Help on Illuminating the Interior of a Blood Vessel

[Byteman3D]

I'm working on a medical animation consisting of a camera travelling inside the human vessel, while several particles are passing by. Furthermore, this is a 360 degrees panoramic animation.

Wherever I put the light, there is always a harsh light explosion on the particles passing close by. Highlight compress helps to some extent but still not enough- plus the image looses contrast.
I need the Light exclude function to exclude the particles but illuminate only the vein walls from the center of the vein (which is possible), while with separate light objects, illuminate the blood particles from outside the vein, which is not possible.

I need a soft illumination without harsh hotspots. Any recommendations?

[wilbertvandenbroek]

Trying to render in seperate scene files / layers and comping them?

[mferster]

Have you tried using an hdri and then just turning off cast shadows on your blood vessels?

Attached is a quick test I came up with using the method I  described above.

Using a combination of a studio style hdri that is being blurred, with the blood vessel having cast shadows turned off.
Then I used a combination of  maps in self illumination to make the blood vessels itself.

[TomG]

Another option to consider, which may or may not be suitable, is to use Self Illumination, or even a Light Mtl with emit light off, for the blood cells. This is a way to get that "electron microscope" look when combined with a falloff controlling the color of the Self Illumination / Light, so could be quite suited for this type of shot. You would create some falloff of reds and plug that in. If going for Self Illumination it could also be simply added in to an existing material just to enhance lighting (meaning the cells wouldn't need a strong actual light to illuminate them).

[Byteman3D]

Thank you all for your kind efforts to help.

@wilbertvandenbroek ,  separate layers will give the best control, but I am not very good at controlling multi layer projects. I frequently change things during scene manipulation (most frequently move the camera) and unintentionally mess up everything. That is why I'm trying to avoid multiple renders.
@TomG I am indeed using falloff maps for some of the particles' materials.
@mferster I have disabled shadow casting of the vein object. (I need it to receive shadows so it is enabled) Placed a light in the center of the vein only lluminating the vein with Include function. The vein interior is OK with this. ( I also have Volume materials creating some sort of fog in the distance)  Also added lights from outside illuminating the particles, excluding the vein. This was also ok with one exception: Shadows were too dark.
Now with the HDR idea shadows are ok, too.