Obstructive sleep apnea in pediatric patients: evaluation with cine MR sleep studies

Cine magnetic resonance (MR) imaging sleep studies have become a useful tool in the evaluation of obstructive sleep apnea in children with certain categories of pathologic conditions. In this article, the author describes a program for the use of cine MR sleep studies in the evaluation of children with obstructive sleep apnea. The following areas are discussed: clinical indications, patient preparation, anatomic considerations, MR technique, technical issues, image interpretation, commonly encountered diagnoses, volume segmentation processing of data, and controversial areas.     

Defining normal upper airway motion in asymptomatic children during sleep by means of cine MR techniques

PURPOSE: To define normal upper airway motion in asymptomatic children during sleep by means of dynamic cine magnetic resonance (MR) techniques. MATERIALS AND METHODS: In children referred for MR of the brain who required sedation, a sagittal midline cine MR sequence was performed. Motion of the nasopharynx, oropharynx, and hypopharynx was characterized as static patent, dynamic patent, intermittent collapse, or static collapsed; maximal diameter and greatest change in size were calculated in millimeters. Mouth position (open or closed) was determined. Parameters were compared with age (t test) and mouth position (Fisher exact test). RESULTS: In the 148 subjects (mean age, 3.4 years), the nasopharynx showed dynamic motion in 53 (36%). The oropharynx was most commonly collapsed in 98 (66%) of the patients. The hypopharynx showed dynamic motion in 72 (49%) of the patients and was never collapsed. Vertical motion was present in 77 (52%) of the patients. The mouth was open in 96 (65%) of the patients. There was a statistically significant correlation between mouth position and dynamic motion in the oropharynx (P =.006) and in the nasopharynx (P <.006) but not in the hypopharynx (P =.655). CONCLUSION: Dynamic changes in diameter were often seen in the nasopharynx and in the hypopharynx of asymptomatic sleeping children. However, collapse of the hypopharynx was not normally encountered.     

正常人和阻塞性睡眠呼吸暂停综合征患者上呼吸道的CT测量及比较

目的：探讨上呼吸道各平面的正常参考值及对阻塞性睡眠呼吸暂停综合征(OSAS)的判断意义。方法：对42例健康人和27例OSAS患者采用螺旋CT自鼻咽顶壁平扫至环状软骨下缘平面，应用图像处理工作站有关测量技术，分别测量正常人和OSAS患者清醒状态下上呼吸道的软腭后区、悬雍垂区、舌后区和会厌后区的横截面积及冠、矢状径。将其测量数值分别除以环状软骨平面气道的相应值；探讨正常参考值范围，并与OSAS患者上呼吸道测量值比较。结果：上呼吸道四个平面的每组参考值各不相同，且男女之问参考值存在差异，而地区、身高和年龄等因素对其影响不大。42例健康人上呼吸道各平面横截面积低于参考值者5例(11．9％)，27例OSAS各平面的横截面积在正常参考值内者4例(14．8％)。结论：上呼吸道各平面的上述参考值有助于判断上呼吸道的狭窄，对OSAS的诊断和治疗方法选择有一定意义。     

Brain parenchyma motion: measurement with cine echo-planar MR imaging.

With echo-planar magnetic resonance (MR) imaging, the authors measured the intrinsic pulsatile motion of brain parenchyma. Phase-sensitive, electrocardiography-gated, two-dimensional cine images were acquired throughout the cardiac cycle by using a spin-echo, blipped echo-planar MR pulse sequence. Transverse and coronal planes were obtained in 14 healthy volunteers. Corrections were made for gross head motion. Brain motion consisted of a rapid displacement in systole, with a slow diastolic recovery. The motion occurred chiefly in the cephalocaudal and lateral directions; the anteroposterior motions were relatively small. Cephalocaudal velocities increase with proximity to the foramen magnum. The lateral motion is mainly a compressive motion of the thalami. Brain parenchymal velocities were as high as 2 mm/sec caudally in the brain stem and 1.5 mm/sec medially in the thalami. Net parenchymal excursions were at most 0.5 mm. Phase-based echo-planar velocity measurements agreed well with echo-planar Fourier velocity zeugmatography measurements and were consistent with reported values. Velocity mapping with echo-planar imaging offers a rapid and flexible method of assessing the pulsation velocities of the human brain.     

