Showing papers on "Perfusion scanning published in 2004"

Cerebral perfusion CT: technique and clinical applications.

Abstract: Perfusion computed tomography (CT) is a relatively new technique that allows rapid qualitative and quantitative evaluation of cerebral perfusion by generating maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). The technique is based on the central volume principle (CBF = CBV/MTT) and requires the use of commercially available software employing complex deconvolution algorithms to produce the perfusion maps. Some controversies exist regarding this technique, including which artery to use as input vessel, the accuracy of quantitative results, and the reproducibility of results. Despite these controversies, perfusion CT has been found to be useful for noninvasive diagnosis of cerebral ischemia and infarction and for evaluation of vasospasm after subarachnoid hemorrhage. Perfusion CT has also been used for assessment of cerebrovascular reserve by using acetazolamide challenge in patients with intracranial vascular stenoses who are potential candidates for bypass surge...

Improved Exercise Capacity and Ischemia 6 and 12 Months After Transendocardial Injection of Autologous Bone Marrow Mononuclear Cells for Ischemic Cardiomyopathy

Abstract: Background—We recently reported the safety and feasibility of autologous bone marrow mononuclear cell (ABMMNC) injection into areas of ischemic myocardium in patients with end-stage ischemic cardiomyopathy. The present study evaluated the safety and efficacy of this therapy at 6- and 12-month follow-up. Methods and Results—Twenty patients with 6- and 12-month follow-up (11 treated subjects; 9 controls) were enrolled in this prospective, nonrandomized, open-label study. Complete clinical and laboratory evaluations as well as exercise stress (ramp treadmill), 2-dimensional Doppler echocardiography, single-photon emission computed tomography (SPECT) perfusion scanning, and 24-hour Holter monitoring were performed at baseline and follow-up. Transendocardial delivery of ABMMNCs was performed with the aid of electromechanical mapping to identify viable myocardium. Each patient received 15 ABMMNC injections of 0.2 mL each. At 6 and 12 months, total reversible defect, as measured by SPECT perfusion scanning, was significantly reduced in the treatment group as compared with the control group. At 12 months, exercise capacity was significantly improved in the treatment group. This improvement correlated well with monocyte, B-cell, hematopoietic progenitor cell, and early hemapoietic progenitor cell phenotypes. Conclusions—The 6- and 12-month follow-up data in this study suggest that transendocardial injection of ABMMNCs in patients with end-stage ischemic heart disease may produce a durable therapeutic effect and improve myocardial perfusion and exercise capacity. (Circulation. 2004;110[suppl II]:II-213–II-218.)

Comparison of Dobutamine Stress Magnetic Resonance, Adenosine Stress Magnetic Resonance, and Adenosine Stress Magnetic Resonance Perfusion

Abstract: Background— Dobutamine stress MR (DSMR) is highly accurate for the detection of inducible wall motion abnormalities (IWMAs) Adenosine has a more favorable safety profile and is well established for the assessment of myocardial perfusion We evaluated the diagnostic value of IWMAs during dobutamine and adenosine stress MR and adenosine MR perfusion compared with invasive coronary angiography Methods and Results— Seventy-nine consecutive patients (suspected or known coronary disease, no history of prior myocardial infarction) scheduled for cardiac catheterization underwent cardiac MR (15 T) After 4 minutes of adenosine infusion (140 μg · kg−1 · min−1 for 6 minutes), wall motion was assessed (steady-state free precession), and subsequently perfusion scans (3-slice turbo field echo-echo planar imaging; 005 mmol/kg Gd-BOPTA) were performed After a 15-minute break, rest perfusion was imaged, followed by standard DSMR/atropine stress MR Wall motion was classified as pathological if ≥1 segment showed IWMAs

Absolute myocardial perfusion in canines measured by using dual-bolus first-pass MR imaging.

