CT and MR imaging of hepatic metastases

Uncertainty quantification via localized gradients for deep learning-based medical image assessments

Objective.Deep learning models that aid in medical image assessment tasks must be both accurate and reliable to be deployed within clinical settings. While deep learning models have been shown to be highly accurate across a variety of tasks, measures that indicate the reliability of these models are less established. Increasingly, uncertainty quantification (UQ) methods are being introduced to inform users on the reliability of model outputs. However, most existing methods cannot be augmented to previously validated models because they are not post hoc, and they change a model's output. In this work, we overcome these limitations by introducing a novel post hoc UQ method, termedLocal Gradients UQ, and demonstrate its utility for deep learning-based metastatic disease delineation.Approach.This method leverages a trained model's localized gradient space to assess sensitivities to trained model parameters. We compared the Local Gradients UQ method to non-gradient measures defined using model probability outputs. The performance of each uncertainty measure was assessed in four clinically relevant experiments: (1) response to artificially degraded image quality, (2) comparison between matched high- and low-quality clinical images, (3) false positive (FP) filtering, and (4) correspondence with physician-rated disease likelihood.Main results.(1) Response to artificially degraded image quality was enhanced by the Local Gradients UQ method, where the median percent difference between matching lesions in non-degraded and most degraded images was consistently higher for the Local Gradients uncertainty measure than the non-gradient uncertainty measures (e.g. 62.35% vs. 2.16% for additive Gaussian noise). (2) The Local Gradients UQ measure responded better to high- and low-quality clinical images (p< 0.05 vsp> 0.1 for both non-gradient uncertainty measures). (3) FP filtering performance was enhanced by the Local Gradients UQ method when compared to the non-gradient methods, increasing the area under the receiver operating characteristic curve (ROC AUC) by 20.1% and decreasing the false positive rate by 26%. (4) The Local Gradients UQ method also showed more favorable correspondence with physician-rated likelihood for malignant lesions by increasing ROC AUC for correspondence with physician-rated disease likelihood by 16.2%.Significance. In summary, this work introduces and validates a novel gradient-based UQ method for deep learning-based medical image assessments to enhance user trust when using deployed clinical models.

Distinct CT imaging features of new liver metastases from primary genitourinary cancers

PURPOSE

To apply natural language processing (NLP) to a large volume of structured radiology reports in the investigation of CT imaging features of new liver metastases from primary genitourinary cancers.

METHODS

In this retrospective study, a previously reported NLP model was applied to consecutive structured CT reports from 2016 to 2022 to predict those patients with primary genitourinary cancer who developed liver metastasis. Pathology or imaging follow-up served as the reference standard for validating NLP predictions. Subsequently, diagnostic CTs of the identified patients were qualitatively assessed by two radiologists, whereby several imaging features of new liver metastasis were assessed. Proportions of the assessed imaging features were compared between primary genitourinary cancers using the Chi-square or Fisher's exact test.

RESULTS

In 112 patients (mean age = 72 years; 83 males), the majority of new liver metastases were hypovascular (73.2%), well defined (76.6%), homogenous (66.9%), and without necrotic/cystic component (73.2%). There was a higher proportion of iso- to hyperdense liver metastases for primary kidney cancer vs other primary genitourinary cancers (42.5% in kidney cancer; 2.3% in ureter/bladder cancer, 8% in prostate cancer, and 0% in testicular cancer; p < 0.05) and a higher proportion of new liver metastases with ill-defined margin for primary prostate cancer vs other primary genitourinary cancers (44.0% in prostate cancer, 15.0% in kidney cancer, 18.6% in ureter/bladder cancer, and 25.0% in testicular cancer; p < 0.05).

CONCLUSION

New liver metastases from primary genitourinary cancers tend to be hypovascular and show several distinct imaging features between different primary genitourinary cancers.

Case report: Poorly differentiated breast carcinoma presenting as a breast abscess

We report a case of 31-year-old female with no past medical history who presented with sudden onset discharging skin ulcer in left inframammary fold with erythema and swelling immediately after she came back from holiday for which she presented to the breast one stop clinic and underwent ultrasound-guided aspiration of the detected cystic lesion in the left breast with impression of breast abscess. Afterwards, as the result of cytology reporting as C5, ultrasound-guided Core-Needle Biopsy was performed, which confirmed poorly differentiated carcinoma of breast. Furthermore, similar necrotizing masses were found in axillary lymph nodes and Liver. The final diagnosis was concluded as poorly differentiated breast carcinoma with metastasis to axillary lymph nodes and the liver. This case reports a very uncommon presentation of breast carcinoma in a young patient with no past medical history, presenting with cystic necrotizing mass which is extremely rare in breast cancer. At the time of presentation, carcinoma had spread to the liver and axillary nodes.

Comprehensive CT Imaging Analysis of Primary Colorectal Squamous Cell Carcinoma: A Retrospective Study

The aim of this study was to evaluate the findings of CT scans in patients with pathologically confirmed primary colorectal squamous-cell carcinoma (SCC). The clinical presentation and CT findings in eight patients with pathologically confirmed primary colorectal squamous-cell carcinoma were retrospectively reviewed by two gastrointestinal radiologists. Hematochezia was the most common symptom (n = 5). The tumors were located in the rectum (n = 7) and sigmoid colon (n = 1). The tumors showed circumferential wall thickening (n = 4), bulky mass (n = 3), or eccentric wall thickening (n = 1). The mean maximal wall thickness of the involved segment was 29.1 mm ± 13.4 mm. The degree of tumoral enhancement observed via CT was well enhanced (n = 4) or moderately enhanced (n = 4). Necrosis within the tumor was found in five patients. The mean total number of metastatic lymph nodes was 3.1 ± 3.3, and the mean short diameter of the largest metastatic lymph node was 16.6 ± 5.7 mm. Necrosis within the metastatic node was observed in six patients. Invasions to adjacent organs were identified in five patients (62.5%). Distant metastasis was detected in only one patient. In summary, primary SCCs that arise from the colorectum commonly present as marked invasive wall thickening or a bulky mass with heterogeneous well-defined enhancement, internal necrosis, and large metastatic lymphadenopathies.

Improving the detection of hypo-vascular liver metastases in multiphase contrast-enhanced CT with slice thickness less than 5 mm using DenseNet

INTRODUCTION

Thinner slices are more susceptible in detecting small lesions but suffer from higher statistical fluctuation. This work aimed to reduce image noise in multiphase contrast-enhanced CT reconstructed with slice thickness thinner than the clinical setting (i.e., 5 mm) using convolutional neural network (CNN) for enabling better detection of hypo-vascular liver metastasis.

METHODS

A DenseNet model was used to generate noise map for multiphase CT reconstructed with slice thickness of 2.5 mm and 1.25 mm. Image denoising was conducted by subtracting the CNN-generated noise map from CT images with reduced photon flux due to thinner slice thickness. The performance of DenseNet was evaluated on CT scans of electron density phantoms and patients with hypovascular liver metastases less than 1.5 cm in terms of Hounsfield Unit (HU) variation, statistical fluctuation, and contrast-to-noise ratio (CNR).

RESULTS

The phantom study demonstrated that the CNN-based denoising method was able to reduce statistical fluctuation in CT images reconstructed with slice thickness of 2.5 mm and 1.25 mm without causing significant edge blurring or variation in HU values. With regards to patient study, it was found that the denoised 2.5-mm and 1.25-mm slices had higher CNR than the conventional 5-mm slices for hypo-vascular liver metastases in all 4 phases of multiphase CT.

