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ABSTRACT |
Thursday, May 4, 1:30 PM-3:30 PM
Abstracts 285-296
Moderators: Stephen F. Hatem, MD and Joel Gross, MD
1:30 PM
285. CT and US in Lower Abdominal or Pelvic Pain: Supplemental or Superfluous?
Kielar A.*; Platt J.; Radiology, University of Michigan Health System, Ann Arbor, MI.
Address correspondence to A. Kielar (aniakielar{at}gmail.com)
Objective: Computed tomography (CT) or ultrasound (US) is commonly performed in patients presenting to the emergency department (ED) with lower abdominal/pelvic pain. If the first exam does not reveal a cause or does not concur with symptoms, a second test may be considered. We studied the incremental value of performing both pelvic ultrasound and CT in emergency patients with this clinical presentation.
Materials and Methods: Retrospective analysis identified 1,062 patients (462 male, 600 female, average age 35 years) who underwent CT after presenting to our tertiary care ED with lower abdominal/pelvic pain between January and July, 2005. Further analysis identified a subset of 98 patients who also underwent pelvic ultrasound within a 48 hour interval. In this study group (6 male, 92 female, average age 26 years), 62 underwent US examination first, and the remaining 36 had CT first. In all cases, the US and CT images were retrospectively reviewed. In each case a determination was made whether the second imaging test had incremental value based on consensus reading of 2 reviewers. A test was felt to have incremental value when the original imaging diagnosis was changed or when additional findings on the second test had an impact on patient care based on a review of clinical, laboratory and subsequent follow-up findings. Pathologic proof was available in 37 cases (35%) and this group was additionally analyzed separately.
Results: In 62 patients undergoing US first, CT had incremental value in 33 cases (53%). When CT was performed first, US had incremental value in only 6 of 36 cases (17%). In the subset of 37 patients with pathologically proven diagnoses, when US was performed first, CT was found to have incremental value in 17 of 25 cases (68%) and changed the diagnosis in 11 cases (44%). Examples of new diagnoses included low lying appendicitis, pelvic diverticulitis and UVJ calculi. When CT was performed first, US provided additional information in only 2 of 12 cases (17%). In these cases, the US had an impact on patient care by better characterizing adnexal and uterine findings.
Conclusion: CT performed after an initial ultrasound examination often provides incremental value in the setting of acute lower abdominal/pelvic pain. Pelvic ultrasound when performed after CT, infrequently changes the original CT diagnosis but better characterizes uterine and adnexal findings which may impact patient management.
286. Importance of Coronal Reformats in the Evaluation of Gastrointestinal Tract with 64-slice MDCT Scanner
Sebastian S.*; Kalra M.K.; Mittal P.K.; Torres W.E.; Saini S.; Small W.C.; Radiology, Emory University School of Medicine, Atlanta, GA.
Address correspondence to S. Sebastian (Sunit.Sebastian{at}emoryhealthcare.org)
Objective: To determine the additional value of multiplanar coronal reformats in the assessment of routine abdomen-pelvis CT performed with a 64 slice MDCT scanner
Materials and Methods: IRB approval was obtained. Study cohort comprised of routine abdomen-pelvis CT studies performed in 50 patients. A 64-slice MDCT was used for all studies with constant scanning parameters: 120 kVp, 12.5 noise index, 75-440 mA range, 0.984:1 pitch, 39.37 mm table travel per gantry rotation, and 0.5 second scan time. Transverse images were reconstructed at 5 mm and 0.625 mm section thickness using standard reconstruction algorithm. Coronal reformats (3 mm thickness) were generated from 0.625 mm transverse image data. Two radiologists underwent a training session with separate cases in order to overcome the learning curve associated with viewing coronal images and to achieve consensus. In the first interpretation session, each radiologist independently reviewed transverse images of all studies. In the subsequent session, each radiologist reviewed transverse and coronal images simultaneously. For each interpretation session, both radiologists noted the number of lesion (s), their location, size of smallest lesion and likely diagnosis. Image quality and confidence for interpretation was also evaluated using 5 point (5 = excel-lent, 3 = acceptable, 1 = not acceptable) and 3 point (3 = excellent, 2 = adequate, 1 = uncertain), respectively. Statistical analysis was performed using paired t-test.