Occlusion and narrowing of the pharyngeal airway in obstructive sleep apnea: evaluation by ultrafast spoiled GRASS MR imaging.

Morphologic abnormalities of the pharyngeal airway are frequently found in patients with obstructive sleep apnea. These structural alterations in the pharyngeal airway can be detected in awake patients by using rapid imaging techniques. Ten patients with clinically proved obstructive sleep apnea had ultrafast spoiled gradient-recalled acquisition in the steady state (GRASS) MR imaging of the pharyngeal airway to determine the presence of occlusions and/or narrowings. Twelve sequential images were obtained at one midsagittal plane and at eight transverse planes through the pharyngeal airway. The scans were obtained at the rate of one image per 1.04 sec while the patient was breathing quietly. Occlusions or narrowings of the pharyngeal airways were detected on MR images in all patients. The site(s) of the occlusions and the site(s) and extent of the narrowings varied. Six patients had occlusions and four had narrowings of one or more sites. This study shows that ultrafast spoiled GRASS MR imaging can be used to evaluate patients with obstructive sleep apnea during tidal breathing and is useful for determining the presence of occlusions and narrowings of the pharyngeal airway.     

阻塞性睡眠呼吸暂停综合征(OSAS)清醒和呼吸暂停时上气道形态改变的CT动态研究

目的 对比研究OSAS患者清醒和呼吸暂停时上气道的形态学改变。方法 对15例OSAS患者上气道进行清醒和睡眠呼吸暂停时的CT扫描，分析清醒和睡眠呼吸暂停时上气道最狭窄处截面积的动态改变。结果 14例OSAS患者睡眠呼吸暂停时上气道最狭窄处面积比清醒时明显变小，1例上气道最狭窄处完全阻塞。结论 OSAS患者睡眠呼吸暂停时上气道最狭窄处截面积比清醒时明显变小或完全阻塞。     

Causes of persistent obstructive sleep apnea despite previous tonsillectomy and adenoidectomy in children with down syndrome as depicted on static and dynamic cine MRI

OBJECTIVE: Our purpose was to evaluate the causes of persistent obstructive sleep apnea despite previous tonsillectomy and adenoidectomy in children with Down syndrome as depicted on cine MRI. MATERIALS AND METHODS: Cine MRI studies performed to evaluate persistent obstructive sleep apnea despite previous tonsillectomy and adenoidectomy were reviewed. MRI was performed under sedation and included cine MR images (fast gradient-echo) obtained in the midline sagittal plane and in the axial plane at the base of the tongue and T1-weighted spin-echo and fast spin-echo inversion recovery images in the axial and sagittal planes. Imaging parameters reviewed included static and dynamic diagnoses made, frequency of recurrence and diameter of tonsillar tissue, and tongue morphology. RESULTS: Twenty-seven patients were identified (mean age, 9.9 years). Diagnoses included glossoptosis in 17 patients (63%), hypopharyngeal collapse in six (22%), recurrent and enlarged adenoid tonsils in 17 (63%), enlarged lingual tonsils in eight (30%), and macroglossia in 20 (74%). Of the 20 patients with macroglossia, 11 (55%) had absence of the normal median sulcus and 12 (60%) had evidence of fatty infiltration of the tongue musculature. CONCLUSION: Persistent obstructive sleep apnea in children with Down syndrome who have undergone previous adenoidectomy and tonsillectomy has multiple causes. The most common causes include macroglossia, glossoptosis, recurrent enlargement of the adenoid tonsils, and enlarged lingual tonsils.     

Third ventriculostomy patency: comparison of findings at cine phase-contrast MR imaging and at direct exploration.

