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

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.

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...

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.

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.

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.

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

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).

Abstract: OBJECTIVE. The purpose of this study was to determine the capability of dynamic perfusion MRI as an alternative to pulmonary perfusion scintigraphy for prediction of postoperative lung function in patients with lung cancer.SUBJECTS AND METHODS. Sixty patients with lung cancer (35 men, 25 women) underwent dynamic perfusion MRI, perfusion scintigraphy, and preoperative and postoperative pulmonary function tests (forced expiratory volume in 1 sec [FEV1]). Perfusion MRIs were obtained with a 3D turbo field-echo sequence (TR/TE, 2.7/0.6; flip angle, 40°; matrix, 128 × 96) using a 1.5-T scanner. Regional blood flow was calculated from the signal intensity–time curves after bolus injection of contrast medium on MRI (QMRI) and uptake ratios of radioisotope on perfusion scintigraphy (QPS). Postoperative lung functions predicted by MRI (FEV1,MRI) and perfusion scintigraphy (FEV1,PS) were calculated from preoperative FEV1 and regional Qs. To determine the capability of MRI as an alternative to scintigraphy, we evalu...

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.

Abstract: Macromolecular contrast-enhanced functional CT was performed to characterize early perfusion changes in hepatocellular carcinoma (HCC). Fourteen rats with chemically induced primary liver tumors ranging pathologically from hyperplasia to HCC and 15 control rats were investigated. Two dynamic CT scans using an experimental macromolecular contrast agent were performed on a single slice 11 and 18 weeks after tumor induction followed by pathological examination. A deconvolution mathematical model was applied, yielding the hepatic perfusion index (HPI), mean transit time (MTT), liver distribution volume (LDV) and arterial, portal and total blood flows (FA, FP, FT). Analysis was performed on one slice per rat, containing overall two hyperplasia, six dysplasia and 15 HCC. On the first scans, HCC at an early pathological stage had a low FP (-30%, P=0.002) but a normal arterial-portal balance. On the scan contemporary to pathology, HCC perfusion parameters showed an inversion of the arterial-portal balance (HPI +212%, P<0.0001), with a high FA (+56%, P=0.002) and a low FP (-69%, P<0.0001). Sensitivity and specificity of detection of HCC by perfusion CT were high (87 and 80%) on late scans; but also on the earlier scans (86 and 65%), even though only one (7%) was visible to the eye. Perfusion-CT allowed early detection of HCC. This technique could contribute in the detection and characterization of liver lesions in clinical studies.

Abstract: Coronary artery disease (CAD) is currently the leading cause of death in developed nations. Reflecting the complexity of cardiac function and morphology, noninvasive diagnosis of CAD represents a major challenge for medical imaging. Although coronary artery stenoses can be depicted with magnetic resonance (MR) and computed tomography (CT) techniques, its functional or hemodynamic impact frequently remains elusive. Therefore, there is growing interest in other, target organ-specific parameters such as myocardial function at stress and first-pass myocardial perfusion imaging to assess myocardial blood flow. This review explores the pathophysiologic background, recent technical developments, and current clinical status of first-pass MR imaging (MRI) of myocardial perfusion.

Abstract: Background— The decision to perform coronary revascularization procedures may hinge on assessment of myocardial perfusion reserve. Blood oxygen level–dependent (BOLD) MRI is a potential method to detect the effects of regional variations in myocardial blood flow during vasodilation. Methods and Results— We imaged dogs (n=13) on a 1.5-T whole-body MRI scanner using a new T2-prepared steady-state free-precession (SSFP) MRI pulse sequence sensitive to BOLD contrast. Images (in-plane resolution ≈1 mm2) of 5 short-axis and 2 long-axis slices of the heart were acquired during graded levels of adenosine infusion via a surgically placed left circumflex (LCx) catheter (n=11) or via a right atrial catheter in animals with an LCx occluder (n=2). Relative myocardial perfusion was measured with the use of fluorescent microspheres. Signal intensity changes in myocardium subtended by the left anterior descending coronary artery were compared with those in the LCx region. Unprocessed T2-weighted images revealed changes i...

Abstract: In addition to coronary artery assessment, contrast-enhanced multidetector spiral computed tomography (CE-MDCT) can provide valuable information about myocardial perfusion. Using CE-MDCT, myocardial perfusion defects are often observed in the early phase of the contrast bolus (early defect (ED)), with residual defects (RDs) and late enhancement (LE) observed in the late phase in myocardial infarction (MI). However, the clinical significance of EDs, RDs, and LE has not yet been fully described. This work reviews myocardial viability and function by CE-MDCT based on our prior data by including contrast-enhanced single-slice (detector) CT (CE-SSCT) and CE-MDCT. Recently, equivalent results were obtained, as seen in CE-SSCT with images by CE-MDCT. In this review, images that were acquired by MDCT will be presented. In this work, the following items will be the focus: myocardial enhancement patterns (EDs, LE, and RDs), early perfusion defects and their relationship to wall thickness (WT) and wall motion, early CT perfusion defects vs. Tl-201 single photon emission CT (SPECT), the protocol for performing dual-phase contrast CT, classification of enhancement patterns, enhancement patterns on dual-phase CE-MDCT vs. left ventricular functional recovery and WT, changes in enhancement patterns in conjunction with healing stage, enhancement patterns on dual-phase CE-MDCT vs. 201Tl/99mTc-pyrophosphate (dual-isotope SPECT), the clinical meaning of each enhancement pattern, pitfalls of enhancement patterns and other diseases, and study limitations and the future of MDCT.