Abstract: PURPOSE: To compare fluorescent microsphere measurements of myocardial blood flow (MBF) with qualitative, semiquantitative, and fully quantitative measurements of first-pass perfusion at magnetic resonance (MR) imaging. MATERIALS AND METHODS: Coronary artery occlusion or intracoronary adenosine infusion was successfully performed in 16 beagles; both procedures were performed simultaneously in one animal. MBF was assessed at microsphere analysis. First-pass myocardial perfusion MR imaging was performed during a dual-bolus administration of gadopentetate dimeglumine (0.0025 mmol/kg followed by 0.10 mmol/kg). The absolute myocardial perfusion at MR imaging was calculated by using Fermi function deconvolution methods. Qualitative, semiquantitative, and absolute myocardial perfusion MR imaging measurements were compared with microsphere MBF measurements by using paired t tests, linear correlation, and Bland-Altman analysis. RESULTS: Fully quantitative (ie, absolute) analysis of MBF at MR imaging correlated wit...

Myocardial First-Pass Perfusion Magnetic Resonance Imaging A Multicenter Dose-Ranging Study

Abstract: Background— MRI can identify patients with obstructive coronary artery disease by imaging the left ventricular myocardium during a first-pass contrast bolus in the presence and absence of pharmacologically induced myocardial hyperemia. The purpose of this multicenter dose-ranging study was to determine the minimally efficacious dose of gadopentetate dimeglumine injection (Magnevist Injection; Berlex Laboratories) for detecting obstructive coronary artery disease. Method and Results— A total of 99 patients scheduled for coronary artery catheterization as part of their clinical evaluation were enrolled in this study. Patients were randomized to 1 of 3 doses of gadopentate dimeglumine: 0.05, 0.10, or 0.15 mmol/kg. First-pass perfusion imaging was performed during hyperemia (induced by a 4-minute infusion of adenosine at a rate of 140 μg · kg−1 · min−1) and then again in the absence of adenosine with otherwise identical imaging parameters and the same contrast dose. Perfusion defects were evaluated subjective...

Dynamic Magnetic Resonance Perfusion Imaging of Brain Tumors

Abstract: In this paper, we review the technique of contrastenhanced magnetic resonance (MR) perfusion imaging of brain neoplasms, with an emphasis on its clinical applications and utility. We start with a discussion of MR perfusion techniques available today and their relative merits and shortcomings. Next, the ability of MR perfusion to provide a preoperative assessment of tumor histology is examined. We also discuss the role of MR perfusion in helping guide tumor biopsy, and its advantages over more conventional methods. We will scrutinize the use of MR perfusion for assessing true lesion extent, in contrast to conventional MR imaging and other MR techniques. We will discuss the role of MR perfusion in differentiating treatment effects, such as radiation necrosis, from tumor recurrence. Finally, the future potential applications of this technology in the setting of novel antiangiogenic therapies for brain tumors will be addressed. The Oncologist 2004;9:528-537

Analysis of myocardial perfusion MRI

Abstract: Rapid MR imaging (MRI) during the first pass of an injected tracer is used to assess myocardial perfusion with a spatial resolution of 2–3 mm, and to detect any regional impairments of myocardial blood flow (MBF) that may lead to ischemia. The spatial resolution is sufficient to detect flow reductions that are limited to the subendocardial layer. The capacity of the coronary system to increase MBF severalfold in response to vasodilation can be quantified by analysis of the myocardial contrast enhancement. The myocardial perfusion reserve (MPR) is a useful concept for quantifying the vasodilator response. The perfusion reserve can be estimated from the ratio of MBFs during vasodilation and at baseline, in units identical to those used for invasive measurements with labeled microspheres, or from dimensionless flow indices normalized by their value for autoregulated flow at rest. The perfusion reserve can be reduced as a result of a blunted hyperemic response and/or an abnormal resting blood flow. The absolute quantification of MBF removes uncertainties in the evaluation of the vasodilator response, and can be achieved without the use of complex tracer kinetic models; therefore, its application to clinical studies is feasible. J. Magn. Reson. Imaging 2004;19:758–770. © 2004 Wiley-Liss, Inc.

