Pancreatic dual-source dual-energy CT: Is it time to discard unenhanced imaging?

doi:10.1016/j.crad.2011.09.004

Clinical Radiology

Volume 67, Issue 4, April 2012, Pages 334-339

https://doi.org/10.1016/j.crad.2011.09.004 Get rights and content

Aim

To compare pancreatic virtual unenhanced (VUE) and true unenhanced (TUE) images and to calculate the potential dose reduction by omitting the conventional unenhanced scan.

Materials and methods

Fifty-one patients with known or suspected pancreatic masses underwent contrast-enhanced computed-tomography (CT) during unenhanced and portal venous phases acquired in single-energy (SE) mode, and pancreatic parenchymal phase acquired in dual-energy (DE) mode. The image quality (IQ) and image noise (IN) of TUE and VUE images were evaluated. The effective dose of a combined DE/SE dual-phase protocol was compared with that of a theoretical standard SE triple-phase protocol. The results were tested for statistical significance using the Cohen’s k, the Wilcoxon’s signed rank test, and the paired t-test; p-values of less than 0.05 were considered significant.

Results

Mean TUE and VUE IQ were 1.5 ± 0.6 and 1.6 ± 0.6 (k = 0.891), with no significant difference (p > 0.05). Mean TUE and VUE IN were 12.3 ± 1.6 and 10.3 ± 1.5 HU, and resulted significantly different (p < 0.001). Mean effective doses for a combined DE/SE dual-phase protocol and SE triple-phase protocol were 8.9 ± 2.4 mSv (range 4.8–16.2 mSv) and 12.1 ± 3.1 mSv (range 6.4–21.1 mSv). The calculated mean dose reduction achievable by omitting the unenhanced scan was 26.7 ± 9.7% (range 10–46.1; p < 0.001).

Conclusion

VUE images are feasible for pancreatic abdominal CT. A combined DE/SE dual-phase protocol permits a significant reduction in dose exposure to patients.

Introduction

The development of dual-source (DS) dual-energy (DE) represents a recent technological advance in computed tomography (CT). In this system, the simultaneous acquisition of multidetector CT data at two photon energy levels, typically 80 and 140 kVp, occurs during a single helical acquisition.1, 2, 3 Thereby, differences in material composition can be detected on the basis of variations in photon absorption at different photon energies. On the basis of reconstruction of complete 80 and 140 kVp image datasets from the raw data, iodine can be subtracted from the images and virtual unenhanced (VUE) images can be generated utilizing various DE post-processing algorithms, which are based on the decomposition principles of three materials.3, 4, 5 In the abdomen, the three materials typically analysed are soft tissue, fat, and iodine.3, 4, 5 Ideally, VUE images could serve as an alternative to conventional true unenhanced (TUE) images, thus obviating the need for a separate unenhanced scan. The use of such an approach could also reduce the radiation dose delivered; this is particularly important in CT studies performed during prolonged follow-up and in young patients. VUE images have already been proposed in several clinical settings.1, 3, 4, 5, 6, 7, 8, 9, 10, 11 To the authors’ knowledge, no previous attempt has been made to compare VUE and TUE images in pancreatic lesions. The purpose of the present study was to compare pancreatic VUE and TUE images and to calculate the potential dose reduction by omitting the conventional unenhanced scan.

Section snippets

Materials and methods

The entire study was approved by our university’s (University of Messina, Italy) ethics committee prior to patient recruitment; written, informed consent was obtained from all patients.

Results

All CT examinations were performed without complications in all patients and all images were fully diagnostically evaluable. VUE images could be reconstructed in all patients. In all cases the pancreas was entirely covered by both detector FOVs.

Final diagnoses obtained by means of surgical biopsy, fine-needle aspiration biopsies guided using CT or endoscopic sonography were: ductal adenocarcinoma (n = 18), neuroendocrine tumour (n = 6), groove pancreatitis (n = 1), pancreatic pseudocyst (n

Discussion

The utility of DS-DECT in abdominal imaging is an exciting area of research. Some advantages have been reported in the evaluation of renal stones and masses, pancreatic or hepatic lesions, and aortic endoleak after endovascular repair.1, 4, 7, 11, 12, 14, 15, 18, 19

DSCT refers to the use of two x-ray sources and two detectors mounted on a single x-ray gantry. This system can operate using a single tube-detector system, as a 64-multidetector row or using both two x-ray tubes, which can operate

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Pancreatic dual-source dual-energy CT: Is it time to discard unenhanced imaging?

Aim

Materials and methods

Results

Conclusion

Introduction

Section snippets

Materials and methods

Results

Discussion

Radiol Clin North Am

Eur J Radiol

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Radiology

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Eur Radiol

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Eur Radiol

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Radiology

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Eur Radiol

Endoleaks after endovascular abdominal aortic aneurysm repair: detection with dual-energy dual-source CT

Radiology

Feasibility of dual-energy CT in the arterial phase: imaging after endovascular aortic repair

AJR Am J Roentgenol

Evaluation of dual-energy CT for differentiating intracerebral hemorrhage from iodinated contrast material staining

Radiology

The assessment of intracranial bleeding with virtual unenhanced imaging by means of dual-energy CT angiography

Eur Radiol

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Eur Radiol

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AJR Am J Roentgenol