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Short communication
Potential role of a new hand-held miniature gamma camera
in performing minimally invasive parathyroidectomy
Joaquin Ortega
1
, Jose Ferrer-Rebolleda
3
, Norberto Cassinello
2
, Salvador Lledo
1
1
Department of Surgery, University of Valencia, Clinic University Hospital, Av. Blasco Ibanez 17, 46010 Valencia, Spain
2
Unit of Endocrinologic and Bariatric Surgery, Clinic University Hospital, Valencia, Spain
3
Department of Nuclear Medicine, Clinic University Hospital, Valencia, Spain
Received: 18 April 2006 / Accepted: 25 June 2006 / Published online: 11 October 2006
© Springer-Verlag 2006
Abstract. Purpose: Sestamibi scans have increased the
use of minimally invasive parathyroidectomy (MIP) to
treat primary hyperparathyroidism (PHPT) when caused
by a parathyroid single adenoma. The greatest concern for
surgeons remains the proper identification of pathological
glands in a limited surgical field. We have studied the
usefulness of a new hand-held miniature gamma camera
(MGC) when used intraoperatively to locate parathyroid
adenomas. To our knowledge this is the first report
published on this subject in the scientific literature.
Methods: Five patients with PHPT secondary to a single
adenoma, positively diagnosed by preoperative sestamibi
scans, underwent a MIP. A gamma probe for radioguided
surgery and the new hand-held MGC were used
consecutively to locate the pathological glands. This new
MGC has a module composed of a high-resolution
interchangeable collimator and a CsI(Na) scintillating
crystal. It has dimensions of around 15 cm×8 cm×9 cm
and weighs 1 kg. The intraoperative assay of PTH (ioPTH)
was used to confirm the complete resection of pathological
tissue.
Results: All cases were operated on successfully by a MIP.
The ioPTH confirmed the excision of all pathological
tissues. The MGC proved its usefulness in all patients,
even in a difficult case in which the first attempt with the
gamma probe failed. In all cases it offered real-time
accurate intraoperative images.
Conclusion: The hand-held MGC is a useful instrument in
MIP for PHPT. It may be used to complement the standard
tools used to date, or may even replace them, at least in
selected cases of single adenomas.
Keywords: Primary hyperparathyroidism – Parathyroid
adenoma – Minimally invasive surgical procedures –
Intraoperative procedures – Miniature gamma camera
Eur J Nucl Med Mol Imaging (2007) 34:165–169
DOI 10.1007/s00259-006-0239-7
Introduction
The introduction of
99m
Tc-sestamibi scintigraphy to
identify and locate preoperatively the parathyroid adeno-
mas in primary hyperparathyroidism (PHPT) opened the
possibility of performing single gland parathyroidectomies
via minimal access, with outcome results similar to those
achieved using bilateral neck exploration [1].
We have used the new hand-held miniature gamma
camera (MGC) Sentinella 102 (GEM-Imaging SL, Spain)
within the surgical field in order to verify its possible value
in the detection of parathyroid adenomas when using
minimally invasive access for parathyroidectomy. The use
of portable hand-held gamma cameras has been reported in
other medical fields, especially in surgery and pre-surgery
sentinel node techniques [2–4] and thyroid scintigraphy
[5]. To our knowledge, this is the first report on use of a
hand-held MGC to intraoperatively locate pathological
parathyroid glands.
Materials and methods
We included five patients with clinical and laboratory findings of
PHPT, with positive
99m
Tc-sestamibi scintigraphy for a single
adenoma. Calcium, phosphorus and parathyroid hormone (PTH)
were registered pre-operatively and 3 months postoperatively. All the
patients included in this study had previously given their informed
consent, and the entire research project was authorised by the
Committee for Ethical Research at the hospital.
A -planar conventional parathyroid scintigraphy (740 MBq, i.e.
