Explanations for the heterogeneity of splenic enhancement derived from blood flow kinetic measurements using dynamic contrast-enhanced CT (DCE-CT)

Development of a non-invasive diagnostic model for high-risk esophageal varices based on radiomics of spleen CT

PURPOSE

To evaluate the diagnostic performance of radiomics models derived from multi-phase spleen CT for high-risk esophageal varices (HREV) in cirrhotic patients.

METHODS

We retrospectively selected cirrhotic patients with esophageal varices from two hospitals from September 2019 to September 2023. Patients underwent non-contrast and contrast-enhanced CT scans and were categorized into HREV and non-HREV groups based on endoscopic evaluations. Radiomics features were extracted from spleen CT images in non-contrast, arterial, and portal venous phases, with feature selection via lasso regression and Pearson's correlation. Ten machine learning models were developed to diagnose HREV, evaluated by area under the curve (AUC). The AUC values of the three groups of models were statistically compared by the Kruskal-Wallis H test and Bonferroni-corrected Mann-Whitney U test. A p-value less than 0.05 was considered statistically significant.

RESULTS

Among 233 patients, 11, 6, and 11 features were selected from non-contrast, arterial, and portal venous phases, respectively. Significant differences in AUC values were observed across phases (p < 0.05), and the arterial phase models showed the highest AUC values. The best model in arterial phase was the logical regression model, whose AUC value was 0.85, sensitivity was 83.3%, specificity was 80% and F1 score was 0.81.

CONCLUSION

Radiomics models based on spleen CT, especially the arterial phase models, demonstrate high diagnostic accuracy for HREV, offering the potential for early detection and intervention.

Computed tomographic heterogeneous enhancement of spleen in healthy cats: comparing with diffuse infiltrative splenic lesions

Introduction

Contrast-enhanced computed tomography (CT) of the spleen in dogs and cats often displays a heterogeneous enhancement pattern. This study aimed to describe the CT appearances and duration of heterogeneous splenic enhancement in clinically healthy cats and to compare those enhancements with diffuse infiltrative splenic lesions (DISL).

Methods

Spleens of 14 healthy cats were imaged using contrast-enhanced CT protocols which were obtained at 10, 25, and 45 s, and then every 40 s thereafter until 245 s had past from the initiation of contrast medium injection. The presence of transient splenic heterogeneity was evaluated. In addition, the relationships of certain variables including age, weight, systolic blood pressure, and splenic volume to the duration and the degree of splenic enhancement were determined. Also, medical records and CT images of five cats with DISL were retrospectively evaluated.

Result

Transient heterogeneous enhancement of the spleen was observed in all 14 healthy cats, and the maximum heterogeneity was observed 25 s after the injection. Splenic heterogeneity lasted more than 5 min in nine of 14 cats (64.3%). No statistically significant relationships were seen between the duration and degree of splenic heterogeneity in the images taken 25 s after the injection and variables including weight, age, systolic blood pressure, and splenic volume.

Discussion

Compared to the healthy group, early homogeneous splenic enhancement along with generalized splenomegaly was observed in all cats with DISL. Transient splenic heterogeneity is highly common in cats undergoing contrast-enhanced CT even in the generally scanned delayed phases, which can help with the interpretation of CT images of feline spleens. In addition, our results suggest that homogeneous splenic enhancement in post-contrast CT scans along with splenomegaly on CT images could be useful as a diagnostic indicator of DISL in cats.

Unidentified bright objects of spleen on arterial phase CT: mimicker of splenic vascular injury in blunt abdominal trauma

PURPOSE

We have described unidentified bright objects of spleen (UBOS), a hitherto undescribed entity, as hyperdense areas on arterial phase (AP) computed tomography (CT) seen in relation to splenic lacerations and are isodense to the normal parenchyma on portal venous phase with no correlate on digital subtraction angiography (DSA). UBOS mimic splenic vascular injuries like active contrast extravasation and pseudoaneurysm and need to be differentiated from them as it would have implications on patient management. We undertook this study to identify CT features of UBOS that can differentiate them from splenic vascular injuries and to calculate their diagnostic accuracy.