Results: Both readers had excellent interobserver agreement for review of transverse and coronal images (r = 0.94-0.96). With simultaneous review of transverse and coronal images, both radiologists recorded additional findings in 10 studies (10/50, 20%) and higher confidence for interpretation in 18 studies (18/50, 36%). Both readers detected 281 lesions on simultaneous review of coronal and transverse images and, 258 and 260 lesions on transverse images alone (p < 0.001). In general, abdominal lymphadenopathy and abdominal drains were better identified on simultaneous review of transverse and coronal images.
Conclusion: We conclude that combined evaluation of transverse images and multiplanar coronal reformats have additional value in evaluation of the gastrointestinal tract.
287. Cost-Effectiveness Analysis of Computed Tomography Imaging versus Clinical Assessment for Evaluation of Patients with Suspected Appendicitis
Mikityansky I.1*; Noyes K.K.2; Holloway R.G.2,3; 1. Department of Radiology, University of Rochester Medical Center, Rochester, NY; 2. Department of Community and Preventive Medicine, University of Rochester Medical Center, Rochester, NY; 3. Department of Neurology, University of Rochester Medical Center, Rochester, NY.
Address correspondence to I. Mikityansky (gor_kit{at}yahoo.com)
Objective: Although computed tomography (CT) is recommended by most authors for use in patients with suspected appendicitis, no formal gender and age specific cost-effectiveness (CE) evaluation has been performed. The goal of this study is to determine the incremental CE of CT compared with clinical assessment (CA) for evaluation of 18-44 year-old males with suspected appendicitis.
Materials and Methods: A Clinical Decision-Analytical Model built with TreeAge was used to compare CE of dual contrast CT and CA for males with suspected appendicitis. The mortality obtained from the literature was used as a measure of effect. The costs were grossly estimated from the Healthcare Cost and Utilization Project data and other published sources. The one-, two-way, and probabilistic sensitivity analyses were performed on probability of CT complications and surgical complications given positive CA or CT, cost of CT, sensitivities and specificities of CT and CA, cost and probability of alternative diagnosis, and probability of dying given alternative diagnosis. Analysis was performed from the societal perspective and targeted to physicians' professional societies with hope to influence guidelines for management of patients with suspected appendicitis.
Results: The base-case analysis resulted in an ICER equal to $562,198.65 per-life-saved. In the absence of established threshold based on this criterion, published data, such as $390,000 per-life-saved for use of intra-operative cholangiogram (IOC) during difficult laparoscopic cholecystectomies that is considered cost-effective, suggests possible cost-effectiveness of CT for suspected appendicitis. Using CT we can save extra 18 people out of 100,000. Furthermore, sensitivity analysis demonstrates that higher CT specificity, lower probability of CT complications, lower probability of death given the presence of alternative diagnosis, lower probability of peri-surgical complications given positive CT and higher one given positive CA make the CT approach more cost-effective.
Conclusion: Although there is no established willingness-to-pay threshold for cost-per-life-saved, this cost for CT evaluation of males with suspected appendicitis is relatively similar to IOC cost, widely used and accepted procedure. Furthermore, translating our findings into practice by stressing radiologists' training, employing screening and premedication for possible CT reactions, and by appropriate treatment of alternative diagnoses, would further increase CE of CT use in this clinical scenario.
288. The CT-Detected Incidental Appendicolith. What is Its Clinical Meaning?
Rabinowitz C.B.*; Egglin T.K; Department of Diagnostic Imaging, Rhode Island Hospital, Providence, RI.
Address correspondence to C.B. Rabinowitz (crabinowitz{at}lifespan.org)
Objective: Appendicoliths have been implicated as a cause of acute appendicitis, and their radiographic detection in patients with abdominal pain had traditionally been considered diagnostic of acute appendicitis. Appendicoliths are often detected on CT in patients without signs/symptoms of appendicitis, but little is known about the natural history of such patients. We sought to determine the correlation of an appendicolith with acute appendicitis, and to study its clinical implication in the normal appendix.