Abstract: Magnetic resonance (MR) physiologic and functional techniques, which augment imaging, can now be performed during most clinical MR imaging examinations. This book’s aim is to present appropriate clinical applications of and to discuss interpretation of results from diffusion imaging, perfusion imaging, and spectroscopy. The editors have attempted to provide a reference for clinical practice with broad applications of functional imaging. The editors are longtime researchers in MR imaging. Gillard and Waldman are neuroradiologists and Barker is an imaging scientist. They have assembled an expert international team of chapter authors. An insightful introduction is provided by R. Nick Bryan, a well-known neuroradiologist experienced with physiologic and functional MR imaging. There are 46 chapters within seven clinical disease sections: cerebrovascular, neoplastic, infection/ inflammatory, epilepsy, neurodegenerative/psychiatric, trauma, and pediatric disorders. There is a six-page list of abbreviations. The abbreviation rCBF, which for decades had been defined as regional cerebral blood flow, has been defined in recent journal articles and now in this book as relative cerebral blood flow, unaccompanied by any explanation of the change of established nomenclature. The term cerebral blood flow (CBF) is subsequently defined separately. Chapter 7 presents deconvolution formulas to calculate CBF values. However, a reader not already familiar with the formulas will not know if they produce true relative CBF values in units of milliliters of blood per 100 cm of brain tissue per minute, the most precise blood flow value. Chapter 8 contains mentions of “regional blood flow” without an explanation of whether regional CBF—or another CBF value—is meant. It is unfortunate that this definitive textbook of neuroimaging physiology does not outline these discrepancies for readers. A limitation of this text is the emphasis on the advances in MR imaging techniques without much in-depth discussion of advanced computed tomographic (CT) techniques such as CT perfusion imaging. Chapter 8 compares MR perfusion imaging with positron emission tomography (PET) and xenon CT, yet mentions nothing about CT perfusion imaging, which is considered by many to be the most efficient way to immediately measure regional CBF, CBF volume, and mean transit time (MTT). CBF volume and MTT measurements without regional CBF measurements dominate reports of clinical MR imaging. CBF volume correlates well with diffusion-weighted MR imaging defects whether done with CT perfusion or MR perfusion. MTT on its own is nonspecific; it reflects the time for blood to arrive, but it does not always reflect the adequacy of blood supply. For example, patients with proximal occlusions and excellent collateral vessels without ischemia (eg, patients with acute stroke) may have markedly delayed MTT values. Chapter 10 describes the advantages of CT perfusion imaging: It is simpler and much quicker to perform than MR perfusion imaging, and is not associated with an unfriendly magnet environment. However, it takes more skill to interpret early infarction on CT images than on diffusion-weighted MR images. Readers who prefer to learn complex new material by repetition will appreciate this book, which is organized according to diseases. Specific techniques, such as MR spectroscopy, are explained multiple times across different chapters. Various peaks on MR spectra become familiar by repetition. Commercial software that identifies various chemical peaks is currently available, which further facilitates the use of MR spectroscopy in clinical practice. Other MR techniques such as tensor imaging, spectroscopy, and functional mapping have no competition from CT. Techniques such as PET are not prevalent in clinical departments, and the future seems to lie with MR for all but time-limited situations. The physiologic and functional MR techniques described in this book are here to stay and already used in the field, beyond academic sites. The editors achieve their goal of providing detailed reference tutorials for neuroimagers to understand current uses. This book is worth the cost as a reference for those who do neuroimaging or refer patients for neuroimaging studies. Reviewed by Allan J. Fox, MD BOOK REVIEWS

Abstract: Cerebral perfusion may be visualized by the dynamic imaging of an intravenously injected bolus (a few milliliters) of clinically approved gadolinium-containing contrast media. During its passage through the vasculature of the brain, the contrast agent induces magnetic field disturbances, which can be seen as signal loss on appropriately weighted dynamic MRI. This article deals with the quantitative analysis of such signal changes, first in terms of tracer concentration and then, via the mathematical approach of deconvolution, in terms of tissue microvascular physiology, culminating in quantitative estimates on a pixel-by-pixel basis of physiologic parameters, such as cerebral blood volume, mean transit time, and cerebral blood flow.