METHODS

This retrospective study was approved by the institutional ethical committee and the need for informed consent was waived. Patients with splenic injury who had undergone dual-phase CT and DSA were included. All the lesions that were hyperdense on AP were evaluated for their outline, their relation to the adjacent/parallel margins of a laceration (margin sign), string of beads appearance, and the presence of adjacent normal parenchyma (adjacent parenchyma sign). The Hounsfield unit (HU) of the lesion and the aorta on the AP were also noted. The diagnostic accuracy of various signs for distinguishing UBOS from splenic vascular injuries was calculated using DSA as the reference standard.

RESULTS

Of 48 patients, 5 were excluded due to suboptimal quality of the examination or a time difference of more than 6 hours between the CT and DSA. A total of 54 hyperdense lesions were detected on AP in 43 patients. These were classified as vascular injuries (pseudoaneurysm, n=11; active contrast extravasation, n=11) and UBOS (n=32) based on DSA. The margin sign, string of beads appearance, and ill-defined outline had high specificity (95%, 86%, and 82%, respectively) but low sensitivity (50%, 65%, and 63%, respectively). The adjacent parenchyma sign had a moderate sensitivity and specificity of 84% and 77%, respectively. ROC analysis showed that a difference of 50 HU between the aorta and the lesion had a high sensitivity and specificity of 88.9% and 90.6%, respectively, with an area under the curve of 0.90.

CONCLUSION

An attenuation difference of over 50 HU between the aorta and the lesion and the presence of normal adjacent parenchyma had the highest diagnostic accuracy, while an ill-defined outline, string of beads appearance, and margin sign had high specificity but low sensitivity for differentiating UBOS from splenic vascular injuries.

Patterns of splenic arterial enhancement on computed tomography scan are related to portal venous hypertension

OBJECTIVES

We have previously shown that patterns of splenic arterial enhancement on computed tomography scan change following liver transplantation. We suggested that this is related to changes in portal venous pressure. The aim of this study was to see if similar patterns occur in patients with and without portal hypertension and in patients before and after portal systemic shunts (transjugular portosystemic shunts).

METHODS

We evaluated contrast enhanced computed tomography scans in patients being evaluated for liver disease and compared those from patients with and without portal hypertension. In addition we evaluated patients who had computed tomography scans before and after transjugular portosystemic shunts shunts. Splenic arterial enhancement was evaluated using Hounsfield units (pixel counts).

RESULTS

Twenty-four patients with clinically significant portal hypertension were compared to 91 without. Mean splenic pixel count was significantly lower in patients with clinically significant portal hypertension (88.2 ± 17.7 vs. 115.2 ± 21.0; m ± SD, P < 0.01). Computed tomography scans were available in 18 patients pre- and post-transjugular portosystemic shunts. Pixel counts were significantly higher in the post-transjugular portosystemic shunts scans (99.7 ± 20.9 vs. 88.9 ± 26.3; P < 0.05).

CONCLUSION

This study supports the hypothesis that changes in portal venous pressure are related to changes in splenic arterial enhancement. We suggest that this reflects changes in the splenic micro-circulation. This mechanism may be part of the innate immune response and may also be important in the pathogenesis of hypersplenism.

Splenic Blood Flow Increases after Hypothermic Stimulus (Cold Pressor Test): A Perfusion Magnetic Resonance Study

