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The Use of Intraoperative Small
https://t.me/med1917
and Large Field of View Gamma
Cameras for Radioguided Surgery
Daan Hellingman and Sergi Vidal-Sicart
3
Contents
3.1 Background 36
3.2 History 36
3.3 Device Characteristics 37
3.3.1 Detectors 39
3.3.2 Field of View 39
3.3.3 Sensitivity 39
3.3.4 Spatial Resolution 39
3.3.5 Energy Resolution 41
3.3.6 Advanced Camera Features 41
3.4 Experiences in Breast Cancer 43
3.4.1 Sentinel Lymph Node Biopsy 44
3.4.2 Radioguided Occult Lesion
Localization and Concurrent Sentinel
Node Biopsy 45
3.4.3 Breast Tumor-Seeking
Radiotracers 46
3.5 Experiences in Melanoma Sentinel
Lymph Node Biopsy 46
3.6 Experiences in Head and Neck
Sentinel Lymph Node Biopsy 47
D. Hellingman
Nuclear Medicine Department , The Netherlands
Cancer Institute-Antoni van Leeuwenhoek Hospital ,
Amsterdam , The Netherlands
d.hellingman@nki.nl
e-mail:
S. Vidal-Sicart (*)
Nuclear Medicine Department ,
Hospital Clínic Barcelona, Institut d’Investigació
Biomèdica August Pi I Sunyer (IDIBAPS) ,
Barcelona , Spain
svidal@clinic.ub.es
e-mail:
3.7 Experiences in Urogenital Sentinel
Node Lymph Biopsy 47
3.8 Experiences in Minimally Invasive
Radioguided Parathyroidectomy
in Primary Hyperparathyroidism 49
3.9 Experiences in Radioguided Bone
Lesion Localization 51
3.10 Experiences in Other Clinical
Applications 51
Conclusions 51
References 52
Abstract
Intraoperative small and large fi eld of view
gamma cameras and handheld gamma cameras, when used in conjuction with standard
handheld gamma detection probes, can help
further facilitate the successful performance of
various radioguided surgery procedures. A
variety of prototype and commercially available intraoperative gamma cameras have been
clinically evaluated in radioguided surgery.
Such intraoperative gamma cameras: (i) must
be portable and stable in design; (ii) have no
delay between image acquistion and display:
(iii) provide continuous monitoring, spatial orientation on screen, real-time quantifi cation, and
display of the counts recorded; and (iv) have an
adequate spatial resolution, sensitivity, and
© Springer International Publishing Switzerland 2016
K. Herrmann et al. (eds.), Radioguided Surgery: Current Applications and Innovative
Directions in Clinical Practice, DOI 10.1007/978-3-319-26051-8_3
35
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D. Hellingman and S. Vidal-Sicart
fi eld of view. Intraoperative gamma cameras
have been clinically applied to many disease
entities, most commonly including breast canceer, melanoma, head and neck malignancies,
parathyroid surgery, urogenital malignancies,
and bone tumors. The application of intraoperative gammma cameras to radioguided sentinel
lymph node (SLN) biopsy procedures is most
advantageous in diffi cult SLN biopsy cases,
such as: (i) when the SLNs are located near the
primary injection site, (ii) when the SLNs are
deeply located within the region of interest, or
(iii) when SLNs have a relaively low level of
radiotracer uptake.
3.1 Background
In most centers, radioguided surgery relies on
preoperative imaging in combination with intraoperative handheld gamma probe guidance. A
handheld gamma probe provides count rate display and variable-pitch audio output based on the
local radioactivity concentration. Radioguided
surgery requires rapid and precise detection, as is
generally provided simply by handheld gamma
detection probes. There are however several limitations: (1) gamma probes do not provide image
documentation for the medical record, (2) its usefulness is dependent on correct gamma probe
positioning and thus highly operator dependent,
(3) deeply located sentinel lymph nodes (SLNs)
may be missed due to low count statistics as a
result of tissue attenuation, and (4) when SLNs
are located in close proximity to the radiotracer
injection site, the high radioactive background
signal may hamper the ability to intraoperative
distinguish the SLNs from the radiotracer injection site. This is referred to as the “shine-through”
effect.