20 mCi,
99m
Tc-sestamibi dual-phase scintigraphy protocol [6, 7]) had
An Editorial commentary on this paper is available at
http://dx.doi.org/10.1007/s00259-006-0250-z
Joaquin Ortega ())
Unit of Endocrinologic and Bariatric Surgery,
Clinic University Hospital,
Valencia, Spain
e-mail: joaquin.ortega@uv.es
Tel.: +34-963-864169, Fax: +34-963-864805
European Journal of Nuclear Medicine and Molecular Imaging Vol. 34, No. 2, February 2007
previously been implemented in all patients using two large field of
view gamma cameras (GE Genie single-head and Elscint Helix dual-
head gamma cameras), both equipped with parallel-hole, low-energy,
high-resolution collimators. Images of the head and mediastinum
were recorded in a 128×128 matrix, 20 min and 2 h post injection. In
four patients a subtraction image was obtained 20 min after the
injection of a standard dose of
99m
Tc-pertechnetate [185 MBq
(5 mCi)] in order to clarify the origin (thyroid vs parathyroid) of
abnormal
99m
Tc-sestamibi uptake. In order to improve the diagnosis,
single-photon emission computed tomography (SPECT) images
were acquired in one patient using the dual-head gamma camera and
the following parameters: circular orbit, 120 steps over 360°, 25 s per
step and a 64×64 matrix.
On the day of the surgery, 111–185 MBq (3–5mCi)of
99m
Tc-
sestamibi (Cardiolite, Bristol Myers Squibb Pharma Belgium Sprl) was
injected in the operating room 10 min before surgery. Next, three to
eight images, each of about 20–30 s, were acquired before and during
the surgery with the Sentinella 102 equipped with a pin-hole 4-mm
collimator and using a 300×300 matrix. Before the surgical incision,
planar imaging was performed, placing the collimator at a distance of
15 cm. This permitted visualisation, at a low resolution, of the cervical
and superior thoracic field, from the salivary glands to the heart.
The MIP was performed through a 2-cm cervical incision, made
over the point of maximal isotope uptake as seen on preoperative
imaging. Surgical telescopes 2.5× (Designs for Vision, USA) were
used by the surgeon to improve the surgical field view.
Intraoperative location of the pathological gland was achieved by
the use of both the gamma probe Navigator GPS (RMD Systems
LLC, USA) and the hand-held MGC Sentinella 102. These devices
were also used to verify the absence of positive radioactivity after
resection of pathological gland. Complete removal of pathological
tissue was confirmed by an intraoperative quick PTH assay (ioPTH)
(PTH intact test, CV intra-assay 1.1%, CV inter-assay 2.8%, Cobas,
Roche Diagnostics GmbH, Germany) before and 15 min after gland
resection. Frozen sections of all resected glands were performed.
The new Sentinella 102 hand-held MGC (Fig. 1) has a head
module composed of a high-resolution interchangeable lead colli-
mator (pin-hole apertures of 1.0, 2.5 and 4.0 mm), a continuous CsI
(Na) scintillating crystal and a flat panel position-sensitive photo-
multiplier tube. This gamma camera has dimensions of around
15 cm×8 cm×9 cm, weighs 1 kg and just requires a single 3-m wire
connection to a laptop computer for proper operation. The real-time
acquisition is controlled by a user software that runs under Windows
XP. It is capable of showing high-quality planar gamma images of the
body, which can be better obtained with the camera coupled to an
articulated arm for good stability. This MGC is characterised by an
intrinsic spatial resolution of 1.6 mm. Due to the use of a pin-hole
collimator, it has a variable field of view (FOV) according to the
aperture and to the distance from the body to the pin-hole, achieving
a 20-cm FOV while maintaining reasonable resolution. The spatial
resolution at a distance of 100 mm is 10 mm (pin-hole 2.5) and
18 mm (pin-hole 4). This small gamma camera offers a high
sensitivity (200–2,000 cpm/μCi 10 mm away, 60–160 cpm/μCi
100 mm away), which allows quick imaging acquisition (less than
20 s). Its ability to localise small hot radiation regions is improved by
means of accessory tools for reference position establishment
between body and gamma image. We tested one of these tools, the
so-called LASER Positioning System (LPS). It provides a LASER
cross pointing at the FOV central point on the body, with a virtual
cross mark at the same position in the gamma image.
