经济学人下载:医学技术 肌肤之下

Science and technology
科学技术

Medical technology
医学技术

Skin deep
肌肤之下

A better way to diagnose skin cancers
诊断皮肤癌的更好方法

DERMATOLOGISTS are good at spotting unusual bits of skin that might or might not be cancers.
皮肤病医学家擅长发现一小块异常皮肤是否有患癌症的可能性。

Testing whether they actually are, though, is quite literally a bloody pain.
但是，要检查出是否真患癌症的确会让人感到出血之痛。

For a piece of skin to be identified as malignant or benign it must be cut out and sent to a laboratory for examination under a microscope.
因为要鉴定一块皮肤是恶性还是良性，就必须剪下来，然后送到实验室的显微镜下检验。

But a team of researchers led by Rainer Leitgeb, a physicist at the Medical University of Vienna, hope to change that.
但是，由维也纳医科大学物理学家Rainer Leitgeb带领的研究小组希望改变这个现状。

As they describe in Biomedical Optics Express, Dr Leitgeb and his colleagues are exploring a technique called optical coherence tomography, which they think will allow skin cancer to be diagnosed in situ.
正如他们在《生物医学快报》上所描述的那样，Leitgeb博士和他的同事正在探寻光学相干断层成像术。在他们看来，使用这种技术能在原皮肤上进行皮肤癌诊断。

OCT is a form of optical echolocation. It works by sending infra-red light into tissues and analysing what bounces back.
OCT的原理是光学回声定位，先向身体组织发射红外线，

The behaviour of the reflected rays yields information on the structures that they collided with.
然后再分析反射回来的红外线。

That, Dr Leitgeb hoped, could be used to generate a map of features just beneath the surface of the skin.
Leitgeb博士希望，这能用来绘制显示皮肤表面下特征的地图。

Similar technology has been employed for nearly two decades by eye doctors and Dr Leitgeb felt that, with a bit of tinkering, it should work for skin as well.
相似的技术应用于眼科已有将近二十年的历史。Leitgeb博士认为，经过小小的改进，也能用于皮肤科。

The OCT systems operated by ophthalmologists use low-power lasers which produce light with a wavelength of 850 nanometres.
眼科医生操作的OCT系统使用的是低功率激光器，能够发出850纳米波长的光线，这刚好超出了眼睛视杆视锥层可感光的范围。

That is just beyond the range detectable by the rods and cones of the eye, and is thus ideal for probing that organ without discomforting the patient.
因此，既能够完成眼睛检查而又不给病人带来不适感，用这种激光再合适不过了。

Skin, however, is insufficiently transparent at this wavelength, so one thing Dr Leitgeb had to do was change it.
但是，皮肤在这种波长下还不够透明，因此Leitgeb博士所要做的就是进行改变。

Another thing which had to change was the speed at which the laser operates. In the ophthalmological system, images are built up from a series of pulses.
除此之外，还需要改变激光器发射的速度。眼科用的是脉冲成像的方法。

The more of these the laser sends in, the more light returns to the device and the higher the resolution of the resulting image.
激光器发射进去的激光越多，反射出来的光线也就越多，所成像的分辨率也就越高。

However, that image must be built up quickly, otherwise movement of the tissue being illuminated will blur it.
但是，必须迅速建构图像，否则受到照射的组织就会运动，使图像变得模糊不清。

For eyes, between 20,000 and 60,000 bursts a second is enough.
用于眼镜检查的脉冲每秒2万至6万就足够了。

But to photograph blood vessels inside skin Dr Leitgeb knew more would be needed. In the end, he commissioned a group of researchers at Ludwig-Maximilians University in Germany to design an instrument which produces light with a wavelength of 1,300 nanometres and has the ability to fire 440,000 pulses a second.
博士最终委托德国慕尼黑大学的一个研究小组设计了能够每秒产生1300纳米波长、44万脉冲的激光器。

With their new laser in hand, Dr Leitgeb and his colleagues set up an experiment that let them test the system on a range of skin conditions, including a healthy human palm, allergy-induced eczema on the forearm, inflammation of the forehead, and two previously diagnosed cases of basal-cell carcinoma.
有了新的激光器，Leitgeb博士和他的同事就开始进行实验，在不同状况的皮肤上测试人的器官系统，包括无任何疾病的手掌，前臂上过敏引起的湿疹皮肤，前额上有炎症的皮肤以及之前诊断过的两例基底细胞癌。

They expected to see normal blood vessels in the healthy palm, increased perfusion caused by dilated and altered vessels in the eczema and the inflammation, and a chaotic jumble of vessels feeding the cancers.
他们期待看到的结果是：无疾病手掌下的血管是正常的；前臂上的湿疹和有炎症的前额下的血管由于扩张和形变造成了灌注量的增加；而为癌细胞供血的血管乱七八糟扭成一团。

And that is exactly what they did see.
他们所看到的结果也正是如此。

Moreover, the images of the vessels supplying blood to the tumours were good enough to allow them to calculate blood-flow rates.
此外，供血给肿瘤的血管的图像十分清晰，他们还能计算出血流流速。

That, Dr Leitgeb suggests, could also help treatment by allowing doctors to identify the times during their development when tumours are most vulnerable to starvation by having their blood supply cut off.
博士认为，这对治疗也有帮助：医生能通过该方式鉴定肿瘤发展中最易因切断血液供给而饿死的阶段。