Materials and Methods: Reports of CTs performed over the past five years were reviewed for the words "appendicolith" or "fecalith." Each patient was counted once, and each stratified by symptoms at presentation and surgical disposition. Electronic records were reviewed to determine surgical findings/pathology in patients who had acute appendicitis, as well as to identify repeat presentations or imaging in those who received other diagnoses.
Results: "Appendicolith" or "fecalith" appeared in reports for 183 patients (109M, 74F, ages 1-94). 166/183 patients presented with pain. 17/183 patients received abdominal/pelvic CTs to evaluate trauma or to assess a pre-existing condition. 90/183 patients underwent appendectomy after initial presentation. Of that group, 40/90 (44%) had appendiceal perforation and 35/90 (39%) had gangrene/necrosis. The remaining 93/183 patients (51%) did not meet CT or clinical criteria for acute appendicitis. 36/93 (39%) had renal stones or hematuria. 7/93 presented at a later date with abdominal pain and were clinically evaluated. 3/7 had an appendicolith on CT or radiography at re-presentation. 6/93 (6.5%) patients with appendicoliths who did not have acute appendicitis on initial presentation later re-presented with acute appendicitis.
Conclusion: More than half of appendicoliths detected with CT were found in patients without acute appendicitis. Only a small minority of these patients with incidental appendicoliths eventually developed appendicitis and of those, the appendicolith was no longer present in half. Thus, patients with a CT detected appendicolith and a normal appendix do not need routine follow-up imaging.
289. 16-MDCT and Integrated Imaging Findings from Ischemia to Infarction of the Small Bowel Due to Mesenteric Vascular Disease
Romano S.1*; Romano L.1; Grassi R.2; 1. Department of Diagnostic Imaging, A. Cardarelli Hospital, Naples, Italy; 2. Institute of Radiology, Second University of Naples, Naples, Italy.
Address correspondence to S. Romano (STEFROMANO{at}LIBERO.IT)
Objective: In the era of MDCT an early diagnosis of intestinal ischemia before infarction development remains an interesting challenge for emergency radiologists. Whereas ischemia may be a totally reversible event, infarction requires surgery or other interventional procedures. Aim of our study was to evaluate the imaging findings of patients with intestinal ischemia or infarction to operate a four stage classification from a phase of initial suspicion to the late diagnosis.
Materials and Methods: We considered the imaging findings (MDCT, Sonography, abdominal plain film) of 115 patient with proven small bowel ischemia or infarction of the small bowel from mesenteric vascular disorders. Patients with ischemia or infarction as consequence of intestinal obstruction were not considered in our series. All diagnoses were confirmed by surgery, pathology and/or interventional vascular procedures. MDCT examination were performed after iv contrast medium administration without endoluminal opacification
Results: A retrospective evaluation of the imaging findings (wall thickness and enhancement; bowel dilation; endoluminal content; superior mesenteric vessels patency; peritoneal fluid; parietal or vascular pneumatosis; sonographic evaluation of the peristalsis) in all three diagnostic methodologies and a four stages classification of the findings was made either for venous and arterial origin. Patient final distribution from damage from arterial origin was the following: 1% in the "initial suspicion"; 18% in "advanced suspicion"; 37 % "confirmed diagnosis" and 44"late diagnosis".
Conclusion: Following the results of the study, our classification may allow an effective correlation with the pathophysiologic features of the small bowel loops from ischemia to infarction. MDCT appears to be the more effective imaging technique in evaluation of vascular disorders of the intestine from arterial or venous origin, to make an early diagnosis of various stage and degree of intestinal ischemia.
290. Postmortem MDCT in the Evaluation of Air-Crash Victims
Lagalla R.1; Iovane A.1; Sorrentino F.1; Brancatelli G.1; Lo Re G.1; Mezzatesta M.2; Procaccianti P.3; 1. Istituto di Radiologia, Università di Palermo, Palermo, Italy; 2. Direzione Sanitaria, Università di Palermo, Palermo, Italy; 3. Legal Medicine, Università di Palermo, Palermo, Italy.