CONCLUSION

Our results demonstrated that the detection of hypo-vascular liver metastases in multiphase contrast-enhanced CT with slice thickness less than 5 mm could be improved by using the CNN-based denoising method.

IMPLICATIONS FOR PRACTICE

Reconstruction slice thickness has a strong influence on the image quality of CT imaging. A CNN-based denoising method was used in this work to reduce the image noise in multiphase contrast-enhanced CT reconstructed with slice thickness less than 5 mm.

Interobserver variation in tumor delineation of liver metastases using Magnetic Resonance Imaging

Background and purpose

Magnetic Resonance Imaging (MRI) guided stereotactic body radiotherapy (SBRT) of liver metastases is an upcoming high-precision non-invasive treatment. Interobserver variation (IOV) in tumor delineation, however, remains a relevant uncertainty for planning target volume (PTV) margins. The aims of this study were to quantify IOV in MRI-based delineation of the gross tumor volume (GTV) of liver metastases and to detect patient-specific factors influencing IOV.

Materials and methods

A total of 22 patients with liver metastases from three primary tumor origins were selected (colorectal(8), breast(6), lung(8)). Delineation guidelines and planning MRI-scans were provided to eight radiation oncologists who delineated all GTVs. All delineations were centrally peer reviewed to identify outliers not meeting the guidelines. Analyses were performed both in- and excluding outliers. IOV was quantified as the standard deviation (SD) of the perpendicular distance of each observer's delineation towards the median delineation. The correlation of IOV with shape regularity, tumor origin and volume was determined.

Results

Including all delineations, average IOV was 1.6 mm (range 0.6-3.3 mm). From 160 delineations, in total fourteen single delineations were marked as outliers after peer review. After excluding outliers, the average IOV was 1.3 mm (range 0.6-2.3 mm). There was no significant correlation between IOV and tumor origin or volume. However, there was a significant correlation between IOV and regularity (Spearman's ρs = -0.66; p = 0.002).

Conclusion

MRI-based IOV in tumor delineation of liver metastases was 1.3-1.6 mm, from which PTV margins for IOV can be calculated. Tumor regularity and IOV were significantly correlated, potentially allowing for patient-specific margin calculation.

Diagnostic Performance of Contrast Enhanced CT Alone or in Combination with (Non-)Enhanced MRI for Colorectal Liver Metastasis

RATIONALE AND OBJECTIVES

To compare the diagnostic performance of contrast enhanced CT (CE-CT), CE-CT combined with non-enhanced MRI (NE-MRI) or contrast enhanced MRI (CE-MRI) for colorectal liver metastasis (CRLM).

MATERIALS AND METHODS

Sixty-six colorectal cancer patients with 198 focal liver lesions who underwent preoperative abdominal CE-CT and MRI examinations were included respectively. The images were assessed independently by two readers in three protocols (1: CE-CT, 2: CE-CT+NE-MRI, 3: CE-CT+CE-MRI). The diagnostic performance of each protocol was analyzed by receiver operating characteristic (ROC) curve and the areas under ROC (AUCs) were calculated and compared.

RESULTS

The detection rates of protocol 2 were 90.9%-92.9% for liver lesions and 86.4%-89.6% for CRLM, and both significantly higher than protocol 1 of 82.8%-85.4% and 76.8%-80.8% (p<0.001-0.001), whereas similar to protocol 3 of 91.9%-94.4% and 87.2%-91.2% (p 0.250-1.000). The AUCs of protocol 2 were greater than protocol 1 for all lesions (0.914-0.934 vs. 0.779-0.799, p<0.001) and lesions < 10mm (0.726-0.776 vs. 0.528-0.561, p<0.001), and were not inferior to that of protocol 3 (0.929-0.949 in all lesions and 0.754-0.821 in lesion < 10mm, p 0.053-0.162).

CONCLUSION

CE-CT combined with NE-MRI offered superior diagnostic performance for CRLM compared to CE-CT alone and showed comparable performance to CE-CT combined with CE-MRI.

Artificial intelligence-powered software detected more than half of the liver metastases overlooked by radiologists on contrast-enhanced CT

PURPOSE

To evaluate the sensitivity of artificial intelligence (AI)-powered software in detecting liver metastases, especially those overlooked by radiologists.

METHODS

Records of 746 patients diagnosed with liver metastases (November 2010-September 2017) were reviewed. Images from when radiologists first diagnosed liver metastases were reviewed, and prior contrast-enhanced CT (CECT) images were checked for availability. Two abdominal radiologists classified the lesions into overlooked lesions (all metastases missed by radiologists on prior CECT) and detected lesions (all metastases if any of them were correctly identified and invisible on prior CECT or those with no prior CECT). Finally, images from 137 patients were identified, 68 of which were classified as "overlooked cases." The same radiologists created the ground truth for these lesions and compared them with the software's output at 2-month intervals. The primary endpoint was the sensitivity in detecting all liver lesion types, liver metastases, and liver metastases overlooked by radiologists.

RESULTS

The software successfully processed images from 135 patients. The per-lesion sensitivity for all liver lesion types, liver metastases, and liver metastases overlooked by radiologists was 70.1%, 70.8%, and 55.0%, respectively. The software detected liver metastases in 92.7% and 53.7% of patients in detected and overlooked cases, respectively. The average number of false positives was 0.48 per patient.

CONCLUSION

The AI-powered software detected more than half of liver metastases overlooked by radiologists while maintaining a relatively low number of false positives. Our results suggest the potential of AI-powered software in reducing the frequency of overlooked liver metastases when used in conjunction with the radiologists' clinical interpretation.

Atypical Manifestation of Primary Hepatocellular Carcinoma and Hepatic Malignancy Mimicking Lesions

Hepatocellular carcinoma (HCC) can be diagnosed noninvasively on multiphasic CT and MRI based on its distinctive imaging findings. These features include arterial phase hyperenhancement and washout on portal or delayed phase images. However, radiologists face significant diagnostic challenges because some HCCs exhibit atypical imaging characteristics. In addition to many HCC-mimicking lesions, such as arterioportal shunts, combined HCC-cholangiocarcinoma, intrahepatic cholangiocarcinoma, and hemangioma present a challenge for radiologists in actual clinical practice. The ability to distinguish HCCs from mimickers on initial imaging examinations is crucial for appropriate management and treatment decisions. Therefore, this pictorial review presents the imaging findings of atypical HCCs and HCCs mimicking malignant and benign lesions and discusses important clues that may help narrow down the differential diagnosis.

Deep learning-based image reconstruction of 40-keV virtual monoenergetic images of dual-energy CT for the assessment of hypoenhancing hepatic metastasis

OBJECTIVES

To evaluate the diagnostic value of deep learning model (DLM) reconstructed dual-energy CT (DECT) low-keV virtual monoenergetic imaging (VMI) for assessing hypoenhancing hepatic metastases.

METHODS

This retrospective study included 131 patients who underwent contrast-enhanced DECT (80-kVp and 150-kVp with a tin filter) in the portal venous phase for hepatic metastasis surveillance. Linearly blended images simulating 100-kVp images (100-kVp), standard 40-keV VMI images (40-keV VMI), and post-processed 40-keV VMI using a vendor-agnostic DLM (i.e., DLM 40-keV VMI) were reconstructed. Lesion conspicuity and diagnostic acceptability were assessed by three independent reviewers and compared using the Wilcoxon signed-rank test. The contrast-to-noise ratios (CNRs) were also measured placing ROIs in metastatic lesions and liver parenchyma. The detection performance of hepatic metastases was assessed by using a jackknife alternative free-response ROC method. The consensus by two independent radiologists was used as the reference standard.

