CT perfusion in hepatocellular carcinoma: Is it reliable?

Imaging Diagnosis of Hepatocellular Carcinoma: A State-of-the-Art Review

Hepatocellular carcinoma (HCC) remains not only a cause of a considerable part of oncologic mortality, but also a diagnostic and therapeutic challenge for healthcare systems worldwide. Early detection of the disease and consequential adequate therapy are imperative to increase patients' quality of life and survival. Imaging plays, therefore, a crucial role in the surveillance of patients at risk, the detection and diagnosis of HCC nodules, as well as in the follow-up post-treatment. The unique imaging characteristics of HCC lesions, deriving mainly from the assessment of their vascularity on contrast-enhanced computed tomography (CT), magnetic resonance (MR) or contrast-enhanced ultrasound (CEUS), allow for a more accurate, noninvasive diagnosis and staging. The role of imaging in the management of HCC has further expanded beyond the plain confirmation of a suspected diagnosis due to the introduction of ultrasound and hepatobiliary MRI contrast agents, which allow for the detection of hepatocarcinogenesis even at an early stage. Moreover, the recent technological advancements in artificial intelligence (AI) in radiology contribute an important tool for the diagnostic prediction, prognosis and evaluation of treatment response in the clinical course of the disease. This review presents current imaging modalities and their central role in the management of patients at risk and with HCC.

A Systematic Review on the Role of the Perfusion Computed Tomography in Abdominal Cancer

Background and purpose

Perfusion Computed Tomography (CTp) is an imaging technique which allows quantitative and qualitative evaluation of tissue perfusion through dynamic CT acquisitions. Since CTp is still considered a research tool in the field of abdominal imaging, the aim of this work is to provide a systematic summary of the current literature on CTp in the abdominal region to clarify the role of this technique for abdominal cancer applications.

Materials and Methods

A systematic literature search of PubMed, Web of Science, and Scopus was performed to identify original articles involving the use of CTp for clinical applications in abdominal cancer since 2011. Studies were included if they reported original data on CTp and investigated the clinical applications of CTp in abdominal cancer.

Results

Fifty-seven studies were finally included in the study. Most of the included articles (33/57) dealt with CTp at the level of the liver, while a low number of studies investigated CTp for oncologic diseases involving UGI tract (8/57), pancreas (8/57), kidneys (3/57), and colon–rectum (5/57).

Conclusions

Our study revealed that CTp could be a valuable functional imaging tool in the field of abdominal oncology, particularly as a biomarker for monitoring the response to anti-tumoral treatment.

CT perfusion for response evaluation after interventional ablation of hepatocellular carcinoma: a prospective study

Background

Computed tomography (CT) perfusion was found to be useful in assessing treatment response in a variety of cancers through the evaluation in the arterial perfusion changes. We investigated the performance of CT perfusion parameters for assessment of hepatocellular carcinoma (HCC) response to radiofrequency ablation (RFA) and trans-arterial chemoembolization (TACE). We conducted a prospective diagnostic test accuracy study that recruited 70 HCC patients who were scheduled to undergo TACE or RFA. For each dynamic CT scan acquisition, four single perfusion CT image maps were generated, including functional maps of blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability surface (PS).

Results

In TACE-treated lesions, the BV achieved a sensitivity and specific of 100% and 83.3%, at a cutoff level of ≤ 122 ml/min/100 gm, for responders. Likewise, at a cutoff level of > 10 s, transit time had a sensitivity of 90.5% and specificity of 100%. At a cutoff level of ≤ 14 ml/min/100 gm, the PS had a sensitivity of 100% and specificity of 83.33% for responders. In RFA-treated lesions, at a cutoff level of ≤ 170 ml/min/100 gm and ≤ 11 ml/100 gm, the BF and BV had a sensitivity of 100% and specificity 100%, respectively, for responders. At a cutoff level of ≤ 11 ml/min/100 gm, PS had a sensitivity 77.27% and specificity 80%.

Conclusions

The present study confirms the feasibility of CT perfusion for assessment of response to TACE and RFA among patients with HCC.

Iterative reconstruction algorithm improves the image quality without affecting quantitative measurements of computed tomography perfusion in the upper abdomen

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Iterative image-reconstruction algorithm (ADMIRE) did not affect the quantitative measurements in CT perfusion.

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Iterative image-reconstruction algorithm (ADMIRE) did not affect the time attenuation curves in CT perfusion.

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Image noise was lower, but the SNR was higher, for iterative reconstructions in CT perfusion examinations with higher strength of noise reduction.

Objective

To investigate differences between reconstruction algorithms in quantitative perfusion values and time-attenuation curves in computed tomography perfusion (CTP) examinations of the upper abdomen.

Methods

Twenty-six CTP examinations were reconstructed with filtered back projection and an iterative reconstruction algorithm, advanced modeled iterative reconstruction (ADMIRE), with different levels of noise-reduction strength. Using the maximum-slope model, quantitative measurements were obtained: blood flow (mL/min/100 mL), blood volume (mL/100 mL), time to peak (s), arterial liver perfusion (mL/100 mL/min), portal venous liver perfusion (mL/100 mL/min), hepatic perfusion index (%), temporal maximum intensity projection (Hounsfield units (HU)) and temporal average HU. Time-attenuation curves for seven sites (left liver lobe, right liver lobe, hepatocellular carcinoma, spleen, gastric wall, pancreas, portal vein) were obtained. Mixed-model analysis was used for statistical evaluation. Image noise and the signal:noise ratio (SNR) were compared between four reconstructions, and statistical analysis of these reconstructions was made with a related-samples Friedman’s two-way analysis of variance by ranks test.

Results

There were no significant differences for quantitative measurements between the four reconstructions for all tissues. There were no significant differences between the AUC values of the time-attenuation curves between the four reconstructions for all tissues, including three automatic measurements (portal vein, aorta, spleen). There was a significant difference in image noise and SNR between the four reconstructions.

Conclusions

ADMIRE did not affect the quantitative measurements or time-attenuation curves of tissues in the upper abdomen. The image noise was lower, and the SNR higher, for iterative reconstructions with higher noise-reduction strengths.