Results
In all cases, all tests were positive. The five patients had
PHPT owing to a single adenoma, and the proper location
was correctly marked by preoperative sestamibi scans. We
intraoperatively used the gamma camera to obtain a
dynamic cervical scan every 10 min, and we could observe
progressive wash-out of isotope from the thyroid and
background, facilitating identification of the adenoma. In
all cases, the MGC provided the same information as the
preoperative imaging, and the initial images always
showed a hot spot for the parathyroid adenomas. The
gamma probe helped us to locate the glands and findings
were always concordant with gamma camera scans.
The gamma camera was always able to locate surgically
the adenomas at a good resolution, the head of the gamma
camera being placed 5–10 cm from the thyroid (Fig. 2).
After the excision, a scan of the gland ex vivo was
performed (Fig. 3), and thereafter an image of the surgical
field was taken in order to confirm absence of the previous
hot spot. In one of the cases, with a preoperative diagnosis
of adenoma in the right inferior parathyroid gland, a normal
gland was found orthotopically although there was a hot
spot and the gamma probe counts were still elevated. The
resection of two small tumours did not alter this condition,
with persistence of a hot spot on dynamic scintigraphy, and
the frozen sections revealed two enlarged adenopathies. A
lateral view of the surgical field with the gamma camera
identified a posterior location of the hot spot (Fig. 2), and
an adenoma was then found in the retro-oesophageal space,
corresponding to a migrated superior parathyroid gland. In
this case the intervention took slightly longer (100 min),
but in the rest of cases, location was quick and easy (always
less than 60 min), and all tools showed their usefulness. In
all cases the results of ioPTH confirmed resection of the
Fig. 1. Sentinella 102 gamma camera, with its connection to a laptop
166
European Journal of Nuclear Medicine and Molecular Imaging Vol. 34, No. 2, February 2007
pathological gland, with an average decrease of 76.9% in
the hormone level.
The average size of the parathyroid adenomas was
2.3 cm×1.3 cm. The postoperative values of calcium,
phosphorus and PTH were normalised in all cases.
Discussion
Most authors agree that
99m
Tc-sestamibi scintigraphy is the
most powerful preoperative diagnostic tool in PHPT, and it
has undoubtedly been responsible for the changes in
therapeutic strategy. The addition of various techniques
has increased the accuracy of
99m
Tc-sestamibi scintigraphy,
the most frequently reported being the double-tracer
subtraction technique with
99m
Tc-pertechnetate and SPECT
[8–10].
Cases of PHPT with a single hot spot on
99m
Tc-
sestamibi scintigraphy and without thyroid pathology are
considered suitable for MIP. The success of radio-guided
surgery and/or ioPTH in locating the glands and confirm-
ing the total excision of pathological tissue has been cited
to justify MIP, and, when used together, these techniques
achieve a high accuracy in selected cases [11]. Never-
theless, it is well established that sestamibi scans fail to
provide information in inappropriate cases and that even
ioPTH, the test reported to be the most accurate [12],
sometimes fails or presents limitations [3, 13].
In our cases we used various diagnostic and therapeutic
tools in an attempt to ascertain whether all the results were
concordant with the findings of planar imaging using the
new MGC. In all patients, the tests were positive for a
single adenoma and these cases were scheduled for MIP.
Immediately prior to surgery, when the patient was in
the operating room, a low dose of
99m
Tc-sestamibi, 111–
185 MBq (3–5 mCi), was injected intravenously. We
decided to perform the initial diagnostic scan and surgery
on different days, similar to Rubello et al. [14], using low
doses of isotope, in order to reduce the threat of radioac-
tivity and to shorten the waiting time after injection. This
allowed rapid wash-out of isotope from the thyroid and
background, and provided better identification of a single
spot of radioactivity. A gamma probe was used to locate the
adenomas and its efficacy was compared with that of the
MGC. In our opinion, use of the gamma probe can be
avoided if an MGC is available: the morphological
expression of anatomical structures on planar images and
the possibility of obtaining lateral views provide more
information than is acquired using a gamma probe, with its
aspecific counts and sounds. Moreover, incomplete wash-
out of the isotope from the thyroid may lead to misleading
records from the gamma probe. In addition, we have
confirmed the feasibility of using the MGC after giving low
doses of isotope, as first indicated by Casara et al. [15, 16].
