU; leg vein aortic arch: 546 HU, descending thoracic aorta at the level of the carina, 603 HU; foot vein aortic arch: 337 ± 122 HU, descending thoracic aorta at the level of the carina, 337 ± 112 HU, and left atrium: 321 ± 40 HU. There was no statistically significant difference in attenuation measurement values among the six different individual IV access injection sites at the level of the aortic arch (p = 0.38), descending thoracic aorta at the level of the carina (p = 0.211), or left atrium (p = 0.37) (p > 0.20 for each comparison, ANOVA). Grouped IV access sites Mean attenuation measurements within the three groups were as follows (Fig. 2): head-neck group (n = 4): aortic arch, 386 ± 177 HU, descending 406 ± 198 HU, and left atrium: 344 ± 88 HU; upper extremity group (n = 27): aortic arch, 399 ± 167 HU, descending thoracic aorta at the level of the carina, 413 ± 172 HU, and left atrium: 387 ± 124 HU; and lower extremity C Fig. 1 Sites at which ROIs were placed and used for qualitative and quantitative evaluation of vessel or chamber of interest opacification. A C, CT images show ROI (arrow) at level of aortic arch (A), ROI (arrow) at level of carina in descending thoracic aorta (B), and ROI (asterisk) placed centrally within left atrium (C) when evaluating pulmonary venous structures for grouped injection sites within head-neck, upper extremity, and lower extremity regions. Actual attenuation measurements from ROI within selected images are provided for reference. A B AJR:204, February

4 Schooler et al. Attenuation (HU) p = Aortic Arch p = 0.57 Descending Thoracic Aorta group (n = 19): aortic arch, 352 ± 130 HU, descending 356 ± 129 HU, and left atrium: 322 ± 40. There was no statistical difference in attenuation measurements among the three injection site groups at the level of the aortic arch (p = 0.68), descending thoracic aorta at the level of the carina (p = 0.57), or left atrium (p = 0.54) (p > 0.50 for each comparison, ANOVA). Discussion The results from our study show that when hand injection of IV contrast material for thoracic CTA is used, a diagnostic examination can be obtained from all six different IV injection sites (head, jugular, arm, hand, leg, and foot veins) in infants and young children with a small IV catheter. No statistically significant difference was identified in the attenuation measurements obtained from the thoracic vessels or cardiac chambers of interest when evaluating the different IV injection sites for both individual and grouped IV access sites. Our findings thus support the use of hand injection of IV contrast material in infants and young children with only available small IV catheters when thoracic CTA studies are performed. To our knowledge, our study is the first to evaluate contrast injection site effectiveness when performing thoracic CTA studies in infants and young children with small IV catheters via hand injection of contrast material. Because of the small body size, it is often possible to place only a small IV catheter in infants and young children undergoing thoracic CTA, which requires a high degree of contrast enhancement for an accurate diagnosis. Our findings confirm and expand on those of a previous study focused on image quality in pediatric cardiovascular p = 0.54 Left Atrium Fig. 2 Graph shows average attenuation values calculated for aortic arch, descending thoracic aorta, and left atrium grouped by IV contrast injection site: head-neck vein (white), upper extremity vein (gray), lower extremity vein (black). Bars for p value are provided for reference. There was no statistical difference in attenuation measurements among three injection site groups at level of aortic arch (p = 0.68), descending thoracic aorta at level of carina (p = 0.57), or left atrium (p = 0.54). CTA from different contrast injection sites by Yang et al. [14]. In that study, the investigators showed that mechanical injection of contrast material via head, arm, and leg vein injection sites can yield diagnostic cardiovascular CTA studies in infants and young children. The results of our study support the findings of their study that diagnostic-quality thoracic CTA studies can be obtained with administration of IV contrast material via various injection sites in infants and young children. However, the difference between our study and that of Yang et al. is the different method of administering IV contrast material. Although mechanical injection of IV contrast material was used in their study, we used hand injection of IV contrast material in our study. The results of our study show a new finding that hand injection via these IV contrast injection sites in infants and young children can also result in diagnostic-quality thoracic CTA studies. When using hand injection of IV contrast material for thoracic CTA studies in infants and young children, it is crucial to initiate scanning when optimal contrast enhancement (> 150 HU) is achieved in the region of interest [15, 17]. Our CT technique using the bolus tracking method to decide when to initiate CT ensured that thoracic CTA studies would be of diagnostic quality. We believe the bolus tracking method should be considered for CT, particularly when hand injection of IV contrast material is used for thoracic CTA studies in this pediatric population. When thoracic CTA is performed, adequate delivery of contrast material is absolutely necessary for obtaining sufficient vascular contrast enhancement for an accurate diagnosis. Despite multiple prior studies that have shown it