Messvolumen

Messvolumen, literally "measurement volume," is a term used in experimental measurement to denote the spatial region from which a signal or measurement originates. It is the effective detection volume defined by an instrument's optics, geometry, and data-processing aperture, and it may differ from the physical sample volume.

In imaging and spectroscopy, the Messvolumen describes the region that contributes to the detected signal. In confocal microscopy, for example, the measurement volume is a small, three-dimensionally confined focal region whose size depends on the objective numerical aperture, wavelength, and pinhole size. In fluorescence correlation spectroscopy and related techniques, the measurement volume is characterized by the instrument's point-spread function and is typically on the order of femtoliters. In flow-based systems such as flow cytometry, it refers to the illuminated and sampled volume as particles pass through the detection region.

The Messvolumen is important for quantification, calibration, and interpretation of measurements. A larger or poorly defined volume can mix signals from heterogeneous samples and introduce partial-volume effects, while a well-defined volume improves localization and accuracy.

Determination and management of the measurement volume often involve calibrations with standards or beads of known size, optical modeling, and PSF measurements. It can vary with refractive index, depth, alignment, and instrument settings.

See also: detection volume, sampling volume, voxel.