BACKGROUND AND PURPOSE: Two-dimensional phase-contrast (PC) MR imaging is a known method for evaluating CSF flow after third ventriculostomy. In this study, we attempted to confirm the accuracy of cine PC MR imaging for determining the patency of a third ventriculostomy as compared with direct reexploration of the floor of the third ventricle. METHODS: We examined 11 patients with third ventriculostomies who had a total of 13 reoperations for symptomatic obstructive hydrocephalus. In 12 of the 13 reexplorations, cine PC MR studies were obtained before repeat surgery, and the diagnoses suggested by imaging were compared with intraoperative findings. RESULTS: Four of five patients who had no flow on MR images had new membranes that covered the orifice; the fifth patient still had a small perforation visible at the time of operation. Three of four patients who had subtle flow on MR images were found to have occlusion with new membranes; the fourth had an incomplete new membrane. Finally, two of three who had a patent ventriculostomy had completely open perforations without membrane formation; the third patient had nonobstructive early membrane formation. At 3 months' follow-up, two flow studies were read as subtle without any clinical symptoms; however, these eventually progressed to become symptomatic, and occlusion with new membrane formation was confirmed during surgical reexploration. CONCLUSION: Cine PC MR imaging is a reliable technique for detecting the patency of a third ventriculostomy, but minor flow, as defined in this report, appears to be an early sign of closure.     

Echo planar MR imaging of the liver: comparison of images with and without motion probing gradients

PURPOSE: To determine whether MR images with motion-probing gradients (MPGs) usefully improve lesion detection in comparison with MR images without MPGs. MATERIALS AND METHODS: Echo planar (EP) images without MPGs and with small and intermediate MPGs (gradient factor b = 2, 18, and 188 second/mm(2), respectively) were acquired for 61 hepatic lesions (21 hepatocellular carcinomas (HCCs), 19 metastases, eight hemangiomas, and 13 cysts). The lesion-to-liver signal intensity ratios (SIRs) of these lesions were calculated using EP images with and without MPGs. Qualitative analysis for detection of HCCs and metastases were also performed between the images without MPGs and with small MPGs. RESULTS: The SIRs of HCCs and metastases for the images with small MPGs were significantly higher than the values for the images without MPGs (P < 0.05), although no significant differences were found in the case of hemangiomas and cysts. In comparison to images without MPGs, images with small MPGs improved lesion detection of three metastases and six HCCs, and worsened lesion detection of two HCCs. CONCLUSION: Images with small MPGs may improve HCC and metastasis detection over images without MPGs.     

Determination of left ventricular volume and mass with use of biphasic spin-echo MR imaging: comparison with cine MR

In this study, the authors compared a new rapid spin-echo magnetic resonance (MR) imaging method, biphasic MR, with cine MR in the determination of left ventricular volume and mass in healthy volunteers. Biphasic spin-echo MR images covering the entire heart were obtained with use of the electrocardiogram R wave and the downslope of the T wave at both end diastole and end systole, respectively. Biphasic MR-determined values correlated well with small standard errors of the estimate (end-diastolic volume = 7.82 cm3, end-diastolic mass = 10.20 g, end-systolic mass = 10.08 g, ejection fraction = 2.62%) and were more reproducible. Cine MR-defined end-systolic volume was significantly larger (P less than .01) and ejection fraction was significantly smaller (P less than .005) than biphasic MR-determined values probably because of the uncertainty in isolating end systole with cine MR. Left ventricular volumes, mass, and ejection fraction are more accurately and reproducibly quantified in a more time-efficient manner with use of biphasic MR than with cine MR because of its significantly shorter image acquisition and reconstruction times.     

