Splenic blood flow: evaluation with computed tomography

Intrapancreatic accessory spleen: Evaluation with CT and MRI

The aim of the present study was to evaluate the characteristics of computed tomography (CT) and magnetic resonance imaging (MRI), particularly diffusion-weighted imaging (DWI), in the imaging of intrapancreatic accessory spleen (IPAS). The clinical and pathological records of 9 patients, including 8 patients with IPAS and 1 patient with splenosis, were reviewed. The patients had undergone plain and triple-phase enhanced CT scanning (n=9) and MRI scanning (n=8). The lesions of the 8 IPAS patients were located in the pancreatic tail, and were round (n=3), oval (n=4) or triangular (n=1) in shape. The CT and/or MRI densities, signal intensities and dynamic enhanced patterns of the lesions were similar to those of the orthotopic spleen. In DWI images (n=5), the IPAS regions presented high signal intensity (SI), and no significant difference in the apparent diffusion coefficient determined using a b-value of 600 sec/mm² was identified between the IPAS and orthotopic spleen (P>0.05). One patient with splenosis complicated with cirrhosis had a nodule located in the pancreatic tail with an unenhanced CT value of 65 HU. In MRI examination, with the exception of the dynamic enhancement pattern, the T1-weighted, T2-weighted and DWI signals of splenosis were inconsistent with those of the normal spleen. In conclusion, in pre-contrast and post-contrast-enhanced CT and MRI images, IPAS exhibits similar characteristics to the orthotopic spleen. CT and MRI used in combination with DWI are important in the diagnosis of IPAS.

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.

Elevation of intra-abdominal pressure by pneumoperitoneum decreases pancreatic perfusion in an in vivo porcine model

BACKGROUND

The goal of this study is to examine changes in pancreatic perfusion due to pneumoperitoneum using perfusion CT in vivo.

METHODS

Three pigs were studied. Under general anesthesia, pneumoperitoneum was induced to 16 mm Hg. Perfusion CT scans were acquired at a rate of 1 image per 2 seconds for 60 seconds. Scans were repeated 5 days later without pneumoperitoneum using the same protocol, in the same animals. The time density curve, color map, peak enhancement, time to peak, blood flow, blood volume, and permeability were evaluated.

RESULTS

In the presence of pneumoperitoneum, peak enhancement in radiodensity was decreased and time to peak was increased, and both blood flow and blood volume decreased. However, there was no consistent change in permeability observed.

CONCLUSION

This study demonstrates that pneumoperitoneum quantitatively results in decreased blood flow and blood volume to the pancreas in an in vivo animal model.

Spleen dynamic contrast-enhanced magnetic resonance imaging as a new method for staging liver fibrosis in a piglet model

Objective

To explore spleen hemodynamic alteration in liver fibrosis with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and to determine how to stage liver fibrosis with spleen DCE-MRI parameters.

Materials and Methods

Sixteen piglets were prospectively used to model liver fibrosis staged by liver biopsy, and underwent spleen DCE-MRI on 0, 5th, 9th, 16th and 21st weekend after modeling this disease. DCE-MRI parameters including time to peak (TTP), positive enhancement integral (PEI), maximum slope of increase (MSI) and maximum slope of decrease (MSD) of spleen were measured, and statistically analyzed to stage this disease.

Results

Spearman's rank correlation tests showed that TTP tended to increase with increasing stages of liver fibrosis (r = 0.647, P<0.001), and that PEI tended to decrease from stage 0 to 4 (r = −0.709, P<0.001). MSD increased slightly from stage 0 to 2 (P>0.05), and decreased from stage 2 to 4 (P<0.05). MSI increased from stage 0 to 1, and decreased from stage 1 to 4 (all P>0.05). Mann-Whitney tests demonstrated that TTP and PEI could classify fibrosis between stage 0 and 1–4, between 0–1 and 2–4, between 0–2 and 3–4, or between 0–3 and 4 (all P<0.01). MSD could discriminate between 0–2 and 3–4 (P = 0.006), or between 0–3 and 4 (P = 0.012). MSI could not differentiate between any two stages. Receiver operating characteristic analysis illustrated that area under receiver operating characteristic curve (AUC) of TTP was larger than of PEI for classifying stage ≥1 and ≥2 (AUC = 0.851 and 0.783, respectively). PEI could best classify stage ≥3 and 4 (AUC = 0.903 and 0.96, respectively).