Predictors of Apparent Diffusion Coefficient Normalization in Stroke Patients

Abstract: Background and Purpose— We sought to describe the frequency of normalization of apparent diffusion coefficient (ADC) values that are decreased in hyperacute stroke and to identify characteristics of tissue demonstrating normalization. Methods— Sixty-eight acute ischemic stroke patients underwent MRI examination (including diffusion/perfusion imaging and MR angiography) within 6 hours (mean, 2.8 hours) after symptom onset, after 24 hours, and again 4 to 7 days later. Lesion volumes with decreased ADC and delayed time to peak in perfusion imaging were determined. In patients showing ADC normalization, volumes with ADC decrease graded as 5 mL tissue with initially decreased ADC) or nonnormalizers (demonstrating ADC normalization in <5 mL tissue). Results— Fourteen patients (19.7%) were classified as normalizers. Eleven of 31 pat...

FAIR true‐FISP perfusion imaging of the kidneys

Abstract: Most arterial spin labeling (ASL) techniques apply echoplanar imaging (EPI) because this strategy provides relatively high SNR in short measuring times. Unfortunately, those techniques are very susceptible to static magnetic field inhomogeneities and perfusion signals from organs with fast transverse relaxation might decrease due to the exchange of water molecules in capillaries and organ tissue combined with relatively long echo times of EPI sequences. To overcome these problems a novel imaging technique, FAIR True-FISP, was developed. It combines a FAIR (flow-sensitive alternating inversion recovery) perfusion preparation and a true fast imaging with steady precession (True-FISP) data acquisition strategy. True-FISP was chosen since this sequence type does not show the mentioned disadvantages of EPI, but provides a similar SNR per measuring time. An important problem of this approach is that True-FISP sequences usually work in a steady state which is independent of a previous preparation of magnetization. For this reason a sequence structure had to be developed which keeps the advantages of True-FISP and makes the signal intensity sensitive to the FAIR preparation. Breathhold and nonbreathhold examinations of kidneys are presented and possible strategies to quantitative flow measurements are reported. It is shown that correction of spatially inhomogeneous receiver coil characteristics is easily feasible and leads to clinically valuable perfusion examinations of kidneys without application of potentially nephrotoxic contrast media.

Regional differences in lung radiosensitivity after radiotherapy for non-small-cell lung cancer.

Abstract: Purpose To study regional differences in lung radiosensitivity by evaluating the incidence of radiation pneumonitis (RP) in relation to regional dose distributions. Methods and materials Registered chest CT and single photon emission CT lung perfusion scans were obtained in 106 patients before curative or radical radiotherapy for non–small-cell lung cancer. The mean lung dose (MLD) was calculated. The single photon-emission CT perfusion data were used to weigh the MLD with perfusion, resulting in the mean perfusion-weighted lung dose. In addition, the lungs were geometrically divided into different subvolumes. The mean regional dose (MRD) for each region was calculated and weighted with the perfusion of each region to obtain the mean perfusion-weighted regional dose. RP was defined as respiratory symptoms requiring steroids. The incidence of RP for patients with tumors in a specific subvolume was calculated. The normal tissue complication probability (NTCP) parameter values for the TD 50 , and an offset NTCP parameter for tumor location were fitted for both lungs and for each lung subvolume to the observed data using maximum likelihood analysis. Results The incidence of RP correlated significantly with the MLD and MRD of the posterior, caudal, ipsilateral, central, and peripheral lung subvolumes ( p between 0.05 and 0.002); no correlation was seen for the anterior, cranial, and contralateral regions Similarly, a statistically significant correlation was observed between the incidence of RP and the perfusion-weighted MLD and perfusion-weighted MRD for all regions, except the anterior lung region. For this region, the dose–effect relation improved remarkably after weighting the local dose with the local perfusion. A statistically significant difference ( p = 0.01) in the incidence of RP was found between patients with cranial and caudal tumors (11% and 40%, respectively). Therefore, a dose-independent offset NTCP parameter for caudal tumors was included in the NTCP model, improving most correlations significantly, confirming that patients with caudal tumors have a greater probability of developing RP. Conclusion The incidence of RP correlated significantly with the MLD and MRD of most lung regions, except for the anterior, cranial, and contralateral regions. Weighting the local dose with the local perfusion improved the dose–effect relation for the anterior lung region. Irradiation of caudally located lung tumors resulted in a greater risk of RP than irradiation of tumors located in other parts of the lungs.