RESULTS

DLM 40-keV VMI, compared to 40-keV VMI and 100-kVp, showed a higher lesion-to-liver CNR (8.25 ± 3.23 vs. 6.05 ± 2.38 vs. 5.99 ± 2.00), better lesion conspicuity (4.3 (4.0-4.7) vs. 3.7 (3.7-4.0) vs. 3.7 (3.3-4.0)), and better diagnostic acceptability (4.3 (4.0-4.3) vs. 3.0 (2.7-3.3) vs. 4.0 (4.0-4.3)) (p < 0.001 for all). For lesion detection (246 hepatic metastases in 68 patients), the figure of merit was significantly higher with DLM 40-keV VMI than with 40-keV VMI (0.852 vs. 0.822, p = 0.012), whereas no significant difference existed between DLM 40-keV VMI and 100-kVp (0.852 vs. 0.842, p = 0.31).

CONCLUSIONS

DLM 40-keV VMI provided better image quality and comparable diagnostic performance for detecting hypoenhancing hepatic metastases compared to linearly blended images.

KEY POINTS

• DLM 40-keV VMI provides a superior image quality compared with 40-keV or 100-kVp for assessing hypoenhancing hepatic metastasis. • DLM 40-keV VMI has the highest CNR and lesion conspicuity score for hypoenhancing hepatic metastasis due to noise reduction and structural preservation. • DLM 40-keV VMI provides higher lesion detectability than standard 40-keV VMI (p = 0.012).

Imaging findings of spontaneous intraabdominal hemorrhage: neoplastic and non-neoplastic causes

Contrary to traumatic and iatrogenic intraabdominal hemorrhages, spontaneous intraabdominal hemorrhage is a challenging clinical situation. A variety of neoplastic and non-neoplastic conditions may cause spontaneous intraabdominal bleeding. Imaging findings vary depending on the source of bleeding and the underlying cause. In this article, we aim to increase the awareness of imagers to the most common causes of spontaneous intraabdominal hemorrhage by using representative cases.

Imaging of Colorectal Liver Metastasis

Colorectal cancer (CRC) is one of the most common cancers in the world. The most important determinant of survival and prognosis is the stage and presence of metastasis. The liver is the most common location for CRC metastasis. The only curative treatment for CRC liver metastasis (CRLM) is resection; however, many patients are ineligible for surgical resection of CRLM. Locoregional treatments such as ablation and intra-arterial therapy are also available for patients with CRLM. Assessment of response after chemotherapy is challenging due to anatomical and functional changes. Antiangiogenic agents such as bevacizumab that are used in the treatment of CRLM may show atypical patterns of response on imaging. It is vital to distinguish patterns of response in addition to toxicities to various treatments. Imaging plays a critical role in evaluating the characteristics of CRLM and the approach to treatment. CT is the modality of choice in the diagnosis and management of CRLM. MRI is best used for indeterminate lesions and to assess response to intra-arterial therapy. PET-CT is often utilized to detect extrahepatic metastasis. State-of-the-art imaging is critical to characterize patterns of response to various treatments. We herein review the imaging characteristics of CRLM with an emphasis on imaging changes following the most common CRLM treatments.

Comparison of diagnostic performance and confidence between contrast-enhanced computed tomography scan and non-contrast-enhanced computed tomography plus abdomen ultrasound for hepatic metastasis in patients with breast cancer

Background:

The purpose of this study was to compare the performance between noncontrast-enhanced computed tomography (NECT) plus abdominal ultrasound (US) (NECT + US) with contrast-enhanced computed tomography (CECT) for the detection of hepatic metastasis in breast cancer patient with postsurgical follow-up.

Methods:

A total of 1470 patients without already diagnosed hepatic metastasis were included. All patients underwent US and multiphase CECT including the NECT. Independent reviewers analyzed images obtained in four settings, namely, abdominal US, NECT, NECT + US, and CECT and recorded liver metastases using a 5-grade scale of diagnostic confidence. Sensitivity, specificity (diagnostic performance), and area under the receiver operating characteristic curve (AUC, diagnostic confidence) were calculated. Interoperator agreement was calculated using the kappa test.

Results:

Reference standards revealed no metastases in 1108/1470 patients, and metastasis was detected in 362/1470 patients. Abdominal US (P < 0.01) and NECT (P = 0.01) significantly differed from CECT, but NECT + US did not significantly differ from CECT in terms of sensitivity (P = 0.09), specificity (P = 0.5), and AUC (P = 0.43). After an additional review of abdominal US, readers changed the diagnostic confidence scores of 106 metastatic lesions diagnosed using NECT. Interobserver agreements were good or very good in all four settings. Additional review of abdominal US with NECT allowed a change in the therapeutic plan of 108 patients.

Conclusion:

Abdominal US + NECT showed better diagnostic performance for the detection of hepatic metastases than did NECT alone; its diagnostic performance and confidence were similar to those of CECT.

Imaging evaluation of the liver in oncology patients: A comparison of techniques

The liver is commonly affected by metastatic disease. Therefore, it is essential to detect and characterize liver metastases, assuming that patient management and prognosis rely on it. The imaging techniques that allow non-invasive assessment of liver metastases include ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET)/CT, and PET/MRI. In this paper, we review the imaging findings of liver metastases, focusing on each imaging modality’s advantages and potential limitations. We also assess the importance of different imaging modalities for the management, follow-up, and therapy response of liver metastases. To date, both CT and MRI are the most appropriate imaging methods for initial lesion detection, follow-up, and assessment of treatment response. Multiparametric MRI is frequently used as a problem-solving technique for liver lesions and has evolved substantially over the past decade, including hardware and software developments and specific intravenous contrast agents. Several studies have shown that MRI performs better in small-sized metastases and moderate to severe liver steatosis cases. Although state-of-the-art MRI shows a greater sensitivity for detecting and characterizing liver metastases, CT remains the chosen method. We also present the controversial subject of the "economic implication" to use CT over MRI.

Comprehensive Imaging Characterization of Colorectal Liver Metastases

Colorectal liver metastases (CRLM) have heterogenous histopathological and immunohistochemical phenotypes, which are associated with variable responses to treatment and outcomes. However, this information is usually only available after resection, and therefore of limited value in treatment planning. Improved techniques for in vivo disease assessment, which can characterise the variable tumour biology, would support further personalization of management strategies. Advanced imaging of CRLM including multiparametric MRI and functional imaging techniques have the potential to provide clinically-actionable phenotypic characterisation. This includes assessment of the tumour-liver interface, internal tumour components and treatment response. Advanced analysis techniques, including radiomics and machine learning now have a growing role in assessment of imaging, providing high-dimensional imaging feature extraction which can be linked to clinical relevant tumour phenotypes, such as a the Consensus Molecular Subtypes (CMS). In this review, we outline how imaging techniques could reproducibly characterize the histopathological features of CRLM, with several matched imaging and histology examples to illustrate these features, and discuss the oncological relevance of these features. Finally, we discuss the future challenges and opportunities of CRLM imaging, with a focus on the potential value of advanced analytics including radiomics and artificial intelligence, to help inform future research in this rapidly moving field.