Objective: Purpose: On August 2005 a Tuninter ATR-72 airplane hit the water off Sicily. We examined the injuries sustained by the victims using postmortem multidetector computed tomography (MDCT).
Materials and Methods: Materials and methods: Sixteen people died and 13 survived. Thirteen victims were scanned. Imaging was performed with a 40-channel MDCT scanner (Brilliance, 40, Philips Medical System, Best, The Netherlands) using the following parameters: 40 x 0.625 mm collimation, 420msec rotation, 120kV, 300mAs. Coronal and sagittal reformats, maximum intensity projections (MIP) and volume rendered (VR) images were created on a workstation (Brilliance, Extended Workspace, Philips Medical System, Best, The Netherlands). We investigated the (I) cause of death, (II) traumatological findings, (III) vital reactions, and we performed reconstruction of injuries. Injuries were assessed by anatomic region and severity.
Results: Blunt trauma and drowning were the primary cause of death in 50% and 42% of the examinations, respectively. Blunt trauma and drowning were combined causes of death in 8%. Head, thoracic, and abdominal injuries were multiple and severe, contributing to the mortality of the occupants. The most commonly occurring bony injuries were fracture of the ribs (50%), skull (69%), facial bones (31), legs (42%) and pelvis (17%). Common organ injuries included hemorrhage of the brain (31%), ground glass opacity (100%) in the lungs, air in the vessels (75%), pneumothorax (75%), pneumomediastinum (58%). Vital reactions (air embolism; water aspiration) were noted (67%). Bone injuries were easily displayed with both MIP and VR techniques.
Conclusion: MDCT provides valuable information in forensic cases.
2:30 PM
291. Radiation Exposure to the Breast during Screening CT Pulmonary Angiography. Is there any Unrecognized Public Health Risk?
Plemmons J.K.1*; Simmons J.2; Shaves S.1; Hadley J.L.1; Gray A.2; Shaves M.2; 1. Department of Radiology, Eastern Virginia Medical School, Norfolk, VA; 2. Department of Radiation Oncology, Eastern Virginia Medical School, Norfolk, VA.
Address correspondence to J.K. Plemmons (jkplemmons{at}cox.net)
Objective: The purpose of this study was to measure radiation exposure to the breast in female patients undergoing screening CT pulmonary angiography (CT PA) for pulmonary embolism (PE), and to survey basic demographic data about patients who received a screening CT PA at a tertiary hospital from March 2004 to August 2005.
Materials and Methods: Over 1,600 screening CT PA exams were included in the study. Patient demographics including gender, age, and patient type (inpatient, emergency (ER), or outpatient) were recorded. Examination outcomes were documented as positive, negative, or non-diagnostic. Radiation exposure to the breast was measured using thermo-luminescent detectors (TLD's) in an anthropomorphic phantom. Radiation exposure was measured for CT PA examinations using standard protocols, on General Electric 4-slice, 8-slice, and 16-slice scanners. Data from BEIR V and VII was used to extrapolate for any potential increased risk of breast cancer in women undergoing screening CT PA.
Results: The average radiation exposure to the breast using the 4-slice scanner was 23.3 mGy, the 8-slice scanner was 34.1 mGy, and the 16-slice scanner was 31.6 mGy. Utilizing the linear, no-threshold model for stochastic radiation effects, the risk of breast cancer induction in a woman age 15 is 0.3%/year per 100 mGy. This decreases to 0.05%/year per 100 mGy for women 25 years of age and to 0.04%/year per 100 mGy for women 35 years of age. Women comprised 62.5% of all patients studied. Six percent of studies were done on women age 25 or younger, with two-thirds of these patients being seen in the ER or as outpatients. The percentage of examinations demonstrating PE for all patients was 10.2%. The percentage of positive exams on women presenting as outpatients or to the ER age 25 or less was 4.6% (p = 0.0086).
Conclusion: One in 10 patients in this study screened for pulmonary embolus had the disease. While the number of positive examinations decreases to 4.6% for women age 25 or less who are screened in an ER or outpatient setting, this positive rate is not unreasonable. Although the radiation risk is not zero, the risk even to young women is probably within an acceptable range given the number of positive studies. In a hypothetical cohort of 10,000 twenty-five year old women as many as 460 could be expected to have emboli versus 5 potential radiation induced cancers per year for the same cohort.
