Computed Tomography Perfusion Protocol Research Articles

Stress-only dynamic computed tomography perfusion protocol (CTP) alone without computed tomography coronary angiography (CCTA) has limited specificity to diagnose ischemia: A retrospective two-center study

PurposeTo investigate diagnostic performance of stress-only dynamic myocardial computed tomography perfusion (CTP) without computed tomography coronary angiography (CCTA) to diagnose ischemia with invasive fractional flow reserve (FFR) as a reference standard. Method135 datasets (68 positive for ischemia with invasive FFR < 0.8) acquired with a 256-slice CT system (Revolution, GE Healthcare, Chicago, IL, USA) were retrieved, postprocessed with a deep learning-based algorithm (Advanced intelligent Clear-IQ Engine (AiCE), Canon Medical Systems, Otawara, Japan) (FC03/cardiac kernel, 8 mm slice thickness), analyzed using a dedicated workstation (Vitrea research 7.11.0. Vital Images, Minnetonka, MN, USA), and loaded into a clinical workstation (CardIQ, GE Healthcare, Chicago, IL, USA) for review. Ten observers with various experience from two research sites evaluated the post-processed images, perfusion slices and maps to indicate presence vs absence of perfusion defect and its probability (five-point Likert scale). Binary decisions and probability scores were used to calculate sensitivity and specificity for each reader, and to create receiver operating characteristics (ROC) curves, respectively. Furthermore, the correlation coefficient (ICC) was computed. ROC AUC of a purely quantitative analysis was obtained thanks to a color-coded map with a fixed scale superimposed on myocardial walls displaying myocardial blood flow (MBF) values. ResultsThe overall case-based sensitivity and specificity for the detection of perfusion deficit were 0.79 and 0.30, respectively. No significant differences were detected in the AUC across readers (p value = 0.66). The AUC values were 0.50, 0.58, 0.63, 0.59, 0.45, 0.60, 0.56, 0.61, 0.52, 0.61. Absolute reader agreement ICC was 0.60 (good agreement) for an average case. ConclusionDynamic CTP alone has good sensitivity, but low specificity when analyzed without CCTA. These findings reinforce the need to guide the interpretation functional test with the knowledge of coronary artery anatomy.

Correlation between quantification of myocardial area at risk and ischemic burden at cardiac computed tomography

PurposeThis study aims to investigate the correlation between myocardial area at risk at coronary computed tomography angiography (CCTA) and the ischemic burden derived from myocardial computed tomography perfusion (CTP) by using the 17-segment model. MethodsForty-two patients with chest pain complaints who underwent a combined CCTA and CTP protocol were identified. Patients with reversible ischemia at CTP and at least one stenosis of ≥ 50% at CCTA were selected. Myocardial area at risk was calculated using a Voronoi-based segmentation algorithm at CCTA and was defined as the sum of all territories related to a ≥ 50% stenosis as a percentage of the total left ventricular (LV) mass. The latter was calculated using LV contours which were automatically drawn using a machine learning algorithm. Subsequently, the ischemic burden was defined as the number of segments demonstrating relative hypoperfusion as a percentage of the total amount of segments (=17). Finally, correlations were tested between the myocardial area at risk and the ischemic burden using Pearson’s correlation coefficient. ResultsA total of 77 coronary lesions were assessed. Average myocardial area at risk and ischemic burden for all lesions was 59% and 23%, respectively. Correlations for ≥ 50% and ≥ 70% stenosis based myocardial area at risk compared to ischemic burden were moderate (r = 0.564; p < 0.01) and good (r = 0.708; p < 0.01), respectively. ConclusionThe relation between myocardial area at risk as calculated by using a Voronoi-based algorithm at CCTA and ischemic burden as assessed by CTP is dependent on stenosis severity.

Predictive Value of CT Brain Perfusion Studies in Acute Ischemic Infarct Taking MRI Stroke Protocol As Gold Standard.

BackgroundAcute ischemic stroke is the leading cause of serious chronic disability worldwide. Imaging plays a key role in early diagnosis and intervention, thus reducing mortality and morbidity related to ischemic stroke. Computed tomography (CT) perfusion study is a valuable imaging tool for the assessment of acute infarction. The objective of this study was to determine the predictive value of CT perfusion in diagnosing acute ischemic infarction taking Magnetic Resonance Imaging (MRI) stroke protocol (including Diffusion Weighted Imaging (DWI)) as a gold standard.MethodsThe cross-sectional validation study was conducted at a teaching hospital in Islamabad from June 2019 to December 2019. The study comprised a total of 125 patients of either gender with suspected acute ischemic stroke. The patients were scanned for CT perfusion and MRI stroke protocol on the same day. Scans were reported separately for the detection of acute ischemic infarction by the same consultant radiologist. The predictive value of CT perfusion was calculated accordingly.ResultsOf the 125 patients, 58% were male and 42% were female. The age of selected patients ranged between 38 to 70 years with a mean age of 56.12 ± 9.69 years. Acute ischemic infarction was detected in 86 (69%) patients by CT perfusion study and in 120 (96%) patients by MRI stroke protocol. The positive predicted value of CT perfusion for the detection of acute infarction was calculated as 98.83 and the negative predicted value was 10.25.ConclusionCT perfusion study provides adequate sensitivity and specificity with good predictive value in the detection of acute ischemic infarct in stroke patients. This widely available and time-effective modality aids in the triage of patients for immediate endovascular intervention leading to maximal neurological benefit and improving outcomes.

