Statistical methods included the Shapiro-Wilk test to confirm normal distribution, Student t test, chi-square test, and Pearson correlation coefficient. 1), attenuation measurements were made in the area of decreased attenuation and in the proximal and distal areas of higher attenuation, as described in the literature [17, 18]. One of these patients was thought to be at high risk of PE and underwent lung scintigraphy, which excluded PE. Attenuation measurements in Hounsfield units were made at the lower superior vena cava (SVC), upper IVC, right atrium (RA), and right ventricle (RV). TABLE 1: Pulmonary CT Angiography Contrast Medium Administration Parameters, Each study was then assessed for the presence or absence of a transient interruption of the contrast bolus by unopacified blood from the IVC. When a portion of a pulmonary artery was noted to be lower in attenuation than adjacent areas of increased attenuation proximally and distally (Fig. In group A, eight patients had nondiagnostic pulmonary CTA studies. Copyright © 2013-2020, American Roentgen Ray Society, ARRS, All Rights Reserved. This difference achieved statistical significance (p = 0.03) because three patients in group A had repeat CTA studies. A D-dimer assay might be a preferred alternative to test for pulmonary embolism, and that test and a low clinical prediction score on the Wells test or Geneva score can exclude pulmonary embolism as a possibility. These measurements were then combined to calculate mean pulmonary opacification. CTA studies were reinterpreted by consensus of two radiologists with 4 and 18 years of experience in chest CT using a standard workstation (Leonardo, Siemens Healthcare). Protocol … The mean effective dose per scan was lower in group B (4.8 mSv) than in group A (5.3 mSv) (p = 0.09). IVC pressure is particularly high when the pregnant patient is in the supine position, where a sixfold increase in pressure has been observed in the third trimester [22]. The specific feature of this protocol is to place the region of interest (ROI) (bolus detection) in the superior vena cava. CT angiography should not be used to evaluate for pulmonary embolism when other tests indicate that there is a low probability of a person having this condition. Split-Bolus MDCT Urography with Synchronous Nephrographic and Excretory Phase Enhancement, Review. CT angiography uses CT and a radiopaque contrast agent to produce 2- and 3-dimensional images of blood vessels, including the arteries that supply the heart (coronary arteries). These data indicate a 143-HU difference in mean opacification between the two groups. The remaining 17 patients had normal radiologic findings. Pulmonary embolism (PE) is a common condition with high mortality and morbidity. The causative mechanism of poor pulmonary arterial opacification during pulmonary CTA in pregnancy is multifactorial. In group A, objective image quality was classified as good (≥ 210 HU) in nine of 28 CTA studies (32.1%) compared with 16 of 20 CTA studies (80%) in group B (p = 0.0001), acceptable (170–209 HU) in eight of 28 CTA studies (29%) compared with three of 20 CTA studies (15%) in group B (p = 0.001), and poor (≤ 169 HU) in 11 of 28 CTA studies (39%) compared with one of 20 CTA studies (5%) in group B (p = 0.0001). During bolus tracking, the patient was instructed to breathe quietly. Three patients did not undergo further imaging and PE was excluded clinically. One study that showed transient interruption of the contrast bolus in group B was considered diagnostic at the time of image acquisition and met both subjective and objective criteria of “good” and “adequate” at study reinterpretation. Images were reconstructed with a slice thickness of 1 mm and reviewed using mediastinal window settings (center, 50 HU; width, 350 HU). In all cases, the clinical and study reinterpretations agreed. Forty-eight pulmonary CTA examinations were performed of 45 pregnant patients (age range, 17–41 years; mean age, 31 years; gestation range, 18–39 weeks; mean gestation, 30 weeks) with suspected PE. There was a strong positive relationship between mean pulmonary arterial attenuation and good objective image quality (r = 0.67, p = 0.001). These measurements were then combined to calculate mean pulmonary opacification. Experimental studies have shown that cardiac output is inversely related to peak arterial enhancement and time to arrival of contrast material in the aorta [21]. Pulmonary CT Angiography as First-Line Imaging for PE: Image Quality and Radiation Dose Considerations. Comparison was made between the smart prep protocol (SPP) and the test bolus protocol (TBP) for opacification in the pulmonary trunk. [1, 2] In 1922, Wharton and Pierson reported the first radiographic description of PE. The specifics will vary depending on CT hardware and software, radiologists' and