Sickle cell disease: continuous arterial spin-labeling perfusion MR imaging in children

Cerebral blood flow (CBF) was measured with continuous arterial spin-labeling perfusion magnetic resonance (MR) imaging in 14 children with sickle cell disease and seven control subjects. Mean CBF values were higher in patients (P <.005) than in control subjects in all cerebral artery territories. Three patients had decreased CBF in right anterior and middle cerebral artery territories compared with CBF on the left, and one patient had a profound decrease in CBF in all three territories in the right hemisphere. Baseline CBF was significantly decreased in territories seen as unaffected on conventional MR images and MR angiograms in four children with sickle cell disease.     

Effect of lung inflation on arterial spin labeling signal in MR perfusion imaging of human lung

The effect of lung inflation on arterial spin-labeling signal in lung perfusion is investigated. Arterial spin-labeling schemes, called alternation of selective inversion pulse (ASI) and its hybrid (HASI), which uses blood water as an endogenous, freely diffusible tracer, were applied to magnetic resonance (MR) perfusion imaging of the lung. Perfusion-weighted images of the lung from nine healthy volunteers were obtained at different time delays. There was a significant signal difference in ASI images acquired at different respiratory phases. Greater signal enhancement has been observed when the volunteers performed breath holding on end expiration than on end inspiration. This is in agreement with the normal physiologic effect of lung inflation on the pressure-flow relationship of pulmonary vasculature. ASI and HASI perfusion-weighted images show similar lung features and image quality. Preliminary results from pulmonary embolism patients indicate that arterial spin labeling is sensitive for the detection of areas of perfusion deficit. J. Magn. Reson. Imaging 2001;13:954-959.     

Pediatric perfusion imaging using pulsed arterial spin labeling

PURPOSE: To test the feasibility of pediatric perfusion imaging using a pulsed arterial spin labeling (ASL) technique at 1.5 T. MATERIALS AND METHODS: ASL perfusion imaging was carried out on seven neurologically normal children and five healthy adults. The signal-to-noise ratio (SNR) of the perfusion images along with T1, M(0), arterial transit time, and the temporal fluctuation of the ASL image series were measured and compared between the two age groups. In addition, ASL perfusion magnetic resonance (MR) was performed on three children with neurologic disorder. RESULTS: In the cohort of neurologically normal children, a 70% increase in the SNR of the ASL perfusion images and a 30% increase in the absolute cerebral blood flow compared to the adult data were observed. The measures of ASL SNR, T1, and M(0) were found to decrease linearly with age. Transit time and temporal fluctuation of the ASL perfusion image series were not significantly different between the two age groups. The feasibility of ASL in the diagnosis of pediatric neurologic disease was also illustrated. CONCLUSION: ASL is a promising tool for pediatric perfusion imaging given the unique and reciprocal benefits in terms of safety and image quality.     

Comparison of arterial spin-labeling techniques and dynamic susceptibility-weighted contrast-enhanced MRI in perfusion imaging of normal brain tissue

OBJECTIVES: To evaluate relative cerebral blood flow (rCBF) in normal brain tissue using arterial spin-labeling (ASL) methods and first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) magnetic resonance imaging (MRI). METHODS: Sixty-two patients with brain metastases were examined on a 1.5 T-system up to 6 times during routine follow-up after stereotactic radiosurgery. Perfusion values in normal gray and white matter were measured using the ASL techniques ITS-FAIR in 38 patients, Q2TIPS in 62 patients, and the first-pass DSC echo-planar (EPI) MRI after bolus administration of gadopentetate dimeglumine in 42 patients. Precision of the ASL sequences was tested in follow-up examinations in 10 healthy volunteers. RESULTS: Perfusion values in normal brain tissue obtained by all sequences correlated well by calculating Pearson's correlation coefficients (P < 0.0001) and remained unchanged after stereotactic radiosurgery as shown by analysis of variance (P > 0.05). CONCLUSION: Both ASL and DSC EPI MRI yield highly comparable perfusion values in normal brain tissue.     