Evaluation of Response to Immune Checkpoint Inhibitors Using a Radiomics, Lesion-Level Approach

Conventional methods to determine the response to immune checkpoint inhibitors (ICIs) are limited by the unique responses to an ICI. We performed a radiomics approach for all measurable lesions to identify radiomic variables that could distinguish hyperprogressive disease (HPD) on baseline CT scans and classify a dissociated response (DR). One hundred and ninety-six patients with advanced lung cancer, treated with ICI monotherapy, who underwent at least three CT scans, were retrospectively enrolled. For all 621 measurable lesions, HPDv was determined from baseline CT scans using the tumor growth kinetics (TGK) ratio, and radiomics features were extracted. Multivariable logistic regression analysis of radiomics features was performed to discriminate DR. Radiomics features that significantly discriminated HPDv on baseline CT differed according to organ. Of the 196 patients, 54 (27.6%) had a DR and 142 (72.4%) did not have a DR. Overall survival in the group with a DR was significantly inferior to that in the group without a DR (log rank test, p = 0.04). Our study shows that lesion-level analysis using radiomics features has great potential for discriminating HPDv and understanding heterogeneous tumor progression, including a DR, after ICI treatment.

Predicting early necrosis of colorectal liver metastases using volumetric enhancement on baseline MRI and oil deposition on post-cTACE unenhanced CT

PURPOSE

To predict tumor necrosis after conventional TACE (cTACE) in patients with colorectal liver metastasis (CRLM) based on volumetric oil deposition on CT one day after treatment.

METHODS

Thirty-four lesions in 20 men and 6 women were included in this IRB-approved HIPAA-compliant, retrospective lesion-by-lesion-based study. Semiautomatic volumetric segmentation of target lesions was performed on baseline MRI and post-treatment CT. Predicted percentage of tumor necrosis was defined as 100%-(%baseline MRI enhancement-%CT oil deposition). Necrosis on post-TACE MRI was measured after volumetric segmentation to assess the accuracy of predicting tumor necrosis. The relationship between predicted necrosis percent and post-cTACE measured necrosis percent on MRI was compared using Pearson correlation analysis. Inter-reader agreement was calculated by intraclass correlation coefficient (ICC) after using the same method.

RESULTS

Patients in this cohort had a mean age of 64 ± 14 years. Mean percentage of the viable tumor on pre-cTACE venous phase MRI was 58.5% ± 23.9%. Mean oil deposition was 19.8% ± 14.6%. Mean percentage of calculated necrosis one month after cTACE was 59.2% ± 22.7% on venous phase MRI, which had a significant correlation with predicted necrotic percentage of 61.3% ± 19.3% (r = 0.89, p < 0.0001). ICC for enhancement percentage on pre-cTACE and post-cTACE venous phase MRIs were 0.93 (95% CI 0.83, 0.97) and 0.86 (95% CI 0.66, 0.94), respectively. ICC for oil deposition was 0.92 (95% CI 0.81, 0.96).

CONCLUSION

Measuring oil deposition of the whole tumor on CT one day after cTACE can assist to predict post-cTACE tumor necrosis.

Follow-up of colorectal cancer and patterns of recurrence

Colorectal cancer is one of the commonest cancers detected as also amongst the most common causes of cancer death. Survival has improved due to better disease understanding and treatment; however, a substantial proportion of patients recur after curative intent therapy. In this article, we will discuss the imaging features of recurrent colorectal cancer and the role of the radiologist in its management.

Errors and Misinterpretations in Imaging of Chronic Liver Diseases

MRI is an important problem-solving tool for accurate characterization of liver lesions. Chronic liver disease alters the typical imaging characteristics and complicates liver imaging. Awareness of imaging pitfalls and technical artifacts and ways to mitigate them allows for more accurate and timely diagnosis.

The role of unenhanced phase of the liver in the scanning protocol of metastatic breast cancer: implications for sensitivity, response evaluation and size measurement

Background

To analyse if performing unenhanced CT of the liver aids in the evaluation of metastatic lesions, response assessment or alter the size of the lesions, compared with portal phase alone, in patients with hepatic metastases from breast carcinoma.

Patients and methods

One-hundred and fifty-three CT scans of 36 women were included. Scans consisted of unenhanced, arterial and portal delayed phases of the liver. Two readers sorted which phase was best for visualization of metastases, evaluated the number of lesions detected in each phase, selected the best phase for assessment of response in two consecutive scans, and measured one target lesion in all the phases. Χ2 was used to compare differences among phases and paired t test for measurement differences.

Results

Unenhanced, arterial and portal phases were considered better phases by readers 1/2 in 68/67%, 27/28% and 69/70%, and some lesions were missed in 2%, 11% and 7%, respectively. Sensitivity was significantly better for unenhanced and portal phases compared to arterial phase. Comparison between consecutive scans was considered better in unenhanced (80/79%), followed by portal (70/69%) and arterial phases (31/31%). Maximum diameter of target lesions was 15% greater in unenhanced phase (p < 0.001).

Conclusions

Portal and unenhanced phases of the liver allow better detection and delineation of metastatic hepatic lesions from breast carcinoma. In most cases, unenhanced CT is the best phase to assess response and provides the largest diameter. Therefore, we recommend the use of unenhanced CT in the evaluation of patients with breast carcinoma and suspected or known hepatic metastatic disease.

Yttrium-90 Radioembolization and Tumor Hypoxia: Gas-challenge BOLD Imaging in the VX2 Rabbit Model of Hepatocellular Carcinoma

RATIONALE AND OBJECTIVES

To use a rapid gas-challenge blood oxygen-level dependent magnetic resonance imaging exam to evaluate changes in tumor hypoxia after ⁹⁰Y radioembolization (Y90) in the VX2 rabbit model.

MATERIALS AND METHODS

White New Zealand rabbits (n = 11) provided a Y90 group (n = 6 rabbits) and untreated control group (n = 5 rabbits). R2* maps were generated with gas-challenges (O₂/room air) at baseline, 1 week, and 2 weeks post-Y90. Laboratory toxicity was evaluated at baseline, 24 hours, 72 hours, 1 hours, and 2 weeks. Histology was used to evaluate tumor necrosis on hematoxylin and eosin and immunofluorescence imaging was used to assess microvessel density (CD31) and proliferative index (Ki67).

RESULTS

At baseline, median tumor volumes and time to imaging were similar between groups (p = 1.000 and p = 0.4512, respectively). The median administered dose was 50.4 Gy (95% confidence interval:44.8-55.9). At week 2, mean tumor volumes were 5769.8 versus 643.7 mm³ for control versus Y90 rabbits, respectively (p = 0.0246). At two weeks, ΔR2* increased for control tumors to 12.37 ± 12.36sec^-1 and decreased to 4.48 ± 9.00sec^-1 after Y90. The Pearson correlation coefficient for ΔR2* at baseline and percent increase in tumor size by two weeks was 0.798 for the Y90 group (p = 0.002). There was no difference in mean microvessel density for control versus Y90 treated tumors (p = 0.6682). The mean proliferative index was reduced in Y90 treated tumors at 30.5% versus 47.5% for controls (p = 0.0071).

CONCLUSION

The baseline ΔR2* of tumors prior to Y90 may be a predictive imaging biomarker of tumor response and treatment of these tumors with Y90 may influence tumor oxygenation over time.

Deep-learning-based image reconstruction in dynamic contrast-enhanced abdominal CT: image quality and lesion detection among reconstruction strength levels

AIM

To evaluate the use of deep-learning-based image reconstruction (DLIR) algorithms in dynamic contrast-enhanced computed tomography (CT) of the abdomen, and to compare the image quality and lesion conspicuity among the reconstruction strength levels.