292. Safety and Effect on Renal Function of a Second Contrast Media Injection within 24 Hours
Ramos Y.M.*; Abujudeh H.H.; Nagtegaal B.; Halpern E.; Novelline R.; Thrall J.; Radiology, MGH, Boston, MA.
Address correspondence to Y.M. Ramos (yanerys_ramos{at}student.hms.harvard.edu)
Objective: The use of high volume contrast media has been associated with Contrast Nephropathy (CN). Infrequently after a CT with IV contrast the referring physician requests a second CT with IV contrast. Little has been published regarding the risk of CN from a second contrast injection performed (within 24 hours). The purpose of this investigation is to better understand the risk of CN when a second contrast injection is given.
Materials and Methods: After obtaining IRB approval, a retrospective review of patients who had two IV CT contrast injections within 24 hours over a period of 3 years was performed. The initial BUN/Cr (INIT), the BUN/Cr between the 2 CT's (MID), and the highest BUN/Cr (LAST) within 48 hours after the second CT were obtained. If the LAST was elevated (above INIT) we followed up the results and made a determination whether it normalized. Prior medical history was reviewed, and different risk factors such as age, ethnicity, sex, and diabetes were noted.
Results: Between May 2002 and June 2005 we identified a total of 183 patients who had 2 CT contrast injections within 24 hours. A total of 107,000 patients had single contrast injection during the same time period. A total of 126 patients had an INIT and a LAST the other 57 were excluded from the investigation. Three patients were on dialysis and excluded from the study. MID was performed in 63/123. Of the 123 patients 44% were female and 72% were Caucasian. Their mean age was 54 years. Diabetes was present in 20%. The mean INIT was 16.12/0.91, sd 8.79/0.29, 6/123 patients had a Cr 1.5 or above. The mean time interval between the 2 CT's was 11.39 hours (sd = 5.59). MID mean was 15.26/0.87, sd 10.21/0.35, 3/63 patients had a Cr 1.5 or above. LAST mean was 14.68/0.93, sd 9.88/0.49, 7/123 patients Cr was 1.5 or above. LAST was higher than INIT in 37 patients (29%). Further follow up revealed normalization of Bun/Cr except for one patient. The renal dysfunction in this patient could be attributed to other concomitant medications.
Conclusion: The data suggests that fear of CN from a second IV contrast injection (within 24 hours) should not be prohibitive particularly in patients with life threatening conditions. A limitation of the study is the possible selection bias (good renal function) of the patients receiving a second contrast injection (patients who display an elevation of Cr initially or after the first injection may have not been given a second injection).
293. Mechanical Power Injection of Central Venous Catheters for Contrast-Enhanced MDCT
Macha D.B.1*; Hollingsworth J.W.2; Nelson R.C.1; Goodman P.1; 1. Radiology, Duke University Medical Center, Durham, NC; 2. Department of Medicine, Division of Pulmonary, Allergy, and Critical Care, Duke University Medical Center, Durham, NC.
Address correspondence to D.B. Macha (doug{at}machas.net)
Objective: Critical care patients with non tunneled central venous catheters (CVC), but no other IV access, are frequently referred for CT angiography (CTA), primarily PE studies. In our hospital CVC contrast injection using mechanical injectors is not allowed for fear of catheter damage. We performed this study to determine if a widely used 20 cm triple lumen CVC (Arrow International) can tolerate CTA flow rates. We investigated: flow rate, flow pressure tolerance limits, site of catheter damage, contrast viscosity effects, hand injection pressures, and fatigue in used catheters.
Materials and Methods: 42 catheters (10 new, 32 used with indwelling times of 1-21 days) were tested in vitro. Catheters were infused with room temperature Isovue 300 or 370 at progressive 1 ml/sec flow rates from 1 ml/sec to failure (catheter bulge) using a power injector. Injection pressure in psig at the hub was measured using a pressure transducer and data logger at 1-second intervals. Infusion rates, concomitant hub pressures, and site of catheter failure were recorded. Twelve hand injections were analyzed.
