Perfusion computed tomography relative threshold values in definition of acute stroke lesions

BACKGROUND: Perfusion computed tomography (CT) is a relatively new technique that allows fast evaluation of cerebral hemodynamics by providing perfusion maps and gives confirmation of perfusion deficits in ischemic areas. Some controversies exist regarding accuracy of quantitative detection of tissue viability: penumbra (tissue at risk) or core (necrosis). PURPOSE: To define brain tissue viability grade on the basis of the perfusion CT parameters in acute stroke patients. MATERIAL AND METHODS: A multimodal CT imaging protocol; unenhanced CT of the brain, CT angiography of head and neck blood vessels, followed by brain perfusion CT and 24 h follow-up brain CT was performed. Perfusion deficits were detected first visually, with subsequent manual quantitative and relative measurements in affected and contra-lateral hemisphere in 87 acute stroke patients. RESULTS: Visual perfusion deficit on perfusion CT images was found in 78 cases (38 women, 40 men; mean age, 30-84 years). Penumbra lesions (n = 49) and core lesions (n = 42) were detected by increased mean transit time (MTT) on perfusion CT maps in comparison to contra-lateral hemispheres. Cerebral blood volume (CBV) mean values in the penumbra group were increased in the penumbra group and decreased in the core group. Cerebral blood flow (CBF) values were decreased in penumbra and markedly decreased in core lesion. CONCLUSION: Perfusion CT measurements are reliable in estimation of penumbra and core lesions in acute stroke patients, if relative threshold values are used. The most accurate parameter of hypoperfusion is increased MTT above 190%. Relative threshold values for irreversible lesion are CBFpublishersversionPeer reviewe

Perfusion Computed Tomography in Traumatic Brain Injury

Introduction: Almost 50 years ago, computed tomography (CT) revolutionized the management of traumatic brain injury (TBI) by imagining intracranial hematomas. This allowed prompt and accurate selection of patients who would benefit from surgical evacuation. Since then, unenhanced CT has been the gold standard imaging modality for patients with acute TBI. Today, multidetector CT can track intravenous contrasts flowing through brain creating maps that depict the speed and the amount of blood at capillary level. This imaging modality takes the name of perfusion CT. Perfusion CT is routinely used during the hyperacute phase of patients suffering from stroke to diagnose areas of penumbra (poorly perfused but still viable brain tissue) that may benefit from revascularization. Here, we summarize the current status of the research on the role of perfusion CT in patients suffering from TBI

Pancreatic Perfusion CT in Early Stage of Severe Acute Pancreatitis

Early intensive care for severe acute pancreatitis is essential for improving SAP mortality rates. However, intensive therapies for SAP are often delayed because there is no ideal way to accurately evaluate severity in the early stages. Currently, perfusion CT has been shown useful to predict prognosis of SAP in the early stage. In this presented paper, we would like to review the clinical usefulness and limitations of perfusion CT for evaluation of local and systemic complications in early stage of SAP

A Database for Estimating Organ Dose for Chest and Head CT Scans for Arbitrary Spectra and Angular Tube Current Modulation

Purpose: The purpose of this study was to develop a database for estimating organ dose in a voxelized patient model for coronary angiography and brain perfusion CT acquisitions with any spectra and angular tube current modulation setting. The database enables organ dose estimation for existing and novel acquisition techniques without requiring Monte Carlo simulations. Methods: The study simulated transport of monoenergetic photons between 5 and 150 keV for 1000 projections over 360◦ through anthropomorphic voxelized female chest and head (0◦ and 30◦ tilt) phantoms and standard head and body CTDI dosimetry cylinders. The simulations resulted in tables of normalized dose deposition for several radiosensitive organs quantifying the organ dose per emitted photon for each incident photon energy and projection angle for coronary angiography and brain perfusion acquisitions. The values in a table can be multiplied by an incident spectrum and number of photons at each projection angle and then summed across all energies and angles to estimate total organ dose. Scanner-specific organ dose may be approximated by normalizing the database-estimated organ dose by the database-estimated CTDIvol and multiplying by a physical CTDIvol measurement. Two examples are provided demonstrating how to use the tables to estimate relative organ dose. In the first, the change in breast and lung dose during coronary angiography CT scans is calculated for reduced kVp, angular tube current modulation, and partial angle scanning protocols relative to a reference protocol. In the second example, the change in dose to the eye lens is calculated for a brain perfusion CT acquisition in which the gantry is tilted 30◦ relative to a nontilted scan. Results: Our database provides tables of normalized dose deposition for several radiosensitive organs irradiated during coronary angiography and brain perfusion CT scans. Validation results indicate total organ doses calculated using our database are within 1% of those calculated using Monte Carlo simulations with the same geometry and scan parameters for all organs except red bone marrow (within 6%), and within 23% of published estimates for different voxelized phantoms. Results from the example of using the database to estimate organ dose for coronary angiography CT acquisitions show 2.1%, 1.1%, and −32% change in breast dose and 2.1%, −0.74%, and 4.7% change in lung dose for reduced kVp, tube current modulated, and partial angle protocols, respectively, relative to the reference protocol. Results show −19.2% difference in dose to eye lens for a tilted scan relative to a nontilted scan. The reported relative changes in organ doses are presented without quantification of image quality and are for the sole purpose of demonstrating the use of the proposed database. Conclusions: The proposed database and calculation method enable the estimation of organ dose for coronary angiography and brain perfusion CT scans utilizing any spectral shape and angular tube current modulation scheme by taking advantage of the precalculated Monte Carlo simulation results. The database can be used in conjunction with image quality studies to develop optimized acquisition techniques and may be particularly beneficial for optimizing dual kVp acquisitions for which numerous kV, mA, and filtration combinations may be investigated. © 2012 American Association of Physicists in Medicine