MATERIALS AND METHODS

This prospective study included 59 patients with 373 hepatic lesions who underwent dynamic contrast-enhanced CT of the abdomen. All images were reconstructed using four reconstruction algorithms, including 40% adaptive statistical iterative reconstruction-Veo (ASiR-V) and DLIR at low, medium, and high-strength levels (DLIR-L, DLIR-M, and DLIR-H, respectively). The signal-to-noise ratio (SNR) of the abdominal aorta, portal vein, liver, pancreas, and spleen and the lesion-to-liver contrast-to-noise ratio (CNR) were calculated and compared among the four reconstruction algorithms. The diagnostic acceptability was qualitatively assessed and compared among the four reconstruction algorithms and the conspicuity of hepatic lesions was compared between <5 and ≥5 mm lesions.

RESULTS

The SNR of each anatomical structure (p<0.0001) and CNR (p<0.0001) were significantly higher in DLIR-H than the other reconstruction algorithms. Diagnostic acceptability was significantly better in DLIR-M than the other reconstruction algorithms (p<0.0001). The conspicuity of hepatic lesions was highest when using 40% ASiR-V and tended to lessen as the reconstruction strength level was getting higher in DLIR, especially in <5 mm lesions; however, all hepatic lesions could be detected.

CONCLUSIONS

DLIR improved the SNR, CNR, and image quality compared with 40% ASiR-V, while making it possible to decrease lesion conspicuity using higher reconstruction strength.

Towards Personalised Contrast Injection: Artificial-Intelligence-Derived Body Composition and Liver Enhancement in Computed Tomography

In contrast-enhanced computed tomography, total body weight adapted contrast injection protocols have proven successful in achieving a homogeneous enhancement of vascular structures and liver parenchyma. However, because solid organs have greater perfusion than adipose tissue, the lean body weight (fat-free mass) rather than the total body weight is theorised to cause even more homogeneous enhancement. We included 102 consecutive patients who underwent a multiphase abdominal computed tomography between March 2016 and October 2019. Patients received contrast media (300 mgI/mL) according to bodyweight categories. Using regions of interest, we measured the Hounsfield unit (HU) increase in liver attenuation from unenhanced to contrast-enhanced computed tomography. Furthermore, subjective image quality was graded using a four-point Likert scale. An artificial intelligence algorithm automatically segmented and determined the body compositions and calculated the percentages of lean body weight. The hepatic enhancements were adjusted for iodine dose and iodine dose per total body weight, as well as percentage lean body weight. The associations between enhancement and total body weight, body mass index, and lean body weight were analysed using linear regression. Patients had a median age of 68 years (IQR: 58–74), a total body weight of 81 kg (IQR: 73–90), a body mass index of 26 kg/m² (SD: ±4.2), and a lean body weight percentage of 50% (IQR: 36–55). Mean liver enhancements in the portal venous phase were 61 ± 12 HU (≤70 kg), 53 ± 10 HU (70–90 kg), and 53 ± 7 HU (≥90 kg). The majority (93%) of scans were rated as good or excellent. Regression analysis showed significant correlations between liver enhancement corrected for injected total iodine and total body weight (r = 0.53; p < 0.001) and between liver enhancement corrected for lean body weight and the percentage of lean body weight (r = 0.73; p < 0.001). Most benefits from personalising iodine injection using %LBW additive to total body weight would be achieved in patients under 90 kg. Liver enhancement is more strongly associated with the percentage of lean body weight than with the total body weight or body mass index. The observed variation in liver enhancement might be reduced by a personalised injection based on the artificial-intelligence-determined percentage of lean body weight.

Cholangiocarcinoma - Part 2, Tumoral and Nontumoral Mimics and Imaging Features Helpful in Differentiation

Each of the 3 morphological subtypes of cholangiocarcinoma has a different set of imaging differentials. Emulators of mass-forming cholangiocarcinoma include other primary and secondary hepatic malignancies, benign tumors and tumor-like mimics such as abscess, hemangioma and confluent hepatic fibrosis. Benign inflammatory biliary strictures constitute the major differential of periductal-infiltrative type and intraductal calculi are the main consideration for intraductal-growth type. CT and MRI are the standard imaging tools for characterization of cholangiocarcinoma and differentiating it from close mimics. Here we will describe the various tumoral and non-tumoral mimics of cholangiocarcinoma and discuss specific imaging features useful in differentiation.

Hepatic perfusional changes on CT and MRI: a radiology primer

Hepatic perfusional changes are common in response to, or as a result of, a multitude of pathological processes. These can be neoplastic, inflammatory, fibrotic, or ischemic in origin, to name a few. The liver, having a dual blood supply, is a unique organ to study using contrast-enhanced CT and MRI imaging due to its varied appearance on multiphasic imaging. Knowledge of the CT and MRI appearance of hepatic perfusional changes, in addition to the clinical presentation, can often result in an accurate differential diagnosis. Many of the conditions that cause these changes in hepatic blood flow result in similar appearances on imaging. As a result, it is important that radiologists be aware of common pitfalls when dealing with hepatic perfusional changes to prevent misdiagnosis or delayed diagnosis. As such, this review will focus on some of the various causes of hepatic perfusional changes and how to accurately identify and diagnose them based on their CT and MRI appearance.

Prognostic Factors of Radiofrequency Ablation plus Systemic Chemotherapy for Unresectable Colorectal Cancer with Liver Metastasis

INTRODUCTION

Survival outcomes in patients with unresectable colorectal cancer (CRC) liver metastasis treated by radiofrequency ablation (RFA) combined with systemic chemotherapy and correlation with potential prognostic factors were investigated. Material and Methods. A retrospective cohort study was conducted on 61 CRC patients with unresectable liver metastasis who underwent liver tumor-directed percutaneous RFA combined with conventional systemic chemotherapy between October 2013 and September 2018. Survival analyses were conducted using the Kaplan-Meier method, and the log-rank test was used to characterize differences in the median survival time and the 1-year, 3-year, and 5-year overall survival rates of subgroups to identify prognostic factors.

RESULTS

Median overall survival and progression-free survival of all patients were 32 and 14 months, respectively. The cumulative survival rates at 1-, 3-, and 5-years were 93.2%; 44.5%, and 38.2%, respectively. Univariate analysis revealed that pre-RFA serum CEA levels, Eastern Cooperative Oncology Group (ECOG) status, number of liver lesions, the size of the largest lesion, and the total lesion size were prognostic factors. However, multivariate analysis demonstrated that only the number of liver lesions and the size of the largest lesion were independent prognostic factors for survival.

CONCLUSION

RFA plus systemic chemotherapy provides an encouraging survival outcome for patients with unresectable CRC liver metastasis. Multivariate analysis demonstrated that the number and size of liver metastatic lesions are independent prognostic factors for survival.

Diagnostic accuracy of non-contrast abdominopelvic computed tomography scans in follow-up of breast cancer patients

OBJECTIVES

To evaluate the effectiveness of follow-up with non-enhanced CT (NECT) in patients with breast cancer.

METHODS

The present retrospective study included 1396 patients with breast cancer. Group A included patients with no metastasis to evaluate the diagnostic performance of NECT in detecting newly developed metastasis. Group B included patients with known hepatic metastasis to evaluate the accuracy of NECT for the assessment of hepatic metastasis.