The effects of baseline length in Computed Tomography perfusion of liver

Objective:Computed Tomography perfusion (CTp) of liver is very attractive for predictive and prognostic purposes, but motion artefacts and radiation dose connected to duration of examinations jeopardize the reproducibility of perfusion values, thwarting CTp daily application in clinics. The goal is showing to what extent these issues can be faced by shortening the CTp unenhanced stage (i.e., the baseline). Methods:59 patients with colorectal cancer underwent undelayed hepatic CTp examinations. For each patient, fifteen virtual examinations Eτsimulating different scan delays τ∈[1..15] s were achieved from the undelayed original sequence E0. Absolute (AD), percentage (PD) and compound differences (CDτ) were computed between E0 and each Eτfor baseline and perfusion values and measured in HU and arbitrary units (a.u.), respectively. Patients were grouped and counted based on the differences achieved. Results:Maximum perfusion CDτ<10 a.u. and baseline CDτ<7 HU were achieved. For τ≤10 s, maximum perfusion CDτ∈[5,6) a.u. was found in one patient only as well as maximum baseline CDτ∈[2,3) HU. Blood flow (BF), hepatic perfusion index and arterial BF showed the lowest CDτ, while portal BF and total BF the highest ones. PD is practically always higher than AD. Conclusion:The approach presented allows clinicians to design the shortest CTp acquisition protocol, selecting the highest delay compliant with the required accuracy for the chosen perfusion parameters, to limit patient’s motion and improve image quality. Significance:A short CTp protocol allows strengthening the reliability of perfusion values, and correctness of clinical outcomes, advancing CTp introduction in the standard clinical practice.

CT Perfusion Protocol for Acute Stroke Expedites Mechanical Thrombectomy.

The evaluation of a patient suspected of having an acute cerebrovascular accident is initiated with computed tomography (CT) and computed tomography angiogram (CTA) cross-sectional imaging of the head. Eligible patients may subsequently receive magnetic resonance imaging (MRI) utilizing a hyperacute stroke protocol. Clinical and imaging selection criteria are used to assess candidates for possible thrombectomy or thrombolysis. Prompt restoration of flow to ischemic regions of the cerebrum may result in improved neurological outcomes. Reducing delays in diagnosis and treatment remains paramount to effective treatment of ischemic cerebrovascular events. In an effort to expedite intra-arterial intervention, we replaced our institutional MRI protocol with a CT perfusion protocol. The amount of time the patient spent undergoing imaging was measured with each protocol and is referred to as "stroke imaging time." The purpose of this study was to compare the difference in the amount of time patients spent undergoing imaging when the acute stroke workup was performed with MRI vs. CT perfusion. Stroke imaging time decreased from an average of 158 minutes to 81 minutes (49%) by substituting CT perfusion for MRI. Utilizing CT perfusion in lieu of MRI in the hyperacute stroke protocol may expedite intra-arterial intervention.

CT brain perfusion: A static phantom study of contrast-to-noise ratio and radiation dose.

Computed tomography perfusion (CTP) is increasingly employed in the diagnosis and management of ischaemic stroke but radiation dose can be significant and optimising contrast-to-noise ratio (CNR) is challenging. This study aimed to quantify and optimise the balance between CNR as a surrogate for image quality and radiation dose. A perspex head phantom with vials of dilute contrast agent was scanned using a Siemens Definition Flash 128-slice scanner. The CTP protocol exposure parameters were adjusted over 70-120kVp and 150-285mAs. Measurements were obtained for the average dose per slice, Hounsfield Units (HU) for iodinated contrast agent, and the image noise for background regions of perspex. The CNR was measured as a function of the volumetric CT dose index (CTDIvol) and kVp. A change from 120 to 80kVp, achieved the same CNR with 60% reduction in dose. Alternatively, for the same dose, the change from 120 to 80kVp improved CNR by +58%. A change from 80 to 70kVp while operating at the same CNR, led to 13% reduction in dose. Alternatively, maintaining the same dose while changing from 80 to 70kVp improved the CNR by +7%. Lower beam energies achieved the same CNR with less dose, or improved CNR at the same dose. A reduction from 80kVp to 70kVp may be clinically useful to optimise CTP acquisitions.

