标题: 256排新式CT扫描机在北美试机 [打印本页] 作者: 天南地北 时间: 2007-5-18 08:38 标题: 256排新式CT扫描机在北美试机 title:new ct scanner - 256-slice - being tested
in north americajohns hopkins medicine has
installed for three months
of initial safety and clinical testing a 256-slice computed tomography (ct)
scanner, believed to be the world'；s most advanced ct
imaging software and machinery. the new 2-metric-ton device - the first
of its kind in north america and only the second outside of japan, where
its manufacturer is based - has four times the detector coverage of its
immediate predecessor, the 64-ct. it can measure subtle changes in blood
flow or minute blockages forming in blood vessels no bigger than the
average width of a toothpick (1.5 millimeters) in the heart and brain.
made by toshiba, the aquilion beta 256 is expected to win approval for
general clinical use within a year, its makers say. hopkins is negotiating
purchase of the equipment, whose sticker price is more than $1 million.
johns hopkins cardiologist jo?o lima, m.d., who will lead all cardiovascular
testing, says the scanner'；s strength means it can find the earliest signs
of restricted blood flow, long before symptoms appear or an organ becomes
permanently damaged. lima, an associate professor at the johns hopkins
university school of medicine and its heart institute, says blockages in
arteries, veins or capillaries in any organ can simmer for years, with signs
of chest pain, severe fatigue and headache emerging only after the disease
has become seriously life-threatening. the key technological advance of
the 256-ct, which looks like a patient table surrounded by a massive,
doughnut-shaped metal ring, called a central gantry, is its greater number
of detectors, which cover in a single scan four times the area of the 64-ct.
hopkins currently has a 64-slice ct scanner. according to company
descriptions, a single rotation of the device'；s x-ray-emitting gantry can
image a diameter of 12.8 centimeters (or 5 inches), a slice thick enough to
capture most individual organs in one swoop, including the brain and heart,
entire joints, and most of the lungs and liver. this is an increase in coverage
from 3.2 centimeters per image with the 64-slice, which required several
rotations or scans to fully image an organ. interventional neuroradiologist
kieran murphy, m.d., an associate professor of radiology at hopkins, says
he believes that whole-head perfusion imaging scans will be able to find
slowed blood flow areas in the brain that are vulnerable to stroke, and with
just one scan. ct imaging consists of x-rays sent through the body to produce
digitized signals that can be detected and reconstructed by computers.
each of the 256 detectors on the new machine picks up a "slice" of an organ
or tissue. the more detectors, the better is the resolution of the picture.
a computer puts all the slices together to render detailed, 3-d images of
the heart or brain and surrounding arteries. in some cases, a patient is
injected with a contrast solution to increase the visual detail.murphy, who is
in charge of neurological testing with the scanner, says the expanded
coverage is a "tremendous advantage" over older machines, where images
had to be matched and stacked, "like reconstructing layers of a marble
statue on top of each other over time," a technologically complex procedure.
cooling systems, he also notes, will no longer be required to deal with the friction
and heat caused by multiple rotations of the gantry, although a cooling system
will still be required for the computer hardware. murphy says the increase in data
traffic will range from 5 gigabytes to 10 gigabytes per scan with the 256-ct.
with 64-ct, the range is 1gigabyte to 2.5 gigabytes. however, he does not
expect the higher volume of data to slow testing, which is expected to speed
up imaging the brain to less than 1 second for the 256-ct, down from 4 or 5
seconds with the 64-ct.作者: 天南地北 时间: 2007-5-18 08:40
约翰-霍普金斯医学安装了一台相信拥有世界最先进ct显像软件和装置的256排ct扫描机，已经开始为期3个月的安全性和临床评估。
这个重达2吨新装置，在北美是第一台，此外，仅日本还有一台，是其前身-----64排ct探测覆盖率的4倍，能够检测血流精细的变化或心脑中不粗于1.5毫米牙签的血管中形成的微小血栓。
生产产家说，产于日本东芝公司的aquilion beta 256 预期在1年之内批准获得广泛临床应用。霍普金斯医学正在协商该装置的价格，其标价为100万美元。
约翰-霍普金斯医学负责所有心血管方面的检测的心血管专家jo?o lima博士说 ，该设备的优势在于在症状出现之前或出现永久器官损害之前能够发现受限血流最早期的迹象。
约翰-霍普金斯大学医学院和心脏研究所副教授lima说，任何器官中动脉、静脉或毛细血管阻塞能够缓慢发展多年，只有在疾病严重到威胁生命时才出现胸痛、重度疲劳和头痛症状。
256-ct的关键技术进步（看起来想病人桌子被巨大的圈饼形状的金属环所围绕，称为中央构架）是更多的探头数量，每个探头扫描范围是64-ct的4倍。霍普金斯医学目前有一台64排ct扫描机。
根据公司介绍，该装置x线发射结构单次旋转能够形成直径为12.8厘米（5英寸）显像，单层厚度足够一次性覆盖大多数单一器官，包括脑、心脏、完整关节、肺的大部和肝脏。这是64排ct3.2厘米显像覆盖范围的提高，64排ct需要几次旋转或扫描完成单个器官的显像。
国际神经系放射专家、霍普金斯大学放射科副教授kieran murphy博士说，他相信整个头部灌注显像扫描能够发现大脑中易于导致中风的血流缓慢区域，且只要一次扫描。
ct显像由x线穿透机体产生可检测的数字信号和计算机重建组成。新式装置中256个探头中每个都可捕获器官或组织一层信号。探头越多，图像的显像度就越好。计算机组合所有层信号并合成详细的心脏或脑及周围血管的三维图像。某些情况下，患者被注射显影剂增加更多的细节。
负责该扫描机在神经学检测的murphy说扩展的覆盖范围比老式机器具有巨大优势，老式机器需要匹配和重叠成像，随时间推移，类似于每层大理石上面重建多层的复杂技术程序。
他也提到，冷却系统不再需要处理因结构多次旋转造成的摩擦和热量，虽然计算机软件仍然需要冷却系统。murphy说256-ct的每层扫描的数据输出量增加至5-10十亿位元组，而64-ct只有1至2.5十亿位元组。
但是，他不期望更高的数据容量减慢检查，256-ct加速至少于1秒钟对大脑显像，64-ct需要4或5秒。lima说，256-ct行心脏检查所需总时间同样降低至1或2秒，而64-ct需要8或10秒.
lima说，新型快速的装置也将使对心律不齐或不规则心律患者扫描成为可能。256-ct只一次心跳间隔时间中完成全部成像，而64-ct需要更长时间-----6或8次心跳间隔时间。他说，连续心跳之间的任何干扰，如心律不齐中产生的，能够导致合成的扫描图像扭曲。
256-ct的单次扫描同样可以提供病情最严重患者全部5个重要的心脏诊断检查或脑部单个检查，使他们暴露在射线中更少，约64排-ct扫描所需剂量的1/8到1/3.
由于256-ct单次扫描应该提供用来检查动脉硬度的患者钙化、血流数据、心跳和脉搏强度，其为更多侵入性检查（如心导管术或脑部血管导管造影术）更准确决定最适患者期待有价值。
新的扫描师和9个技师从东芝公司美国医疗系统有限公司租借至霍普斯金。霍普斯金的临时安装和更新费用也由东芝公司承担。