RESULTS

Group A included 895 patients (mean age 52.8 years). Among them, 145 patients had 160 metastases. The per-patient sensitivities for diagnosing newly developed metastasis were 68.3 and 53.8% according to the two reviewers, while the per-lesion sensitivities were 89.4 and 85.0%. Sensitivities for bone metastasis were 98.9 and 95.9%, while sensitivities for hepatic metastasis were 73.7 and 68.4%. In group B, the accuracy of hepatic metastasis response evaluation according to the RECIST criteria was 70.8% for reviewer 1 and 63.8% for reviewer 2.

CONCLUSIONS

NECT showed inadequate diagnostic performance in detecting newly developed metastasis and in evaluating the response of hepatic metastasis. However, NECT can be utilized as a follow-up modality in patients with decreased renal function or hypersensitivity to iodinated contrast media.

ADVANCES IN KNOWLEDGE

The risk of side effects of contrast media should be considered as important when NECT can be utilized as a follow-up modality in decreased renal function patients.

Imaging performance and preoperative differential diagnosis of multiple myopericytoma in the liver: A case report

Myopericytoma is a rare type of benign tumor, which commonly affects all four limbs. The occurrence of myopericytoma in the liver is extremely rare. Myopericytoma with a size of >1 cm in diameter in the liver has not been previously reported. Due to the limited number of cases, the preoperative diagnosis of liver myopericytoma based on laboratory and imaging examinations is difficult. In the present case report, a patient with multiple myopericytoma in the liver, with a maximum diameter of 4.5 cm was described, with accompanying computed tomography (CT) and positron emission tomography/CT (PET/CT) imaging profiles. The aim of the present report was to discuss the preoperative differential diagnosis between myopericytoma and other common liver neoplasms, such as intrahepatic cholangiocarcinoma or liver metastasis.

Enhanced Rim on MDCT of Colorectal Liver Metastases: Assessment of Ability to Predict Progression-Free Survival and Response to Bevacizumab-Based Chemotherapy

OBJECTIVE. The purpose of this article is to evaluate the enhanced rim on the portal venous phase (PVP) on MDCT as a predictor of 1-year progression-free survival (PFS) and response to bevacizumab-based chemotherapy in patients with colorectal liver metastases (CRLM). MATERIALS AND METHODS. We retrospectively identified 111 patients with primary unresectable CRLM treated with bevacizumab-based chemotherapy at two institutions between 2012 and 2018. Pretreatment contrast-enhanced MDCT images were reviewed and data on clinical characteristics were collected from the electronic medical records. Univariable and multivariable analyses were conducted to assess several imaging features and clinical characteristics as potential predictors of 1-year PFS and objective response rate (ORR). RESULTS. After 1 year of follow-up, liver metastatic tumor progression was detected in 52 patients (46.8%) after bevacizumab-based chemotherapy. A log-rank test showed that enhanced rim on PVP (chi-square test, 5.862; p = 0.015) and the occurrence of liver resection surgery (chi-square test, 7.836; p = 0.005) were significant predictors of 1-year PFS. Multivariable analysis showed that enhanced rim on PVP images was an independent predictor of 1-year PFS (hazard ratio, 0.510; 95% CI, 0.282-0.926; p = 0.027) and ORR (odds ratio, 4.694; p < 0.001). CONCLUSION. The presence of an enhanced rim on PVP MDCT is an independent predictor of survival and response to bevacizumab-based chemotherapy among patients with CRLM.

Multimodality Approach in Detection and Characterization of Hepatic Metastases

Early detection of liver metastases is important in patients with known primary malignancies. This plays an important role in treatment planning and impacts on further management of certain primary malignancies.

Magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography-computed tomography scans are reported to have high accuracy in the diagnosis of intrahepatic lesions. MRI in particular has the advantages of its high tissue sensitivity and its multiparametric approach.

Hepatic metastatic lesions have considerable overlap in their radiological appearance, and in this article the imaging appearance of various hepatic metastasis and approach is described.

Bile duct adenoma: imaging features and radiologic-pathologic correlation

PURPOSE

This study aimed to reveal characteristic imaging features of bile duct adenoma (BDA) by radiologic-pathologic correlation.

MATERIALS AND METHODS

We retrospectively analyzed pathological and imaging findings of seven patients with BDA.

RESULTS

The median maximum diameter of BDA was 5.5 mm. Six lesions had hemispheric morphology. Seven lesions were located in the liver subcapsular region, and proliferation of bile ductules without atypia and fibrous stroma was observed. Two lesions had different microscopic findings. In both lesions, proliferation of bile ductules without atypia was observed in the margin. In one lesion, the percentage of fibrosis and hyalinization was higher at the center than at the margin. In the other lesion, inflammatory cell infiltration was observed in the center. On contrast-enhanced imaging, BDAs showed hypervascularity in the early phase and prolonged enhancement in the delayed phase. On contrast-enhanced multidetector computed tomography during hepatic arteriography, two lesions showed ring-like enhancement in the first phase and prolonged enhancement in the second phase. These were the different histopathologic features of BDAs between the margin and center.

CONCLUSION

Bile duct adenoma can be characterized as a small semicircular lesion located in the liver subcapsular region, which show hypervascularity in the early phase with prolonged enhancement.

Intrahepatic and intra-abdominal splenosis: A case report and review of literature

BACKGROUND

Splenosis is defined as the process by which tissue from the spleen disseminates through the body and grows in an ectopic location following trauma or a splenectomy. Visceral sites of splenosis are rare.

CASE SUMMARY

We report a case of intrahepatic splenosis in a 57-year-old man with a history of trauma over 40 years ago who initially presented with chest pain. Findings initially mimicked malignancy but a diagnosis of intrahepatic splenosis was confirmed using computed tomography and scintigraphy with technetium-99m heat-denatured red blood cells (Tc-99 DRBC).

CONCLUSION

Scintigraphy with Tc-99 DRBC is a reliable technique to diagnose splenosis and should be performed before using more invasive procedures are carried out. Splenosis should be considered as a possible differential diagnosis for a hepatic nodule in any patient with a history of abdominal trauma, previous splenectomy or atypical radiological features on imaging.

Liver metastasis in colorectal cancer: evaluation of segmental distribution

Introduction

It is known that the liver is the main target for metastasis in colorectal cancer. However, we do not know enough from the literature to describe the segmental distribution of liver metastatic lesions of colorectal cancers.

Aim

To investigate which liver segment is affected.

Material and methods

A total of 326 patients (female/male, n = 115/221; age: 53 ±8/51 ±7 years) were included in our study, classified according to their pathological diagnosis. After liver metastases of the patients were determined, they were divided according to Couinaud classification.

Results

While the total number of metastases detected in the right lobe was 691 (70.1%), the number of metastases detected in the left lobe was 294 (29.9%), and the difference was highly significant (p < 0.0001). Metastases in the right lobe anterior segment amounted to 279 (40.4%), and metastasis in right lobe posterior segment was 412 (59.6%), and the difference was significant. When the total number of metastatic lesions is evaluated by excluding segment I, the largest number of lesions were observed in segment VIII. The liver segments with the highest number of metastatic lesions were, respectively, VII, IV, VI, V, III, and II. In this case, the fewest metastatic lesions were observed in segment II.

Conclusions

Liver metastases of colorectal cancer are more common in the right lobe than in the left lobe. The right lobe posterior segment (segment VI) is the main target of metastases.

Liver metastasis in colorectal cancer: evaluation of segmental distribution

INTRODUCTION

It is known that the liver is the main target for metastasis in colorectal cancer. However, we do not know enough from the literature to describe the segmental distribution of liver metastatic lesions of colorectal cancers.