Admission perfusion CT: prognostic value in patients with severe head trauma.

Abstract: PURPOSE: To assess the prognostic value of admission perfusion computed tomography (CT) in patients with severe head trauma. MATERIALS AND METHODS: This prospective study included 130 patients with severe trauma, aged 19–86 years, admitted with a Glasgow Coma Scale score of 8 or less. They underwent perfusion CT as part of their admission CT survey. Clinical data, unenhanced cerebral CT findings, and perfusion CT scans were evaluated with respect to the Glasgow Outcome Scale (GOS) score at 3 months. Perfusion CT features were evaluated in patients with intracranial hypertension, cerebral contusions, and juxtadural hematomas. Ordered logistic regression was used to determine risk factors for an unfavorable GOS score at 3 months. RESULTS: Perfusion CT was more sensitive than conventional unenhanced CT in the detection of cerebral contusions. Perfusion CT featured specific patterns with respect to patient outcome, with normal brain perfusion or hyperemia in patients with favorable outcome, and oligemia in pa...

A laser speckle imaging technique for measuring tissue perfusion

Abstract: Laser Doppler imaging (LDI) has become a standard method for optical measurement of tissue perfusion, but is limited by low resolution and long measurement times. We have developed an analysis technique based on a laser speckle imaging method that generates rapid, high-resolution perfusion images. We have called it laser speckle perfusion imaging (LSPI). This paper investigates LSPI output and compares it to LDI using blood flow models designed to simulate human skin at various levels of pigmentation. Results show that LSPI parameters can be chosen such that the instrumentation exhibits a similar response to changes in red blood cell concentration (0.1%-5%, 200 /spl mu/L/min) and velocity (0-800 /spl mu/L/min, 1% concentration) and, given its higher resolution and quicker response time, could provide a significant advantage over LDI for some applications. Differences were observed in the LDI and LSPI response to tissue optical properties. LDI perfusion values increased with increasing tissue absorption, while LSPI perfusion values showed a slight decrease. This dependence is predictable, owing to the perfusion algorithms specific to each instrument, and, if properly compensated for, should not influence each instrument's ability to measure relative changes in tissue perfusion.

Assessment of human pulmonary function using oxygen-enhanced T1 imaging in patients with cystic fibrosis

Abstract: Indirect qualitative MRI of pulmonary function is feasible using the paramagnetic effects of oxygen physically dissolved in blood. In this study, a more quantitative oxygen-enhanced pulmonary function test based on the slope of a plot of R1 vs. oxygen concentration—the oxygen transfer function (OTF)—was developed and tested in a pool of five healthy volunteers and five patients with cystic fibrosis (CF). The lung T1 relaxation rate, R1, under normoxic conditions (room air, 21% O2), and the response to various hyperoxic conditions (40%–100% O2) were studied. Lung T1 in healthy volunteers showed a relatively homogeneous distribution while they breathed room air, and a homogeneous decrease under hyperoxic conditions. Lung T1 in CF patients showed an inhomogeneous distribution while they breathed room air, and the observed lung T1 decrease under hyperoxia depended on the actual state of the diseased lung tissue. In the selected group of CF patients, areas with reduced OTF also showed reduced perfusion, as confirmed by qualitative contrast-enhanced MR pulmonary perfusion imaging. The results demonstrate that this completely noninvasive oxygen-enhanced pulmonary function test has potential for clinical applications in the serial diagnosis of lung diseases such as CF. Magn Reson Med 51:1009–1016, 2004. © 2004 Wiley-Liss, Inc.

