Comparison of free breathing versus breath-hold in perfusion imaging using dynamic volume CT

Kidney computed tomography perfusion in patients with ureteral obstruction

INTRODUCTION

Kidney perfusion on CT is an encouraging surrogate for renal scintigraphy in assessing renal function. However, data on dynamic volumetric CT in patients with kidney obstruction is lacking. Thus, the aim of this study is to determine the feasibility of CT-based renal perfusion using a dynamic volume to assess renal hemodynamics at different degrees and durations of obstruction.

MATERIALS AND METHODS

We included patients with unilateral kidney obstruction in our single-center, prospective study. The patients were divided into three groups. Patients without dilatation of the pelvicalyceal system (PCS) and normal parenchyma thickness were included into Group 1; patients with PCS dilatation and parenchyma thickness 1.8-2.4 cm-into Group 2; and patients with ureteropyelocalicoectasia and parenchyma thickness less than 1.8 cm-into Group 3.

RESULTS

Total of 56 patients were enrolled. In Group 1 mean values of cortical and medullar arterial blood flow, blood volume, and extraction fraction were within the normal range. Changes in contralateral kidney were not determined. Patients from Group 2 showed significant differences in blood flow parameters in the cortical and medulla of the obstructed kidney. No changes in perfusion values in the contralateral kidney was observed. In patients from Group 3 there was a marked decrease in perfusion on the side of obstruction compared to Group 2, indicating that the degree of expansion of the PCS directly correlates with the change in blood flow. However, in the contralateral kidney, these indicators exceeded the normal values of perfusion.

CONCLUSION

CT perfusion allows to objectively assess changes in blood flow in the setting of renal obstruction. The degree of obstruction directly affects the measured rate of blood flow.

Use of full-dose contrast-enhanced CT for extrahepatic staging using Gallium-68-DOTATATE PET/CT in patients with neuroendocrine tumors

PURPOSE

Studies have demonstrated that positron emission tomography/computed tomography (PET/CT) with Gallium-68 (68Ga)-labeled somatostatin analogues are effective at detecting metastatic disease in neuroendocrine tumors (NET), especially extrahepatic metastases. However, PET in combination with full-dose contrast-enhanced CT (ceCT) exposes patients to higher radiation (~25 mSv). The use of non-contrast-enhanced low-dose CT (ldCT) can reduce radiation to about 10 mSv and may avoid contrast-induced side effects. This study seeks to determine whether ceCT could be omitted from NET assessments.

METHODS

We retrospectively compared the performance of PET/ldCT versus PET/ceCT in 54 patients (26 male, 28 female) who had undergone a 68Ga-DOTATATE PET/CT. The selection criteria were as follows: available ldCT and ceCT, histologically confirmed NET, and follow-up of at least 6 months (median, 12.6 months; range, 6.1-23.2 months). The PET/ldCT and PET/ceCT images were analyzed separately. We reviewed metastases in the lungs, bones, and lymph nodes. The results were compared with the reference standard (clinical follow-up data).

RESULTS

The PET/ceCT scans detected 139 true-positive bone lesions compared with 140 lesions detected by the PET/ldCT scans, 106 true-positive lymph node metastases (PET/ceCT) compared with 90 metastases detected by the PET/ldCT scans, and 26 true-positive lung lesions (PET/ceCT) compared with 6 lesions detected by the PET/ldCT scans. The overall lesion-based sensitivity for full-dose PET/ceCT was 97%, specificity 86%, negative predictive value (NPV) 93%, and positive predictive value (PPV) 93%. The overall lesion-based sensitivity for PET/ldCT was 85%, specificity 73%, NPV 72%, and PPV 85%.

CONCLUSION

This study presents the first evidence that ceCT should not be omitted from extrahepatic staging using 68Ga-DOTATATE PET/CT in patients with NET. ceCT alone can be used as a follow-up to reduce radiation exposure when the patient has already undergone PET/ceCT and suffers from non-DOTATATE-avid NET.

