医疗城 · 设备实验室 · 第 16 台，共 69 台
热疗系统
Hyperthermia System
BMEssentia 医疗城设备实验室中的热疗系统。以可交互 3D 打开设备，逐个部件拆解，了解其工作原理，然后在 BMEssentia 平台上系统学习，并向 Essentia 提问。
本页的设备实验室内容为英文，与医疗城中的内容一致。
- 10 个部件
- 设备实验室中有 2 种配置
设备实验室
Hyperthermia System
56 MHz through a matching network. At this frequency the wavelength in muscle is about a metre, so nothing here is a wave: the electrodes drive a current and the field is whatever the plates and the body between them make it. A water bolus sits against the skin under each electrode, and it is the only reason the arrangement is usable at all.
配置
设备实验室中的各个版本。
Capacitive radiofrequency heating between opposed electrodes
56 MHz through a matching network. At this frequency the wavelength in muscle is about a metre, so nothing here is a wave: the electrodes drive a current and the field is whatever the plates and the body between them make it. A water bolus sits against the skin under each electrode, and it is the only reason the arrangement is usable at all.
Phased microwave applicator array with a steered focus
Eight water-loaded apertures in a ring around the patient, each on its own amplifier with its own amplitude and phase against a common reference. At these frequencies the wavelength in muscle is comparable to the body, so the elements interfere, and setting the phases so that their contributions arrive together at one point steers a focus there. The bolus that fills the ring is part of the antenna rather than an accessory to it.
工作原理
在设备实验室中探索。
The exchange rate, and why it breaks
Set a temperature and a time and read four numbers together: the dose rate at that temperature, the dose rate one degree above it, one degree below it, and the time each of those would need to reach the same total.
The coldest point governs, and nothing looks for it
Set a perfusion spread across the target and read the temperature at both of its poles, then the dose at each, then the ratio between them.
Perfusion answers back
Step the power up in equal increments and watch the temperature. It does not rise in equal increments, and the reason is in the denominator.
One ratio, and the two configurations invert it
Compute the specific absorption in fat against the specific absorption in muscle, twice, for the two ways a field can meet a layer.
The focus, and the frequency that makes it useless
Step the frequency through the range the array offers and read two numbers at each setting: how far the field penetrates, and how wide the interference maximum is.
部件
逐个部件讲解。
Radiofrequency generator, exciter and final amplifier
Two rack modules low in the cabinet, one of them small and one of them most of the weight. The small one is a crystal oscillator and a driver; the large one is a bank of transistors bolted to a finned heatsink, with a circulator and a load bolted beside it.
Impedance matching network and tuner
A box on the applicator support rather than in the cabinet, close enough to the applicator that the line between them is short. Inside it two glass cylinders with copper spirals visible through them, a coil of heavy copper wire, and a small stepper motor on top of each cylinder.
Directional coupler and forward-reflected power measurement
A short length of line with two small ports on it and a detector behind each one, inside the cabinet on the way out. It is the least impressive object in the energy chain and it is the only one that can tell you the difference between the power the generator made and the power the patient accepted.
Coaxial feed line, balun and applicator connector
Rigid silvered line inside the cabinet, a flexible braided run out to the applicator support, and a heavy threaded connector at every change. At the applicator end there is a short cylinder around the cable that is not a connector at all: it is a balun, and without it the outside of the cable is half the antenna.
Temperature-controlled water bolus and membrane
On the capacitive pair, two flat bags of water: one between the upper electrode and the skin, one recessed into a cut-out in the couch pad under the patient’s back. On the array, a single volume of water filling the whole bore, with the patient inside it.
Deionised water circuit, chiller and degasser
The bottom third of the cabinet. A refrigeration unit with a compressor and a finned condenser, a reservoir with a sight level, a roller pump, a tall clear column that removes dissolved gas, a small stainless cell with two electrodes in it, and a heater.
Multi-sensor fibre-optic thermometry and its catheters
Fine fibres inside closed-tip catheters about a millimetre and a half across, with small beads visible along the last few centimetres of each one and a connector block on the front of the console. There is no wire anywhere in them.
Thermometry mapping drive and reference bath
A small motorised carriage on a stand at the head of the couch, with a lead screw, a clamp holding the proximal end of a fibre, a scale along the travel, and a stirred stainless vessel beside it. The carriage moves about a hundred millimetres in five-millimetre steps and it does so throughout the treatment.
Thermal-dose accumulator and power controller
A board in the cabinet with a processor, a small integrator block and a non-volatile store. Nothing about it looks like the most interesting component in the machine and it is: it is the part that converts a temperature into a dose, and the relationship it applies is the one thing on this device that has to be understood rather than trusted.
Surface-temperature, reflected-power and patient-stop interlocks
Three unrelated things wired into one chain. Small sensor patches under the edge of the bolus where the hottest skin is.