The concordance between the preoperative conventional
sestamibi scans and the immediate presurgical MGC
images leads us to think that, after more experience has
been acquired, dynamic imaging could even replace the
previous diagnostic scans, at least in order to decide upon
the type of intervention. The initial low-resolution imaging,
performed at a distance of 15 cm, permitted us to identify
the adenomatous gland and to rule out the presence of
ectopic tissue. Next, scans were performed at a shorter
distance to increase resolution, permitting more accurate
anatomical mapping. A quick ioPTH assay was performed
in all patients before surgery and 10–15 min post adenoma
Fig. 2.
99m
Tc-sestamibi scintigraphy with the Sentinella 102. Lateral
view of the cervical field shows anterior thyroid activity and a
posterior parathyroid adenoma
Fig. 3.
99m
Tc-sestamibi scintigraphy with the Sentinella 102.
Parathyroid adenoma after its removal
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European Journal of Nuclear Medicine and Molecular Imaging Vol. 34, No. 2, February 2007
resection. The aim of evaluating the completeness of
removal of all hyperfunctioning parathyroid tissue was
achieved in all cases using the MGC, which allowed us to
see the complete disappearance of hot spots.
We have found just a single reference to the use of a
gamma camera in the operating room for hyperparathy-
roidism, even though it was not hand-held and portable.
This was a case report by Kitagawa et al. [17], who
presented the use of a solid-state multi-crystal gamma
camera for
99m
Tc-sestamibi scintigraphy preoperatively
and intraoperatively, 1 h after injection of a large dose of
600 MBq (16.2 mCi) of isotope.
We have not found any mention in the scientific
literature of the use of a portable hand-held MGC for
intraoperative techniques related to the parathyroid.
Although there are references on the use of portable
hand-held gamma cameras for sentinel node detection
[2– 4], it seems that surgeons are not completely sure about
introducing small gamma cameras into the operating room.
Imaging is perhaps not worthwhile if it sacrifices a lot of
operating time and if quick and precise node localisation is
not assured. These problems are significantly reduced by
the high sensitivity of the Sentinella 102 and by using the
LPS. The acquisition of valid images on the screen was
very fast, and in some cases 20 s was enough to obtain a
positive scan. Furthermore, we could verify a very good
function with small amounts of isotope, confirming rapid
wash-out of the isotope, as suggested by Rubello’s group
[9, 14–16] for radio-guided surgery. Moreover, radiation
exposure of the surgeon and his team was much reduced.
In our opinion this new device is useful for localisation
of pathological glands in cases of PHPT. It is easy to
manage and allows different views to be taken, even lateral
ones, permitting viewing of the entire surgical field or even
of other parts of the body. It can substitute for gamma
probes, whose determinations can be misleading in difficult
cases, as occurred with one of our cases. On the other hand,
it proved effective in identifying all the pathological tissue
and in confirming its complete excision. Goldstein et al.
[18] reported a very good cure rate of 98% in patients
undergoing minimally invasive radioguided surgery with-
out the intraoperative use of PTH measurement. This
indicates that even without ioPTH, our method would be
more accurate by virtue of the morphological information
provided.
In conclusion, for the kind of case reported by us (PHPT
due to a single adenoma, with positive uptake for sestamibi),
our preliminary results indicate the proposed procedure to be
very cost-effective. MIP was effective with the help of only
the intraoperative MGC, after a very low dose of preoper-
ative
99m
Tc-sestamibi, which permitted localisation and
confirmation of complete removal of pathological tissue. In
our opinion, the MGC could completely replace the
intraoperative use of gamma probes. It would even be
possible to replace the preoperative conventional sestamibi
scans and the intraoperative determinations of PTH,
although more experience is needed to confirm this exciting
and cost-effective possibility.
Acknowledgement. This work was partially funded by a Grant for the
Development of Research Programmes in Matters of Health (S.P.-
0037/2005) from the Conselleria de Sanitat de la Generalitat
Valenciana.
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