diagnostic tool, Dr. Alireza Ghassemi

1. Nuklearmedizin 5/2012
201© Schattauer 2012Original article
Bone graft scintigraphy
A new diagnostic tool to assess perfusion during surgery
T. Krohn1
; A. Ghassemi2
; M. Gerressen2
; F. A. Verburg1
; F. M. Mottaghy1
; F. F. Behrendt1
1Department of Nuclear Medicine, University Hospital Aachen, RWTH Aachen, Germany; 2Department of Oral,
Maxillofacial and Plastic Facial Surgery, University Hospital Aachen, RWTH Aachen, Germany
Keywords
Intraoperative imaging, scintigraphy, per-
fusion, transplantation, microsurgical bone
graft
Summary
Aim:To evaluate a scintigraphic tool for intra-
operative assessment of vascularized bone
graft perfusion before and after transplan-
tation. Patients, methods: This pilot study in-
cluded three patients scheduled for surgical
segmental mandibulectomy followed by re-
construction with a vascularized iliac bone
graft. A continuous 99m
Tc-pertechnetate infu-
sion was applied selectively arterial into the
blood vessel supplying the respective graft
before osteotomy as well as after transplan-
tation. Perfusion was analysed by scintigrams
acquired using the intraoperative camera sys-
tems declipseSPECT and Sentinella. Results
were compared qualitatively. Results: Before
harvesting the graft, intraoperative scinti-
graphy revealed a clearly delineated area of
the iliac crest with a relatively homogenous
pertechnetate distribution representing good
perfusion.After osteotomy,transplantation to
the mandibula and re-anastomosis of the
nutrient vessels, scintigraphy in all patients
showed a moderately inhomogenous
distribution pattern of the pertechnetate indi-
cating an adequate perfusion of the bone
transplant through the arterial anastomosis.
Conclusion: Intraoperative assessment of
bone graft perfusion is possible with the im-
aging systems Sentinella as well as with
declipseSPECT using a continuous intra-arter-
ial infusion of 99m
Tc-pertechnetate.
Correspondence to:
Thomas Krohn, MD
University Hospital Aachen
Department of Nuclear Medicine
Pauwelsstr. 30, 52074 Aachen, Germany
Tel. +49/(0)241/8088743
E-mail: tkrohn@ukaachen.de
Schlüsselwörter
Intraoperative Bildgebung, Szintigraphie, Per-
fusion, Transplantation, mikrochirurgisches
Knochentransplantat
Zusammenfassung
Ziel: Evaluierung einer szintigrafischen Metho-
de zur intraoperativen Beurteilung vaskulari-
sierter Knochentransplantate vor und nach
Transplantation. Patienten, Methoden: Die Pi-
lotstudie bezieht sich auf drei Patienten,bei de-
nen wegen einer bösartigen Erkrankung eine
Unterkieferteilresektion vorgenommen wurde
mit nachfolgender Defektrekonstruktion durch
ein vaskularisiertes Knochentransplantat aus
dem Beckenkamm. Intraoperativ wurde kon-
tinuierlich 99m
Tc-Pertechnetat arteriell in den
zum Transplantat führenden Gefäßstiel infun-
diert. Zur Beurteilung der Perfusion wurden
SzintigrammemittelsintraoperativerFreehand-
SPECT (declipseSPECT) und Sentinella akqui-
riert. Die Ergebnisse beider Kamerasysteme
wurden qualitativ verglichen.Ergebnisse:Initial
zeigte die intraoperative Perfusionsszintigrafie
beidendreiPatienteneineklarabgrenzbare,re-
lativ homogen perfundierte Region im knöcher-
nen Beckenkamm, aus der dasTransplantat ge-
wonnen wurde. Nach Transplantation des Kno-
chenstücks in den Unterkiefer und Re-Anasto-
mosierungderversorgendenGefäßezeigtesich
in jedem Fall eine weiterhin erhaltene,etwas in-
homogenere Tracerverteilung als Zeichen der
adäquaten Re-Perfusion. Schlussfolgerung:
Intraoperativ ist mit declipseSPECT oder Senti-
nella die szintigrafische Beurteilung der Kno-
chentransplantatperfusion bei kontinuierlicher
arterieller 99m
Tc-Pertechnetat-Infusion in den
versorgenden Gefäßstiels möglich.