Early MRI Findings in Patients Receiving Tissue Plasminogen Activator Predict Outcome: Insights into the Pathophysiology of Acute Stroke in the Thrombolysis Era

Abstract: We measured ischemic brain changes with diffusion and perfusion MRI in 42 ischemic stroke patients before and 2 hours (range approximately 1.5 to 4.5 hours) after standard intravenous tissue plasminogen activator (tPA) therapy. The median time from stroke onset to tPA was 131 minutes. Clinical and MRI variables (change in perfusion and/or diffusion weighted lesion volume) were compared between those with excellent outcome defined as 3-month modified Rankin score (mRS) of 0 to 1 and those with incomplete recovery (mRS >1). In multivariate logististic regression analysis, the most powerful independent predictor for excellent outcome was improved brain perfusion: hypoperfusion volume on mean transit time (MTT) map decrease >30% from baseline to 2-hour post tPA scan (p=0.009; odds ratio [95% confidence interval], 20.7 [2.1-203.9]). Except for age < 70 years, no other baseline clinical or imaging variable was an independent predictor of outcome. We propose MTT lesion volume decrease more than 30% 2 hours after tPA as an early marker of long-term clinical benefit of thrombolytic therapy.

Magnetic Resonance Versus Radionuclide Pharmacological Stress Perfusion Imaging for Flow-Limiting Stenoses of Varying Severity

Abstract: Background— Although magnetic resonance first-pass imaging (MRFP) has potential advantages in pharmacological stress perfusion imaging, direct comparisons of current MRFP and established radionuclide techniques are not available. Methods and Results— Graded regional differences in coronary flow were produced during global coronary vasodilation in chronically instrumented dogs by partially occluding the left circumflex artery. Regional differences in full-thickness flow quantified using microspheres were compared with regional differences obtained with MRFP and radionuclide SPECT imaging (99mTc-sestamibi and 201Tl). Relative regional flows (RRFs) derived from the initial areas under MRFP signal intensity-time curves were linearly related to reference microsphere RRFs over the full range of vasodilation (y=0.93x+4.3; r2=0.77). Relationships between 99mTc-sestamibi and 201Tl RRFs and microsphere RRFs were curvilinear, plateauing as flows increased. The high spatial resolution of the MRI enabled transmural fl...

Brain Perfusion in Children: Evolution With Age Assessed by Quantitative Perfusion Computed Tomography

Abstract: Objective. The objective of this study was to assess the age-related variations of brain perfusion through quantitative cerebral perfusion computed tomography (CT) results in children without brain abnormality. Methods. Brain perfusion CT examinations were performed in 77 children, aged 7 days to 18 years. These patients were admitted at our institution for both noncontrast and contrast-enhanced cerebral CT. Only children whose conventional cerebral CT and clinical/radiologic follow-up, including additional investigations, were normal were taken into account for this study (53 of 77). Results. The average regional rCBF amounts to 40 (mL/100 g per minute) for the first 6 months of life, peaks at ∼130 (mL/100 g per minute) at ∼2 to 4 years of age, and finally stabilizes at ∼50 (mL/100 g per minute) at ∼7 to 8 years of age, with a small increase of rCBF values at ∼12 years of age. The rCBF in the gray matter averages 3 times that in the white matter, except for the first 6 months of life. The global CBF represents 10% to 20% of the global cardiac output for the first 6 months of life, peaks at ∼55% by 2 to 4 years of age, and finally stabilizes at ∼15% by 7 to 8 years of age. Specific age-related evolution patterns were identified in the different anatomic areas of the cerebral parenchyma, which could be related to the development of neuroanatomic structures and to the emergence of corresponding cognitive functions. Conclusions. Quantitative perfusion CT characterization of brain perfusion shows specific age variations. Brain perfusion of each cortical area evolves according to a specific time course, in close correlation with the psychomotor development.