is both safe and effective to perform mechanical injection of contrast material through both central and peripheral venous access devices in the pediatric population [19 21], many imaging centers are often reluctant to use mechanical injection of contrast material in infants and young children via a smallcaliber IV catheter, mainly because of the potential complications of catheter rupture or contrast extravasation. To avoid mechanical injection of contrast material in this pediatric population, contrast material can be hand injected, but the effectiveness of hand injection of contrast material at different injection sites with a small IV catheter has often been questioned. From a practical standpoint, the combined results of the previously published study and our study suggest that both mechanical and hand injection of contrast material via a small IV catheter at various injection sites can provide diagnostic-quality thoracic CTA studies in infants and young children. Although one study in adults indicated no statistically significant difference in the incidence of contrast extravasation at the IV access site when comparing mechanical and hand injection methods of contrast material delivery [22], there is a paucity of literature currently available regarding the safety of hand injection of IV contrast material via peripheral IV access, particularly in the pediatric population. Much of the available literature focuses on the safety of contrast administration via central venous catheter, particularly by mechanical administration. A study measuring in vitro pressure generated within central venous catheters by hand injection of contrast material compared with power injection of contrast material revealed that hand injection tended to have a higher peak pressure for equivalent average flow rates when compared with mechanical injection [23]. In our patient population, all 50 CTA studies were performed without complication, including those related to contrast media administration, which somewhat ensures the safety of hand injection of IV contrast material in infants and young children with a small IV catheter. However, we believe that future studies consisting of larger study populations are needed to better elucidate the safety of hand injection of contrast material via small peripheral IV sites in the pediatric population. We recognize that there are several potential limitations to our study. First, the patient population size of our study was modest. Considering our relatively modest study population, a future multicenter study with a larger patient population is necessary to confirm our 426 AJR:204, February 2015

5 Injection Sites for CTA in Children preliminary recommendation that hand injection is sufficient for obtaining diagnostic thoracic CTA in infants and young children with a small IV catheter at various access sites. Second, we recognize that the mean age of 8 months in our patient population is young and may not provide an accurate representation of results in an older pediatric patient population. However, we emphasize that, in clinical practice, many of the patients who undergo thoracic CTA under the conditions in our study, with hand injection of IV contrast material and variable IV access sites, are infants and young children. Older children with secure and larger peripheral IV access typically undergo thoracic CTA studies with mechanical injection of IV contrast material similar to the adult population. Third, vascular contrast enhancement largely depends on the contrast injection rate. Because of the hand injection of contrast material evaluated in our study, contrast injection rates could not be standardized. However, we expect the variability in the contrast injection rate to be small when the hand injection technique is used by an experienced pediatric nurse trained to administer the contrast material at an approximate rate of 1 ml/s. In conclusion, our data show that diagnostic quality thoracic CTA can be achieved with hand injection of IV contrast material in infants and young children independent of IV access sites. We believe the results of our study can be used by the radiologists who often have to make a decision regarding the use of hand injection of IV contrast material in infants and young children with a small IV catheter at various access sites when performing thoracic CTA. References 1. Lee EY, Siegel MJ, Hildebolt CF, Gutierrez FR, Bhalla S, Fallah JH. 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Evaluation of angioarchitecture of pulmonary sequestration in pediatric patients using 3D MDCT angiography. AJR 2004; 183: Lee EY, Boiselle PM, Cleveland RH. Multidetector CT evaluation of congenital lung anomalies. Radiology 2008; 247: Lee EY, Tracy DA, Mahmood SA, Weldon CB, Zurakowski D, Boiselle PM. Preoperative MDCT evaluation of congenital lung anomalies in children: comparison of axial, multiplanar, and 3D images. AJR 2011; 196: Lee EY, Dorkin H, Vargas SO. Congenital pulmonary malformations in pediatric patients: review and update on etiology, classification, and imaging findings. Radiol Clin North Am 2011; 49: Victoria T, Mong A, Altes T, et al. Evaluation of pulmonary embolism in a pediatric population with high clinical suspicion. Pediatr Radiol 2009; 39: Sunidja AP, Prabhu SP, Lee EY, Sena L. 64-row- MDCT evaluation of postoperative congenital heart disease in children: review of technique and imaging findings. Semin Roentgenol 2012; 47: Hlavacek AM. 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