Minimally invasive input function for 2-<Superscript>18</Superscript>F-fluoro-A-85380 brain PET studies

Purpose  

Quantitative neuroreceptor positron emission tomography (PET) studies often require arterial cannulation to measure input function. While population-based input function (PBIF) would be a less invasive alternative, it has only rarely been used in conjunction with neuroreceptor PET tracers. The aims of this study were (1) to validate the use of PBIF for 2-¹⁸F-fluoro-A-85380, a tracer for nicotinic receptors; (2) to compare the accuracy of measures obtained via PBIF to those obtained via blood-scaled image-derived input function (IDIF) from carotid arteries; and (3) to explore the possibility of using venous instead of arterial samples for both PBIF and IDIF.     

Image-derived input function in dynamic human PET/CT: methodology and validation with 11C-acetate and 18F-fluorothioheptadecanoic acid in muscle and 18F-fluorodeoxyglucose in brain

Purpose  

Despite current advances in PET/CT systems, blood sampling still remains the standard method to obtain the radiotracer input function for tracer kinetic modelling. The purpose of this study was to validate the use of image-derived input functions (IDIF) of the carotid and femoral arteries to measure the arterial input function (AIF) in PET imaging. The data were obtained from two different research studies, one using ¹⁸F-FDG for brain imaging and the other using ¹¹C-acetate and ¹⁸F-fluoro-6-thioheptadecanoic acid (¹⁸F-FTHA) in femoral muscles.     

Therapeutic effects of percutaneous vertebroplasty for vertebral metastases

Purpose  

We have performed percutaneous vertebroplasty (PV) using polymethylmethacrylate (PMMA) for patients with vertebral metastases since 2002. This study investigated the therapeutic effects of PV on vertebral metastases.     

Is prophylactic embolization of the hepatic falciform artery needed before radioembolization in patients with <Superscript>99m</Superscript>Tc-MAA accumulation in the anterior abdominal wall?

Purpose  

While influx of chemoembolic agents into the hepatic falciform artery (HFA) from the hepatic artery can cause supraumbilical skin rash, epigastric pain and even skin necrosis, the significance of a patent HFA in patients undergoing radioembolization is not completely clear. Furthermore, the presence of tracer in the anterior abdominal wall seen in ^99mTc-macroaggregated albumin (^99mTc-MAA) images, which is generally performed prior to radioembolization, has been described as a sign of a patent HFA. The aim of this retrospective study was to evaluate the incidence and consequences of ^99mTc-MAA accumulation in the anterior abdominal wall, indicating a patent HFA, in patients undergoing radioembolization of liver tumours.     

Perfusion parameters derived from bolus‐tracking perfusion imaging are immune to tracer recirculation

Purpose:

To investigate the impact of tracer recirculation on estimates of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT).

Materials and Methods:

The theoretical model used to derive CBF, CBV, and MTT was examined. CBF and CBV estimates with and without tracer recirculation were compared in computer simulations to examine the effects of tracer recirculation.

Results:

The equations used to derive CBF, CBV, and MTT assume that the arterial input function and tissue tracer signals define the input and output signals, respectively, of a linear time‐invariant system. As a result of the principle of superposition, these perfusion parameters are immune to tracer recirculation, which was confirmed by computer simulation. However, limited acquisition durations can lead to CBV and CBF errors of up to 50%.

Conclusion:

Tracer recirculation does not impact estimation of CBF, CBV, or MTT. However, previous approaches used to remove recirculation effects may be beneficial when used to compensate for limited acquisition durations in which the passage of the bolus is not adequately captured. J. Magn. Reson. Imaging 2010;31:753–756. © 2010 Wiley‐Liss, Inc.     

Four-dimensional velocity mapping of the hepatic and splanchnic vasculature with radial sampling at 3 tesla: a feasibility study in portal hypertension

Purpose:

To demonstrate the feasibility of PC‐VIPR (Phase Contrast Vastly undersampled Imaging with Projection Reconstruction) for the depiction and hemodynamic analysis of hepatic and splanchnic vessels in patients with portal hypertension.

Materials and Methods:

Twenty‐four cirrhotic patients (55.9 ± 10.4years) were scanned using 5‐point PC‐VIPR for high spatial resolution imaging with large volume coverage at 3 Tesla (T) using a 32‐channel body coil. Vessel segmentation and hemodynamic visualization included color‐coded three‐dimensional (3D) streamlines and particle traces. Segmentation quality was compared with contrast‐enhanced multi‐phase liver imaging. Flow pattern analysis was performed in consensus of three readers. The MELD score was calculated to estimate disease severity and was correlated to image quality.