With these limitations to handheld gamma
detection probes, intraoperative gamma cameras
have been designed to facilitate radioguided surgery. These systems must meet several requirements to be employed in the operating room: (1)
a portable and stable design, (2) no delay between
image acquisition and display, and (3) the possibility for continuous monitoring, spatial orientation on screen, real-time quantifi cation, and
display of the counts recorded. Last, such
systems should also have an adequate spatial resolution, sensitivity, and fi eld of view [ 1 ].
Real-time imaging with an intraoperative
gamma camera provides a larger fi eld of view
than a gamma probe can cover and visual assistance in localization and verifi cation of resection of the targeted tissue. Its position can be
adjusted to also show SLNs near the radiotracer
injection site or to distinguish between two
radiolabeled tissues, which can easily be overlooked by using a conventional handheld
gamma probe. Still it is advised to use an intraoperative gamma camera in conjunction with a
handheld gamma probe for most radioguided
surgery procedures, because both systems have
their added value.
Intraoperative maneuverability determined by
the outer dimensions and weight of the detector
head is one of the most important characteristics
of such intraoperative gamma cameras.
Intraoperative gamma cameras can be divided
into two categories: handheld gamma cameras
and portable/mobile gamma cameras. Small
gamma cameras weighing about 1 kg or less can
be physically held and positioned by the average
person for the time necessary to achieve the
required image, 10–60 s on average. These systems are referred to as handheld gamma camera.
However, those gamma cameras weighing 2 kg or
more cannot be easily held by the average person
and need some sort of adjunct stabilization/
support system. These systems are referred to as
portable gamma cameras (PGCs). Finally, the
term “small fi eld of view” (SFOV) gamma camera applies to those systems having a fi eld of view
that is 5×5 cm
2
or smaller in size, while gamma
cameras with a larger fi eld of view are considered
“large fi eld of view” gamma cameras.
3.2 History
The fi rst prototype handheld gamma camera, the
“imaging probe,” was patented by Soluri et al. in
1997 [ 2 ]. The imaging probe was a small gamma
camera having a fi eld of view of 22.8 × 22.8 mm 2 .
Advancements in the development of positionsensitive photomultiplier tubes (PS-PMTs)
3 The Use of Intraoperative Small and Large Field of View Gamma Cameras for Radioguided Surgery
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37
allowed for new gamma cameras designs with
improved high resolution (spatial resolution
smaller than 4 mm). As example, a prototype
gamma camera, “preoperative”, compact imager
(POCI), was developed by Menard et al. and the
fi rst clinical results of both systems in sentinel
lymph node (SLN) procedures were published in
1999 [ 3 , 4 ]. These early systems used conventional
continuous thallium-doped cesium iodide CsI(Tl)
or sodium-doped cesium iodide CsI(Na) scintillation crystals linked to a PS-PMT or
PS-photodiode (PD). The main problems with
these early units were their SFOV and the resulting large number of images required to scan the
whole surgical fi eld.
In 2001, Soluri et al. improved the spatial resolution and sensitivity of their imaging probe by
integrating the crystals into the collimator holes
[ 5 ]. A prototype large fi eld of view PGC, 2020tc
imager, based on CsI(Tl)-photodiode coupling,
was tested in minimally invasive radioguided
parathyroidectomy by Kitagawa et al. in 2002
[ 6 ]. Pitre et al. improved the POCI system by
reducing the weight and increasing its detector
fi eld of view and sensitivity in 2003 [ 7 ]. In the
same year, the fi rst prototype solid-state cameras
were presented by two different groups [ 8 , 9 ].
These solid-state systems were based on
crystal- photodiode coupling or semiconductors
crystals, such as cadmium telluride (CdTe) or
zinc cadmium telluride (CdZnTe).
Thereafter, commercially available SFOV
gamma cameras were developed and clinically
evaluated. While the fi rst prototypes were heavy
handheld devices, the newer commercially available SFOV gamma cameras were either lighter
handheld gamma camera systems or were PGCs
equipped with a stabilization/support system
[
10 ]. The pioneering of the commercially avail-
able systems has led to their commonplace application to many aspects of radioguided surgery,
including radioguided parathyroidectomy, as
well as radioguided SLN biopsy procedures for
melanoma and breast cancer. Additionally, the
clinical application of PGCs and handheld
gamma cameras has been described for radioguided bone surgery [ 11 ] and for radioguided SLN
biopsy procedures for head/neck cancers [ 12 ]
and for urogenital cancers [ 13 , 14 ].