Conclusion

Spleen DCE-MRI has potential to monitor spleen hemodynamic alteration and classify liver fibrosis stages.

Assessment of splenic perfusion in patients with malignant hematologic diseases and spleen involvement, liver cirrhosis and controls using volume perfusion CT (VPCT): a pilot study

RATIONALE AND OBJECTIVES

The aim of this study was to assess splenic perfusion in patients with spleen involvement in malignant hematologic diseases and liver cirrhosis and in controls without hepatosplenic disease using volume perfusion computed tomography.

MATERIALS AND METHODS

Between October 2009 and December 2011, 14 hematologic patients with known spleen involvement were recruited. An additional 17 consecutive patients without known splenic or liver disease were enrolled as controls, as well as 29 patients with liver cirrhosis and portal hypertension. A 40-second volume perfusion computed tomographic scan of the upper abdomen was performed. Analysis included measurement of splenic volume, blood flow (BF), blood volume (BV), K(trans), and mean transit time (MTT).

RESULTS

In lymphoma patients, mean splenic volume and perfusion parameters were as follows: splenic volume, 1125.34 mL; BF, 61.24 mL/100 mL/min; BV, 16.53 mL/100 mL; K(trans), 37.00 mL/100 mL/min; and MTT, 12.42 seconds. All perfusion values of patients with lymphoma and cirrhosis differed significantly, except for BV, compared to controls. For patients with lymphoma, significant correlations were found between splenic volume and BF (r = -0.683, P = .000), splenic volume and BV (r = -0.525, P = .002), and splenic volume and MTT (r = 0.543, P = .001). During treatment, significant correlations between the diameters of nodular lymphoma target lesions, splenic volume, and the perfusion parameters were present for splenic volume (r = 0.601, P = .002), BF (r = -0.777, P = .000) and BV (r = -0.500, P = .011).

CONCLUSIONS

Volume perfusion computed tomography represents a novel tool for the assessment of splenic perfusion. Preliminary results in patients with spleen involvement reveal lower perfusion values compared to controls or patients with cirrhosis. Therefore, this technique might provide additional information in clinical routine.

Perfusion measurement of the whole upper abdomen of patients with and without liver diseases: initial experience with 320-detector row CT

OBJECTIVES

To report initial experience of upper abdominal perfusion measurement with 320-detector row CT (CTP) for assessment of liver diseases and therapeutic effects.

MATERIALS AND METHODS

Thirty-eight patients who were suspected of having a liver disease underwent CTP. There were two patients with liver metastases, two with hemangiomas, and four with cirrhosis (disease group). CTP was repeated for four patients with cirrhosis or hepatocellular carcinoma (HCC) after therapy. Hepatic arterial and portal perfusion (HAP and HPP) and arterial perfusion fraction (APF), and arterial perfusion (AP) of pancreas, spleen, stomach, and intra-portal HCC were calculated. For disease-free patients (normal group), the values were compared among liver segments and among pancreatic and gastric parts. The values were compared between groups and before and after therapy.

RESULTS

No significant differences were found in the normal group except between APFs for liver segments 3 and 5, and fundus and antrum. Mean HAP and APF for the disease group were significantly higher than for the normal group. APF increased after partial splenic embolization or creation of a transjugular intrahepatic portosystemic shunt. HPP increased and AP of intra-portal HCC decreased after successful radiotherapy.

CONCLUSIONS

320-Detector row CT makes it possible to conduct perfusion measurements of the whole upper abdomen. Our preliminary results suggested that estimated perfusion values have the potential to be used for evaluation of hepatic diseases and therapeutic effects.