Perfusion MR imaging of brain tumors.

Abstract: Brain tumors rank second as the cause of cancer-related deaths in children and adults younger than 34 years old, and they are seen in adults of all ages. Primary malignant brain tumors are associated with the third highest cancer-related mortality rate and a disproportionate level of disability and morbidity. Considering this, accurate diagnosis and grading of brain tumors are critical to determining prognosis and therapy. Equally important is to evaluate for tumor status during therapy to assess for therapeutic response and treatment-related complications. Brain tumors can be characterized as a heterogeneous group of neoplasm with a correspondingly wide variation in malignant phenotype and a diverse array of imaging features. Magnetic resonance (MR) imaging with intravenous contrast agent is the test of choice to diagnose and monitor brain tumors before, during, and after therapy. Recent advances in imaging methods such as diffusion-weighted imaging, perfusion imaging, and spectroscopic imaging all have in common the ability to provide quantitative cellular, hemodynamic, and metabolic information that may enhance our understanding of brain tumor biology, help us to better assess treatment response, more accurately determine tumor activity during therapy, and differentiate recurrent tumor and treatment related complications. In this article, we will review the basics of brain tumor imaging and focus on the role of perfusion MR imaging in improving accurate diagnosis and monitoring brain tumors during therapy. Both strengths and shortcomings of perfusion MR imaging over standard anatomic MR imaging will be discussed as will important pitfalls of the technique.

The Diagnostic and Prognostic Value of ECG-Gated SPECT Myocardial Perfusion Imaging

Abstract: Since the development of gated SPECT imaging approximately 10 y ago, this technique is now almost universally used as an adjunct for radionuclide perfusion imaging, enabling the assessment of perfusion along with determination of regional and global left ventricular function in the same examination The gated SPECT determination of the left ventricular ejection fraction and volumes has been extensively validated Additionally, this method allows for the improved identification of soft-tissue artifacts and enhances the detection of multivessel coronary artery disease Furthermore, gated SPECT provides powerful information for the risk assessment of patients with known or suspected coronary artery disease and aids in the assessment of myocardial viability Gated SPECT imaging has clearly become an integral part of radionuclide myocardial perfusion imaging

Magnetic resonance imaging evaluation of myocardial perfusion and viability in congenital and acquired pediatric heart disease.

Abstract: This study examined the feasibility and potential clinical utility of magnetic resonance imaging (MRI) evaluation of myocardial perfusion (first-pass contrast enhancement) and viability (myocardial delayed enhancement) in 30 patients with congenital and acquired pediatric heart disease. Good agreement was found between MRI evaluation of myocardial perfusion and viability and analysis of segmental wall motion as well as coronary angiography (n = 10) and single photon emission computed tomography (n = 6).

High-resolution myocardial perfusion mapping in small animals in vivo by spin-labeling gradient-echo imaging.

Abstract: An ECG and respiration-gated spin-labeling gradient-echo imaging technique is proposed for the quantitative and completely noninvasive measurement and mapping of myocardial perfusion in small animals in vivo. In contrast to snapshot FLASH imaging, the spatial resolution of the perfusion maps is not limited by the heart rate. A significant improvement in image quality is achieved by synchronizing the inversion pulse to the respiration movements of the animals, thereby allowing for spontaneous respiration. High-resolution myocardial perfusion maps (in-plane resolution = 234 × 468 μm2) demonstrating the quality of the perfusion measurement were obtained at 4.7 T in a group of seven freely breathing Wistar-Kyoto rats under isoflurane anesthesia. The mean perfusion value (group average ± SD) was 5.5 ± 0.7 ml g–1min–1. In four animals, myocardial perfusion was mapped and measured under cardiac dobutamine stress. Perfusion increased to 11.1 ± 1.9 ml g–1min–1. The proposed method is particularly useful for the study of small rodents at high fields. Magn Reson Med 51:62–67, 2004. © 2003 Wiley-Liss, Inc.