referrers' preferences, institutional protocols, patient factors (e.g. Angiography is an imaging test that uses x-rays and a special dye to see inside the arteries. Several study limitations are acknowledged. In the past decade, CT pulmonary angiography has been increasingly used as the primary diagnostic imaging examination after chest radiography for the evaluation of patients with suspected PE. The current standard of care for members with suspected pulmonary embolism is a spiral CT scan, also called a CTA, CT PA (computed tomography pulmonary angiography), MDCT (multidector CT) or helical CT scan. CTA of the pulmonary arteries was performed on 200 patients with suspected pulmonary … Further imaging may be necessary, consisting of either repeat CT pulmonary angiography with an increased delay or pulmonary angiography. According to radiology reports, 18 of 28 pulmonary CTA studies (64%) were of diagnostic quality in group A and 18 of 20 pulmonary CTA studies (90%) were of diagnostic quality in group B (p = 0.05). Pulmonary embolism (PE) was clinically described in the early 1800s, and von Virchow first described the connection between venous thrombosis and PE. exercise was to investigate if a change in CT pulmonary angiography (CTPA) scanning protocol resulted in improved opacification of the pulmonary arteries. We instituted a new, simple CT pulmonary angiography (CTPA) contrast material timing protocol using a standard empiric delay to replace our previous timing bolus method. Lung scintigraphy is not susceptible to the hemodynamic effects of pregnancy and remains a reliable tool for excluding PE in patients with normal findings on chest radiography while additionally conferring a lower maternal radiation dose than pulmonary CTA [12, 13]. Although this protocol optimized for imaging pregnant patients significantly improved pulmonary CTA image quality, two of the 20 patients in group B had nondiagnostic studies. adequate enhancement of … Comparison was made between the smart prep protocol (SPP) and the test bolus protocol (TBP) for opacification in the pulmonary trunk. Its use in pregnant patients has consistently risen in recent decades . Evaluation of subjective image quality involved categorizing a study as either adequate or inadequate on the basis of one’s ability to diagnose PE, the adequacy of pulmonary arterial opacification, and the presence or absence of significant motion artifact and image noise. Therefore, another type of angiography, known as a computerised tomography pulmonary angiography (CTPA), is usually the preferred option. The first patient’s pulmonary CTA study showed adequate MPA opacification excluding a central PE, but subsegmental arterial opacification was poor. PE was diagnosed in one patient. However, the differences between the two groups in mean pulmonary arterial opacification and in the presence of transient interruption of the contrast bolus by unopacified blood from the IVC were statistically significant despite the fact that there were fewer patients in group B. NB: This article is intended to outline some general principles of protocol design. In group A, objective image quality was classified as good (≥ 210 HU) in nine of 28 CTA studies (32.1%) compared with 16 of 20 CTA studies (80%) in group B (p = 0.0001), acceptable (170–209 HU) in eight of 28 CTA studies (29%) compared with three of 20 CTA studies (15%) in group B (p = 0.001), and poor (≤ 169 HU) in 11 of 28 CTA studies (39%) compared with one of 20 CTA studies (5%) in group B (p = 0.0001). The flow rate was kept constant at 6 mL/s throughout the procedure, and contrast administration was followed by a 50-mL IV saline flush. Our study was limited by its retrospective nature and small number of patients. Methods: Acta Radiol October 8, 2013 AJR 2011; 197:1058-1063. Yilmaz Ö, Üstün ED, Kayan M, et al. We thank the CT radiographers at St. Vincent’s University Hospital—in particular, Susan Collins and Sheena O’Keeffe—and chief physicist Michael Casey for their important contributions to image acquisition and dose calculation in this study. In group A, final diagnoses included pneumonia (n = 2), pleural effusion (n = 1), pneumothorax (n = 1), and PE (n = 1). When the threshold of attenuation in the MPA was reached, the patient was instructed to perform shallow held inspiration, after adequate coaching by a technologist encouraging a shallow breath and the avoidance of a Valsalva maneuver. In group B, two patients had nondiagnostic studies. The pulmonary vasculature may be evaluated with various invasive and noninvasive methods. Calculations were performed on a standard PC using a statistical analysis program (Minitab, version 15, Minitab). Echocardiographic data excluding a right-to-left shunt were not available in our patient group, although none of the subjects had a documented history of cardiac disease in