Results: Injecting Isovue-370 generates more pressure than using Isovue-300, as would be predicted by Poiseulle's Law. All catheters failed in the same location, with a longitudinal bulge followed by a split in the tubing between the 16g hub and the triple lumen confluence. There were no instances of failure in the portion of the catheter that would be internal to the patient. The lowest flow rate at which catheter failure occurred was 9 ml/sec for a used CVC injected with Isovue-370. The lowest hub pressure at failure was 262 psig and 213 psig for new and used catheters respectively. Mean pressure at rupture was 328 (range 299-351) for new and 288 psig (range 232-331) for used CVC (p = 0.0002, two-tailed Student T). The average peak pressure across all catheters at typical injection rates of 2,3,4,5, and 6 cc/sec were 32, 48, 67, 86 and 105 psig for Isovue-300 and 54, 81, 109, 137 and 165 psig for Isovue 370. By comparison, hand injection of Isovue-300 generated peak hub pressures ranging from 35 to 72 psig.
Conclusion: Typical injection rates for CTA are 3-6 ml/sec. Our study demonstrates a considerable safety margin for power injection when using this particular CVC when no alternatives exist.
294. Evidence-Based Deep Venous Thrombosis Imaging
Subramaniam R.1,2*; Heath R.2; Chou T.2; 1. Department of Medical Imaging, Canberra Hospital & Australian National University, Canberra, Australia; 2. Department of Radiology, Waikato Hospital, Hamilton, New Zealand.
Address correspondence to R. Subramaniam (rathan.subramaniam{at}act.gov.au)
Objective: To establish the accuracy of `Simplify' D dimer assay and Hamilton Score for diagnosis of Deep Venous Thrombosis (DVT).
Materials and Methods: 453 patients presented to the emergency department with suspected first episode of lower limb DVT were prospectively recruited from 2001 to 2003. A previously established pre test probability score (Hamilton Score), `Simplify' D dimer and a complete, single lower limb compression ultrasound examination were performed in all patients. All patients with a negative ultrasound examination were followed up for 3 months.
Results: Of the 227 patients with a negative `Simplify' D dimer assay, 214 patients had negative ultrasound examinations and 13 patients had isolated calf DVT. Among the 226 patients with a positive D dimer assay, 74 patients had DVT and 152 patients had negative ultrasound examinations for DVT. The sensitivity, specificity, positive and negative predictive values were 85.1% (95% CI 75.8 - 91.8%), 58.5% (95% CI 53.4 - 63.5%), 32.7% (95% CI 26.6 - 38.9%) and 94.3% (95% CI 90.4 - 96.9%), respectively. 165 patients had an unlikely Hamilton Score and a negative D dimer assay. The negative predictive value of `Simplify' D dimer in an unlikely Hamilton score population was 98.8% (95% CI 95.7-99.8%).
Conclusion: A negative Simplify D dimer and Unlikely probability Hamilton Score exclude DVT and lower limb ultrasound examinations are unnecessary in these patients. 25% of cost related to DVT ultrasound imaging can be saved by applying this diagnostic strategy.
295. 64 slice "Triple rule-out" Cardiac CT: Impact of ECG-based Current Modulation and Lowered Heart Rate on Patient Radiation Dose
Kinahan P.E.1*; Kohlmyer S.2; Kanal K.1; Stewart B.1; Kolokythas O.1; Warren B.1; Procknow K.2; Ramos M.1; Shuman W.1; 1. Department of Radiology, University of Washington, Seattle, WA; 2., GE Healthcare Technologies, Waukesha, WI.
Address correspondence to P.E. Kinahan (kinahan{at}u.washington.edu)
Objective: Triple rule-out 64 slice cardiac CT performed to evaluate for coronary artery disease, thoracic aortic dissection, and pulmonary embolism requires scanning of the entire chest with low pitch (0.20-0.25) technique, which could deliver over 40 millisieverts of radiation. ECG-based current modulation has the potential to substantially reduce patient radiation dose, but the amount of reduction is in part dependant on the patient's heart rate. We wished to study the impact of EKG-based current modulation during simulation scanning and patient scanning using three different types of reconstruction techniques which are based on the heart rate range during "Triple rule out" cardiac CT.