Pancreatic perfusion imaging method that reduces radiation dose and maintains image quality by combining volumetric perfusion CT with multiphasic contrast enhanced-CT

OBJECTIVES

The aim of this study is to propose and evaluate a new method of volumetric perfusion computed tomography (PCT) incorporated into pancreatic multiphasic contrast enhanced (CE)-CT in the clinical setting.

METHODS

In this ethically approved study, PCT was incorporated into our existing scanning protocol in 17 patients and effective doses related to PCT were evaluated. CT values and signal-to-noise ratio (SNR) of anatomical structure were compared in diagnostic images that were acquired using 320-detector volumetric scan mode and 64-detector helical scan mode. In addition, focal lesion depiction was qualitatively assessed in the two groups. Perfusion parameters in normal pancreas were measured by two radiologists and the interobserver-reliability was assessed.

RESULTS

The effective dose of PCT was 5.1 ± 0.3 mSv. The actual effective dose (AED) including the dose used in volumetric scans for diagnostic imaging was 22.8 ± 5.3 mSv and the putative effective dose (PED) was 21.9 ± 9.1 mSv on average. There was no significant difference between AED and PED (p = 0.404). Compared with conventional helical scans, volumetric scans did not decrease CT values or SNR, but rather significantly increased those of the aorta in the arterial phase. Both groups had acceptable qualitatively assessed image quality with no significant difference in the depiction of each structure. There was almost perfect interobserver agreement in the measurement of perfusion parameters (mean ICCs > 0.9).

CONCLUSIONS

Our scanning protocol for pancreatic perfusion CT provides high-quality images while requiring lower radiation doses than conventional methods.

Interobserver and Intraobserver Reproducibility with Volume Dynamic Contrast Enhanced Computed Tomography (DCE-CT) in Gastroesophageal Junction Cancer

The purpose of this study was to assess inter- and intra-observer reproducibility of three different analytic methods to evaluate quantitative dynamic contrast-enhanced computed tomography (DCE-CT) measures from gastroesophageal junctional cancer. Twenty-five DCE-CT studies with gastroesophageal junction cancer were selected from a previous longitudinal study. Three radiologists independently reviewed all scans, and one repeated the analysis eight months later for intraobserver analysis. Review of the scans consisted of three analysis methods: (I) Four, fixed small sized regions of interest (2-dimensional (2D) fixed ROIs) placed in the tumor periphery, (II) 2-dimensional regions of interest (2D-ROI) along the tumor border in the tumor center, and (III) 3-dimensional volumes of interest (3D-VOI) containing the entire tumor volume. Arterial flow, blood volume and permeability (k^trans) were recorded for each observation. Inter- and intra-observer variability were assessed by Intraclass Correlation Coefficient (ICC) and Bland-Altman statistics. Interobserver ICC was excellent for arterial flow (0.88), for blood volume (0.89) and for permeability (0.91) with 3D-VOI analysis. The 95% limits of agreement were narrower for 3D analysis compared to 2D analysis. Three-dimensional volume DCE-CT analysis of gastroesophageal junction cancer provides higher inter- and intra-observer reproducibility with narrower limits of agreement between readers compared to 2D analysis.

Quantitative analysis of respiration-related movement for abdominal artery in multiphase hepatic CT

Objectives

Respiration-induced motion in the liver causes potential errors on the measurement of contrast medium in abdominal artery from multiphase hepatic CT scans. In this study, we investigated the use of hepatic CT images to quantitatively estimate the abdominal artery motion due to respiration by optical flow method.

Materials and Methods

A total of 132 consecutive patients were included in our patient cohort. We apply the optical flow method to compute the motion of the abdominal artery due to respiration.

Results

The minimum and maximum displacements of the abdominal artery motion were 0.02 and 30.87 mm by manual delineation, 0.03 and 40.75 mm calculated by optical flow method, respectively. Both high consistency and correlation between the present method and the physicians’ manual delineations were acquired with the regression equation of movement, y = 0.81x+0.25, r = 0.95, p<0.001.