AIM

To investigate which liver segment is affected.

MATERIAL AND METHODS

A total of 326 patients (female/male, n = 115/221; age: 53 ±8/51 ±7 years) were included in our study, classified according to their pathological diagnosis. After liver metastases of the patients were determined, they were divided according to Couinaud classification.

RESULTS

While the total number of metastases detected in the right lobe was 691 (70.1%), the number of metastases detected in the left lobe was 294 (29.9%), and the difference was highly significant (p < 0.0001). Metastases in the right lobe anterior segment amounted to 279 (40.4%), and metastasis in right lobe posterior segment was 412 (59.6%), and the difference was significant. When the total number of metastatic lesions is evaluated by excluding segment I, the largest number of lesions were observed in segment VIII. The liver segments with the highest number of metastatic lesions were, respectively, VII, IV, VI, V, III, and II. In this case, the fewest metastatic lesions were observed in segment II.

CONCLUSIONS

Liver metastases of colorectal cancer are more common in the right lobe than in the left lobe. The right lobe posterior segment (segment VI) is the main target of metastases.

68Ga-PSMA-PET/CT for the evaluation of liver metastases in patients with prostate cancer

Background

The purpose of this study was to evaluate the imaging properties of hepatic metastases in ⁶⁸Ga-PSMA positron emission tomography (PET) in patients with prostate cancer (PC).

Methods

⁶⁸Ga-PSMA-PET/CT scans of PC patients available in our database were evaluated retrospectively for liver metastases. Metastases were identified using ⁶⁸Ga-PSMA-PET, CT, MRI and follow-up scans. Different parameters including, maximum standardized uptake values (SUV_max) of the healthy liver and liver metastases were assessed by two- and three-dimensional regions of interest (2D/3D ROI).

Results

One hundred three liver metastases in 18 of 739 PC patients were identified. In total, 80 PSMA-positive (77.7%) and 23 PSMA-negative (22.3%) metastases were identified. The mean SUV_max of PSMA-positive liver metastases was significantly higher than that of the normal liver tissue in both 2D and 3D ROI (p ≤ 0.05). The mean SUV_max of PSMA-positive metastases was 9.84 ± 4.94 in 2D ROI and 10.27 ± 5.28 in 3D ROI; the mean SUV_max of PSMA-negative metastases was 3.25 ± 1.81 in 2D ROI and 3.40 ± 1.78 in 3D ROI, and significantly lower than that of the normal liver tissue (p ≤ 0.05). A significant (p ≤ 0.05) correlation between SUV_max in PSMA-positive liver metastases and both size (ρ_Spearman = 0.57) of metastases and PSA serum level (ρ_Spearman = 0.60) was found.

Conclusions

In ⁶⁸Ga-PSMA-PET, the majority of liver metastases highly overexpress PSMA and is therefore directly detectable. For the analysis of PET images, it has to be taken into account that also a significant portion of metastases can only be detected indirectly, as these metastases are PSMA-negative.

Spectrum of Pitfalls, Pseudolesions, and Misdiagnoses in Noncirrhotic Liver

OBJECTIVE

The purpose of this article is to illustrate the various pitfalls, mimics, and atypical features that can lead to inaccurate diagnosis of focal lesions in a noncirrhotic liver. The content includes relevant pathogenesis and background as well as specific clues that can be used to reach an accurate diagnosis.

CONCLUSION

When assessing focal hepatic lesions, it is important to avoid pitfalls and misdiagnoses that can alter the management plan. Helpful strategies for avoiding pitfalls include paying close attention to the clinical history of the patient, carefully evaluating all of the available imaging studies, and being aware of the various radiologic mimics.

Bleeding Liver Masses: Imaging Features With Pathologic Correlation and Impact on Management

OBJECTIVE. The purposes of this article are to discuss a variety of liver masses that can present with hemorrhage, including their characteristic imaging features, and to propose a diagnostic approach. CONCLUSION. A broad spectrum of pathologic conditions can present as spontaneous hemorrhage within or surrounding the liver and may present acutely or as a chronic or incidental finding. Imaging characteristics and clinical history can often narrow the differential diagnosis and guide management.

Imaging Characteristics of Liver Metastases Overlooked at Contrast-Enhanced CT

OBJECTIVE

The purpose of this study was to evaluate the imaging characteristics of liver metastases overlooked at contrast-enhanced CT.

MATERIALS AND METHODS

The records of 746 patients with a diagnosis of liver metastases from colorectal, breast, gastric, or lung cancer between November 2010 and September 2017 were reviewed. Images were reviewed when liver metastases were first diagnosed, and images from prior contrast-enhanced CT examinations were checked if available. These lesions were classified into two groups: missed lesions (those missed on the prior images) and detected lesions (those correctly identified and invisible on the prior images or there were no prior images). Tumor size, contrast-to-noise ratio, location, presence of coexisting liver cysts and hepatic steatosis, and indications for examination were compared between the groups. The t test and Fisher exact test were used to analyze the imaging characteristics of previously overlooked lesions.

RESULTS

The final analysis included 137 lesions, of which 68 were classified as missed. In univariate analysis, contrast-to-noise ratio was significantly lower in missed lesions (95% CI, 2.65 ± 0.24 vs 3.90 ± 0.23; p < 0.001). The proportion of subcapsular lesions (odds ratio, 3.44; p < 0.001), hepatic steatosis (odds ratio, 6.35; p = 0.007), and examination indication other than survey of malignant tumors (odds ratio, 9.07; p = 0.02) were significantly higher for missed lesions.

CONCLUSION

Liver metastases without sufficient contrast enhancement, those in patients with hepatic steatosis, those in subcapsular locations, and those found at examinations for indications other than to assess for tumors were significantly more likely to be overlooked.

Differentiation of hepatic abscess from metastasis on contrast-enhanced dynamic computed tomography in patients with a history of extrahepatic malignancy: emphasis on dynamic change of arterial rim enhancement

OBJECTIVES

The objective of the study is to identify computed tomography (CT) findings that differentiate hepatic abscess from hepatic metastasis in a patient with a history of extrahepatic malignancy.

MATERIALS AND METHODS

This retrospective study included 30 patients with 93 hepatic abscesses and 40 patients with 125 hepatic metastases who had a history of extrahepatic malignancy and underwent contrast-enhanced dynamic CT with arterial phase (AP) and portal venous phase (PVP). The diagnosis of hepatic abscess and hepatic metastasis was made using pathological confirmation or clinical diagnosis. Margin, patchy parenchymal enhancement, arterial rim enhancement, dynamic change of arterial rim enhancement, size discrepancy of lesions between arterial and portal phases, bile duct dilatation, perilesional hyperemia, and perilesional low density were evaluated by two radiologists independently. Significant findings for differentiating two groups were identified at univariate and multivariate analysis with nomogram for predicting hepatic abscess. Interobserver agreement was also analyzed for each variable.

RESULTS

Multivariate analysis revealed that patchy parenchymal enhancement (P < 0.001), arterial rim enhancement persistent through PVP (P < 0.001), and perilesional hyperemia (P = 0.013) were independent significant findings to predict hepatic abscess than metastasis. Among them, arterial rim enhancement persistent through PVP showed a highest odds ratio (OR 33.73) on multivariate analysis and a highest predictor point on a nomogram for predicting hepatic abscess. When two of these three criteria were combined, 80.7% (75/93) of hepatic abscess were correctly identified, with a specificity of 85.6% (107/125). When all three criteria were satisfied, specificity was up to 100% (125/125).