Quantitative CT perfusion measurements in characterization of solitary pulmonary nodules: new insights and limitations

Although computed tomography (CT) scans remain the basis of morphologic evaluation in the characterization of solitary pulmonary nodules (SPNs), perfusion CT can represent an additional feasible technique offering reproducible measurements, at least in SPNs with a diameter >10 mm. In particular, CT perfusion could reduce the number of SPNs, diagnosed as undetermined at morphologic CT, avoiding long term follow-up CT, FDG-PET studies, biopsy or unnecessary surgery with a significant reduction in healthcare costs. In order to reduce the radiation dose, an optimization of the CT perfusion protocol could be obtained using axial mode acquisition, using shorter acquisition time and adaptative statistical iterative reconstruction algorithm.

CT perfusion technique for assessment of early kidney allograft dysfunction: preliminary results

To assess the benefit of quantitative computed tomography (CT) perfusion for differentiating acute tubular necrosis (ATN) and acute rejection (AR) in kidney allografts. Twenty-two patients with acute kidney allograft dysfunction caused by either AR (n = 6) or ATN (n = 16) were retrospectively included in the study. All patients initially underwent a multiphase CT angiography (CTA) protocol (12 phases, one phase every 3.5s) covering the whole graft to exclude acute postoperative complications. Multiphase CT dataset and dedicated software were used to calculate renal blood flow. Renal biopsy or clinical course of disease served as the standard of reference. Mean effective radiation dose and mean amount of contrast media were calculated. Renal blood flow values were significantly lower (P = 0.001) in allografts undergoing AR (48.3 ± 21ml/100ml/min) compared with those with ATN (77.5 ± 21ml/100ml/min). No significant difference (P = 0.71) was observed regarding creatinine level with 5.65 ± 3.1mg/dl in AR and 5.3 ± 1.9mg/dl in ATN. The mean effective radiation dose of the CT perfusion protocol was 13.6 ± 5.2mSv; the mean amount of contrast media applied was 34.5 ± 5.1ml. All examinations were performed without complications. CT perfusion of kidney allografts may help to differentiate between ATN and rejection. • Quantitative CT perfusion of renal transplants is feasible. • CT perfusion could help to non-invasively differentiate AR from ATN. • CT perfusion might make some renal biopsies unnecessary.

CT Perfusion of Renal Cell Carcinoma

To assess the feasibility, image quality, and radiation dose of computed tomography (CT) renal perfusion imaging in the adaptive 4-dimensional (4D)-spiral mode in patients with renal cell carcinoma (RCC), and to compare quantitative measurements between 2-dimensional regions-of-interest (2D-ROI) and 3-dimensional volumes-of-interest (3D-VOI). Twenty-one patients (13 male; age, 67.4 ± 9.5 years) with 24 histologically proven RCCs underwent CT perfusion imaging (100 kV, 100 mAs/rotation, scan range 10 cm, examination time 40.17 seconds) in a 4D-spiral mode with dual-source 128-slice CT. The ability to suspend respiration during CT perfusion imaging was visually monitored. Two independent readers assessed motion artifacts of CT perfusion imaging data sets on a 4-point scale before and after automated motion correction. Qualitative (enhancement pattern) and quantitative perfusion analysis (blood flow [BF], blood volume [BV], flow extraction product [KTrans]) were performed in the tumor and in healthy ipsi- and contralateral renal cortex applying the maximum-slope and a modified Patlak approach for quantitative analysis in 2D-ROI and 3D-VOI, the latter including the entire RCCs. Of the 21 patients, 8 (38%) could suspend respiration throughout the perfusion scan. Of 21 RCCs, 18 (86%) were completely included in the scan range. Motion artifacts were significantly reduced after automated motion correction (P < 0.001). All 24 RCCs could be included in the qualitative perfusion analysis, and 22 of 24 (92%) were eligible for quantitative perfusion analysis. Enhancement was homogenous in 4 (17%), peripheral in 4 (17%), and heterogeneous in 16 (66%) tumors (good interobserver agreement, κ=0.74). A high correlation was found between the 2 readers regarding quantitative perfusion parameters (r=0.93-0.94, P < 0.01). Quantitative measurements in 3D-VOIs revealed significantly lower BV, BF, and K in RCCs than in normal renal cortex (P < 0.001). In solid tumor periphery, BV was similar to the renal cortex (P=0.299), while BF and K were significantly lower (P < 0.01 and <0.001) in tumor tissue. Comparison of tumor measurements in 3D-VOIs with those obtained from 2D-ROIs revealed considerable differences in perfusion parameters beyond the 95% confidence limits in 46% to 68% of the tumors. KTrans was significantly higher in the contralateral than in healthy ipsilateral renal cortex (P < 0.01). Estimated effective radiation dose of the CT perfusion protocol was 16.3 mSv. CT perfusion imaging using an adaptive 4D-spiral mode is feasible and enables, after use of automated motion correction, the reliable analysis of renal perfusion in patients with RCCs. Considerable tumor heterogeneity was found, with differences in perfusion parameters between 2D-ROI and 3D-VOI analysis, reinforcing the use of volumetric techniques for perfusion imaging and analysis. Differences between ipsi- and contralateral healthy renal cortex KTrans suggest a compensatory increase in glomerular filtration rate in the healthy contralateral kidney.

