Some of the Reiki styles that have developed in Japan with little or no input from the West, use a system for sensing imbalances in the body called "byosen". Below are quoted extracts from Frank Arjava Petter's newsletters on the "byosen".
what is byosen scanning?
Byosen is the frequency that is emitted from a tense, injured or ill part of the body. But that’s not all there is to it. It is also the reaction of the body to the incoming Reiki energy. Resulting from that, an experienced practitioner can estimate the å needed for a treatment and the time needed for the recovery of the client.
All of the above sounds a little negative, but the good news is that the byosen is a sign of Life! You are alive!! Our body is in a constant movement of finding its natural balance.
the different processes in the body
The first step is to become aware of all the different processes in the body. You feel the energy flowing through your hand and into your client. You probably feel the pulse of your client. You may be aware of an energetic pulse of the body that you are touching. You may feel the movement of energy in the body you are touching. You feel the temperature, the texture and the density of the body. And, you may feel the byosen. Because of the multitude of the impressions, it is easier to feel the byosen in someone else's body. Because of that, it is easier to begin practicing with another. The easiest way to practice is with a client who is unwell, because the byosen will be strong and tangible.
levels of byosen
The byosen has five levels, all of which you probably have experienced in your practice. But you may not have been aware of the fact that there is a system to it. In general the following is universally true. But you may discover your own individual way of experiencing the byosen. Let it teach you.
the five levels are:
Heat. This heat is above body temperature.
Strong heat. This heat makes your palms sweat
Tingling. The tingling can be experienced as pins and needles, as a magnetic feeling or as your hands falling asleep / feeling numb.
Pulsation, cold. The pulsation can be strong or weak, slow or fast. When the place you touch feels cold, it is not the fault of your hands, but a sign of Byosen level 4.
Pain in the hand of the practitioner. This pain may be felt in the hand, in the fingers or in the back of the hand. It may move up your hand into the forearm and may continue all the way up to your shoulder. If that happens, don't worry. Koyama Sensei said that pain happens when positive Reiki Energy flows into a strongly negatively charged body area. All that you need to do is to stay there until it goes away. Change your hands if it becomes too uncomfortable or take them off for a while. Then place them on the same spot again. Don't be afraid to be contaminated by "bad" energy. Reiki is a one-way street.
Byosen doesn’t remain constant, but it moves in cycles. Usually these cycles come and go in intervals of 10- 15 minutes. That means you have to focus for longer periods of time in order to be able to detect the byosen.