CONCLUSIONS

At contrast-enhanced dynamic CT, patchy parenchymal enhancement, arterial rim enhancement persistent through PVP, perilesional hyperemia, and their combinations may be reliable CT features for differentiating hepatic abscess from metastasis in patients with a history of primary extrahepatic malignancy.

Diagnosis and treatment of hepatic pseudolymphoma

Pseudolymphoma, also known as reactive lymphoid hyperplasia or nodular lymphoid lesion, can occur in the gastrointestinal tract, pancreas, eyelids, skin, etc.; however, pseudolymphoma of the liver rarely occurs. Because of the small number of individual case reports of hepatic pseudolymphoma in most institutions, there is a lack of information available regarding its pathogenesis, optimal treatment, and prognosis. Patients with hepatic pseudolymphoma often present non-specific clinical and imaging features, without specific tumor markers. The diagnosis of this disease mainly depends on postoperative pathological and immunohistochemical evaluations and genetic examination; timely and complete surgical resection is currently the most important treatment.

Quantitative Imaging Biomarkers for 90Y Distribution on Bremsstrahlung SPECT After Resin-Based Radioembolization

Our purpose was to identify baseline imaging features in patients with liver cancer that correlate with ⁹⁰Y distribution on postprocedural SPECT and predict tumor response to transarterial radioembolization (TARE). Methods: This retrospective study was approved by the institutional review board and included 38 patients with hepatocellular carcinoma (HCC) (n = 23; 18/23 men; mean age, 62.39 ± 8.62 y; 34 dominant tumors) and non-HCC hepatic malignancies (n = 15; 9/15 men; mean age, 61.13 ± 11.51 y; 24 dominant tumors) who underwent 40 resin-based TARE treatments (August 2012 to January 2018). Multiphasic contrast-enhanced MRI or CT was obtained before and Bremsstrahlung SPECT within 2 h after TARE. Total tumor volume (cm³) and enhancing tumor volume (ETV [cm³] and % of total tumor volume), and total and enhancing tumor burden (%), were volumetrically assessed on baseline imaging. Up to 2 dominant tumors per treated lobe were analyzed. After multimodal image registration of baseline imaging and SPECT/CT, ⁹⁰Y distribution was quantified on SPECT as tumor-to-normal-liver ratio (TNR). Response was assessed according to RECIST1.1 and quantitative European Association for the Study of the Liver criteria. Clinical parameters were also assessed. Statistical tests included Mann-Whitney U, Pearson correlation, and linear regression. Results: In HCC patients, high baseline ETV% significantly correlated with high TNR on SPECT, demonstrating greater ⁹⁰Y uptake in the tumor relative to the liver parenchyma (P < 0.001). In non-HCC patients, a correlation between ETV% and TNR was observed as well (P = 0.039). Follow-up imaging for response assessments within 1-4 mo after TARE was available for 23 patients with 25 treatments. The change of ETV% significantly correlated with TNR in HCC (P = 0.039) but not in non-HCC patients (P = 0.886). Additionally, Child-Pugh class B patients demonstrated significantly more ⁹⁰Y deposition in nontumorous liver than Child-Pugh A patients (P = 0.021). Conclusion: This study identified ETV% as a quantifiable imaging biomarker on preprocedural MRI and CT to predict ⁹⁰Y distribution on postprocedural SPECT in HCC and non-HCC. However, the relationship between the preferential uptake of ⁹⁰Y to the tumor and tumor response after radioembolization could be validated only for HCC.

Imaging of pathology involving the space around the hepatic veins: "perivenous pattern"

We aimed to illustrate diseases involving the potential space around the hepatic veins. Perivenous halo sign can be seen in patients with congestive heart failure or fluid overload. Perivenous involvement can be observed in patients with alcoholic fatty liver disease, which can be focal or diffuse. Metastasis and primary liver tumor spread can also involve this space most likely due to involvement of lymphatics around hepatic veins.

Major pancreatic resections: normal postoperative findings and complications

Objectives

(1) To illustrate and describe the main types of pancreatic surgery; (2) to discuss the normal findings after pancreatic surgery; (3) to review the main complications and their radiological findings.

Background

Despite the decreased postoperative mortality, morbidity still remains high resulting in longer hospitalisations and greater costs. Imaging findings following major pancreatic resections can be broadly divided into “normal postoperative alterations” and real complications. The former should regress within a few months whereas complications may be life-threatening and should be promptly identified and treated.

Imaging findings

CT is the most effective postoperative imaging technique. MRI and fluoroscopy are used less often and only in specific cases such as assessing the gastro-intestinal function or the biliary tree. The most common normal postoperative findings are pneumobilia, perivascular cuffing, fluid collections, lymphadenopathy, acute anastomotic oedema and stranding of the peri-pancreatic/mesenteric fat. Imaging depicts the anastomoses and the new postoperative anatomy. It can also demonstrate early and late complications: pancreatic fistula, haemorrhage, delayed gastric emptying, hepatic infarction, acute pancreatitis of the remnant, porto-mesenteric thrombosis, abscess, biliary anastomotic leaks, anastomotic stenosis and local recurrence.

Conclusions

Radiologists should be aware of surgical procedures, postoperative anatomy and normal postoperative imaging findings to better detect complications and recurrent disease.

Teaching Points

• Morbidity after pancreatic resections is high.

• CT is the most effective postoperative imaging technique.

• Imaging depicts the anastomoses and the new postoperative anatomy.

• Pancreatic fistula is the most common complication after partial pancreatic resection.

A data-driven statistical model that estimates measurement uncertainty improves interpretation of ADC reproducibility: a multi-site study of liver metastases

Apparent Diffusion Coefficient (ADC) is a potential quantitative imaging biomarker for tumour cell density and is widely used to detect early treatment changes in cancer therapy. We propose a strategy to improve confidence in the interpretation of measured changes in ADC using a data-driven model that describes sources of measurement error. Observed ADC is then standardised against this estimation of uncertainty for any given measurement. 20 patients were recruited prospectively and equitably across 4 sites, and scanned twice (test-retest) within 7 days. Repeatability measurements of defined regions (ROIs) of tumour and normal tissue were quantified as percentage change in mean ADC (test vs. re-test) and then standardised against an estimation of uncertainty. Multi-site reproducibility, (quantified as width of the 95% confidence bound between the lower confidence interval and higher confidence interval for all repeatability measurements), was compared before and after standardisation to the model. The 95% confidence interval width used to determine a statistically significant change reduced from 21.1 to 2.7% after standardisation. Small tumour volumes and respiratory motion were found to be important contributors to poor reproducibility. A look up chart has been provided for investigators who would like to estimate uncertainty from statistical error on individual ADC measurements.

Liver metastases: Detection and staging

The liver is more often involved with metastatic disease than primary liver tumors. The accurate detection and characterization of liver metastases are crucial since patient management depends on it. The imaging options, mainly consisting of contrast-enhanced ultrasound (CEUS), multidetector computed tomography (CT), magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), extra-cellular contrast media and liver-specific contrast media as well as positron emission tomography/computed tomography (PET/CT), are constantly evolving. PET/MRI is a more recent hybrid method and a topic of major interest concerning liver metastases detection and characterization. This review gives a brief overview about the spectrum of imaging findings and focus on an update about the performance, advantages and potential limitations of each modality as well as current developments and innovations.