自由呼吸状态下宽体探测器CT单心动周期冠脉造影的可行性

目的:探讨心率75次/min患者在自由呼吸状态下行320排CT冠脉造影(coronary CT angiography, CCTA)的可行性,并评价图像质量及辐射剂量。方法:共有94例心率75次/min的疑似冠心病患者,采用联影320排CT以前瞻性心电门控技术,单个心动周期扫描行CCTA。根据患者呼吸方式分为2组:屏气组47例,自由呼吸组47例。测量各组患者主动脉的信噪比(SNR),左主干(LM)近段和中段、前降支(LAD)近段、回旋支(LCX)近段、右冠状动脉(RCA)近段及中段的对比噪声比(CNR),主动脉、LM和RCA的CT值及主动脉的标准值。由2名放射科医生以5分法对94例患者进行冠脉18分段图像质量进行双盲评价,分数≥3分符合诊断标准。结果:2组患者的CNR、SNR和CT值差异均无统计学意义。屏气组和自由呼吸组冠脉节段评分5分者分别占68.8%、67.4%,4分者分别占18.0%、20.3%,3分者分别占10.2%、10.4%,差异无统计学意义。自由呼吸组辐射剂量少于屏气组(P0.01)。结论:对于心率75次/min的患者,采用自由呼吸与标准屏气进行320排宽体CT进行CCTA的图像质量无明显差异,说明对于该类患者,自由呼吸CCTA是一种可行方案。     

The trigeminocardiac reflex – a comparison with the diving reflex in humans

The trigeminocardiac reflex (TCR) has previously been described in the literature as a reflexive response of bradycardia, hypotension, and gastric hypermotility seen upon mechanical stimulation in the distribution of the trigeminal nerve. The diving reflex (DR) in humans is characterized by breath-holding, slowing of the heart rate, reduction of limb blood flow and a gradual rise in the mean arterial blood pressure. Although the two reflexes share many similarities, their relationship and especially their functional purpose in humans have yet to be fully elucidated. In the present review, we have tried to integrate and elaborate these two phenomena into a unified physiological concept. Assuming that the TCR and the DR are closely linked functionally and phylogenetically, we have also highlighted the significance of these reflexes in humans.     

主动呼吸控制结合光学体表监测在左侧乳腺癌深吸气屏气放疗呼吸训练中的应用

目的探讨左侧乳腺癌深吸气屏气(Deep Inspiration Breath-Hold,DIBH)放疗中使用主动呼吸控制(Active Breathing Coordinator,ABC)下光学体表监测DIBH的可行性以及幅度变化范围,比较两种呼吸状态下剂量学差异。方法15例左侧乳腺癌保乳术后拟行全乳放疗患者,使用ABC设备控制病人吸气量,同时使用光学体表监测设备监测病人体表呼吸幅度变化。分别在自由呼吸(Free Breathing,FB)以及最大吸气量的80%状态采集CT图像,使用Pinnacle计划系统分别在两套图像上计划设计,对CT图像上两种状态双肺体积差值与ABC吸气量阈值配对t检验。计算光学体表DIBH幅度与最大吸气幅度比值;DIBH幅度与FB幅度比值;DIBH使用ABC控制显示吸气量无变化的情况下,光学体表幅度下降超过3 mm的百分比,比较两种呼吸状态下剂量学差异。结果15例患者FB与DIBH的CT影像上双肺体积差值与ABC吸气量阈值无明显差异(P>0.05)。80%最大吸气量幅度平均为12.1 mm,95%CI为(11.4~14.1)mm。80%最大吸气量幅度与最大吸气幅度比值为0.78±0.12,80%最大吸气量幅度与FB幅度比值为3.24±1.08。DIBH使用ABC控制显示吸气量无变化的情况下,光学体表幅度下降超过3 mm,占比10.8%。DIBH与FB相比,心脏平均剂量、V₁₀、V₂₀、左肺平均剂量、全肺V₂₀均显著减低(P<0.001)。结论在左侧乳腺癌保乳术后放疗呼吸训练中,使用光学体表监测设备实现高质量DIBH是有效的。     

深吸气屏气技术在左侧乳腺癌保乳术后动态容积旋转调强放疗中的剂量学分析

目的:比较深吸气屏气(deep inspiration breath-hold,DIBH)和自由呼吸(free breathing,FB)两种呼吸模式在左侧乳腺癌保乳术后动态容积旋转调强（volumetric modulated arc therapy,VMAT）放疗中的剂量学差异,探寻左侧乳腺癌保乳术后放疗最佳呼吸模式。方法:选取11例左侧乳腺癌保乳术后女性患者,分别在DIBH-CT和FB-CT图像上设计切线弧t-VMAT计划。结果:DIBH呼吸模式下心脏V5、V10、V20、V30、Dmean、左冠状动脉前降支Dmean、左肺Dmean、右肺V5、Dmean及右侧乳腺V5、Dmean均低于FB呼吸模式,且差异均有统计学意义（P均＜0.05）,其中心脏、左冠状动脉前降支LAD及左肺平均剂量分别下降26.2%、47.7%和11.8%。结论:DIBH呼吸模式显著降低了心脏及左冠状动脉前降支等危及器官的受照剂量,采用t-VMAT计划缩短了深吸气屏气技术的治疗时间,提高了患者舒适度,更好的保证治疗顺利进行。     