Results:

Good to excellent visualization quality was achieved in 23/24 cases. All arterial vessels and 144/168 vessels of the portal venous (PV) circulation were unambiguously identified. No correlation with the MELD score was found. Eight of 148 vessels of the PV circulation demonstrated reverse (hepatofugal) flow. Hepatofugal flow in small tributaries to PV flow were present in three cases despite hepatopetal flow in the PV.

Conclusion:

This feasibility study demonstrates the feasibility of PC‐VIPR for simultaneous morphological and hemodynamic assessment of the hepatic and splanchnic vasculature in cirrhosis and portal hypertension. Future studies with quantitative analyses are warranted. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

The potential use of 2-[<Superscript>18</Superscript>F]fluoro-2-deoxy-<Emphasis Type="SmallCaps">D</Emphasis>-galactose as a PET/CT tracer for detection of hepatocellular carcinoma

Purpose  

The aim of the study was to evaluate the feasibility of using the hepatocyte-specific positron emission tomography (PET) tracer 2-[¹⁸F]fluoro-2-deoxy-D-galactose (FDGal) as a tracer for hepatocellular carcinoma (HCC).     

Quantification of [<Superscript>18</Superscript>F]-FDG uptake in atherosclerotic plaque: impact of renal function

Objective  

Impaired renal function causes both increased and prolonged tracer availability in the blood-pool which might result in increased tracer accumulation in atherosclerotic lesions. Therefore, the aim of this study was to investigate a possible correlation between the intensity of tracer uptake in atherosclerotic lesions and renal function.     

Kinetic analysis of FDG in rat liver: Effect of dietary intervention on arterial and portal vein input

IntroductionDietary conditions may affect liver [¹⁸F]FDG kinetics due to arterial and portal vein (PV) input. The purpose of this study was to evaluate kinetic models of [¹⁸F]FDG metabolism under a wide range of dietary interventions taking into account variations in arterial (HA) and portal vein (PV) input.MethodsThe study consisted of three groups of rats maintained under different diet interventions: 12 h fasted, 24 h fasted and those fed with high fructose diet. [¹⁵O]H₂O PET imaging was used to characterize liver flow contribution from HA and PV to the liver's dual input function (DIF). [¹⁸F]FDG PET imaging was used to characterize liver metabolism. Differences in [¹⁸F]FDG kinetics in HA, PV and liver under different diet interventions were investigated. An arterial to PV Transfer Function (TF) was optimized in all three dietary states to noninvasively estimate PV activity. Finally, two compartment 3-parameter (2C3P), two compartment 4-parameter (2C4P), two compartment 5-parameter (2C5P), and three compartment 5-parameter (3C5P) models were evaluated and compared to describe the kinetics of [¹⁸F]FDG in the liver across diet interventions. Sensitivity of the compartmental models to ratios of HA to PV flow fractions was further investigated.ResultsDifferences were found in HA and PV [¹⁸F]FDG kinetics across 12 h fasted, 24 h fasted and high fructose fed diet interventions. A two exponential TF model was able to estimate portal activity in all the three diet interventions. Statistical analysis suggests that a 2C3P model configuration was adequate to describe the kinetics of [¹⁸F]FDG in the liver under wide ranging dietary interventions. The net influx of [¹⁸F]FDG was lowest in the 12 h fasted group, followed by 24 h fasted group, and high fructose diet.ConclusionsA TF was optimized to non-invasively estimate PV time activity curve in different dietary states. Several kinetic models were assessed and a 2C3P model was sufficient to describe [¹⁸F]FDG liver kinetics despite differences in HA and PV kinetics across wide ranging dietary interventions. The observations have broader implications for the quantification of liver metabolism in metabolic disorders and cancer, among others.     

Portal vein variations in 1000 patients: surgical and radiological importance

Objective:

The purpose of the study was to evaluate the spectrum and incidence of intrahepatic portal vein (PV) variations on triphasic abdomen multidetector CT (MDCT) and to discuss the surgical and radiological implications.

Methods:

A retrospective review of 1000 triphasic MDCT abdomen scans was performed in patients sent for various liver and other abdominal pathologies between January 2014 and August 2014. A total of 967 patients (N = 967) were included in the study. The variations in branching pattern of PV were classified according to classification used by Covey et al (Covey AM, Brody LA, Getrajdman GI, Sofocleous CT, Brown KT. Incidence, patterns, and clinical relevance of variant portal vein anatomy. AJR Am J Roentgenol 2004; 183: 1055–64) and Koç et al (Koç Z, Oğuzkurt L, Ulusan S. Portal vein variations: clinical implications and frequencies in routine abdominal CT. Diagn Interv Radiol 2007; 13: 75–80).