3.3 Device Characteristics
Several prototype or commercially available intraoperative gamma cameras have been clinically
evaluated in radioguided surgery. SFOV PGCs
(Fig. 3.1 ) and handheld (Fig. 3.2 ) gamma cameras
are optimized for the detection of technetium- 99 m
99m
(
Tc), having an energy photopeak of 140 keV;
however, such devices have a global energy range
from 30 to 250 keV. This energy range enables
detection of multiple other low- and mediumgamma photon energy- emitting radiotracers, such
as cobalt-57 ( 57 Co), gallium-67 ( 67 Ga), indium-111
111
(
In), iodine-123 (
technology used for the different cameras is very
heterogeneous (Table 3.1 ). Performance charac-
teristics were obtained using widely differing
Fig. 3.1 Portable small fi eld of view gamma camera
“Sentinella S102” (Provided courtesy of Oncovision
GEM Imaging S.A., Valencia, Spain)
123
I), and
125
I. Nevertheless, the
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D. Hellingman and S. Vidal-Sicart
Fig. 3.2 Small fi eld of view handheld gamma cameras; ( a )
compact gamma camera “CGC” (Provided courtesy of John
E.W. Lees Space Research Centre, University of Leicester,
Leicester, United Kingdom), ( b ) CrystalCam, ( c ) Minicam
II (Provided courtesy of Dr. Juan I. Rayo, Complejo
Hospitalario Universitario de Badajoz, Badajoz, Spain)
Table 3.1 Technical characteristics of portable and handheld gamma cameras
Handheld or
Camera (manufacturer)
portable Collimator Detector
Small fi eld of view
a
Sentinella S102
[ 17 ]
(Oncovision, Spain)
Minicam II
a
Portable Pinhole (2.5 and
4.0 mm)
CsI (Na)
PS-PMT
Handheld Parallel hole CdTe 70 × 170 ×
(Eurorad, France)
CrystalCam [
96 ] (Crystal
Handheld Parallel hole CdZnTe 60 × 60 ×
Photonics, Germany)
NODE VIEWTM
(Intra-Medical Imaging,
a
[ 97 ]
Handheld Parallel hole NaI(Tl)
PS-PMT
USA)
IP Guardian II [
(Li-Tech, Italy)
eZ-SCOPE [
8 ] (Anzai
98 ]
Handheld Parallel hole CsI (Tl)
PS-PMT
Handheld Parallel hole CdZnTe 77 × 73 ×
Medical, Japan)
a
CGC
[ 99 ] (Gamma
Technologies, UK)
GammaCAM/OR [
34 ]
(Gamma Medica, USA)
CarolIReS [
35 ] (prototype,
France)
POCI [
7 ] (Prototype,
France)
Handheld Pinhole
CsI(Tl) CCD Ø 95 × 200 1.0
(0.5 mm)
Portable Parallel hole NaI(Tl)
PS-PMT
Portable Parallel hole Gd2SiO5 (Ce)
PS-PMT
Handheld Parallel hole CsI (Na)
PS-PD
Large fi eld of view
a
[ 81 ] (Digirad, USA) Portable Parallel hole CsI(Tl) PS-PD 421 × 284 ×
Ergo
Mobile gamma camera
[
55 ] (prototype, USA)
a
Updated information was obtained from commercial brochure or corresponding author
b
Missing information
Portable Parallel hole NaI(Tl)
PS-PMT
Size detector
head (mm 3 ) Weight (kg)
154 × 82 ×
1.3
80
0.7
250
0.8
140
64 × 64 × 76 1.1
– b 1.2
0.8
212
– b 10
78 × 78 ×
2.5
275
Ø 95 × 90 1.2
193
102
b
–
– b
experimental designs, and therefore, a precise
comparison is not always possible. For example,
different source-to-collimator distances will affect
the sensitivity and spatial resolution of each system. A uniform standard to examine performance
characteristics is required for precise comparison.
Existing National Electrical Manufacturers
Association (NEMA) protocols for assessing the
performance characteristics of conventional large
fi eld of view gamma cameras can be inappropriate
and require modifi cation for use with SFOV
gamma camera systems [
15 , 16 ].