Abstract: Background and Purpose— Color-coded perfusion maps can be calculated from ultrasound harmonic gray-scale imaging data after ultrasound contrast agent bolus injection to analyze brain tissue perfusion. First reports indicate that this method can display cerebral perfusion deficits in acute ischemic stroke. We performed a prospective patient study to evaluate this approach. Methods— Thirty consecutive patients suffering from acute middle cerebral artery infarction who presented to our department within 12 hours after symptom onset were investigated with ultrasound perfusion harmonic imaging (PHI) after Levovist bolus injection. Color-coded perfusion maps were calculated from the ultrasound data. In addition, the original gray-scale images were analyzed in cine mode. Findings were compared with those of cranial CT. Results— All 30 patients suffered from acute ischemic stroke of the middle cerebral artery territory (median National Institutes of Health Stroke Scale score, 16 points). Twenty-three of the 30 pa...

Abstract: In order to evaluate the clinical utility of non-enhanced CT with perfusion and angio CT in the assessment of acute ischaemic stroke, 42 patients with symptoms of acute stroke were examined within the first 6 h from onset of symptoms with non-enhanced CT (NECT), perfusion CT (PCT) and CT angiography (CTA). Maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were analysed visually, and after drawing regions of interest (ROIs) in the territory of anterior, middle and posterior cerebral arteries, maximum-intensity projection and volume-rendering images of the cervical and cerebral vessels were created. All patients underwent a control CT or MR examination 24-48 h after the initial examination. Twenty-nine patients developed an area of infarction at control examinations. Significant perfusion abnormalities were found in 27 cases, whilst in two patients the perfusion studies were considered to be normal. All the cases with perfusion abnormalities showed arterial stenoses or occlusions on angio CT. Small infarctions at levels other than the ones selected for perfusion CT, and arteriosclerotic changes, were observed in the two cases with no perfusion abnormalities. In conclusion, combining non-enhanced CT with PCT and CTA is a simple and a very valuable tool in the initial assessment of acute stroke.

Abstract: Purpose To compare signal-to-noise ratio (SNR), contrast-to-noise (CNR) ratio, and diagnostic accuracy of a newly developed saturation recovery (SR)-TrueFISP-two-dimensional (2D) sequence with an SR-TurboFLASH-2D sequence. Materials and Methods In seven healthy subjects and nine patients with coronary artery disease (CAD), contrast-enhanced perfusion imaging (with Gd-DTPA) was performed with SR-TrueFISP and SR-TurboFLASH sequences. Hypoperfused areas were assessed qualitatively (scale = 0–4). Furthermore, SNR and CNR were calculated and semiquantitative perfusion parameters were determined from signal intensity (SI) time curves. Standard of reference for patient studies was single-photon emission computer tomography (SPECT) and angiography. Results The perception of perfusion deficits was superior in TrueFISP images (2.6 ± 1.0) than in TurboFLASH (1.4 ± 0.6) (P < 0.001). Phantom measurements yielded increased SNR (143 ± 34%) and CNR (158 ± 64%) values for TrueFISP. In patient/volunteer studies SNR was 61% to 100% higher and signal enhancement was 110% to 115% higher with TrueFISP than with TurboFLASH. Qualitative and semiquantitative assessment of perfusion defects yielded higher sensitivities for detection of perfusion defects with TrueFISP (68% to 78%) than with TurboFLASH (44% to 59%). Conclusion SR-TrueFISP-2D perfusion imaging provides superior SNR and CNR than TurboFLASH imaging. Moreover, the dynamic range of SIs was found to be higher with TrueFISP, resulting in an increased sensitivity for detection of perfusion defects. J. Magn. Reson. Imaging 2004;19:555–563. © 2004 Wiley-Liss, Inc.

Abstract: Rationale and Objectives: Our purpose was to validate contrast-enhanced computed tomography (CECT)-derived quantitative measures of perfusion and permeability against gold standard techniques of fluorescent microspheres and Evan's Blue dye, respectively. Materials and Methods: Normal and tumor-bearing (R3230AC) Fischer 344 rats were used. CECT perfusion measurements of normal and tumor tissue were compared with quantitative fluorescent microsphere perfusion measures. CECT permeability measurements from tumors were compared with semiquantitative Evan's Blue Dye permeability estimates. CT images were obtained precontrast and an imaging plane was selected. Serial, stationary images were obtained every 2 seconds for 2 minutes after intravenous bolus of iodinated contrast. Permeability and perfusion were measured by applying Patlak analysis to time-density data from normal tissue or tumor and femoral artery. Results: There was good correlation between fluorescent microsphere and CECT measurements of perfusion (r 2 = 0.681, P « 0.001) and between Evan's Blue Dye and CECT measurements of permeability (r2 = 0.873, P = 0.0007). Conclusions: CECT provides useful, quantifiable measures of perfusion and permeability in peripheral tumors.