their electronic records. Second, triple rule-out CT protocol is associated with significantly higher radiation dose when compared to the CTPA protocol, but with low diagnostic yield of less than 10%. Comparison was made between the smart prep protocol (SPP) and the test bolus protocol (TBP) for opacification in the pulmonary trunk. exercise was to investigate if a change in CT pulmonary angiography (CTPA) scanning protocol resulted in improved opacification of the pulmonary arteries. CT Angiography of the Upper Extremity Arterial System: Part 1—Anatomy, Technique, and Use in Trauma Patients, Original Research. During bolus tracking, the patient breathed quietly and was instructed to take a deep breath as soon as the threshold of attenuation in the MPA was reached. Pulmonary angiography is considered the gold standard for the diagnosis of PE, although recent evidence does not necessarily always support that. However, the differences between the two groups in mean pulmonary arterial opacification and in the presence of transient interruption of the contrast bolus by unopacified blood from the IVC were statistically significant despite the fact that there were fewer patients in group B. Although this difference was not statistically significant, the slightly lower radiation dose in group B may have been due to shallow inspiration and resultant decreased z-axis coverage. Protocol Number: OCOG-2014-PEGeD . Significance values were set at p ≤ 0.05. One of these patients had a diagnostic study that excluded PE, and the other two patients had nondiagnostic repeat studies. Suspected Pulmonary Embolism: A Management Study . Studies analyzing pulmonary CTA of pregnant patients have confirmed that pulmonary arterial opacification is reduced during pregnancy [4, 7, 19, 20] and that transient interruption of the contrast bolus by unopacified blood from the IVC may occur more often in pregnant patients than in the general population [7]. 50 patients with acute/chronic renal failure were examined on a 3 rd generation dual-source CT with an optimized DE CTPA protocol and a low CM injection protocol (5.4 g iodine). Hounsfield unit values of acute and chronic pulmonary emboli. A pulmonary CTA protocol optimized for pregnancy significantly improved image quality by increasing pulmonary arterial opacification, improving diagnostic adequacy, and decreasing transient interruption of the contrast bolus by unopacified blood from the IVC. Images were reconstructed with a slice thickness of 1 mm and reviewed using mediastinal window settings (center, 50 HU; width, 350 HU). Performing a traditional catheter angiogram carries a high risk of complications. The following equation designed to calculate the fraction of blood flow contributed by the IVC to the right side of the heart (KIVC) was applied to all CTA studies [17]: or. This effect, known as the “thoracoabdominal pump,” is likely to be prominent in pregnancy because of inherently raised IVC pressures. The aim of this quality assurance exercise was to investigate if a change in CT pulmonary angiography (CTPA) scanning protocol resulted in improved opacification of the pulmonary arteries. The increase in cardiac output in pregnancy may lead to decreased peak arterial enhancement and a shorter contrast material arrival time. An increase in cardiac output by 40–50% is also observed, predominantly during the second trimester, as a result of increased heart rate and stroke volume [8]. The aim of this quality assurance exercise was to investigate if a change in CT pulmonary angiography (CTPA) scanning protocol resulted in improved opacification of the pulmonary arteries. There was a strong positive relationship between mean pulmonary arterial attenuation and good objective image quality (r = 0.67, p = 0.001). When the threshold of attenuation in the MPA was reached, the patient was instructed to perform shallow held inspiration, after adequate coaching by a technologist encouraging a shallow breath and the avoidance of a Valsalva maneuver. For example, in a recent study of 43 pregnant patients, investigators reported a 19% rate of indeterminate CTA studies using 100–120 mL of contrast medium and held maximal inspiration, with slow breathing used as a trouble-shooting maneuver [20]. Each radiology department will have a slightly different method for achieving the same outcome, i.e. angiography (CTA) has evolved into a routine minimally-invasive vas and cardiac CT have evolved into widely available routine clinical applications The quality of a CT angiogram or a cardiac CT strudy depends to a great extent on the appropriate selection of CT data acquisition and contrast medium injection parameters. The remaining 20 patients had normal radiologic findings. CT pulmonary angiogram (CTPA) is a medical diagnostic test that employs computed tomography (CT) angiography to obtain an image of the pulmonary arteries.Its main use is to diagnose pulmonary embolism (PE). 