Single breath-hold volumetric imaging of the heart using magnetization-prepared 3-dimensional segmented echo planar imaging

We show the feasibility of single breath-hold volumetric imaging of the heart using a three-dimensional (3D) segmented echo planar Imaging (EPI) pulse sequence. Fifteen healthy subjects were evaluated using three magnetization preparation schemes: (a) a driven equilibrium T2-weighted preparation for bright blood and dark myocardium; (b) a STEAM magnetization preparation for dark blood; and (c) fat suppression for coronary artery Imaging. An interleaved EPI trajectory encoding six echoes per Interleave with a 1090 Hz/pixel readout bandwidth was used to collect a 126 × 256 matrix in 22 heartbeats with data acquisition windows per cardiac cycle of 71–285 msec for 8–32 sections. Multiplanar reconstructions could be used if thin (1–3 mm) sections were acquired. Breath-hold volumetric imaging with 3D segmented EPI holds promise for rapid volumetric evaluation of cardiac anatomy.     

EPI Imaging of Global Increase of Brain MR Signal with Breath-hold Preceded by Breathing O2

Brain MR signal has been observed to decrease during cessation of breathing due to the increase of deoxyhemoglobin in the blood. However, for both animal and human studies, we have demonstrated that if the subjects breathed 100% oxygen in advance of apnea for a short time, T₂*-weighted MR brain signal increased when breathing was stopped for a period of 30–60 s. This demonstrates the possibility of measuring responses to hemodynamic change throughout the entire brain with a single respiratory perturbation in a rapid, reliable, and robust manner.     

A monitoring,feedback, and triggering system for reproducible breath-hold MR imaging

A technique is described that provides improved reproducibility of breath-holding for MR image acquisition by monitoring the superior-inferior (S/I) position of the diaphragm. The method incorporates detection of the level of inspiration using an MR signal, rapid display to the patient of diaphragm position to enable breath-hold adjustment, and triggering of image data acquisition once appropriate position is attained. The response time of the system is short, approximately 10 ms. Studies in six volunteers using this method demonstrate a considerable decrease in the S/I range of diaphragm position over 10 consecutive periods of suspended respiration. The mean range is 1.3 mm with the system, while it is 8.3 mm without using it is expected that this method will be of assistance in many abdominal and cardiothoracic studies that use breath-hold techniques.     

A novel technique for localization of small pulmonary nodules

BACKGROUND: To show the safety and accuracy of a new marking technique using an image-guided technique for preoperative localization of a small pulmonary nodule. METHODS: CT data of a patient with a peripheral pulmonary nodule < 20 mm were transmitted to a surgical navigation system (StealthStation Treon Treatment Guidance System; Medtronic; Louisville, KY). To match preoperative CT image data to the physical space occupied by the patient during surgery, five to six superficial skin fiducials were used for registration. A 16-gauge needle attached by a positioning sensor was advanced into or immediately adjacent to the nodule for injection of methylene blue under guidance of the StealthStation system. Then the lesion marked by the methylene was thoracoscopically resected. RESULTS: Seventeen patients (12 men and 5 women; mean age, 51.3 years) underwent this procedure, and all the nodules were identified due to the precise location of the probe. They were resected with sufficient margins. There were no surgical complications. The average time of registration was 4.8 +/- 0.9 min (+/- SD). Registration error was on average 2.7 +/- 0.2 mm. CONCLUSIONS: Image-guided navigation is useful, accurate, and safe in the localization of small peripheral lung lesions.     

The human diving response, its function, and its control

The purpose of this review is to outline the physiological responses associated with the diving response, its functional significance, and its cardiorespiratory control. This review is separated into four major sections. Section one outlines the diving response and its physiology. Section two provides support for the hypothesis that the primary role of the diving response is the conservation of oxygen. The third section describes how the diving response is controlled and provides a model that illustrates the cardiorespiratory interaction. Finally, the fourth section illustrates potential adaptations that result after regular exposure to an asphyxic environment. The cardiovascular and endocrine responses associated with the diving response and apnea are bradycardia, vasoconstriction, and an increase in secretion of suprarenal catecholamines. These responses require the integration of both the cardiovascular system and the respiratory system. The primary role of the diving response is likely to conserve oxygen for sensitive brain and heart tissue and to lengthen the time before the onset of serious hypoxic damage. We suggest that future research should be focused towards understanding the role of altered ventilatory responses in human breath-hold athletes as well as in patients suffering from sleep-disordered breathing.     

Percutaneous MR Imaging–Guided Cryoablation of Small Renal Masses in a 3-T Closed-Bore MR Imaging Environment: Initial Experience

Purpose

To assess the feasibility of percutaneous magnetic resonance (MR) imaging–guided cryoablation of small renal masses (SRMs) in a 3-T environment and to evaluate intraprocedural imaging, procedural safety, and initial outcomes.