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Background:
Tc-99m TRODAT-1 and I-123 IBZM are potential agents for dopamine
transporter (DAT) and dopamine receptor (DR) SPECT, respectively.
Mainly involving pre-synaptic neurons, Parkinson's disease
(PD) could be differentiated from other movement disorders
such as essential tremor and secondary parkinsonism using
TRODAT-1 and IBZM SPECT. This study further investigates the
value of TRODAT/ IBZM-specific uptake ratios (SUR) of striatum
(ST) and putamrn (PU) in evaluating early PD.
Methods
and Materials:
A total of 13 subjects (8 H&Y stage 1, 5 stage II and
5 age-matched controls) were studied. Tc-99m TRODAT-1 (925
MBq) and then I-123 IBZM (259 MBq) SPECT were performed separately
within a month using a dual-head camera equipped with an ultra-high
resolution fan beam collimator (Helix SPX, Elscint). Ratios
of SURs of TRODAT-1 vs. IBZM (RSUR) were measured.
Results:
Significant differences in averaged SUR of TRODAT-1 were found
among controls and patients with stages I and II (2.03, 1.69
and 1.27, p<0.01 respectively). The averaged SUR of IBZM,
however, was significantly decreased only in the contralateral
ST of the stage II patients. There was a significant decrease
of RSUR of ST and PU in diseased groups especially in the
contralateral side. Notably, less overlap in putaminal RSURs
between diseased groups, either ipisilaterally or contralaterally,
and controls was found.
Conclusion:
The function of DR might be preserved in early PD. The better
discrimination of diseased groups from controls using putaminal
RSUR might be due to up-regulated DR, which provided a clue
to differentiating idiopathic PD from other pakinsonism at
the early stage.
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