Correlation on cine MR imaging of size of adenoid and palatine tonsils with degree of upper airway motion in asymptomatic sedated children

OBJECTIVE: The objective of this study was to use MR fluoroscopy to evaluate variations in size of the adenoid and palatine tonsils and the relationship between tonsil enlargement and airway motion dynamics in asymptomatic children during sleep. SUBJECTS AND METHODS: We performed sagittal midline cine MR imaging (fast gradient-echo series: TR/TE, 8.2/3.6 sec; flip angle, 80 degrees; slice thickness, 8 mm; 128 consecutive images; imaging time, 2 min; displayed in cine mode) in children referred for MR imaging of the brain who required sedation. The largest transverse diameter of the adenoids was recorded. A subjective impression was made as to whether the adenoids were enlarged or normal in size. Palatine tonsils were considered enlarged when a soft-tissue mass was identified on the midline cine images, and maximum diameter was recorded. Enlarged and nonenlarged adenoid and palatine tonsil groups were compared using motion parameters (chi-square or Fisher's exact test): mouth position (opened or closed); vertical motion (present, absent); nasopharyngeal, oropharyngeal, and hypopharyngeal motion (static patent, dynamic patent, intermittent collapsed, or static collapsed, and greatest change in size). RESULTS: We studied 148 subjects who had a mean age of 3.4 years. The adenoid tonsils were considered enlarged in 64 patients (43%), and the palatine tonsils were considered enlarged in 29 patients (20%). The mean size of the enlarged adenoid tonsils was 11.6 mm and of the nonenlarged adenoid tonsils was 6.2 mm. Enlarged adenoids correlated with the open mouth position (p = 0.0242) and increased dynamic motion of the oropharynx (p = 0.0413). A trend was also seen for increased dynamic motion of the nasopharynx (p = 0.0723). Enlarged palatine tonsils correlated with an increased frequency of dynamic motion of the oropharynx (p = 0.0006) and the nasopharynx (p = 0.0033) and a trend for increased frequency of the open mouth position (p = 0.0692). CONCLUSION: Large adenoid and palatine tonsil size affects breathing dynamics of the upper airway even in asymptomatic children.     

Assessment of myocardial infarction in humans with (23)Na MR imaging: comparison with cine MR imaging and delayed contrast enhancement

PURPOSE: To demonstrate the feasibility of sodium 23 ((23)Na) magnetic resonance (MR) imaging for assessment of subacute and chronic myocardial infarction and compare with cine, late enhancement, and T2-weighted imaging. MATERIALS AND METHODS: Thirty patients underwent MR imaging 8 days +/- 4 (subacute, n = 15) or more than 6 months (chronic, n = 15) after myocardial infarction by using a (23)Na surface coil with a double angulated electrocardiogram-triggered three-dimensional gradient-echo sequence at 1.5 T. In addition, cine, inversion-recovery gradient-echo, and, in the subacute group, T2-weighted images (n = 9) were obtained. Myocardial infarction mass was depicted as elevated signal intensity or wall motion abnormalities and expressed as a percentage of total left ventricular mass for all modalities. Correlations were tested with correlation coefficients. RESULTS: All patients after subacute infarction and 12 of 15 patients with chronic infarction had an area of elevated (23)Na signal intensity that significantly correlated with wall motion abnormalities (subacute; r = 0.96, P <.001, and chronic; r = 0.9, P <.001); three patients had no wall motion abnormalities or elevated (23)Na signal intensity. Only 10 patients in the subacute and nine in the chronic group revealed late enhancement; significant correlation with (23)Na MR imaging occurred only in subacute group (r = 0.68, P <.05). Myocardial edema in subacute infarction correlated (r = 0.71, P <.05) with areas of elevated (23)Na signal intensity but was extensively larger. CONCLUSION: (23)Na MR imaging demonstrates dysfunctional myocardium caused by subacute and chronic myocardial infarction.     