Conclusion

We estimated the motion of abdominal artery due to respiration using the optical flow method in multiphase hepatic CT scans and the motion estimations were validated with the visualization of physicians. The quantitative analysis of respiration-related movement of abdominal artery could be used for motion correction in the measurement of contrast medium passing though abdominal artery in multiphase CT liver scans.

Time-to-peak values can estimate hepatic functional reserve in patients undergoing surgical resection: a comparison between perfusion CT and indocyanine green retention test

OBJECTIVE

To evaluate the potential usefulness of perfusion computed tomography (CT) for the estimation of hepatic functional reserve in patients scheduled for surgical resection and to compare the results with those of the indocyanine green retention test results.

METHODS

Thirty-one patients with hepatobiliary malignancies were included. Perfusion CT and indocyanine green retention test were performed on the same day, and their results were compared using Pearson correlation test.

RESULTS

A strong correlation was found between perfusion CT time-to-peak values and indocyanine green retention rate at 15 minutes and indocyanine green plasma disappearance rate values (R, 0.789 and -0.790; R, 0.832 and -0.823, respectively; P < 0.0001).

CONCLUSIONS

Perfusion CT may be useful for the preoperative noninvasive estimation of hepatic functional reserve for patients undergoing liver resection.

Quantitative assessment of effects of motion compensation for liver and lung tumors in CT perfusion

RATIONALE AND OBJECTIVES

To study the effects of four different rigid alignment approaches on both time-concentration curves (TCCs) and perfusion maps in computed tomography perfusion (CTp) studies of liver and lung tumors.

MATERIALS AND METHODS

Eleven data sets in patients who were subjected to axial CTp after contrast agent administration were assessed. Each data set consists of four different sequences, according to the different rigid alignment configurations considered to compute blood flow perfusion maps: no alignment, translational, craniocaudal, and three dimensional (3D). The color maps were built on TCCs according to the maximum slope method. The effects of motion correction procedures on the reliability of TCCs and perfusion maps were assessed both quantitatively and visually.

RESULTS

TCCs built after 3D alignments show the best indices as well as producing the most reliable maps. We show examinations in which the translational alignment only yields more accurate TCCs, but less reliable perfusion maps, than those achieved with no alignment. Furthermore, we show color maps with two different perfusion patterns, both considered reliable by radiologists, achieved with different motion correction approaches.

CONCLUSIONS

The quantitative index we conceived allows relating quality of 3D alignment and reliability of perfusion maps. A better alignment does not necessarily yield more reliable perfusion values: color maps resulting from either alignment procedure must be critically assessed by radiologists. This achievement will hopefully represent a step forward for the clinical use of CTp studies for staging, prognosis, and monitoring values of therapeutic regimens.

Computed Tomography (CT) Perfusion in Abdominal Cancer: Technical Aspects

Computed Tomography (CT) Perfusion is an evolving method to visualize perfusion in organs and tissue. With the introduction of multidetector CT scanners, it is now possible to cover up to 16 cm in one rotation, and thereby making it possible to scan entire organs such as the liver with a fixed table position. Advances in reconstruction algorithms make it possible to reduce the radiation dose for each examination to acceptable levels. Regarding abdominal imaging, CT perfusion is still considered a research tool, but several studies have proven it as a reliable non-invasive technique for assessment of vascularity. CT perfusion has also been used for tumor characterization, staging of disease, response evaluation of newer drugs targeted towards angiogenesis and as a method for early detection of recurrence after radiation and embolization. There are several software solutions available on the market today based on different perfusion algorithms. However, there is no consensus on which protocol and algorithm to use for specific organs. In this article, the authors give an introduction to CT perfusion in abdominal imaging introducing technical aspects for calculation of perfusion parameters, and considerations on patient preparation. This article also contains clinical cases to illustrate the use of CT perfusion in abdominal imaging.