CT Angiography

Rationale and Objectives

The study aimed to improve the detection of pulmonary embolism via an iodine contrast enhancement tool in patients who underwent suboptimal enhanced computed tomography angiography (CTA).

Materials and Methods

We evaluated the CT examinations of 41 patients who underwent CTA for evaluation of the pulmonary arteries which suffered from suboptimal contrast enhancement. The contrast enhancement of the reconstructed images was increased via a post-processing tool (vContrast). Image noise and contrast-to-noise ratio (CNR) were assessed in eight different regions: main pulmonary artery, right and left pulmonary arteries, right and left segment arteries, muscle, subcutaneous fat, and bone. For subjective image assessment, three experienced radiologists evaluated the diagnostic quality.

Results

While employing the post-processing algorithm, the CNR for contrast-filled lumen and thrombus/muscle improves significantly by a factor of 1.7 (CNR without vContrast = 8.48 ± 6.79/CNR with vContrast = 14.46 ± 5.29) ( P < 0.01). No strengthening of artifacts occurred, and the mean Hounsfield unit values of the muscle, subcutaneous fat, and the bone showed no significant changes. Subjective image analysis illustrated a significant improvement using post-processing for clinically relevant criteria such as diagnostic confidence.

Conclusions

vContrast makes CT angiograms with inadequate contrast applicable for diagnostic evaluation, offering an improved visualization of the pulmonary arteries. In addition, vContrast can help in the significant reduction of the iodine contrast material.

Introduction

Pulmonary embolism (PE) is a leading cause of morbidity and mortality among hospitalized patients, with an overall incidence of 15.9% in adult medical autopsies . Therefore, it is important to have a diagnostic procedure offering a fast and reliable detection of PE. Computed tomography angiography (CTA) of the pulmonary arteries is a safe and highly accurate tool to detect or rule out PE . Nowadays, CT has become the standard imaging modality for patients with suspected PE , with the CTA representing a highly relevant diagnostic feature in clinical routine .

In day-to-day clinical routine, CTA is a robust imaging technique to evaluate pulmonary arteries. However, some examinations suffer from a suboptimal contrast opacification of the pulmonary vessels, eg, because of delayed image acquisition, heart failure, or dilution by non-contrasted blood from the inferior vena cava. As a consequence, image quality may be substantially decreased, and the CT images may be non-diagnostic with regard to PE. Potential improvement of arterial opacification can be achieved, for example, by a higher injection rate or a higher concentration, ie, a higher dose of contrast agent . However, an increase in contrast agent arises the risks of contrast medium-induced nephropathy and acute renal failure, respectively .

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Materials and Methods

Patient Population

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CT Technique and Image Reconstruction

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Post-processing Tool

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Low Contrast Clustering (LCC) Estimate

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Structures Enhancement

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Quantitative Image Analysis

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SNR=μvσm S

CNR=(μv−μm)σm C

(

−

)

where µ v is the mean HU value of the vessel lumen, µ m is the mean HU value of the muscle, and σ m is the image noise. The mean values of the CNR with and without employing vContrast were assessed for the pulmonary arteries by averaging the values of the five pulmonary arteries.

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Qualitative Image Analysis

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Ranking Score

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Statistical Analysis

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Results

Quantitative Image Analysis

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TABLE 1

Mean CT Values, SNR, and CNR of the Different Segments of the Pulmonary Artery Tree on Standard and vContrast Images

CT Value (HU) SNR CNR Standard vContrast_P_ Value Standard vContrast_P_ Value Standard vContrast_P_ Value Main PA 165.90