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3.3.1 Detectors
The development of high-resolution gamma
cameras resulted in four different detectors
technologies: (1) scintillation crystals coupled with
a PS-PMT, (2) scintillation crystals coupled with
photodiodes, (3) scintillation crystals coupled with
a CCD detector, and (4) semiconductor crystals
(CdTe and CdZnTe, whose charge is directly read
by dedicated electronics). Scintillation-based
detection devices are cheaper than semiconductorsbased detection devices. Semiconductors are direct
converters of photons to energy, with no light conversion. Because of this, there is no spread of light
and corresponding cross talk, as occurs with scintillating crystals. Semiconductors show less peripheral problems (e.g., reduced peripheral dead zones)
than scintillation crystals coupled with a
PS-PMT. The main difference is that semiconductors have a better energy resolution than most scintillators, while scintillators have a higher sensitivity.
Photodiodes can offer the advantages of semiconductors, such as reduced peripheral dead zone and
high energy resolution, and the benefi ts of the
PS-PMTs, such as a high sensitivity. Finally, scintillators coupled with a CCD detector have naturally a better spatial resolution due to the smaller
pixel size than the other detectors. Most of the cameras listed in Table 3.1 are built with scintillators.
3.3.2 Field of View
Another important feature is the detector’s fi eld
of view, which is the actual patient region of
interest that can be scanned in one image by the
gamma camera. The fi eld of view depends on the
type of collimator and on the detector dimensions. Some systems are equipped with interchangeable collimators. It is important to choose
an appropriate collimator for the specifi c surgical
application, secondary to the trade-off between
sensitivity and spatial resolution. If the fi eld of
view is too small, it may be diffi cult to completely encompass the targeted region of interest
and multiple images will be needed. On the other
hand, a large detector with a large fi eld of view
may not allow optimal maneuverability during
any given surgical procedure. Systems using a
parallel-hole collimator have a fi xed fi eld of view
limited to the detector dimensions. A pinhole collimator enables imaging with a fi eld of view
larger than the detector dimensions, which is
ideal for scanning the whole surgical fi eld using
only a small camera system. When the camera is
moved further away from the patient, increasing
the source-to-pinhole collimator distance, the
image fi eld of view will become larger. However,
a larger source-to-pinhole collimator distance
will drastically lower the spatial resolution and
sensitivity of the system, reducing the overall
image quality. Most of the cameras listed in
3.2 are SFOV systems (5×5 cm or smaller)
Table
even those using pinhole collimators, enabling
larger fi eld of view imaging, since the classifi cation is based on the detector dimensions.
3.3.3 Sensitivity
Sensitivity is expressed as counts per second per
unit activity (cps/Bq) and depends on the
collimator- detector geometry (geometrical effi ciency) multiplied by the detector effi ciency. The
sensitivity increases as the square of the collimator hole size and decreases as the square of the
hole length. Source-to-collimator distance is
inversely quadratic related to the sensitivity of
pinhole collimators. The sensitivity of a parallelhole collimator is in theory independent of
source-to-collimator distances, but in reality a
minimal decrease in sensitivity due to scattering
will be detected at larger distances. A high sensitivity is important in the operating room to image
low activities. Image acquisition times can be
reduced using high-sensitivity systems, which
means that the surgeon does not lose too much
time looking for radiotracer tissue uptake in the
areas of interest. All sensitivity values in Table
are based on
99m
Tc 140 keV measurements.
3.2
3.3.4 Spatial Resolution
The spatial resolution of a system can be
expressed as intrinsic and extrinsic resolution.