Results:

Normal anatomy (Type I) was seen in 773 patients (79.94%) out of 967 patients in our study. Trifurcation (Type II) anomaly was seen in 66 (6.83%) of cases. Right posterior vein as first branch of main PV (Type III) anomaly was seen in 48 (4.96%) of cases. Type IV anomaly and Type V anomaly was seen in 26 (2.69%) and 13 (1.34%) cases, respectively. 19 cases showed other types of variations.

Conclusion:

Variations in the hepatic PV branching patterns are commonly seen that are similar to variations in hepatic artery and biliary anatomy. Knowledge of these variations is extremely important for transplant surgeons and intervention radiologists.

Advances in knowledge:

Awareness of the variations in PV branching patterns is essential for intervention radiologists and vascular surgeons and avoids major catastrophic events.     

Quantitative analysis of vertebral bone marrow perfusion using dynamic contrast-enhanced MRI: initial results in osteoporotic patients with acute vertebral fracture

Purpose:

To evaluate the potential of quantitative dynamic contrast‐enhanced MRI (DCE‐MRI) in vertebral bone marrow (vBM) of patients with acute osteoporotic vertebral compression fractures.

Materials and Methods:

Twenty‐six patients with acute osteoporotic fractures (16 female, 10 male, median age 72, range 48–89) and 10 subjects without known history of osteoporosis (6 female, 4 male, median 65, range 31–77) were examined 2D‐DCE‐MRI. Region of interest (ROI) data in fractured (n = 26) and normal‐appearing vertebrae (n = 271) were analyzed with a two‐compartment tracer‐kinetic‐model, providing estimates of at least three independent parameters: plasma flow (PF), plasma volume (PV), and extraction flow (EF). Parameters were correlated with dual x‐ray absorptiometry (DXA) (n = 15) and quantitative computed tomography (QCT) densitometry (n = 10).

Results:

Mean PF was significantly higher in fractures than in normal‐appearing vertebrae (69.37 vs. 11.72 mL/100 mL/min). Similarly, mean PV and EF differed significantly. Mean PF was significantly decreased in normal‐appearing vBM osteoporotic patients compared to the control group. Mean PF and PV were significantly decreased in lumbar compared to thoracic vertebrae. PV showed a significant correlation with QCT.

Conclusion:

Perfusion parameters were decreased significantly in normal‐appearing vBM of patients. Furthermore, significant perfusion alterations were observed in acute osteoporotic vertebral fractures compared to normal‐appearing vertebrae. J. Magn. Reson. Imaging 2011;33:676–683. © 2011 Wiley‐Liss, Inc.     

Hepatic Artery Embolization for Postoperative Hemorrhage: Importance of Arterial Collateral Vessels and Portal Venous Impairment

PurposeTo investigate the association between hepatic ischemic complications and hepatic artery (HA) collateral vessels and portal venous (PV) impairment after HA embolization for postoperative hemorrhage.Materials and MethodsFrom October 2003 to November 2019, 42 patients underwent HA embolization for postoperative hemorrhage. HA collateral vessels were classified according to visualization after embolization (grade 1, none; grade 2, 1–4 segmental HA; and grade 3, ≥4 segmental HA). Transhepatic portal vein stent placements were performed in the same session for 5 patients (11.9%) with poor HA collateral vessels (grade 1 or 2) and compromised PV flow (>70% stenosis). Hepatic ischemic complications were analyzed for relevance to HA collateral vessels and PV compromise.ResultsAfter HA embolization, HA flow was found to be preserved (grade 3) through intra- and/or extrahepatic collateral vessels in 23 patients (54.8%), and hepatic complications did not occur regardless of PV flow status (0%). Of the 19 patients (45.2%) with poor HA collateral vessels (grade 1 or 2), segmental hepatic infarction occurred in 2 of 15 patients (13.3%) with preserved PV flow (10 naïve and 5 stented). The remaining 4 patients with poor HA collateral vessels and untreated compromised PV flow experienced multisegmental hepatic infarction (n = 3) or hepatic failure (n = 1) (100%) (P < .005).ConclusionsAfter HA embolization, preserved HA flow (≥4 segmental HA) lowered the risk of hepatic complications regardless of the PV flow. Based on these findings, transhepatic PV stent placement seems to be an effective intervention for the prevention of hepatic complications in cases of poor HA collateral vessels and compromised PV flow.     

Effect of tracer dose on left ventricular mechanical dyssynchrony indices by phase analysis of gated single photon emission computed tomography myocardial perfusion imaging

Background  

There are limited data on the effect of tracer dose on the reproducibility and accuracy of left ventricular (LV) mechanical dyssynchrony indices by phase analysis of gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI).     

Improving dynamic susceptibility contrast MRI measurement of quantitative cerebral blood flow using corrections for partial volume and nonlinear contrast relaxivity: A xenon computed tomographic comparative study

Purpose

To test whether dynamic susceptibility contrast MRI‐based CBF measurements are improved with arterial input function (AIF) partial volume (PV) and nonlinear contrast relaxivity correction, using a gold‐standard CBF method, xenon computed tomography (xeCT).