±38.95 284.51

±42.58 <0.01 11.46

±6.11 17.42

±6.03 <0.01 8.36

±4.98 14.66

±5.24 <0.01 Left PA 160.02

±35.73 279.05

±44.83 <0.01 10.99

±5.48 17.13

±6.15 <0.01 7.89

±4.35 14.37

±5.36 <0.01 Right PA 157.24

±34.60 276.76

±46.09 <0.01 10.86

±5.73 17.03

±6.31 <0.01 7.76

±4.58 14.27

±5.50 <0.01 Right upper lobe PA 183.73

±129.61 274.51

±45.28 <0.01 12.89

6.61 16.77

±5.33 <0.05 9.79

±5.33 14.01

±4.51 <0.05 Left lower lobe PA 170.39

±41.89 287.17

44.09 <0.01 11.72

±6.02 17.74

±6.80 <0.01 8.62

±4.89 14.97

±5.96 <0.01

CNR, contrast-to-noise ratio; CT, computed tomography; HU, Hounsfield units; PA, pulmonary artery; SNR, signal-to-noise ratio.

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Subjective Image Analysis

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Discussion

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References

1. Kakkar N., Vasishta R.K.: Pulmonary embolism in medical patients: an autopsy-based study. Clin Appl Thromb Hemost 2008; 14: pp. 159-167.
2. Tsai J., Grosse S.D., Grant A.M., et. al.: Correlates of in-hospital deaths among hospitalizations with pulmonary embolism: findings from the 2001–2008 National Hospital Discharge Survey. PLoS ONE 2012; 7: e34048
3. Schoepf U.J., Goldhaber S.Z., Costello P.: Spiral computed tomography for acute pulmonary embolism. Circulation 2004; 109: pp. 2160-2167.
4. Schoepf U.J., Costello P.: CT angiography for diagnosis of pulmonary embolism: state of the art. Radiology 2004; 230: pp. 329-337.
5. Blanke P., Apfaltrer P., Ebersberger U., et. al.: CT detection of pulmonary embolism and aortic dissection. Cardiol Clin 2012; 30: pp. 103-116.
6. Stein P.D., Woodard P.K., Weg J.G., et. al.: Diagnostic pathways in acute pulmonary embolism: recommendations of the PIOPED II investigators. Radiology 2007; 242: pp. 15-21.
7. Zhang L.J., Lu G.M., Meinel F.G., et. al.: Computed tomography of acute pulmonary embolism: state-of-the-art. Eur Radiol 2015; 25: pp. 2547-2557.
8. Hansmann J., Fink C., Jost G., et. al.: Impact of iodine delivery rate with varying flow rates on image quality in dual-energy CT of patients with suspected pulmonary embolism. Acad Radiol 2013; 20: pp. 962-971.
9. Wong G.T., Irwin M.G.: Contrast-induced nephropathy. Br J Anaesth 2007; 99: pp. 474-483.
10. Wong P.C.Y., Li Z., Guo J., et. al.: Pathophysiology of contrast-induced nephropathy. Int J Cardiol 2012; 158: pp. 186-192.
11. Nash K., Hafeez A., Hou S.: Hospital-acquired renal insufficiency. Am J Kidney Dis 2002; 39: pp. 930-936.
12. Noël P.B., Bendik E., Münzel D., et. al.: A method for improving iodine contrast enhancement in abdominal computed tomography: experimental study in a pig model. Eur Radiol 2013; 4: pp. 985-990.
13. Estrada-Y-Martin R.M., Oldham S.A.: CTPA as the gold standard for the diagnosis of pulmonary embolism. Int J Comput Assist Radiol Surg 2011; 6: pp. 557-563.
14. Sadigh G., Kelly A.M., Cronin P.: Challenges, controversies, and hot topics in pulmonary embolism imaging. AJR Am J Roentgenol 2011; 196: pp. 497-515.
15. Mayo J., Thakur Y.: Pulmonary CT angiography as first-line imaging for PE: image quality and radiation dose considerations. AJR Am J Roentgenol 2013; 200: pp. 522-528.
16. Kerl J.M., Lehnert T., Schell B., et. al.: Intravenous contrast material administration at high-pitch dual-source CT pulmonary angiography: test bolus versus bolus-tracking technique. Eur J Radiol 2012; 81: pp. 2887-2891.
