Report of Activities 2002 - Research - Mayo Clinic

44 REHABILITATION
mainly due to the fact that the tremor that results
as sequelae for differing pathologies will have a
different modal frequency. Our algorithm takes
not only the modal frequency into account, but
also quantifies the magnitude of the tremor signal
as well.
Hand velocity data is derived from position
data recorded by a 3-DOF electromagnetic tracking
device. Activities measured include reaching
from the subject’s left to right as though manipulating
objects on a table, and reaching from a tabletop
towards their mouth to simulate feeding.
The frequency content of the signals is then calculated
via fast Fourier transformation, and the
subsequent power spectral densities (PSD) are
calculated as well. The area under the modal frequency
peak on the PSD plots is taken as the
power of the tremor.
In preliminary studies, tremor severity as
measured by QMA has shown promise in its ability
to predict surgical efficacy (Figure 57). There
appears to be a threshold in tremor severity, as
measured by QMA, above which the attempt at
surgical reduction of tremor is warranted. These
findings are also supported by the qualitative results
of “Excellent”, “Good”, and “Poor” as assigned
by the patients’ neurosurgeon.
In previously published abstracts, QMA has
been shown to be repeatable and sensitive to
changes in condition. Ongoing efforts in the
Figure 57: Correlation between baseline QMA scores and
QMA improvement. Note the agreement in the results
with the subjective evaluation by the neurosurgeon.
tremor project currently center around refinement
of the peak-defining algorithm and application of
QMA in discerning between cerebellar tremor
and other motion disorders, such as ataxia. Other
efforts by the laboratory will also include expanding
the database of collected patient scores
to include those with other pathologies to determine
if a similar threshold for surgical efficacy
may exist.
Publications
Guo, LY; ET AL. Modeling of manual wheelchair
propulsion using optimization. American
Society of Biomechanics 2002.
Guo, LY; Su, FC; An, KN: Optimum propulsion
technique in different wheelchair handrim diameter.
J Med Biol Eng 22(1):1-10, 2002.
Kotajarvi, BR; Basford, JR; An, KN; Sabick, M:
Does elbow angle affect wheelchair propulsion
effectiveness. American Association of Physical
Medicine and Rehabilitation 2002.
Kotajarvi BR; Basford, JR; An, KN: Upperextremity
torque production in men with paraplegia
who use wheelchairs. Arch Phys Med Rehabil
83(4):441-446, 2002.
Morrow, DA; Matsumoto, J; Rabatin, AE; Kaufman,
KR: Comparison of quantitative measures
of tremor as predictors of surgical outcome.
American Society of Biomechanics 2002.
Morrow, DA; Matsumoto, J; Rabatin, AE; Kaufman,
KR: Comparison of quantitative measures
of tremor as predictors of surgical outcome.
Fourth World Congress of Biomechanics 2002.
Morrow, DA; Matsumoto, J; Rabatin, AE; Kaufman,
KR: Quantitative analysis for predicting
surgical reduction of ms tremor. Gait and Clinical
Movement Analysis Society 2002.