持续气道正压通气治疗代谢综合征合并阻塞性睡眠呼吸暂停综合征

目的:观察持续气道正压通气(CPAP)治疗代谢综合征(MetS)合并阻塞性睡眠呼吸暂停综合征(OSAS)的效果。方法:35例诊断为MetS及OSAS患者,进行3个月的CPAP治疗。抽血检测CPAP治疗前后生化标记物的变化,包括血浆氮氧化合物(NOx,NO2-+NO3-)、非对称二甲基精氨酸、硫代巴比妥酸反应物、血浆IL-1β、IL-6、IL-8以及TNF-α等。结果:治疗3个月后,血浆NO水平明显增加,二甲基精氨酸、硫代巴比妥酸反应物质水平减低。血浆TNF-α、IL-6及IL-8水平也显著降低。结论:CPAP治疗可减轻OSAS合并MetS患者的炎症反应及氧化应激。     

Intravoxel incoherent motion diffusion-weighted MR imaging in differentiation of lung cancer from obstructive lung consolidation: comparison and correlation with pharmacokinetic analysis from dynamic contrast-enhanced MR imaging

Objectives

To test whether parameters derived from intravoxel incoherent motion (IVIM) can be used to distinguish lung cancer from obstructive pulmonary consolidation by comparing them with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)-derived parameters and to evaluate the correlation between these quantitative parameters.

Methods

A total of 31 lung cancer patients, confirmed by pathology and obstructive consolidations confirmed by positron emission tomography/computed tomography (PET-CT), were recruited. All of them were assessed with structural MRI and IVIM and 17 of them underwent additional DCE-MRI examinations. Parameters derived from IVIM and DCE-MRI in the tumour and consolidation were analysed, and the optimal cut-off values in differential diagnosis were obtained.

Results

ADC_total, D and f values were lower (P?<?0.05), while IAUC₆₀ was higher in lung cancers (P?=?0.013) compared with obstructive pulmonary consolidations. According to the ROC curve, ADC_total outperformed other perfusion and diffusion parameters with the optimal cut-off value of 1.409?×?10^-3 mm²/s (AUC?=?0.95). Poor correlations were found between parameters derived from IVIM and DCE-MRI.

Conclusions

IVIM-MRI is potentially useful in the differentiation of lung cancer and obstructive pulmonary consolidation. ADC_total, D and f may be reliable independent discriminating markers, but D ^* is variable with low diagnostic accuracy.

Key Points

? Lung cancer and consolidation differentiation is essential for treatment decision-making. ? Perfusion and diffusion characteristics of lesions could help differential diagnosis. ? IVIM can separate reflection of tissue diffusivity and microcapillary perfusion. ? The relationship between perfusion quantified by IVIM and DCE-MRI is controversial.     

MR spectroscopy features of brain in patients with mild and severe obstructive sleep apnea syndrome

PurposeWe investigated whether there are differences in metabolite ratios of different brain regions between mild and severe obstructive sleep apnea (OSA) patients.Materials and methodsA total of 17 mild OSA and 14 severe OSA patients were enrolled. N-acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr and NAA/Cho ratios were calculated by using multivoxel magnetic resonance spectroscopy (MRS) (TR: 1500, TE: 135 ms) from hippocampus, putamen, insular cortex, thalamus and temporal white matter. The relationship between the two groups was evaluated with Mann–Whitney U test.ResultsNAA/Cr ratios obtained from hippocampus was found to be significantly increased in severe OSA patients compared to mild OSA patients (P= .004). Cho/Cr ratios obtained from hippocampus and putamen in severe OSA patients were significantly increased when compared to mild OSA patients (P= .003 and P= .004, respectively). In addition, NAA/Cho ratios of putamen were significantly decreased in severe OSA patients when compared to mild OSA (P= .032).ConclusionMRS identified hypoxia-related metabolite and microstructural changes in hippocampus and putamen. The metabolite changes of increase in NAA/Cr and Cho/Cr ratios and decrease in NAA/Cho ratio were more pronounced with increasing severity of OSA syndrome.     

