collimator called slithole has been developed which needs further testing in animal
models [16]. The CZT system provides higher energy resolution [17] which is
beneficial for using multiple radiotracers with a different energy in a single scan
[18]. Also, silicon photomultipliers (SiPMs) coupled with pixelated crystal showed
higher spatial resolution and emerged as a prominent alternative to PMTs in
SPECT. SiPMs have a significant advantage that it can be used in SPECT/MR
system as well [19, 20].
15.2.2 SPECT/CT and SPECT/MR in Radionanomedicine
In the field of radionanomedicine, SPECT is used primarily for evaluation of
in vivo biodistribution of injected theranostic NPs. In one study, vascular
endothelial growth factor (VEGF) loaded
99m
Tc labeled chitosan hydrogel NPs
were injected into a rat model of myocardial ischemia and showed alleviation of
ischemia. In the meantime, SPECT imaging was used to monitor the whereabouts
of the radionanomedicines which may be used for dose adjustment in the following
experiment or clinical trial [21]. In another study,
111 In labeled mesoporous silica
NPs (MSNs) was used to tracking neural stem cells in the orthotopic glioblastoma
model of mouse. For the monitoring of injected neural stem cells (NSCs),
111 In
labeled MSN was taken up by NSCs before the injection to the mouse. NSC was
injected to the brain of the mouse model and the migration of the NSC to the cancer
lesion was observed by SPECT/CT imaging (Fig. 15.3) [22]. Parrott et al. reported
the renal clearance of
99m Tc labeled polyester dendrimers using SPECT/CT
imaging [23]. In another study, silver NPs were radiolabeled with
125 I for SPECT
Table 15.1 Radionuclides
for PET and SPECT
Radionuclide
Decay
Photon energy (keV)
Half-life
11
C
b+
511
20.3 min
13
N
b+
511
10.0 min
15
O
b+
511
2.07 min
18
F
b+
511
110 min
68
Ga
b+
511
68 min
82
Rb
b+
511
1.25 min
64
Cu
b+
511
12.7 h
89
Zr
b+
511
3.3 day
99m
Tc
IT
140
6.03 h
111
In
EC
172, 247
2.81 day
123
I
EC
159
13.0 h
125
I
E C
2 7 –35
59.4 day
201
Tc
EC
68–80
3.05 day
IT Isomeric transition; EC electron capture. Reproduced with
permission [34]
282
H.-J. Im and G. J. Cheon
models [16]. The CZT system provides higher energy resolution [17] which is
beneficial for using multiple radiotracers with a different energy in a single scan
[18]. Also, silicon photomultipliers (SiPMs) coupled with pixelated crystal showed
higher spatial resolution and emerged as a prominent alternative to PMTs in
SPECT. SiPMs have a significant advantage that it can be used in SPECT/MR
system as well [19, 20].
15.2.2 SPECT/CT and SPECT/MR in Radionanomedicine
In the field of radionanomedicine, SPECT is used primarily for evaluation of
in vivo biodistribution of injected theranostic NPs. In one study, vascular
endothelial growth factor (VEGF) loaded
99m
Tc labeled chitosan hydrogel NPs
were injected into a rat model of myocardial ischemia and showed alleviation of
ischemia. In the meantime, SPECT imaging was used to monitor the whereabouts
of the radionanomedicines which may be used for dose adjustment in the following
experiment or clinical trial [21]. In another study,
111 In labeled mesoporous silica
NPs (MSNs) was used to tracking neural stem cells in the orthotopic glioblastoma
model of mouse. For the monitoring of injected neural stem cells (NSCs),
111 In
labeled MSN was taken up by NSCs before the injection to the mouse. NSC was
injected to the brain of the mouse model and the migration of the NSC to the cancer
lesion was observed by SPECT/CT imaging (Fig. 15.3) [22]. Parrott et al. reported
the renal clearance of
99m Tc labeled polyester dendrimers using SPECT/CT
imaging [23]. In another study, silver NPs were radiolabeled with
125 I for SPECT
Table 15.1 Radionuclides
for PET and SPECT
Radionuclide
Decay
Photon energy (keV)
Half-life
11
C
b+
511
20.3 min
13
N
b+
511
10.0 min
15
O
b+
511
2.07 min
18
F
b+
511
110 min
68
Ga
b+
511
68 min
82
Rb
b+
511
1.25 min
64
Cu
b+
511
12.7 h
89
Zr
b+
511
3.3 day
99m
Tc
IT
140
6.03 h
111
In
EC
172, 247
2.81 day
123
I
EC
159
13.0 h
125
I
E C
2 7 –35
59.4 day
201
Tc
EC
68–80
3.05 day
IT Isomeric transition; EC electron capture. Reproduced with
permission [34]
282
H.-J. Im and G. J. Cheon