A comparison of reconstruction and viewing parameters on image quality and accuracy of stress myocardial CT perfusion

Myocardial stress computed tomography perfusion (CTP) has similar diagnostic accuracy for detecting perfusion defects (PDs) versus single-photon emission computed tomography (SPECT). However, the optimal diagnostic viewing and image processing parameters for CTP are unknown. We sought to compare the diagnostic accuracy of different image processing techniques, cardiac phases, slice thicknesses, and viewing parameters for detection of PDs. A stress and rest dual-source CTP protocol was performed with adenosine. Twelve subjects with severe stenosis proven by quantitative coronary angiography (QCA), with corresponding territorial defects at SPECT, were selected as well as 7 controls (subjects with similar clinical suspicion but negative QCA and SPECT). Short-axis stress images were processed with 3 techniques: minimum intensity projection (MinIP), maximum intensity projection, and average intensity multiplanar reconstruction (MPR), 3 thicknesses (1, 3, 8 mm), and 2 phases (systolic, mid-diastolic). The resulting images (n = 1026) were randomized and interpreted by independent readers. Diastolic reconstructions (8-mm MPR) showed the highest sensitivity (81%) to detect true PDs. The highest accuracy was achieved with the 8-mm (61%) and 1-mm (61%) MPR diastolic images. The most sensitive and accurate systolic reconstructions were 3-mm MinIP images. These findings related to viewing in relatively narrow window width and window level settings. Viewing parameters for optimal accuracy in detection of perfusion defects on CTP differ for systolic and diastolic images.

Semiautomated Motion Correction of Tumors in Lung CT-perfusion Studies

To compare the relative performance of one-dimensional (1D) manual, rigid-translational, and nonrigid registration techniques to correct misalignment of lung tumor anatomy acquired from computed tomography perfusion (CTp) datasets. Twenty-five datasets in patients with lung tumors who had undergone a CTp protocol were evaluated. Each dataset consisted of one reference CT image from an initial cine slab and six subsequent breathhold helical volumes (16-row multi-detector CT), acquired during intravenous contrast administration. Each helical volume was registered to the reference image using two semiautomated intensity-based registration methods (rigid-translational and nonrigid), and 1D manual registration (the only registration method available in the relevant application software). The performance of each technique to align tumor regions was assessed quantitatively (percent overlap and distance of center of mass), and by a visual validation study (using a 5-point scale). The registration methods were statistically compared using linear mixed and ordinal probit regression models. Quantitatively, tumor alignment with the nonrigid method compared to rigid-translation was borderline significant, which in turn was significantly better than the 1D manual method: average (± SD) percent overlap, 91.8 ± 2.3%, 87.7 ± 5.5%, and 77.6 ± 5.9%, respectively; and average (± SD) DCOM, 0.41 ± 0.16 mm, 1.08 ± 1.13 mm, and 2.99 ± 2.93 mm, respectively (all P < .0001). Visual validation confirmed these findings. Semiautomated registration methods achieved superior alignment of lung tumors compared to the 1D manual method. This will hopefully translate into more reliable CTp analyses.

Unusual enhancement pattern of liver lesions in hepatosplenic candidiasis

To describe an unusual enhancement pattern of hepatosplenic candidiasis (HSC) liver lesions in biphasic spiral liver computed tomography (CT). Twenty-one patients with suspected HSC were scanned with a biphasic liver CT perfusion protocol. The liver lesions detected were assessed for their morphology and enhancement pattern during both perfusion phases. A liver biopsy was performed in 11/21 patients. The majority of hepatic lesions in 15/21 patients showed the well-known abscess-like pattern. In 6/21 patients an uncommon central contrast enhancement with a peripheral double ring was detected in the arterial phase. In some cases the lesions showed decreased diameter or even seemed to disappear completely in the portalvenous phase. CT in the arterial phase showed an unusual enhancement pattern of liver lesions in HSC. Scanning only in the portalvenous phase implies possible pitfalls, because lesions may be overlooked or undersized. Therefore, biphasic liver CT is considered essential in the diagnosis and follow-up of HSC in clinical practice.