Intrinsic resolution refers to how well the detector
localizes an interaction in the scintillator or semiconductor crystals. Extrinsic resolution is a combination of the intrinsic resolution and collimator
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Energy resolution
(FWHM)
D. Hellingman and S. Vidal-Sicart
Co)
57
15.9 %
(at
d
b
b
or 345–150
c
Extrinsic sensitivity (cps/
Extrinsic resolution
Intrinsic resolution
Detector fi eld of
145–59
MBq)
d
or 4.6–8.7
c
(FWHM in mm)
(FWHM in mm)
)
2
view (mm
5.2 %
f
or 554
e
30–50 mm)
237
(at
e
250 5–7%
b
(at 13–50 mm)
25–50 mm)
f
e
204 20 %
f
e
0–15 mm)
8.6 %
or 477
184
214 (at 3 mm) 58 %
or 3.0–9.1
(at 10–50 mm)
13–50 mm)
290 32 %
61 –
b
–
b
10–50 mm)
405 –
b
–
b
Tc (140 keV)
99m
Image matrix
size
Camera (manufacturer)
Table 3.2 Performance characteristics of portable and handheld gamma cameras
Small fi eld of view
300 × 300 40 × 40 1.8 2.6–5.5
[ 17 ] (Oncovision,
a
Spain)
Sentinella S102
16 × 16 40 × 40 1.9 3.8–4.9
29 × 29 50 × 50 1.8 1.8 (at 6 mm) 135 12 %
[ 97 ] (Intra-Medical
a
96 ] (CrystalPhotonics,
(Eurorad, France) 16 × 16 40 × 40 2.5 –
a
Germany)
Minicam II
CrystalCam [
NODE VIEWTM
98 ] (Li-Tech, Italy) 18 × 18 44 × 44 2.2 2.5–2.9 (at
8 ] (Anzai Medical, Japan) 16 × 16 32 × 32 1.9 2.3–8.0
Imaging, USA)
eZ-SCOPE [
IP Guardian II [
125 × 125 –
b
–
34 ] (Gamma
[ 99 ] (Gamma Technologies, UK) 125 × 125 8 × 8 0.6 1.28–2.9 (at
a
CGC
GammaCAM/OR [
35 ] (prototype, France) 50 × 50 50 × 50 3 10 (at 30 mm) 1000 (theoretical) 45 % (
7 ] (prototype, France) 50 × 50 Ø 40 2.3 3.9–7.6 mm (at
CarolIReS [
Medica, USA)
POCI [
40 × 40 130 × 130 –
55 ] (prototype,
[ 81 ] (Digirad, USA) 512 × 512 396 × 310 3.3 10.3 (at 100 mm) 113 7.9 %
a
Mobile gamma camera [
Ergo
USA)
All performance characteristics are measured using
Large fi eld of view
Missing information
Updated information was obtained from commercial brochure or corresponding author
a
4.0 mm pinhole collimator
2.5 mm pinhole collimator
Low-energy high-resolution (LEHR) collimator
Low-energy high-sensitivity (LEHS) collimator
b
c
d
e
f
3 The Use of Intraoperative Small and Large Field of View Gamma Cameras for Radioguided Surgery
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41
resolution. In practice, the intrinsic resolution of
a detector is small compared to the extrinsic resolution. For this reason, a comparison of extrinsic
spatial resolution provides a better indication of
how a camera will behave in clinical practice.
Spatial resolution, expressed as the full width at
half maximum (FWHM), is linear inversely
related the source-to-collimator distance for both
pinhole and parallel-hole collimators. At short
distances, gamma camera systems fi tted with a
pinhole collimator have a higher resolution than
when parallel collimators are used.
3.3.5 Energy Resolution
As mentioned above sensitivity partly defi nes the
image acquisition time. But a good quality image
is also related to the capacity of the detector to
reject diffuse (scattered) photons whose trajectories do not point back to the initial source and
therefore must be eliminated. This is done by
applying a proper energy window that mainly
selects the direct gamma photons coming from the
source. The energy resolution of the detector is
expressed as the FWHM of the
99m
Tc or 57 Co photopeak, 140 or 122 keV, respectively, and plays an
important role: the lower (better) it is, the stricter
the selection in photon energy can be. In conclusion, a large energy window is needed for detectors
having a broad energy photopeak (large FWHM)
to retain the sensitivity of the detector. However, a
larger energy window will misinterpreted scattered
photons for direct photons and therefore reduce the
contrast and overall quality of your image.
3.3.6 Advanced Camera Features
The above mentioned technical performance
characteristics are the major determinates for any
given gamma camera in the clinical setting.
However, there are some additional features that
might infl uence the performance of any given
radioguided surgery procedure. For example, the
Sentinella S102 camera has evolved over the
years from a handheld device to an articulated
system with a stabilization/support arm, thus
enabling stable imaging over longer image acquisition times [
14 , 17 ]. A laser pointer is included in
the supporting structure and displays a red cross
over the patient’s skin (Fig. 3.3 ). The position of
this red cross is virtually visible on the computer
screen of the camera. If the virtual laser pointer
matches the radioactive hotspot signal on screen,
this indicates that the radiolabeled tissue has been
precisely localized. The laser pointer facilitates
the image interpretation for the surgeons, who
must relate the output image of the portable
gamma camera (PGC) to the visible surface of the
surgical fi eld. An additional advantage is that the
camera can be easily positioned in the same position for comparing pre- and post- excision images.
All systems should have software tools for
fl exible display windowing, convenient regionof- interest defi nition, and rapid image analysis.