Materials and Methods: We recorded the estimated dose to adults for a 30 cm axial CT scan using a 64-slice GE VCT scanner. Varying patient heart-rates from 40 to 210 BPM were simulated and the effect on patient dose was estimated from the CTDI and DLP values. ECG current modulation with a peak mA for 10% or 20% of the cardiac cycle (centered at 75%) was used with minimum mA 20% of the peak current for the remainder of the cycle.
Results: There is in general, a significant reduction in radiation dose with the use of ECG-based current modulation. The amount of reduction, For a fixed mA, dose decreased with increasing heart rate in the range of 40 to 75 BPM since pitch is increased to shorten scan duration. For heart rates of 75-114 BPM the rotation speed of 0.35s does not provide sufficient temporal resolution, so data acquired from two cardiac cycles are used, increasing the overall dose. Above 115 BPM data acquired from three or more cardiac cycles are used, further increasing overall dose. Within each of these three heart-rate ranges the use of ECG-based current modulation reduced the patient dose by averages of 42%, 31%, and 13%.
Conclusion: There is in general, a significant reduction in radiation dose with the use of ECG-based current modulation. The amount of reduction, however, depends in a complex manner on patient heart rate. Patient dose and the potential for motion artifacts are reduced as the heart rate is reduced from 115+ BPM to 75-114 BPM, or from 75-114 BPM to 40-75 BPM. There are significant dose reduction benefits from the combination of lowered heart rate and ECG-based current modulation for patients undergoing triple rule out CT protocols.
296. CTA to Rule Out PE—Stop the Madness
Costantino M.M.*; Gosselin M.; Brandt M.S.; Spinning K.A.; Diagnostic Radiology, Oregon Health & Science University, Portland, OR.
Address correspondence to M.M. Costantino (costanti{at}ohsu.edu)
Objective: The high rate of negative pulmonary CT angiograms to rule out PE at our institution led to a review of all of the CTA's that had been performed over the previous 2 years. We were particularly interested in the rate of negative scans preformed on women younger than 35, in whom increased radiogenic breast cancer is of concern.
Materials and Methods: We conducted a retrospective chart review of 630 hospitalized (45%), ED (42%) and clinic (14%) patients who underwent CTA to rule out PE over the course of two years at our institution. We reviewed demographic data, assigned each patient a clinical probability using the Wells clinical criteria, reviewed CTA results, and evaluated the results of the d-dimer.
Results: Data show an 8.85% rate of positive CTA for PE (8.53% ED, 11.83% inpatient, 1.18% outpatient). A d-dimer was obtained on 36% of patients. Of d-dimer results 17% were negative, 47% were intermediate and 36% were positive. We assume that the ordering physician deemed patients who did not undergo d-dimer testing high clinical probability. In assigning clinical probability we found, of 630 patients 3 (0.51%) were high clinical probability, 282 were intermediate clinical probability (48%) and 300 were low clinical probability (51%). Seventy-seven (12.22%) of studies were preformed on women < 35 and 3 (3.89%) of these studies were positive.
Conclusion: Several years of observing the high rate of negative CTA's led us to review CTA results for the previous two years. We found that clinicians are not appropriately applying Well's criteria and are deeming the majority of patients "high clinical probability" when our data show that very few meet high clinical probability criteria. "High clinical probability" patients are most likely deemed as such because of what has been referred to as a "best clinical guess," and not because validated criterion are being applied. Second, given the very low rate of PE in the cohort of women < 35 years old, clinicians should ardently seek other explanations for the patient's symptoms before ordering the CTA, and the radiation that comes with it, in this cohort. Finally, the high rate of intermediate d-dimer results emphasized the importance of clinical probability. In a truly low clinical probability patient, the clinician may wish to forego the d-dimer and thereby prevent necessary further work-up for PE if the d-dimer result is intermediate.
* Will present paper
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