Whole-Organ CT Perfusion of the Pancreas: Impact of Iterative Reconstruction on Image Quality, Perfusion Parameters and Radiation Dose in 256-Slice CT-Preliminary Findings

Abstract

BackgroundThis study was performed to assess whether iterative reconstruction can reduce radiation dose while maintaining acceptable image quality, and to investigate whether perfusion parameters vary from conventional filtered back projection (FBP) at the low-tube-voltage (80-kVp) during whole-pancreas perfusion examination using a 256-slice CT.Methods76 patients with known or suspected pancreatic mass underwent whole-pancreas perfusion by a 256-slice CT. High- and low-tube-voltage CT images were acquired. 120-kVp image data (protocol A) and 80-kVp image data (protocol B) were reconstructed with conventional FBP, and 80-kVp image data were reconstructed with iDose4 (protocol C) iterative reconstruction. The image noise; contrast-to-noise ratio (CNR) relative to muscle for the pancreas, liver, and aorta; and radiation dose of each protocol were assessed quantitatively. Overall image quality was assessed qualitatively. Among 76 patients, 23 were eventually proven to have a normal pancreas. Perfusion parameters of normal pancreas in each protocol including blood volume, blood flow, and permeability-surface area product were measured.ResultsIn the quantitative study, protocol C reduced image noise by 36.8% compared to protocol B (P<0.001). Protocol C yielded significantly higher CNR relative to muscle for the aorta, pancreas and liver compared to protocol B (P<0.001), and offered no significant difference compared to protocol A. In the qualitative study, protocols C and A gained similar scores and protocol B gained the lowest score for overall image quality (P<0.001). Mean effective doses were 23.37 mSv for protocol A and 10.81 mSv for protocols B and C. There were no significant differences in the normal pancreas perfusion values among three different protocols.ConclusionLow-tube-voltage and iDose4 iterative reconstruction can dramatically decrease the radiation dose with acceptable image quality during whole-pancreas CT perfusion and have no significant impact on the perfusion parameters of normal pancreas compared to the conventional FBP reconstruction using a 256-slice CT scanner.

Does Iterative Reconstruction Improve Image Quality and Reduce Dose in Computed Tomography?

“…28,29,31,[33][34][35]37,38,43,49,54,55 The extent of the noise reduction achieved however varies and depends on various factors, such as the type of IR algorithm used, the acquisition parameter settings, patient size and the type of CT examination performed. Newer generations of IR algorithms, such as MBIR and ASIR-V, allow for significantly increased noise reduction when compared to older algorithms such as ASiR, as demonstrated in the studies by Lim et al 20 and Ning et al…”

“…While the study on CT perfusion scans of the pancreas reported no notable dif-ferences in subjective image quality and mean CNR values between reduced-dose (10.81 mSv) iDose 4 images and standarddose (23.37 mSv) FBP images, improvements in both objective and subjective image quality in iDose 4 images were noted in another study performed in chest-abdomen-pelvis CT scans, with an effective dose reduction of 46.5% (7.1 mSv versus 12.9 mSv). 49,52 Interestingly, reduced-dose iDose 4 images were given poorer subjective image quality scores by radiologists when compared to standard-dose FBP images in the study involving low-dose CT scans of the brain, despite lower objective noise levels in the iDose 4 images.…”

“…One such study assessed the performance of the iDose 4 algorithm in CT perfusion scans of the pancreas, and reported a noise reduction of 36.8% (10.6 versus 16.9 Hounsfield Units) when comparing iDose 4 images to FBP images at 80 kV. 49 Similarly, subjective image quality scores were markedly higher in iDose 4 images, when compared to FBP images in another study involving low-dose CT scans of the brain (2.91 versus 2.72, p-value<0.0055). 50 In addition, no changes in spatial resolution were noted with the use of the iDose 4 algorithm in another study which investigated the performance of FBP and iDose 4 algorithms at different acquisition parameter settings with the use of a Catphan phantom.…”

The Role of Volume Perfusion CT in the Diagnosis of Pathologies of the Pancreas

“…7.1 mSv for normal weight female patients [17]. In the future there will be possibilities for reducing dose using iterative reconstruction [18]. A further reduction possibility is provided by new detector technologies which promise a potential dose reduction of > 30 % [19,20].…”

The feasibility of low-concentration contrast and low tube voltage in computed tomography perfusion imaging: an animal study

“…This technique has been widely employed in the quantitative analysis of acute ischemic stroke in the brain [1][2][3]. As post-processing strategies and software have developed, the application of CTPI has expanded to more settings, including the assessment of hepatic and pancreatic lesions [4][5][6][7][8][9][10]. Specifically, liver CTPI has been shown to provide valuable information for the diagnosis and prognosis of liver diseases such as hepatic cirrhosis, hepatocellular carcinoma, and cancer metastasis to the liver [7][8][9][10][11][12][13][14].…”