Cerebral border zones between distal end branches of intracranial arteries: MR imaging

This study had institutional review board approval; informed consent was obtained from all participants. The study purpose was to prospectively determine whether a longer arterial transit time (ATT), from the proximal vasculature in the neck toward the distal end branches of the intracranial arteries, can be utilized to identify cerebral border zone regions. A magnetic resonance (MR) imaging method based on noninvasive arterial spin-labeling (ASL) perfusion MR imaging with image acquisition at a series of increasing delay times was used to quantify regional ATTs. Fifteen healthy volunteers (age range, 22-34 years; nine men, six women) were included. ASL perfusion MR imaging demonstrated an increase in ATT in the cerebral border zone regions, extending from the frontal and occipital horns of the lateral ventricle to the frontal and parietooccipital cortices, relative to ATT in non-border zone regions. Cerebral blood flow and arterial blood volume in these anterior and posterior border zone regions were significantly lower (P < .001) than in non-border zone regions.     

Pulmonary perfusion: respiratory-triggered three-dimensional MR imaging with arterial spin tagging--preliminary results in healthy volunteers.

The authors used a spin-tagging method of magnetic resonance perfusion imaging to measure pulmonary perfusion in eight healthy volunteers with use of a respiratory-triggered three-dimensional pulse sequence. The average signal intensity (SI) decrease upon arterial labeling was 24%. The perfusion SI increased by 21% after exercise (P = .02). Focal blood flow abnormalities were observed in a patient with chronic obstructive pulmonary disease.     

Arterial spin-labeling in routine clinical practice: a preliminary experience of 200 cases and correlation with MRI and clinical findings

We described our experience with a heterogeneous collection of 200 arterial spin-labeling (ASL) perfusion cases. ASL imaging was performed on a 1.5-T magnetic resonance imaging unit with a receive head coil using a second version of quantitative perfusion imaging. Sixty-four (32%) patients exhibited normal perfusion, 107 (53.5%) patients exhibited hypoperfusion, and 29 (14.5%) exhibited hyperperfusion. This ASL study illustrates the usefulness of ASL perfusion studies in a number of pathological conditions and that perfusion imaging can be implemented successfully in a routine clinical neuroimaging protocol.     

彩色多普勒超声在小儿睾丸扭转诊断中的价值

目的探讨彩色多普勒超声对小儿睾丸扭转的诊断价值。方法对44例临床疑诊睾丸扭转男孩(年龄1岁～15岁,平均8岁)首先用二维超声显示双侧睾丸附睾形态、结构及内部回声,再用彩色多普勒观察血流情况,所有病例经手术证实。结果44例中的41例睾丸扭转患者患侧睾丸血流减少或消失。结论彩色多普勒诊断睾丸扭转有很高的特异性,简便无创,应作为诊断睾丸扭转的首选方法。     

MR regional perfusion imaging: visualizing functional collateral circulation

SUMMARY: We applied regional perfusion imaging (RPI), a new arterial spin-labeling MR imaging method that selectively studies regions of the brain perfused by individual carotid and basilar arteries. In a patient with cerebrovascular disease, RPI showed cerebral tissue perfused by pial collateral vessels, thereby demonstrating the relationship between anatomic and functional information, which was lacking in conventional x-ray angiography. RPI may be useful to study functional collateral circulation and hence guide therapy in ischemic disease.     

Perfusion-weighted imaging of interictal hypoperfusion in temporal lobe epilepsy using FAIR-HASTE: comparison with H(2)(15)O PET measurements.

To detect perfusion abnormalities in areas of high magnetic susceptibility in the brain, an arterial spin-labeling MRI technique utilizing flow-sensitive alternating inversion recovery (FAIR) and half-Fourier single shot turbo spin-echo (HASTE) for spin preparation and image acquisition, respectively, was developed. It was initially tested in a functional study involving visual stimulation, and was able to detect significant activation with an increase (approximately 70%) in relative cerebral blood flow. Subsequently, it was applied in a clinical situation in eight patients with temporal lobe epilepsy (TLE). The perfusion-weighted images obtained showed no susceptibility artifacts even in the region of the inferior temporal lobe and were able to detect interictal hypoperfusion in TLE. The results were compared with those derived from H(2)(15)O PET perfusion imaging in each patient. A statistically significant correlation (r = 0.75, P < 0.05) was found between results acquired from these two modalities. Magn Reson Med 45:431-435, 2001.     