The Cold Pressor Test (CPT) is a novel diagnostic strategy to noninvasively assess the myocardial microvascular endothelial-dependent function using perfusion magnetic resonance imaging (MRI). Spleen perfusion is modulated by a complex combination of several mechanisms involving the autonomic nervous system and vasoactive mediators release. In this context, the effects of cold temperature on splenic blood flow (SBF) still need to be clarified. Ten healthy subjects were studied by MRI. MRI protocol included the acquisition of GRE T1-weighted sequence (“first pass perfusion”) during gadolinium administration (0.1mmol/kg of Gd-DOTA at flow of 3.0 ml/s), at rest and after CPT. Myocardial blood flow (MBF) and SBF were measured by applying Fermi function deconvolution, using the blood pool input function sampled from the left ventricle cavity. MBF and SBF values after performing CPT were significantly higher than rest values (SBF at rest: 0.65 ± 0.15 ml/min/g Vs. SBF after CPT: 0.90 ± 0.14 ml/min/g, p: <0.001; MBF at rest: 0.90 ± 0.068 ml/min/g Vs. MBF after CPT: 1.22 ± 0.098 ml/min/g, p<0.005). Both SBF and MBF increased in all patients during the CPT. In particular, the CPT-induced increase was 43% ± 29% for SBF and 36.5% ± 17% for MBF. CPT increases SBF in normal subjects. The characterization of a standard perfusion response to cold might allow the use of the spleen as reference marker for the adequacy of cold stimulation during myocardial perfusion MRI.

Patterns of splenic arterial enhancement on computed tomography are related to changes in portal venous pressure

OBJECTIVES

One of the striking features of splenic imaging is variable heterogeneous gyriform arterial enhancement on dynamic computed tomography (CT). We speculated that these patterns of arterial enhancement may reflect changes in splenic micro-circulation related to changes in portal venous pressure.

PATIENTS AND METHODS

To test this hypothesis, we evaluated arterial phase CT scans performed before and after liver transplantation (n=91), as this is the most effective way of alleviating portal hypertension. We developed novel grading systems to assess heterogeneity. Two control groups were used: patients with cirrhosis undergoing transarterial chemoembolization (TACE) (n=28) and patients with cirrhosis on the liver transplant waiting list who had repeated CT scans (n=28).

RESULTS

Splenic arterial heterogeneity increased in 55% of transplant patients compared with 14% in the TACE patients and 4% in the waiting list patients (P<0.0001). Mean Hounsfield units in areas of splenic enhancement were 71.7±2 before transplant and 90.1±2.5 after transplant (P<0.01). In contrast, there were no significant changes following TACE (86.3±4.2 vs. 83.5±4.5; P=NS) or in waiting list patients (80.9±4.6 vs. 73.8±3.7; P=NS).

CONCLUSION

We have shown the heterogeneous gyriform enhancement patterns significantly increase following liver transplantation but not after TACE or in waiting list patients. We suggest that these changes are due to the reduction in portal venous pressure and likely reflect changes in splenic micro-circulation. These changes may be important in the pathophysiology of hypersplenism.

Noninvasive prediction of portal pressure with MR elastography and DCE-MRI of the liver and spleen: Preliminary results

BACKGROUND

Portal hypertension (PH), defined by hepatic venous pressure gradient (HVPG) ≥5 mmHg and clinically significant PH, defined by HVPG ≥10 mmHg, are complications of chronic liver disease.

PURPOSE

To assess the diagnostic performance of MR elastography (MRE) and dynamic contrast-enhanced MRI (DCE-MRI) of the liver and spleen for the prediction of PH and clinically significant PH, in comparison with a qualitative PH imaging scoring system.

STUDY TYPE

IRB-approved prospective study.

POPULATION

In all, 34 patients with chronic liver disease who underwent HVPG measurement.

FIELD STRENGTH/SEQUENCE

1.5/3T examination including 2D-GRE MRE (n = 33) and DCE-MRI of the liver/spleen (n = 28).

ASSESSMENT

Liver and spleen stiffness were calculated from elastogram maps. DCE-MRI was analyzed using model-free parameters and pharmacokinetic modeling. Two observers calculated qualitative PH imaging scores based on routine images.

STATISTICAL TESTS

Imaging parameters were correlated with HVPG. Receiver operating characteristic (ROC) analysis was performed for prediction of PH and clinically significant PH.