Perfusion CT and US of colorectal cancer liver metastases: a correlative study of two dynamic imaging modalities

The purpose of this study was to evaluate the correlation between dynamic-contrast-enhanced computed tomography (DCE-CT) and first-pass dynamic-contrast-enhanced ultrasound (DCE-US) of normal appearing liver parenchyma and of colorectal cancer liver metastases. Thirty patients with hepatic metastases from colorectal cancer underwent DCE-CT and DCE-US. To obtain DCE-US reproducibility measurements, double contrast-passages (2 × 2.4 mL SonoVue intravenous) were acquired. From several DCE-US-derived perfusion indices, the slope-value scored best with a reproducibility concordance correlation coefficient ranging from 0.75-0.93 and overall highest correlation to DCE-CT-derived variables (r = 0.52 to 0.73). The DCE-US-based tumor-to-liver perfusion gradient also showed a low test-retest variability and moderately correlated to DCE-CT (concordance correlation coefficient 0.87-0.92; r = 0.57 to 0.59). To conclude, DCE-US-based slope-value and tumor-to-liver perfusion gradient correlate best with DCE-CT perfusion values. However, both techniques cannot be used interchangeably. DCE-US should be restricted for studies in which a considerable change in perfusion is expected and for patients with a relatively high tumor blood flow at baseline.

Intrapancreatic accessory spleen: findings on MR Imaging, CT, US and scintigraphy, and the pathologic analysis

Although the tail of the pancreas is the second most common site of an accessory spleen, intrapancreatic accessory spleen (IPAS) has rarely been noted radiologically. However, as the imaging techniques have recently advanced, IPAS will be more frequently detected as an incidental pancreatic nodule on CT or MRI. Because accessory spleens usually pose no clinical problems, it is important to characterize accessory spleens as noninvasively as possible. An IPAS has similar characteristics to those of the spleen on the precontrast and contrast-enhanced images of all the imaging modalities. In particular, inhomogeneous enhancement of an IPAS in its early phases may be a diagnostic clue. Superparamagnetic iron oxide (SPIO)-enhanced MRI and Levovist-enhanced US, and the mechanisms of which are theoretically similar to that of Tc-99m scintigraphy, can be used as alternative tools to confirm the diagnosis of IPAS. An IPAS shows a significant signal drop similar to the spleen on the SPIO-enhanced T2 or T2*-weighted imaging and prolonged enhancement on the delayed hepatosplenic phase of contrast-enhanced US. We review and illustrate the differential points between IPAS and hypervascular pancreatic tumors in this manuscript.

The use of perfusion CT for the evaluation of therapy combining AZD2171 with gefitinib in cancer patients

The purpose of this study was to determine the feasibility of dynamic contrast-enhanced perfusion CT (CTP) in evaluating the hemodynamic response of tumors in the chest and abdomen treated with a combination of AZD2171 and gefitinib. Thirteen patients were examined just before and every 4-6 weeks after starting therapy. Following intravenous injection of a contrast agent, dynamic image acquisition was obtained at the level of a selected tumor location. To calculate perfusion, the maximum-slope method was used. Pre-treatment average perfusion for extra-hepatic masses was 84 ml/min/100 g, for liver masses arterial perfusion was 25 ml/min/100 g, and a portal perfusion of 30 ml/min/100 g was found. After the administration of AZD2171 and gefitinib, in extra-hepatic masses an initial decrease in perfusion of 18% was followed by a plateau and in liver masses an initial decrease of 39% within the lesions and of 36% within a rim region surrounding the lesions was followed by a tendency to recovery of hepatic artery flow. In conclusion, CTP is feasible in showing changes of perfusion induced by anti-angiogenic therapy.