These features should be readily available and be
easily controlled by the individual positioning
the camera. For example, the Sentinella S102
camera has copied some software tools (dynamic
imaging, dual-isotope imaging, and virtually
shielding the highly radioactive injection site)
from conventional large fi eld of view gamma
cameras; however, these tools are still unique
among the SFOV devices. Dynamic imaging can
facilitate SLN detection by imaging directly after
radiotracer injection in situations when an intraoperative injection is performed. Dual-isotope
imaging can be helpful in those radioguided
interventions using two different radioisotopes,
such as in the simultaneous use of an
125
I seed to
guide breast-conserving tumor excision and
99m
Tc-nanocolloid for SLN biopsy in breast cancer [ 18 ]. In the clinical scenario in which the
SLNs are located near the radiotracer injection
site, visualization of the SLNs can be hampered
by the background radioactivity from radiotracer
injection site, even when the PGC is pointing at
the most optimal angle. Thus, in this diffi cult
clinical scenario, covering the radiotracer injection site with a software tool that simulates a lead
shield (masking the injection activity) can facilitate SLN visualization [ 19 ].
Up until recently, all SFOV PGCs and handheld gamma cameras have been based on just one
single imaging modality (gamma imaging), which
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D. Hellingman and S. Vidal-Sicart
Fig. 3.3 Lateral ( a ) planar lymphoscintigraphic image
showing SLNs caudal from the site of 99mTc-nanocolloid
injection around a preauricular-located melanoma. These
SLNS are displayed on 3D volume rendering SPECT/CT
( b ) for a better anatomical recognition. The PGC upgraded
with an optical camera module was placed above the lymphatic fi eld to obtain an image at a distance of approxi-
provides no correlative anatomical information,
thus sometimes hampering image interpretation.
In order to overcome this limitation, new multimodality system confi gurations have been
described that combine optical and gamma imaging. Haneishi et al. were the fi rst who proposed a
parallel optical and gamma camera confi guration
[ 20 , 21 ]. This portable hybrid camera system
projects the obtained gamma image onto an optical image. Later Lees et al. described an optical
camera upgrade for a handheld compact gamma
camera enabling fused optical and gamma imag-
mately 12 cm. The red laser pointer cross is pointing
towards a near the highly radioactive injection site located
SLN. Combined optical and scintigraphic imaging visualizes the image fi eld of view and two anatomical SLN locations ( white arrows ) ( c ). A second combined optical and
scintigraphic image visualizes the SLN cluster in the
lower part of the neck ( d )
ing with a matched image fi eld of view [ 22 , 23 ].
Hellingman et al. were the fi rst who evaluated a
prototype portable hybrid camera for preoperative
lymphatic mapping in SLN procedures in 2015
[ 24 ]. Fused optical and gamma imaging makes it
easier to relate the position of the radioactive
hotspots and the image fi eld of view with the reallife situation (Fig. 3.3 ).
Another interesting development is the navigation system called “declipseSPECT” (SurgicEye,
München, Germany), which expands the applications of radioguided interventions. declipseSPECT
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Fig. 3.4 Preoperative SPECT/CT scan of patient
visualized as video overlay on the live video of the patient
( a ). Pre-incision freehand SPECT acquisition using a
position- tracked gamma probe ( b ). Subsequently, the
is another type of imaging system that integrates a
positioning system attached to a conventional
gamma probe [ 25 ]. A freehand single-photon
emission computed tomography (SPECT) scan,
few minutes of manual scanning using an optically
tracked gamma probe, can provide additional
depth information using a 3D reconstruction of the
radioactive target lesions (Fig. 3.4 ). The position
of the gamma probe relative to the attached device
is tracked by infrared technology, and the output of
the gamma probe is co-registered in the surgical
fi eld (depicted by a video camera) and displayed
on a monitor where the surgeon can easily check
the location and depth of the foci of radioactivity.
A unique feature of the “CrystalCam” is the pos-
gathered data is reconstructed to visualize the radioactive
foci projected onto the live video of the patient ( c ) and in
a ( d ) 3D virtual reality view from the perspective of the
gamma probe
sibility to integrate this SFOV handheld gamma
camera into the declipseSPECT system. FreehandSPECT scans can be made using the CrystalCam,
which has a higher resolution and sensitivity than
a conventional gamma probe. The fi rst clinical
reports of this feature were reported by Freesmeyer
et al. in 2014 [ 26 , 27 ].