RESULTS

There were significant correlations between DCE-MRI parameters (liver time-to-peak, r = 0.517 / P = 0.006, liver distribution volume, r = 0.494 / P = 0.009, liver upslope, r = -0.567 / P = 0.002), liver stiffness (r = 0.478 / P = 0.016), PH imaging score (r = 0.441 / P = 0.009), and HVPG. ROC analysis provided significant area under the ROC (AUROCs) for PH (liver upslope 0.765, liver stiffness 0.809, spleen volume/diameter 0.746-0.731, PH imaging score 0.756) and for clinically significant PH (liver and spleen perfusion parameters 0.733-0.776, liver stiffness 0.742, PH imaging score 0.742). The ratio of liver stiffness to liver upslope had the highest AUROC for diagnosing PH (0.903) and clinically significant PH (0.785).

DATA CONCLUSION

These preliminary results suggest that the combination of liver stiffness and perfusion metrics provide excellent accuracy for diagnosing PH, and fair accuracy for clinically significant PH. Combined MRE and DCE-MRI outperformed qualitative imaging scores for prediction of PH.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1091-1103.

CT perfusion imaging of the liver and the spleen in patients with cirrhosis: Is there a correlation between perfusion and portal venous hypertension?

OBJECTIVES

To correlate hepatic and splenic CT perfusion parameters with hepatic venous pressure gradient (HVPG) measurements in patients with cirrhosis.

METHODS

Twenty-one patients with cirrhosis (males, 17; females, 4; mean ± SD age, 57 ± 7 years) underwent hepatic and splenic perfusion CT on a 320-detector row volume scanner as well as invasive measurement of HVPG. Different CT perfusion algorithms (maximum slope analysis and Patlak plot) were used to measure hepatic arterial flow (HAF), portal venous flow (PVF), hepatic perfusion index (HPI), splenic arterial flow (SAF), splenic blood volume (SBV) and splenic clearance (SCL). Hepatic and splenic perfusion parameters were correlated with HVPG, and sensitivity and specificity for detection of severe portal hypertension (≥12 mmHg) were calculated.

RESULTS

The Spearman correlation coefficient was -0.53 (p < 0.05) between SAF and HVPG, and -0.68 (p < 0.01) between HVPG and SCL. Using a cut-off value of 125 ml/min/100 ml for SCL, sensitivity for detection of a HVPG of ≥12 mmHg was 94%, and specificity 100%. There was no significant correlation between hepatic perfusion parameters and HVPG.

CONCLUSION

CT perfusion in patients with cirrhosis showed a strong correlation between SCL and HVPG and may be used for detection of severe portal hypertension.

KEY POINTS

• SAF and SCL are statistically significantly correlated with HVPG • SCL showed stronger correlation with HVPG than SAF • 125 ml/min/100 ml SCL-cut-off yielded 94 % sensitivity, 100 % specificity for severe PH • HAF, PVF and HPI showed no statistically significant correlation with HVPG.

Sonographic Bands of Hypoechogenicity in the Spleen in Children: Zebra Spleen

OBJECTIVE

Zebra spleen is the normal pattern of splenic enhancement during the arterial phase of CT and MRI and is attributed to different flow rates. The purpose of this study was to describe the appearance and occurrence of bands of hypoechogenicity in the spleen on unenhanced sonograms of children with no splenic abnormalities.

MATERIALS AND METHODS

We reviewed 100 abdominal ultrasound studies to evaluate the ultrasound characteristics of the spleen. Demographic data were collected for all patients.

RESULTS

Homogeneous echogenicity of the spleen was found in 92 children. Heterogeneous echogenicity was present in eight. Three of the eight had discrete macronodules due to known splenic disease. The other five had bands of hypoechogenicity. These five had no known splenic disease, but one had mild splenomegaly of unknown cause.

CONCLUSION

The pattern of hypoechoic bands occurred in 5% of our series. This pattern cannot be explained simply by different flow rates and probably reflects different structural components of the parenchyma. At ultrasound this pattern should be considered a normal finding that may simulate a splenic mass.