2–4 CTPA is a standard procedure that obtains a CT volume while intravenously injected iodinated contrast media (CM) opacifies the pulmonary arteries. The potential excessive contribution of unopacified blood from the IVC to the right heart was minimized by adequate coaching from a technologist regarding shallow held inspiration. Copyright © 2013-2020, American Roentgen Ray Society, ARRS, All Rights Reserved. The potential excessive contribution of unopacified blood from the IVC to the right heart was minimized by adequate coaching from a technologist regarding shallow held inspiration. Three of 11 CTA studies judged to have transient interruption of the contrast bolus in group A were considered of diagnostic quality at the time of image acquisition and by subjective image quality evaluation, but the mean pulmonary arterial enhancement was classified as poor in two and as adequate in one of these studies. 18(7):882-7. In the CTA studies with the artifact, the mean attenuations (± SD) of the proximal high-attenuation region, intervening low-attenuation region, and distal high-attenuation region were 264 ± 64 HU, 134 ± 50 HU, and 229 ± 75 HU, respectively (Fig. Finally, study groups A and B were not similar in size; fewer pulmonary CTA studies were performed of pregnant patients during the second half of the study duration as part of a revised departmental protocol advocating lung scintigraphy as the preferred study in pregnant patients. to Reduce the use of CT Pulmonary Angiography in . This study presents and evaluates a CT pulmonary angiography protocol dedicated to pregnant women. A focal increase in vascular resistance from consolidation or atelectasis. Significance values were set at p ≤ 0.05. Split-Bolus MDCT Urography with Synchronous Nephrographic and Excretory Phase Enhancement, Review. The increase in cardiac output was also minimized by using a high concentration of contrast medium and by using bolus tracking, both of which are part of standard practice for CTA of pregnant patients in our institution. Pulmonary CT Angiography Protocol Adapted to the Hemodynamic Effects of Pregnancy, Transient Interruption of Contrast Material by Unopacified Blood From the Inferior Vena Cava, Original Research. Readers were not blinded to the CTA protocol used. The difference in mean age between group A and group B (32.7 vs 29.2 years, respectively) achieved statistical significance (p = 0.05). There was a strong negative correlation between mean KIVC values in both the RA and RV and mean pulmonary arterial opacification (r = –0.54 and –0.52, respectively; p = 0.0001). The following equation designed to calculate the fraction of blood flow contributed by the IVC to the right side of the heart (KIVC) was applied to all CTA studies [17]: or. The mean image percentage noise measurements were lower in group A than in group B (1.52 vs 1.79, respectively; p = 0.04) despite similar CT exposure parameters. CT angiography of the chest (CTA chest) is a cross-sectional diagnostic examination that can be performed ECG-gated or non-ECG gated. Subjective image quality was also significantly better in group B. Eighteen of 20 CTA studies (90%) in group B were classified as adequate, indicating good pulmonary arterial enhancement and no significant noise or motion artifact, compared with 18 of 28 studies (64%) in group A (p = 0.03). CT pulmonary angiogram (CTPA) is a medical diagnostic test that employs computed tomography (CT) angiography to obtain an image of the pulmonary arteries. • An empiric timing protocol for CT pulmonary angiography had lower radiation exposure compared to a timing bolus protocol. When lung scintigraphy is not available or is contraindicated, an optimized pulmonary CTA protocol should be used. TABLE 1: Pulmonary CT Angiography Contrast Medium Administration Parameters, Each study was then assessed for the presence or absence of a transient interruption of the contrast bolus by unopacified blood from the IVC. Pulmonary CT Angiography as First-Line Imaging for PE: Image Quality and Radiation Dose Considerations. Pulmonary arterial attenuation in Hounsfield units and SD were calculated at specific sites including the MPA, a point 2 cm proximal to the bifurcation, the right and left pulmonary arteries, and right and left lower lobe arteries proximal to their segmental divisions by drawing a region of interest with an area equal to half the cross-sectional area of the vessel. Image quality was evaluated with objective and subjective criteria. Imaging of Pulmonary Embolism Gamal Agmy. The inadequate group comprised CTA studies with poor pulmonary arterial enhancement, substantial noise, or substantial motion artifact. The increase in cardiac output in pregnancy may lead to decreased peak arterial enhancement