Arterial spin labeling blood flow magnetic resonance imaging for the characterization of metastatic renal cell carcinoma(1)

RATIONALE AND OBJECTIVE: This study sought to assess the feasibility of arterial spin labeling (ASL) blood flow (BF) magnetic resonance imaging (MRI) for the study of metastatic renal cell carcinoma (RCC) in the body, where the respiratory, cardiac, and peristaltic motions present challenges when applying ASL. MATERIALS AND METHODS: ASL was performed using a background-suppressed single-section flow-alternating inversion recovery (FAIR) preparation and a single-shot fast spin-echo imaging sequence on a 3.0-T whole body imager. Tumor BF was evaluated for 26 patients with RCC metastatic to the liver, bone, lung, or lymph nodes before VEGF receptor inhibitor therapy. Two cases with tumor size change after treatment were also scanned 1 month after therapy. For validation, kidney cortex BF in five normal volunteers was measured with the same technique and compared with literature values. RESULTS: ASL was successfully performed in all normal volunteers and in 20 of 26 patients. The six failures resulted from a systematic error, which can be avoided in future studies. For normal volunteers, measured kidney cortex BF was 275 +/- 14 mL/min/100 g, a value consistent with the literature. ASL determined tumor BF averaged across tumor volume and subjects was 194 mL/min/100 g (intersubject SD = 100), resulting in high perfusion signal and conspicuity of lesions. Bright signal was also seen in large vessels and occasionally in bowel. In the two cases studied 1 month after therapy, ASL perfusion changes were consistent with tumor size changes. CONCLUSION: With background suppression, ASL MRI is a feasible method for quantifying BF in patients with renal cell carcinoma. This technique may be useful for evaluating tumor response to antiangiogenic agents.     

Human brain: reliability and reproducibility of pulsed arterial spin-labeling perfusion MR imaging

The Committee of Human Research of the University of California San Francisco approved this study, and all volunteers provided written informed consent. The goal of this study was to prospectively determine the global and regional reliability and reproducibility of noninvasive brain perfusion measurements obtained with different pulsed arterial spin-labeling (ASL) magnetic resonance (MR) imaging methods and to determine the extent to which within-subject variability and random noise limit reliability and reproducibility. Thirteen healthy volunteers were examined twice within 2 hours. The pulsed ASL methods compared in this study differ mainly with regard to magnetization transfer and eddy current effects. There were two main results: (a) Pulsed ASL MR imaging consistently had high measurement reliability (intraclass correlation coefficients greater than 0.75) and reproducibility (coefficients of variation less than 8.5%), and (b) random noise rather than within-subject variability limited reliability and reproducibility. It was concluded that low signal-to-noise ratios substantially limit the reliability and reproducibility of perfusion measurements.     

Arterial spin-labeling magnetic resonance imaging: the timing of regional maximal perfusion-related signal intensity revealed by a multiphase technique

Purpose  

We investigated the time interval from labeling to peak (TLP) of perfusion-signal intensity (SIs) in normal brain using a multiphase arterial spin-labeling (ASL) magnetic resonance imaging (MRI) technique as a fundamental study to assess the temporal characteristics of perfusion SIs.     

Partially parallel three-dimensional magnetic resonance imaging for the assessment of lung perfusion--initial results

RATIONALE: Contrast-enhanced magnetic resonance imaging (MRI) of lung perfusion requires a high spatial and temporal resolution. Partially parallel MRI offers an improved spatial and temporal resolution. OBJECTIVE: To assess the feasibility of partially parallel MRI for the assessment of lung perfusion. METHODS: Two healthy volunteers and 14 patients were examined with a contrast-enhanced 3D gradient-echo pulse sequence with partially parallel image acquisitions (TE/TR/alpha: 0.8/1.9 milliseconds/40 degrees; voxel size 3.6 x 2.0 x 5.0 mm3, TA: 1.5 seconds). The image analysis included an analysis of the signal-to-noise ratio in the lungs in areas with normal and impaired perfusion. 3D MR perfusion image data were analyzed for perfusion defects and compared with radionuclide perfusion scans, which were available for 10 of 14 patients. RESULTS: The analysis of the 3D perfusion-weighted data allowed a clear differentiation of perfusion abnormalities: MRI showed normal lung perfusion in 9 of 16 cases, whereas perfusion abnormalities were observed in 7 cases. When compared with the radionuclide perfusion scans, a good intermodality agreement was shown (kappa = 0.74). When compared with normally perfused lung a significantly lower signal to noise ratio was observed in hypoperfused lung (7 versus 17; P = 0.02). CONCLUSION: Partially parallel MRI might be used for the assessment of lung perfusion. Future studies are required to further evaluate the diagnostic impact of this technique.     

