  We present a new investigation of the mass-temperature (\MTrelation) relation
of 22 nearby clusters based on the analysis of their ROSAT X-ray surface
brightness profiles ($S_{X}(r)$) and their ASCA emission weighted temperatures.
Two methods of the cluster mass estimations are employed and their results are
compared: (1) the conventional $\beta$ model for gas distribution along with
the isothermal and hydrostatic equilibrium assumptions, and (2) the NFW profile
for dark matter distribution whose characteristic density and length are
determined by the observed $S_{X}(r)$. These two models yield essentially the
same goodness of fits for $S_{X}(r)$ and the similar \MTrelation relations,
with the latter demonstrating a significant departure from the simple
gravitational scaling of $M_{tot}\propto T_X^{3/2}$. It is also shown that the
best-fit \MTrelation relations could be reconciled with the theoretical
expectation if the low-temperature clusters ($T_X<3.5$ keV) are excluded from
the list, which lends support to the scenario that the intra-cluster medium is
preheated in the early phase of cluster formation. Together with the
entropy-temperature distribution, the existence of a similarity break at
$T_X=3-4$ keV in the dynamical scaling relations for galaxy clusters has been
confirmed.