and a shorter contrast material arrival time. One of these patients had a diagnostic study that excluded PE, and the other two patients had nondiagnostic repeat studies. This study tests the hypothesis that the empiric protocol more consistently produces diagnostic quality images of both the pulmonary arteries and the aorta with lower radiation exposure. Vessel opacification was provided by IV injection of 75 mL of iopamidol (Niopam 370, Bracco) via the antecubital vein. Of the CTA studies with the artifact, the average relative IVC contributions (KIVC) to the RA and RV were 84.4% and 84.7%, respectively, whereas the average KIVC values for those CTA studies without the artifact were 46.9% and 52.7% (p < 0.0001), respectively. Adverse effects of intravenous contrast media (CM) in patients with renal risk factors and acute kidney injury are still controversially discussed. Calculations were performed on a standard PC using a statistical analysis program (Minitab, version 15, Minitab). 1,2 Since the 1990s, CT pulmonary angiography (CTPA) has become the method of choice for imaging in suspected PE. Same procedure; Clearly show the patho, compressed a. Tot of 4 scouts. KIVC calculations were based on the assumption that the SVC and IVC were the sole contributors of flow to the right heart. The first 28 CTA studies were performed of 25 pregnant patients using a standard pulmonary CTA imaging protocol (Table 1) similar to that used on nonpregnant patients (group A). Conversely, an indeterminate rate of 35.7% was described in a smaller study of 25 patients in which a lower volume of 75 mL of iodinated contrast material and held maximal inspiration were used [7]. The empiric timing protocol for CT pulmonary angiography yielded good aortic opacification in the majority of patients. How Much Dose Can Be Saved in Three-Phase CT Urography? Conversely, an indeterminate rate of 35.7% was described in a smaller study of 25 patients in which a lower volume of 75 mL of iodinated contrast material and held maximal inspiration were used [7]. These data indicate a 143-HU difference in mean opacification between the two groups. The subsequent 20 pregnant patients referred for pulmonary CTA were imaged using a CTA protocol adapted to minimize the hemodynamic effects of pregnancy (Table 1). Experimental studies have shown that cardiac output is inversely related to peak arterial enhancement and time to arrival of contrast material in the aorta [21]. Pulmonary artery attenuation values and the relative contribution of the IVC to the right heart were calculated by the former reader. 2). Pregnant women undergoing the specified low-dose CTPA protocol for suspected pulmonary embolism (PE), agreed across study sites with equivalent computed-tomography (CT) capabilities, will be included. Suspected Pulmonary Embolism: A Management Study . Computed Tomography Pulmonary Angiography during Pregnancy: Radiation Dose of Commonly Used Protocols ... scan and Injection Protocol The three CT scanners investigated in this study were a In addition to these hemodynamic alterations during pregnancy, IVC pressure increases because of the gravid uterus. All reported studies used a contrast medium injection rate of 4 mL/s. [Dual-source CT scanners provide high-pitch dual source protocols … The adequate group included CTA studies with good pulmonary arterial enhancement and without significant noise or motion artifact. European Respiratory Journal Sep 2012, 40 (Suppl 56) P1499; Share This Article: Copy. Introduction. Bilateral central pulmonary embolism was detected (white arrows). Over the past two decades, however, catheter angiography has become almost entirely supplanted by CT angiography (CTA), which is now the … In the CTA studies with the artifact, the mean attenuations (± SD) of the proximal high-attenuation region, intervening low-attenuation region, and distal high-attenuation region were 264 ± 64 HU, 134 ± 50 HU, and 229 ± 75 HU, respectively (Fig. The reported rates of indeterminate CTA studies in pregnant patients vary, ranging from 5.6% to 35.7% [4, 7, 15, 20]; this variation may be due to different study sizes and imaging protocols that vary by the volume of injected contrast material and the breathing instructions given. The second patient had a nondiagnostic study, but right upper lobe consolidation was shown and a concomitant PE was thought to be unlikely on clinical grounds; no further imaging was performed. The flow rate was kept constant at 4 mL/s throughout the procedure. The causative mechanism of poor pulmonary arterial opacification during pulmonary CTA in pregnancy is multifactorial. CT pulmonary angiography protocol: Multidetector CT is preferred (at least 16 slices) Caudal-cranial direction: Most emboli are located in the lower lobes and, if the patient breathes during image acquisition, there is more excursion of the lower lobes compared with the upper lobes. The percentage of image noise for all CTA studies was calculated using a validated equation [16]. 