The normal and abnormal scrotum in children: evaluation with color Doppler sonography.

The use of color Doppler sonography to evaluate the symptomatic testes in children with scrotal pain or swelling was prospectively studied with a fourth-generation color sonographic unit with a 7-MHz linear transducer. The 32 patients were 1 day to 18 years old (mean age, 8.6 years). Results were correlated with scintigraphic findings in 23 patients, with the final diagnosis established by surgery in 12 patients, and with clinical follow-up in all patients. Eight cases of testicular torsion, including two of acute torsion and six of late torsion, were correctly detected by color Doppler sonography and confirmed surgically. In the remaining patients, perfusion of the testis was correctly detected by color Doppler examination. The final diagnoses in these patients included torsion of the appendix testis (15 patients), epididymitis (five patients), epididymo-orchitis (one patient), yolk sac tumor of the testis (one patient), hydrocele (one patient), and local reaction to an insect bite (one patient). The ability to detect blood flow in the normal contralateral testis was also evaluated in 28 patients. Blood flow was demonstrated in normal testes larger than 1 cm3. Detection of flow in the very small normal prepubertal testis was often difficult, and no flow was identified in one testis. Flow was identified in central arteries in only six of 13 testes smaller than 1 cm3. We conclude that color Doppler sonography is helpful in the initial evaluation of pediatric testes, providing accurate evaluation of the involved hemi-scrotum in our patients and also providing the benefit of both structural and flow information. Until our sensitivity to low-velocity flow improves, we would not suggest the exclusive use of color Doppler sonography in the evaluation of testicular perfusion in the prepubertal patient. We advocate the addition of testicular scintigraphy to corroborate the presence of testicular perfusion when flow in intratesticular arteries cannot be established with certainty by color Doppler sonography.     

Contrast-enhanced magnetic resonance imaging of hypoperfused myocardium.

Contrast-enhanced magnetic resonance (MR) imaging can define myocardial perfusion defects due to acute coronary occlusion. However, since most clinically important diagnostic examinations involve coronary arteries with subtotal stenoses, we investigated the ability of MR imaging with a manganese contrast agent to detect perfusion abnormalities in a canine model of partial coronary artery stenosis. The contrast agent was administered after the creation of a partial coronary artery stenosis with the addition of the coronary vasodilator dipyridamole in six of 12 animals. The hearts were imaged ex situ using gradient reversal and spin-echo sequences, and images were analyzed to determine differences in signal intensity between hypoperfused and normally perfused myocardium. Comparison of MR images with regional blood flow and thallium-201 measurements showed good concordance of hypoperfused segments in those animals given dipyridamole, with 75% of the abnormal segments correctly identified. In those animals not given dipyridamole, 48% of segments were correctly identified. Thus, ex vivo MR imaging with a paramagnetic contrast enhancement can be used to detect acute regional myocardial perfusion abnormalities due to severe partial coronary artery stenoses.     

Color Doppler ultrasound of the normal testis

Color Doppler ultrasound with point spectral analysis was performed on 30 testes of 15 asymptomatic volunteers. Intratesticular arteries and testicular capsular arteries were imaged in all 30 cases. Waveforms from these vessels were similar and consistently showed a low-impedance pattern with high levels of diastolic flow. This reflects the low vascular resistance of the testis. Supratesticular arteries were also identified in all 30 cases. In addition to the low-impedance-type waveforms from the testicular artery, waveforms obtained in the supratesticular region also originated from the deferential and/or cremasteric arteries. This resulted in some waveforms with high-impedance patterns, reflecting the high vascular resistance of the epididymis and peritesticular tissues. We believe that color Doppler ultrasound is capable of reliably showing the normal testicular arterial anatomy by imaging intraarterial blood flow. Knowledge of the normal color Doppler appearance and waveform characteristics of the testicular artery should aid in diagnosing scrotal conditions that alter blood flow.     