17. Saade C., Bourne R., El-Merhi F., et. al.: An optimised patient-specific approach to administration of contrast agent for CT pulmonary angiography. Eur Radiol 2013; 23: pp. 3205-3212.
18. Yuan R., Shuman W.P., Earls J.P., et. al.: Reduced iodine load at CT pulmonary angiography with dual-energy monochromatic imaging: comparison with standard CT pulmonary angiography–a prospective randomized trial. Radiology 2012; 262: pp. 290-297.
19. Nance J.W., Henzler T., Meyer M., et. al.: Optimization of contrast material delivery for dual-energy computed tomography pulmonary angiography in patients with suspected pulmonary embolism. Invest Radiol 2012; 47: pp. 78-84.
20. Wittram C., Maher M.M., Yoo A.J., et. al.: CT angiography of pulmonary embolism: diagnostic criteria and causes of misdiagnosis. Radiographics 2004; 24: pp. 1219-1238.
21. Niemann T., Zbinden I., Roser H., et. al.: Computed tomography for pulmonary embolism: assessment of a 1-year cohort and estimated cancer risk associated with diagnostic irradiation. Acta Radiol 2013; 54: pp. 778-784.
22. Bendik E., Noël P.B., Münzel D., et. al.: Evaluation of a method for improving the detection of hepatocellular carcinoma. Eur Radiol 2014; 24: pp. 250-255.
23. Noël P.B., Renger B., Fiebich M., et. al.: Does iterative reconstruction lower CT radiation dose: evaluation of 15,000 examinations. PLoS ONE 2013; 26: e81141
24. Noël P.B., Fingerle A.A., Renger B., et. al.: Initial performance characterization of a clinical noise-suppressing reconstruction algorithm for MDCT. AJR Am J Roentgenol 2011; 197: pp. 1404-1409.
25. Marin D., Nelson R.C., Schindera S.T., et. al.: Low-tube-voltage, high-tube-current multidetector abdominal CT: improved image quality and decreased radiation dose with adaptive statistical iterative reconstruction algorithm–initial clinical experience. Radiology 2010; 254: pp. 145-153.
26. Hara A.K., Paden R.G., Silva A.C., et. al.: Iterative reconstruction technique for reducing body radiation dose at CT: feasibility study. AJR Am J Roentgenol 2009; 193: pp. 764-771.
27. Aly O., Vakil E., Kousha M., et. al.: Frequency of contrast induced nephropathy in patients who undergo computed tomography pulmonary angiography for pulmonary embolism. Chest 2014; 145: pp. 524A.
28. Solomon R., Barrett B.: Follow-up of patients with contrast- induced nephropathy. Kidney Int Suppl 2006; 100: pp. S46-S50.
29. Kooiman J., Seth M., Share D., et. al.: The association between contrast dose and renal complications post PCI across the continuum of procedural estimated risk. PLoS ONE 2014; 13: e90233
30. Barrett B.J., Parfrey P.S.: Clinical practice. Preventing nephropathy induced by contrast medium. N Engl J Med 2006; 354: pp. 379-386.
31. Lu G.M., Luo S., Meinel F.G., et. al.: High-pitch computed tomography pulmonary angiography with iterative reconstruction at 80 kVp and 20 mL contrast agent volume. Eur Radiol 2014; 24: pp. 3260-3268.
32. Li X., Ni Q.Q., Schoepf U.J., et. al.: 70-kVp high-pitch computed tomography pulmonary angiography with 40 mL contrast agent: initial experience. Acad Radiol 2015; 22: pp. 1562-1570.

CT Angiography

Rationale and Objectives

Materials and Methods

Results

Conclusions

Introduction

Materials and Methods

Patient Population

CT Technique and Image Reconstruction

Post-processing Tool

Low Contrast Clustering (LCC) Estimate

Structures Enhancement

Quantitative Image Analysis

Qualitative Image Analysis

Ranking Score

Statistical Analysis

Results

Quantitative Image Analysis

Subjective Image Analysis

Discussion

References

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