Materials and Methods

Eighteen patients with cerebrovascular disease underwent xeCT and MRI within 36 h. PV was measured as the ratio of the area under the AIF and the venous output function (VOF) concentration curves. A correction was applied to account for the nonlinear relaxivity of bulk blood (BB). Mean CBF was measured with both techniques and regression analyses both within and between patients were performed.

Results

Mean xeCT CBF was 43.3 ± 13.7 mL/100g/min (mean ± SD). BB correction decreased CBF by a factor of 4.7 ± 0.4, but did not affect precision. The least‐biased CBF measurement was with BB but without PV correction (45.8 ± 17.2 mL/100 g/min, coefficient of variation [COV] = 32%). Precision improved with PV correction, although absolute CBF was mildly underestimated (34.3 ± 10.8 mL/100 g/min, COV = 27%). Between patients correlation was moderate even with both corrections (R = 0.53).

Conclusion

Corrections for AIF PV and nonlinear BB relaxivity improve bolus MRI‐based CBF maps. However, there remain challenges given the moderate between‐patient correlation, which limit diagnostic confidence of such measurements in individual patients. J. Magn. Reson. Imaging 2009;30:743–752. © 2009 Wiley‐Liss, Inc.     

Postprocedural CT for perivertebral cement leakage in percutaneous vertebroplasty is not necessary—results from VERTOS II

Introduction  

During percutaneous vertebroplasty (PV), perivertebral cement leakage frequently occurs. There is some concern that cement deposits may migrate towards the lungs via the veins during follow-up. We used baseline and follow-up computed tomography (CT) to assess the incidence and extend of late cement migration in a large consecutive patient cohort.     

Non-invasive estimation of hepatic glucose uptake from [18F]FDG PET images using tissue-derived input functions

Purpose

The liver is perfused through the portal vein and hepatic artery. Quantification of hepatic glucose uptake (HGU) using PET requires the use of an input function for both the hepatic artery and portal vein. The former can be generally obtained invasively, but blood withdrawal from the portal vein is not practical in humans. The aim of this study was to develop and validate a new technique to obtain quantitative HGU by estimating the input function from PET images.

Methods

Normal pigs (n?=?12) were studied with [¹⁸F]FDG PET, in which arterial and portal blood time-activity curves (TAC) were determined invasively to serve as reference measurements. The present technique consisted of two characteristics, i.e. using a model input function and simultaneously fitting multiple liver tissue TACs from images by minimizing the residual sum of square between the tissue TACs and fitted curves. The input function was obtained from the parameters determined from the fitting. The HGU values were computed by the estimated and measured input functions and compared between the methods.

Results

The estimated input functions were well reproduced. The HGU values, ranging from 0.005 to 0.02 ml/min per ml, were not significantly different between the two methods (r?=?0.95, p?<?0.001). A Bland-Altman plot demonstrated a small overestimation by the image-derived method with a bias of 0.00052 ml/min per g for HGU.

Conclusion

The results presented demonstrate that the input function can be estimated directly from the PET image, supporting the fully non-invasive assessment of liver glucose metabolism in human studies.     

Percutaneous Portal Vein Embolization Using a Simplified Sheathless 18-Gauge Trocar Needle Approach: Review of Efficacy and Safety

Purpose

Portal vein (PV) embolization (PVE) is traditionally performed via a PV sheath with selective embolization of PV branches. Here, the efficacy and safety of PVE with the use of only an 18-gauge needle is reported.

New software for raw data mask processing increases diagnostic ability of myocardial SPECT imaging

Objective  

Increased activity of myocardial perfusion tracer technetium-99m in liver and hepatobiliary system causes streak artifacts, which may affect clinical diagnosis. We developed a mask-processing tool for raw data generated using technetium-99m as a myocardial perfusion tracer. Here, we describe improvements in image quality under the influence of artifacts caused by high accumulation in other organs.     

Test-retest variability of quantitative [<Superscript>11</Superscript>C]PIB studies in Alzheimer’s disease

Purpose  

The aim of this study was to assess the test-retest variability of [¹¹C]PIB studies in patients with Alzheimer’s disease (AD) and healthy controls using several tracer kinetic models and to assess the suitability of the cerebellum as reference tissue.     

Fused 99m-Tc-GSA SPECT/CT imaging for the preoperative evaluation of postoperative liver function: can the liver uptake index predict postoperative hepatic functional reserve?

Purpose  

To evaluate the role of hepatic asialoglycoprotein receptor analysis in the preoperative estimation of postoperative hepatic functional reserve.