3.4 Experiences in Breast Cancer
SFOV and large fi eld of view PGCs and handheld
gamma cameras have been widely utilized in
radioguided breast cancer procedures. Part of
these experiences has been reported in a recent
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D. Hellingman and S. Vidal-Sicart
review [ 28 ]. The use of these systems in the sur-
gical management of breast cancer has included:
preoperative and intraoperative lymphatic mapping in SLN procedures, radioguided occult
lesion localization (ROLL), sentinel node and
occult lesion localization (SNOLL), and breast
cancer detection using
99m
Tc-mikusestamibi.
3.4.1 Sentinel Lymph Node Biopsy
In most centers, preoperative planar lymphoscintigraphy is performed using a large conventional
gamma camera to visualize lymphatic drainage
from the radiotracer injection site. Sequential
planar images will show successive stages of
drainage and thereby help to determine the number and location of SLNs. Goto and colleagues
studied the ability to perform preoperative lymphatic mapping using a large fi eld of view PGC
and compared the results with conventional lymphoscintigraphy [ 29 ]. Concordant results were
obtained in 15/19 patients with both cameras. In
four (21 %) patients, axillary SLNs were correctly detected using the PGC whereas these hot
spots could not be seen with the conventional
lymphoscintigraphy. According to the authors,
the better performance of the PGC is due to a
combination of a close imaging distance and a
better signal-to-noise ratio that allows the PGC to
distinguish SLNs located near the injection site.
Kerrou and colleagues were the fi rst who compared a SFOV handheld gamma camera with
conventional lymphoscintigraphy in 138 patients
[
30 ]. Multiple images were needed using this
SFOV device to scan the whole axillary and
extra-axillary region. Although the handheld
gamma camera was used after conventional lymphoscintigraphy, benefi ting from a longer radiotracer migration, fewer SLNs were detected with
this handheld gamma camera in 34 of the 138
(25 %) patients. Concordant results were obtained
in 54/138 patients and more SLNs were detected
in 50/138 (36 %) patients using the handheld
camera. Another study was performed using a
SFOV PGC fi tted with a pinhole collimator to
overcome the need to make multiple images due
to the limited fi eld of view [ 31 ]. The PGC was
placed at 18 cm distance to cover a 20×20 cm
fi eld of view. SLN visualization was seen in 39 of
52 patients (75 %) using the PGC, while conventional lymphoscintigraphy showed SLN visualization in 49 of 52 patients (94 %). When a lead
shield was used to mask the injection activity,
conventional lymphoscintigraphy and the PGC
visualized a SLN in 41 of 43 patients (95 %) and
38 of 43 cases (88 %), respectively. The poor performance of the PGC was attributed to the low
spatial resolution and sensitivity at this large
source-to-collimator distance.
Scopinaro and colleagues published the fi rst
intraoperative breast cancer SLN studies including only a limited number of patients [
32 , 33 ].
The fi rst validation of new portable and handheld gamma cameras generally occurs in breast
cancer SLN procedures [ 7 , 32 , 34 , 35 ]. In intra-
operative setting, portable and handheld gamma
cameras are often compared to conventional
gamma probes to evaluate their clinical value.
Although most studies include only a small
number of patients (<20 patients), these reports
describe clearly the usefulness of intraoperative
imaging. Firstly, high-resolution imaging using
portable or handheld gamma cameras facilitates
the detection of near the injection site located
SLNs which are missed by preoperative lymphoscintigraphy or gamma probe screening [ 14 , 32 ,
36 ]. Secondly, they provide detection of SLNs
(deeply located or low tracer uptake nodes)
which were initially missed by gamma probe
screening [
7 , 14 , 36 – 40 ]. Thirdly, intraoperative
imaging provides more confi dence about SLN
localization and excision using pre- and postexcision images [ 33 , 34 , 41 ]. Additionally, some
studies demonstrated that intraoperative imaging
reduces operating time since SLNs are faster
found and excised compared to procedures in
which only a gamma probe is used [ 42 , 43 ]. In
this sense, the application of intraoperative
imaging in the parasternal area overcomes the
problem of very faint uptake of these tiny nodes
and helps the surgeon to precisely localize the
correct intercostal space to make the incision
[ 15 ]. Finally, Goñi and colleagues conducted a
retrospective study using a prospective database
of 754 patients who had undergone a SLN biopsy
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