約翰-霍普金斯醫(yī)學(xué)安裝了一臺(tái)相信擁有世界最先進(jìn)CT顯像軟件和裝置的256排CT掃描機(jī)，已經(jīng)開始為期3個(gè)月的安全性和臨床評(píng)估。

這個(gè)重達(dá)2噸新裝置，在北美是第一臺(tái)，此外，僅日本還有一臺(tái)，是其前身-----64排CT探測(cè)覆蓋率的4倍，能夠檢測(cè)血流精細(xì)的變化或心腦中不粗于1.5毫米牙簽的血管中形成的微小血栓。

生產(chǎn)產(chǎn)家說(shuō)，產(chǎn)于日本東芝公司的Aquilion beta 256 預(yù)期在1年之內(nèi)批準(zhǔn)獲得廣泛臨床應(yīng)用。霍普金斯醫(yī)學(xué)正在協(xié)商該裝置的價(jià)格，其標(biāo)價(jià)為100萬(wàn)美元。

約翰-霍普金斯醫(yī)學(xué)負(fù)責(zé)所有心血管方面的檢測(cè)的心血管專家João Lima博士說(shuō) ，該設(shè)備的優(yōu)勢(shì)在于在癥狀出現(xiàn)之前或出現(xiàn)永久器官損害之前能夠發(fā)現(xiàn)受限血流最早期的跡象。

約翰-霍普金斯大學(xué)醫(yī)學(xué)院和心臟研究所副教授Lima說(shuō)，任何器官中動(dòng)脈、靜脈或毛細(xì)血管阻塞能夠緩慢發(fā)展多年，只有在疾病嚴(yán)重到威脅生命時(shí)才出現(xiàn)胸痛、重度疲勞和頭痛癥狀。

256-CT的關(guān)鍵技術(shù)進(jìn)步（看起來(lái)想病人桌子被巨大的圈餅形狀的金屬環(huán)所圍繞，稱為中央構(gòu)架）是更多的探頭數(shù)量，每個(gè)探頭掃描范圍是64-CT的4倍。霍普金斯醫(yī)學(xué)目前有一臺(tái)64排CT掃描機(jī)。

根據(jù)公司介紹，該裝置X線發(fā)射結(jié)構(gòu)單次旋轉(zhuǎn)能夠形成直徑為12.8厘米（5英寸）顯像，單層厚度足夠一次性覆蓋大多數(shù)單一器官，包括腦、心臟、完整關(guān)節(jié)、肺的大部和肝臟。這是64排CT3.2厘米顯像覆蓋范圍的提高，64排CT需要幾次旋轉(zhuǎn)或掃描完成單個(gè)器官的顯像。

國(guó)際神經(jīng)系放射專家、霍普金斯大學(xué)放射科副教授Kieran Murphy博士說(shuō)，他相信整個(gè)頭部灌注顯像掃描能夠發(fā)現(xiàn)大腦中易于導(dǎo)致中風(fēng)的血流緩慢區(qū)域，且只要一次掃描。

CT顯像由X線穿透機(jī)體產(chǎn)生可檢測(cè)的數(shù)字信號(hào)和計(jì)算機(jī)重建組成。新式裝置中256個(gè)探頭中每個(gè)都可捕獲器官或組織一層信號(hào)。探頭越多，圖像的顯像度就越好。計(jì)算機(jī)組合所有層信號(hào)并合成詳細(xì)的心臟或腦及周圍血管的三維圖像。某些情況下，患者被注射顯影劑增加更多的細(xì)節(jié)。

負(fù)責(zé)該掃描機(jī)在神經(jīng)學(xué)檢測(cè)的Murphy說(shuō)擴(kuò)展的覆蓋范圍比老式機(jī)器具有巨大優(yōu)勢(shì)，老式機(jī)器需要匹配和重疊成像，隨時(shí)間推移，類似于每層大理石上面重建多層的復(fù)雜技術(shù)程序。他也提到，冷卻系統(tǒng)不再需要處理因結(jié)構(gòu)多次旋轉(zhuǎn)造成的摩擦和熱量，雖然計(jì)算機(jī)軟件仍然需要冷卻系統(tǒng)。Murphy說(shuō)256-CT的每層掃描的數(shù)據(jù)輸出量增加至5-10十億位元組，而64-CT只有1至2.5十億位元組。

但是，他不期望更高的數(shù)據(jù)容量減慢檢查，256-CT加速至少于1秒鐘對(duì)大腦顯像，64-CT需要4或5秒。Lima說(shuō)，256-CT行心臟檢查所需總時(shí)間同樣降低至1或2秒，而64-CT需要8或10秒。Lima說(shuō)，新型快速的裝置也將使對(duì)心律不齊或不規(guī)則心律患者掃描成為可能。256-CT只一次心跳間隔時(shí)間中完成全部成像，而64-CT需要更長(zhǎng)時(shí)間-----6或8次心跳間隔時(shí)間。他說(shuō)，連續(xù)心跳之間的任何干擾，如心律不齊中產(chǎn)生的，能夠?qū)е潞铣傻膾呙鑸D像扭曲。

256-CT的單次掃描同樣可以提供病情最嚴(yán)重患者全部5個(gè)重要的心臟診斷檢查或腦部單個(gè)檢查，使他們暴露在射線中更少，約64排-CT掃描所需劑量的1/8到1/3。由于256-CT單次掃描應(yīng)該提供用來(lái)檢查動(dòng)脈硬度的患者鈣化、血流數(shù)據(jù)、心跳和脈搏強(qiáng)度，其為更多侵入性檢查（如心導(dǎo)管術(shù)或腦部血管導(dǎo)管造影術(shù)）更準(zhǔn)確決定最適患者期待有價(jià)值。

新的掃描師和9個(gè)技師從東芝公司美國(guó)醫(yī)療系統(tǒng)有限公司租借至霍普斯金。霍普斯金的臨時(shí)安裝和更新費(fèi)用也由東芝公司承擔(dān)。

點(diǎn)評(píng)：從16到64再到256，隨技術(shù)的進(jìn)步，成像技術(shù)會(huì)越來(lái)越先進(jìn)，但是任何診療過(guò)程均應(yīng)以醫(yī)師為主、檢查為輔，國(guó)內(nèi)部分醫(yī)院盲目引進(jìn)、跟風(fēng)引進(jìn)，不顧國(guó)情，導(dǎo)致患者和醫(yī)院負(fù)擔(dān)加重，資源浪費(fèi)。

New CT Scanner - 256-slice - Being Tested In North America

Johns 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 João 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。Lima says the overall time required for testing the heart will similarly decline to 1 or 2 seconds with the 256-CT, from eight to 10 seconds with the 64-CT。

Lima says the new, faster device will also make it possible to scan patients with arrhythmia, or irregular heartbeats。The 256-CT can acquire a full image in the time it takes for just one beat, whereas the 64-CT takes longer, as much as six or eight heartbeats。Any disturbances between successive beats, he notes, such as those produced in arrhythmia, can lead to distortions in the composite scanned image.

A single scan with the 256-CT device can also perform a full bank of five key diagnostic tests on hearts or single tests in the brain of the most severely ill patients, exposing them to far less radiation, as little as one-eighth to one-third of the dose required in testing with the 64-slice scanner。

Because single scans with the 256-CT should provide a patient's calcium score, to detect hardening of the arteries, along with