Renal disease: value of functional magnetic resonance imaging with flow and perfusion measurements

PURPOSE: To differentiate healthy kidneys from diseased kidneys, we propose a combined magnetic resonance (MR) examination that includes measurements of renal arterial blood flow and parenchymal perfusion. MATERIALS AND METHODS: A total of 130 kidneys (patients/healthy volunteers: 83/47) were examined using renal artery MR flow measurements and renal parenchymal perfusion measurements, as well as contrast-enhanced MR angiography. Cine phase-contrast-flow measurements were performed using an ECG-gated fast low angle shot pulse sequence; perfusion was measured with an arterial spin labeling flow-sensitive alternating inversion recovery technique. Contrast-enhanced MR angiography was performed with a fast 3D gradient echo sequence in a single breath hold. For evaluation, kidneys were divided into groups based on nephrologic diagnosis of the patient. Recursive partitioning and Wilcoxon rank-sum tests were used to separate the different groups. RESULTS: Significant differences in mean renal artery flow and parenchymal perfusion were found in kidneys with renal artery stenosis as well as parenchymal disease as compared with healthy kidneys. Using a classification tree derived from the recursive partitioning, a specificity of 99% and sensitivity of 69% with a positive/negative predictive value of 97%/84% was achieved for the separation of healthy kidneys from kidneys with vascular, parenchymal or combined disease. The overall accuracy was 88%. CONCLUSION: The combination of cine PC flow measurements and MR perfusion measurements offers a comprehensive assessment of both renovascular and renoparenchymal disease and provide a noninvasive approach to differentiate between these kidneys and normal kidneys.     

FAIR and dynamic susceptibility contrast-enhanced perfusion imaging in healthy subjects and stroke patients

PURPOSE: To compare dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) and the flow-sensitive alternating inversion recovery (FAIR) technique for measuring brain perfusion. MATERIALS AND METHODS: We investigated 12 patients with acute stroke, and 10 healthy volunteers with FAIR and DSC maps of regional cerebral blood volume (rCBV), mean transit time (MTT), and regional cerebral blood flow (rCBF). RESULTS: In volunteers good gray/white-matter contrast was observed in FAIR, rCBF, and rCBV maps. Regions with high signal intensities in FAIR matched well with high values of rCBV and rCBF. In ischemic stroke patients a high correlation (r = 0.78) of the ipsi- to contralateral signal intensity ratios in FAIR and rCBF was observed in areas with perfusion abnormalities. In contrast, FAIR and rCBV (r = 0.50), and FAIR and MTT (r = -0.22) correlated only modestly. Furthermore, FAIR and rCBF demonstrated similar sizes of perfusion abnormality. CONCLUSION: This study demonstrates for the first time that FAIR and rCBF depict similar relations of perfusion in ischemic stroke patients and healthy subjects.     

动脉自旋标记与动态对比增强MRI脊柱骨髓灌注成像对照研究

目的：分析动脉自旋标记（ASL）与动态对比增强MRI（DCE—MRI）脊柱骨髓灌注成像参数间的相关性,探讨ASL测量脊柱骨髓血流灌注的可行性。方法：对27位志愿者的54个腰椎椎体行ASL及DCE—MRI扫描,将原始图像传入GEAW4．4工作站分剐采用Functool及Cinetool软件进行后处理,每个椎体用一个兴趣区（R01）覆盖,记录椎体骨髓的ASL灌注血流量（BFM）及DCE-MRI灌注参数（Ktrans,Kep,Ve）,并用Pearson法分析BFAsL与Ktrans,Kep,Ve间的相关性。结果：腰椎脊髓灌注的BFAsL与Ktrans,Kep,Ve正相关,r值分别为0．646（P〈0．001）、0．387（P=0．004）,与V。值无相关性,r=0．239（P=0．082）。结论：用ASI。法可以得到脊柱骨髓灌注BFAs值,而且BFASL与DCE—MRI脊柱骨髓灌注参数间存在相关性,ASL技术有评估腰椎骨髓血流灌注的潜能。