Factors affecting the quantitative liver-spleen scan in normal individuals

The quantitative liver-spleen scan (QLSS) can estimate the functional hepatic mass and the organ volumes by precise measurement of sulfur colloid (SC) distribution. The normal range determined in prior studies was estimated from patients with absence of chronic liver disease in which intense fasting appeared to produce slightly abnormal values. This study was to determine the effect of fasting or fed status and colloid particle size on quantitative measurements from the QLSS in a small cohort of normal individuals. Twelve persons without any medical problems had QLSS taken twice, 2 weeks apart, one fasting and one postprandial. Patients were scanned after injection of 5-6 mCi of SC; six patients were given solution A (5- to 12-microm particle size) and six patients solution B (2- to 12-microm particle size). SPECT and planar analysis were performed. SC distribution of total counts between the liver and the spleen {[L/(L + S)]t ratio}, liver-spleen index (LSI), and liver-bone marrow index (LBI) were calculated. The perfused hepatic mass (PHM) is the average of the LSI and LBI. Spleen and liver volumes are expressed as milliliters per pound ideal body weight (IBW). Results showed that the liver and spleen volumes (solution B postprandial, 9.27 +/- 2.48 and 1.47 +/- 0.57 ml/lb IBW, respectively) and LBI were not affected by the type of SC solution or by ingestion status. L/(L + S) total and pixel count ratios were significantly higher for solution B and postprandial studies. [L/(L + S)]t, LSI, and PHM increased significantly (P < 0.05) from fasting to postprandial for solution A (0.71 +/- 0.13 vs 0.79 +/- 0.08, 80 +/- 14 vs 91 +/- 8, and 102 +/- 10 vs 106 +/- 8, respectively) and for solution B (0.81 +/- 0.05 vs 0.90 +/- 0.02, 86 +/- 4 vs 95 +/- 3, and 101 +/- 5 vs 110 +/- 3). Neither fasting nor postprandial LSI and PHM were significantly different between solution A and solution B. We conclude the following. (1) The QLSS functional indices in "true" normal patients fall within the previously reported normal range. (2) Calculated liver and spleen volumes are not altered by fasting or sulfur colloid particle size. (3) Fasting significantly decreased the [L/(L + S)]t, LSI, and PHM. (4) A postprandial scan may be preferable since the normal values for [L/(L + S)]t, LSI, and PHM are greater, with a narrower range, than fasting values.

Quantitative perfusion map of malignant liver tumors, created from dynamic computed tomography data

RATIONALE AND OBJECTIVES

To apply perfusion computed tomography (CT) technique to variable malignant liver tumors, and to define the usefulness of quantitative color mapping.

MATERIALS AND METHODS

Perfusion CT images were created for 36 malignant liver tumors in 28 patients (age, 66.4 +/- 10.1 years; range, 48-85) with metastatic liver tumors (n = 17; nine colorectal carcinomas, eight other malignant tumors) and hepatocellular carcinomas (n = 11). A single-slice dynamic CT was performed after an intravenous bolus injection of 40 mL of contrast material (320 mgI/mL) with 8 mL/sec. The parameters were calculated pixel-by-pixel using maximum slope method, and quantitative maps of arterial and portal perfusion were created. In four patients who underwent transcatheter arterial chemoembolization, perfusion CT was performed before and after transcatheter arterial chemoembolization.

RESULTS

In all patients, liver tumors were shown as hypervascular lesions on arterial perfusion CT. The average arterial perfusion value of the metastatic tumors from the colorectal carcinomas was 0.67 +/- 0.33 mL/min/mL, and that of hepatocellular carcinomas was 0.94 +/- 0.26 mL/min/mL (P = .03). The other metastatic tumors from various primary tumors showed a wide range (0.19-1.45 mL/min/mL) of arterial perfusion. Arterial perfusion of the liver tumors was obviously decreased after successful transcatheter arterial chemoembolization. In 12 of 15 tumors, in which portal perfusion CT images could be created, region-of-interest analysis showed no portal perfusion in the tumors. In two cases, decreased portal perfusion in the segments, which malignant tumors involved, was demonstrated.

CONCLUSION

Perfusion CT can provide quantitative information about arterial and portal perfusion of liver tumors, combined with good anatomic detail in one image. This technique has a potential to evaluate the angiogenesis of liver tumors, to show secondary changes in perfusion, such as decreased portal perfusion in apparently normal liver adjacent to metastases, and to monitor the therapeutic response in vivo.

Development of perfusion CT software for personal computers

RATIONALE AND OBJECTIVES

The authors developed software for creating quantitative maps of arterial and portal perfusion in the upper abdominal organs on personal computers. The image quality of these perfusion computed tomographic (CT) images was visually evaluated.

