sample positioning, stability, and
probe-sample contact guidance v2.0
overview
Sample positioning, stability and probe-sample contact are very important to
consider when using BioDentTM. This document suggests some general
considerations for preparing to measure a sample.
safety
Before proceeding, be sure to familiarize yourself with the most current version of
the BioDentTM User’s Guide, available at www.activelifescientific.com.
Specifically, re-familiarize yourself with all safety warnings and precautions listed
in the guide.
sample preparation
Sample preparation is defined as any process that a sample must go through prior
to measurement. BioDentTM typically requires minimal or no sample preparation
prior to measurement. Depending on your study, sample preparation requirements
for BioDentTM are as follows:
1.
Ensure measurement area is accessible.
Certain features of the sample may be inaccessible to the Probe
Assembly. For example, when measuring through soft tissue,
the thickness of the soft tissue must be less than the length of the
cannula on the Reference Probe. The length of the Reference
Probe cannula should be indicated on the Probe Assembly
packaging.
2.
Maintain sample hydration.
Accurate BioDentTM measurements of biological materials can
be dependent on the sample’s hydration state. If you are
conducting a study on hydrated samples, make sure to keep your
samples hydrated throughout your study.
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sample positioning and stability
Sample positioning is the way a sample is held relative to the Measurement Head
Unit (MHU) during measurement. This plays a critical role in obtaining reliable
BioDentTM data. Active Life recommends the following guidelines for positioning
a sample:
1.
Sample direction and orientation.
During measurement it is easy to lose track of where
measurements have already been made. Many Active Life
Application Packages and Stages come equipped with an XY
positioner that can be used to help keep track of each
measurement location. In any use case, it is the end user’s
responsibility to position and manipulate the sample. However, it
is suggested to plan out the study setup ahead of time and to
consider marking the sample, or placing a label under it so that
consistent data are taken. Also, consider preparing and
positioning your sample such that it is easy to reference direction
and orientation.
2.
Minimize sample flexing.
Use positioning techniques which directly support the sample
region being measured.
The reference force or Test Probe indentation can cause samples
to flex. Flexing usually occurs when the sample positioning and
manipulation points are far from the measurement location. For
example, fixing a long mouse bone by only supporting it from
under its distal and medial condyles will likely result in the bone
flexing, causing inaccurate measurement data. To minimize
flexing, it is recommended that you support the sample directly
under the probe-sample contact point.
3.
Prevent lateral displacement.
Samples should be positioned to prevent lateral displacement.
If a sample moves during a measurement, even a microscopic
amount, the data becomes questionable. Fortunately, Reference
Point Indentation is designed to prevent most lateral
displacement through the use of a Reference Point which can act
as a stabilizer for the sample. This does not mean, however, that
no lateral fixation is required; to prevent lateral displacement,
ensure bone stability.
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4.
Prevent sample rotation.
Prevent rotation by using a positioning technique which holds the
region of interest in a stable manner.
Sample rotation happens when the sample is held in an unstable
manner and the weight of the MHU, or the moving Test Probe
during a measurement, causes the sample to rotate. This is often
observed when trying to measure a specific sample region that is
not perfectly perpendicular to the Probe Assembly.
probe-sample contact
Sample positioning and stability are extremely important to ready the sample
beneath the Probe Assembly prior to measurement. It is equally important to pay
attention to the contact made between your probe and sample. The optimal
technique typically depends on the samples in your study. In general there are
some typical guidelines that should be followed:
1.
Ensure appropriate reference force.
When attached to the Measurement Stand, the MHU will exert a
measured reference force on the sample. In order to prevent
unnecessary stressing or damage to the sample, the Measurement
Stand has built-in mechanisms to increase or decrease the
reference force applied to the sample. Essentially, the reference
force will increase when you continue to lower the MHU onto
your sample after making probe-sample contact, and vise-versa.
2.
Use care when lowering the Measurement Head Unit.
Regardless of sample type, the MHU and Probe Assembly should
be lowered slowly onto a sample, with the application of
reference force being carefully controlled.
3.
Ensure perpendicularity to the sample being measured.
The Probe Assembly typically operates across an effective range
of ±7.5°, perpendicularly from the probe-sample contact point.
Any measurements outside of this range may return inconsistent
and inaccurate data.
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