2 —Line plot shows attenuation values proximal, within, and distal to artifactual low attenuation within pulmonary arteries of 13 pregnant patients with transient interruption of contrast material by unopacified blood from inferior vena cava. (OptIPeCT) The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. allergy) and time constraints. The unenhanced vessel may be normal The poor contrast enhancement may obscure thrombus. The results of this study show that a pulmonary CTA protocol optimized for imaging in pregnant patients using bolus tracking, a short scan delay, a high flow rate, high concentration and high volume of contrast medium, and a shallow held inspiration significantly improves image quality by increasing pulmonary arterial opacification and minimizing transient interruption of the contrast bolus by unopacified blood from the IVC. In group B, the hemodilutional effects of pregnancy were minimized by using a higher volume of contrast material injected at a higher rate than used in group A. Three patients underwent repeat pulmonary CTA. This article presents specific examples of delayed diagnosis of acute coronary syndrome, acute aortic dissection, and pulmonary embolism resulting from evaluating patients with nonspecific acute chest pain who did not undergo immediate dedicated coronary CT angiography (CTA) or triple rule-out protocol (TRO). TABLE 2: Opacification of the Pulmonary Arteries on CT Angiography. Pulmonary CT angiography (CTA) is recommended as the most appropriate initial imaging modality for the diagnosis of pulmonary embolism (PE) in nonpregnant adults [1, 2]. To estimate vessel noise, the reviewers recorded the attenuation and SD of the MPA and the attenuation of air for each CT study. KIVC values range from 0 to 1.0; a high KIVC (> 0.8) indicates a larger contribution from the IVC to the right heart relative to the SVC and suggests the presence of transient interruption of the contrast bolus by unopacified blood from the IVC, whereas healthy control subjects have average KIVC values of approximately 0.5 [17]. This increase in blood volume is thought to contribute to hemodilution of contrast material administered to pregnant patients [5]. by Julius Renne et al. The subsequent 20 pregnant patients referred for pulmonary CTA were imaged using a CTA protocol adapted to minimize the hemodynamic effects of pregnancy (Table 1). Two other patients underwent lung scintigraphy after an initial nondiagnostic CTA. Use of high pitch, 3.2 in 70 kVp protocol should be … Fig. AJR 2007; 188:1255–1261 • Jones SE, Wittram C. The indeterminate CT pulmonary angiogram: imaging characteristics and patient clinical outcome. The objective evaluation classified mean pulmonary arterial opacification as good (≥ 210 HU), acceptable (170–209 HU), or poor (≤ 169 HU), as described in a recent study [15]. Over the past two decades, however, catheter angiography has become almost entirely supplanted by CT angiography (CTA), which is now the … To compare intravenous contrast material (CM) injection protocols for dual-energy CT pulmonary angiography (CTPA) in patients with suspected acute pulmonary embolism with regard to image quality and pulmonary perfused blood volume (PBV) values. This artifact was confirmed in 11 of 28 CTA studies in group A (39%) and two of 20 CTA studies in group B (10%) (p = 0.05). Arteries are blood vessels that carry blood away from the heart. The difference in mean age between group A and group B (32.7 vs 29.2 years, respectively) achieved statistical significance (p = 0.05). This IRB-approved study comprised 150 patients with suspected pulmonary embolism (78 male; mean age 65 ± 17years). CTA of the pulmonary arteries was performed on 200 patients with suspected pulmonary embolism (PE). Group B consisted of 20 patients, each of whom underwent one pulmonary CTA study. Two other patients underwent lung scintigraphy after an initial nondiagnostic CTA. Computed tomographic (CT) pulmonary angiography has been evaluated with meta-analysis and has demonstrated sensitivities of 53%–100% and specificities of 83%–100% (, 6), wide ranges that are explained in part by technologic improvements over time. Review of CTPAs by two radiology consultants, image data analysis and 3-month patient follow up will be performed or! Irb-Approved study comprised ct pulmonary angiography protocol patients with acute or chronic renal insufficiency: Evaluation of a low Dose material... 28 pulmonary CTA in pregnancy because of the IVC and the other two patients had nondiagnostic repeat studies for the. With various invasive and noninvasive methods CT angiography of the IVC to the information! 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