Knochentransplantat-Szintigraphie – Ein neues
diagnostisches intraoperatives Verfahren
Nuklearmedizin 2012; 51: 201–204
doi:10.3413/Nukmed-0469-12-01
received: January 23, 2012
accepted in revised form: May 21, 2012
prepublished online: June 12, 2012
During surgical treatment of malignant or
infectious lesions of the oral cavity a
segmental mandibulectomy is often
necessary.Reconstruction of such bone de-
fects-canbeperformedwithnon-vascular-
ized or vascularized bone grafts (6).
The advantage of vascularized grafts is the
independent blood supply which offers
better long-term results for transplant
survival (2).
However, the surgical procedure of vascu-
larized grafts is complex due to the partly
difficult harvesting and anastomosis of the
small vessels. Furthermore, the exact intra-
operative delineation of the area of the
donor site which is supplied by the vascular
pedicle is challenging.In order to ensure an
adequate perfusion of the bone graft and
thereby a long survival a precise identifica-
tion and preparation of the feeding vessels
and the concerning area of the donor bone
is absolutely necessary.
The aim of this study was to evaluate a
novel intraoperative diagnostic tool using
perfusion scintigraphy to define the precise
part of the donor site fed by the dissected
artery. Furthermore, perfusion of the bone
graft after transplantation and anastomosis
of the nutrient vessels should be assessed
intraoperatively with the potential possi-
bility of an instantaneous revision.
Patients, material, methods
Patients
This pilot study included three patients (2
men, 1 woman; age: 63±5 years) scheduled
for mandibular reconstruction after seg-
mental mandibulectomy due to a carcino-
ma of the oral cavity. The three patients
signed an informed consent to participate
in this additional diagnostic approach
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2. Nuklearmedizin 5/2012 © Schattauer 2012
202 T. Krohn et al.: Intraoperative bone perfusion scintigraphy
under German laws on compassionate use
of medical products.
Gamma cameras
Recently, two portable camera systems for
intraoperative use have been introduced.
● Sentinella® (OncoVision, Valencia,
Spain)isaplanargammacamerasystem
using a CsI(Na) scintillator. In our
study, a pinhole collimator (4 mm hole
diameter) was used. Images can be dis-
played in real time on a persistence
scope and as planar scintigrams. For
anatomical correlation, a 153Gd pointer
is included. Its position is automatically
detected by Sentinella and displayed on-
line within the acquired scintigram.
● DeclipseSPECT™ (surgicEye, Munich,
Germany) consists of a handheld
gammaprobefittedwithathree-dimen-
sional optical tracking system. The pa-
tient is monitored by an optical camera.
Probe and patient position are continu-
ously monitored via additional infrared
cameras and sphere markers. Image ac-
quisition is performed by scanning the
volume of interest with the gamma
probe from several angles after which a
three dimensional image reconstruction
algorithm is started. The resulting
scintigram is displayed as a fusion on
top of the optical patient image.
Surgical procedure and
intraoperative scintigraphy
Patients were pretreated with perchlorate
in order to block thyroid uptake for reasons
of radiation protection and to achieve a
lower background activity in the cervical
region. Resection of the carcinoma of the
oralcavityincludedasegmentalmandibul-
ectomy. For secondary reconstruction of
the resulting bone defect, a vascularized
bone graft from the iliac crest was har-
vested. Preparation of the graft included a
precise dissection of the pars horizontalis
of the deep circumflex iliac artery (DCIA).
After clear delineation of the artery a small
catheter (26G) was inserted into the femo-
ral artery close to the DCIA supplying the
bone graft.