Stroke versus seizure : perfusion computerized tomography in a patient with aphasia

Both stroke and seizures have varied clinical presentations and their differentiation in the acute setting is not always straightforward. We present the case of a patient who presented at the emergency room with acute onset aphasia. Clinically acute ischemic stroke was suspected. Perfusion CT was performed and demonstrated cortical hypervascularity in the left partietotemporal region. Additional MRI and EEG were performed and a final diagnosis of postictal aphasia was made. This case illustrates that perfusion CT is not only a useful tool for acute stroke management, but can also aid in the detection of seizures in patients presenting with stroke-like symptoms

Perfusion computed tomography in prediction of functional outcome in patients with acute ischaemic stroke

PURPOSE: To determine the value of perfusion computed tomography (CT) in prediction of the clinical course and late functional outcome in patients with acute ischaemic stroke who had unremarkable initial brain CT examination. MATERIAL AND METHODS: Single slice perfusion CT was performed in 55 consecutive patients (27 women, mean age 67 &#177; &#177; 11 years) with acute ischaemic stroke within 6 hours (median 2.26 hours) from onset of symptoms. Values of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) obtained from affected hemisphere were compared to respective values in non-affected hemisphere (relative parameters). Initial neurological deficits were estimated using NIH Stroke Scale (NIHSS) score and correlated with perfusion CT values, employing Spearman rank correlation coefficient (r). Values of perfusion CT parameters in prediction of functional outcome were determined by comparing against scores on modified Rankin Scale (mRS) and Glasgow Outcome Scale (GOS) after three months of onset of stroke. RESULTS: All perfusion CT parameters significantly correlated with initial neurological deficit. The highest correlation with the NIHSS was found for relative CBF, which correlated better than absolute CBF (rCBF r = 0.69; CBF r = 0.50, P < 0.001). In prediction of favourable outcome (mRS &#8804; 2) the commonly employed thresholds (in parentheses) and associated sensitivity, specificity, positive and negative predictive values were: 87%, 44%, 79%, and 58% for CBF (10 ml/min/100 g), 59%, 81%, 88%, and 49% for rCBF (48%), 49%, 56%, 73%, and 31% for CBV (2 ml/100 g), 87%, 44%, 79% and 58% for rCBV (60%), 41%, 81%, 84% and 36% for MTT (6 s) and 54%, 81%, 87% and 49% for rMTT (145%), respectively, while for prediction of excellent outcome (mRS &#8804; 1), the only statistically significant respective accuracy measures were for rCBV, 90%, 35%, 60%, 75%, and for rCBF, 62%, 69%, 69% and 62%. CONCLUSIONS: In patients within the first 6 hours from stroke onset, and without a hypodensity sign on initial routine CT examination, perfusion CT provides quantitative parameters that correlate well with initial neurological status and late functional outcome

A Comparative Study for 2D and 3D Computer-aided Diagnosis Methods for Solitary Pulmonary Nodules

Many computer-aided diagnosis (CAD) methods, including 2D and 3D approaches, have been proposed for solitary pulmonary nodules (SPNs). However, the detection and diagnosis of SPNs remain challenging in many clinical circumstances. One goal of this work is to investigate the relative diagnostic accuracy of 2D and 3D methods. An additional goal is to develop a two-stage approach that combines the simplicity of 2D and the accuracy of 3D methods. The experimental results show statistically significant differences between the diagnostic accuracy of 2D and 3D methods. The results also show that with a very minor drop in diagnostic performance the two-stage approach can significantly reduce the number of nodules needed to be processed by the 3D method, streamlining the computational demand

Insular cortex hypoperfusion and acute phase blood glucose after stroke: a CT perfusion study

&lt;p&gt;&lt;b&gt;Background and Purpose:&lt;/b&gt; Insular cortex ischemia is proposed to mediate a sympathetic stimulus that leads to acute hyperglycemia after stroke.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods:&lt;/b&gt; We retrospectively analyzed insular perfusion on perfusion CT (median 180 minutes after onset) in 35 patients.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Results:&lt;/b&gt; We found no association of hypoperfusion (relative cerebral blood flow &#60;0.51) with early (&#60;6 hours) or delayed (&#60;72 hours) hyperglycemia, or hemispheric lateralization.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusions:&lt;/b&gt; Insular cortex hypoperfusion &#60;6 hours after stroke onset was not associated with hyperglycemia.&lt;/p&gt

Dynamic perfusion CT in brain tumors.

Dynamic perfusion CT (PCT) is an imaging technique for assessing the vascular supply and hemodynamics of brain tumors by measuring blood flow, blood volume, and permeability-surface area product. These PCT parameters provide information complementary to histopathologic assessments and have been used for grading brain tumors, distinguishing high-grade gliomas from other brain lesions, differentiating true progression from post-treatment effects, and predicting prognosis after treatments. In this review, the basic principles of PCT are described, and applications of PCT of brain tumors are discussed. The advantages and current challenges, along with possible solutions, of PCT are presented

Perfusion CT image of pulmonary thromboembolism: data acquisition using single-detector helical CT scanner

AbstractWe report a case of pulmonary thromboembolism, in which we used conventional single-detector helical CT scanner to obtain dynamic CT data, and the decrease in pulmonary parenchymal perfusion was clearly demonstrated on perfusion CT image