MATERIALS AND METHODS

In 58 patients (38 men, 20 women; mean age, 63.9 years +/- 11.9; range, 22-85 years) with various diseases of the upper abdomen, 91 single-section dynamic CT studies were obtained. The data were transferred on-line to a personal computer, and quantitative maps of arterial and portal perfusion were created by means of the maximum-slope method. Perfusion CT images were reviewed by a radiologist and a radiation technologist, and image quality was rated according to a four-category scoring system (1 = good quality, 2 = moderate, 3 = poor, 4 = images could not be created).

RESULTS

Arterial perfusion CT images could be created in 81 (89%) of 91 examinations, and 74 images (81%) were scored as 1 or 2. Portal perfusion CT images could be created in 60 (68%) of 88 examinations, in which a portal trunk was included in the section, and 33 of them (38%) were scored as 1 or 2. Patient motion during dynamic CT sequences resulted in poor image quality in seven arterial and 27 portal perfusion images.

CONCLUSION

Perfusion CT can combine quantitative perfusion maps with good anatomic detail in one image, although patient movement frequently degrades image quality in portal perfusion CT.

Rib artifacts in electron beam tomography: incidence and severity without and with the cone beam reconstruction algorithm

Electron beam tomography (EBT) may be compromised by rib artifacts. Two hundred forty-seven abdominal studies were performed without (Group A, n = 222) or with (Group B, n = 25) the cone beam algorithm. One hundred eighty-six (83.8%) and nine (36%) studies of Groups A and B, respectively, displayed some level of artifact. In Groups A and B, major, minor, and no artifacts were found in 115 (51.5%) and 0 (0%), 71 (32.3%) and 9 (36%), and 36 (16.2%) and 16 (64%) patients, respectively (p < 0.01). The cone beam algorithm improves EBT studies of the abdomen.

Pulmonary perfusion in supine and prone positions: an electron-beam computed tomography study

Acute respiratory distress syndrome is characterized by alterations in the ventilation-perfusion ratio. Present techniques for studying regional pulmonary perfusion are difficult to apply in the critically ill. Electron-beam computed tomography was used to study the effects of prone positioning on regional pulmonary perfusion in six healthy subjects. Contrast-enhanced sections were obtained sequentially in the supine, prone, and (original) supine positions at full inspiration. Regions of interest were placed along the nondependent to dependent axis and relative perfusion calculated. When corrected for the redistribution of lung parenchyma, a gravitational gradient of pulmonary perfusion existed in both supine and prone positions. The distribution of perfusion between the supine or prone positions did not differ, but data analysis using smaller regions of interest demonstrated marked heterogeneity of perfusion between anatomically adjacent regions of lung. The distribution of lung parenchyma was more uniform in the prone position. Gravity was estimated to be responsible for 22-34% of perfusion heterogeneity in the supine and 27-41% in the prone positions. These data support the hypothesis that factors other than gravity may be at least as important in determining the distribution of pulmonary perfusion in humans. The influence of nongravitational factors may not be detectable if techniques that sample large tissue volumes are employed.

Hepatic perfusion changes after transcatheter arterial embolization (TAE) of hepatocellular carcinoma: measurement by dynamic computed tomography (CT)

We observed the hemodynamic changes at the level of the hepatic parenchyma induced by transcatheter arterial embolization (TAE) for hepatocellular carcinoma in 22 patients. TAE was performed by administration of a mixture of iodized oil, adriamycin, and mitomycin C, followed by injection of gelatin sponge particles (1-mm pieces). Perfusion measurements (arterial and portal) were done by dynamic computed tomography (CT). Arterial perfusion was increased two to six days after TAE (0.146 +/- 0.073 ml/min/ml, P < 0.0002) compared with that before TAE (0.064 +/- 0.039), but decreased again one month after TAE (0.086 +/- 0.038). Portal perfusion was decreased two to six days after TAE (0.541 +/- 0.180, P < 0.001) compared with that before TAE (0.733 +/- 0.263) and was grossly unchanged one month after TAE (0.651 +/- 0.214). We suspected that these perfusion changes were due to acute inflammatory responses. Quantification of tissue perfusion by dynamic CT was useful for studying hemodynamic changes after TAE.