Uterine peristalsis: comparison of transvaginal ultrasound and two different sequences of cine MR imaging

PURPOSE: To compare uterine peristalsis as seen on two different magnetic resonance (MR) imaging sequences and transvaginal ultrasound (TVUS), so as to better determine the best method for evaluating uterine peristalsis. MATERIALS AND METHODS: Eleven women in the periovulatory phase of the menstrual cycle underwent TVUS and cine MR imaging within a time period of three hours. Findings on cine MR images obtained with a serial 60 half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence and a 300 true fast imaging with steady-state precession (FISP) sequence were compared with TVUS. RESULTS: The image quality of the HASTE technique was the best among the three methods, followed by TVUS, and then true FISP technique (P < 0.001). Uterine peristalsis was detected in 100% of subjects using HASTE, 82% with True FISP, and 100% with TVUS. With HASTE technique, true FISP, and TVUS, respectively, endometrial stripping movement was identified in 100%, 82%, and 100%; direction was identified in 100%, 45% (P = 0.014), and 73%; and wave conduction toward the outer myometrium was identified in 55%, 9% (P = 0.025), and 0% (P = 0.014). CONCLUSION: Cine MR imaging by HASTE technique with a time resolution of two seconds best delineated uterine peristalsis compared to that by true FISP technique or with TVUS.     

呼吸睡眠暂停低通气患者脑功能的功能性MRI诊断

目的:探讨静息状态下呼吸睡眠暂停低通气((SAHS)患者脑功能是否发生异常及经持续正压通气(CAPP)治疗后脑功能的改变情况.方法:搜集25例中重度OSAHS患者(患者组)及25例健康志愿者(对照组).患者CAPP治疗前后及健康志愿者均进行MRI平扫及血氧依赖水平功能性磁共振成像(BOLD-fMRI)检查.结果:与对照组相比,患者组治疗前右侧额中回等脑区的局部一致性减低,右侧岛叶等脑区的低频振幅(ALFF)值减低,右侧额下回等脑区的低频振幅比率(fALFF)值减低.与对照组相比,患者组治疗后右侧小脑半球等脑区的局部一致性减低,右侧楔叶等脑区的ALFF减低,右侧额下回等脑区的fALFF减低.与治疗前相比.患者组治疗后右侧颞下回等脑区的局部一致性明显增高,右侧小脑半球等脑区的ALFF增高,左侧枕中回等脑区的fALFF增高.结论:静息状态下OSAHS患者脑功能状态存在异常,经CAPP治疗后脑功能异常的脑区可部分逆转.功能性MRI对呼吸睡眠暂停低通气患者脑功能的诊断具有重要价值.     

evaluation of communication between intracranial arachnoid cysts and cisterns with phase-contrast cine MR imaging

BACKGROUND AND PURPOSE: The demonstration of communication between arachnoid cysts (ACs) and the adjacent subarachnoid space is a prerequisite for their proper management. CT cisternography (CTC) is the conventional method for functional evaluation of ACs. The sensitivity of MR imaging to CSF flow has been demonstrated, but reports of the clinical usefulness of MR CSF flow techniques in this application are limited. The purpose of our study was to prospectively evaluate the accuracy of MR CSF flow study as an alternative to CTC in this setting. METHODS: MR CSF flow study with retrospective ECG-gated 2D, fast low-angle shot, phase-contrast (PC), cine gradient-echo sequence was performed in 39 patients with an intracranial AC. Results were compared with intraoperative and CTC findings. RESULTS: PC cine MR imaging results were compatible with operative or CTC findings in 36 (92.3%) of 39 patients. Twenty-four cysts were noncommunicating, and 15 were communicating. Three cysts were evaluated as being noncommunicating on PC cine MR imaging (false-negative) but demonstrated contrast enhancement on CTC. No false-positive diagnoses occurred. All cysts regarded as being communicating on PC cine MR imaging were also found to be communicating on both confirmation methods. CONCLUSION: MR CSF flow imaging with a PC cine sequence can be incorporated in the imaging work-up of ACs. This is a reliable alternative to invasive CTC for the functional evaluation of ACs.