Via this access, 99mTc-pertechnetate was
continuously injected at a rate of 5 MBq/
min.Afteroneminuteof infusion,anactiv-
ityequilibriumwithinthegraftcouldbeas-
sumed. Image acquisition was performed
with Sentinella as well as with declipse-
SPECT for one minute; afterwards the in-
fusion was stopped.
When scintigraphy revealed a tracer up-
take within the entire region planned to be
harvested as a bone graft, an adequate per-
fusion was assumed. The graft was osteo-
tomized preserving the blood supply. Per-
technetate infusion was started again and
scintigrams were acquired as described
previously in order to visualize the per-
fusion of the resected bone.
Afterwards, the blood vessels were cut
and the bone graft was transplanted into the
mandibular defect region. The vessels were
anastomosed to the lingual or facial vessels.
A 26G catheter was inserted into the exter-
nalcarotidarteryjustbelowtheoriginof the
Fig. 1
Scintigraphy with de-
clipseSPECT reveals
a clearly delineated
area of the iliac crest
with a homogenous
distribution of the
pertechnetate, repre-
senting a good per-
fusion of the area
destined to be the
bone graft. For better
orientation, an ana-
tomical image of a
pelvis is inserted
where the scinti-
graphic finding is
marked.
Fig. 2 The result of declipseSPECT is confirmed
by scintigraphy with Sentinella. However, cor-
relation with the intraoperative situs is more
difficult with Sentinella.
Tab. 1
Grading scheme for
the quality of tracer
distribution within
the bone graft
grade engraftement tracer distribution
1 poor no tracer accumulation detectable
2 fair very inhomogeneous
3 good moderately inhomogeneous
4 excellent homogenous within the entire bone area
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3. © Schattauer 2012 Nuklearmedizin 5/2012
203T. Krohn et al.: Intraoperative bone perfusion scintigraphy
recipient artery, pertechnetate infusion was
started again and scintigrams of the man-
dible were acquired as described.
Image analysis
Scintigrams were judged by two board cer-
tified nuclear medicine physicians accord-
ing to visual criteria concerning homo-
geneity, comparability and mismatch find-
ings of tracer distribution between images
acquired from the same patient with the
two systems. In addition, a score-based vis-
ual analysis was performed.
The quality of tracer distribution was
gradedaccordingtoafour-pointscalefrom
1 (no tracer accumulation) to 4 (homogen-
ous tracer distribution). ǠTable 1 sum-
marizes the grading criteria. Mean score
values were calculated from the two ob-
servers for the tracer distribution within
the graft before osteotomy and after trans-
plantation to the mandibula.
Results
Before osteotomy, scintigraphy revealed a
clearly delineated area of the iliac crest with
a relatively homogenous distribution of
pertechnetate. Visual scoring revealed a
mean value of 3.67 for both observers so
that a good perfusion was assumed (ǠFig.
1, ǠFig. 2). In all cases, a part of this iliac
crest area was chosen for harvesting of the
bone graft because adequate perfusion
could be assumed. After osteotomy with
still preserved vascular pedicle, tracer dis-
tribution within the graft was still homo-
genous in scintigraphy (ǠFig. 3).
After transplantation and revasculariz-
ation of the bone graft, scintigraphy still
showed a moderate to good tracer accumu-
lation with a more inhomogeneous dis-
tribution pattern (ǠFig. 4). Mean scores of
the two observers were 2.33 and 2.67, re-
spectively (overall mean score 2.5). This
was considered as an adequate anastomosis
function and sufficient perfusion of the
bone transplant.
Comparison of scintigrams acquired
with Sentinella and declipseSPECT reveal-
ed comparable visual results without any
relevant differences.
In our three patients,clinical follow-up by
thesurgeonsrevealedthegoodviabilityof the
transplants. Osteosynthesis plates could be
removed six months postoperatively. In two
patientsclinicalexaminationshowedsuchan
excellent structural stability that dental im-
plants were inserted into the transplants.
Discussion
Vascularized bone grafts are the preferred
transplants for reconstruction after seg-
mental mandibulectomy or maxillectomy
because of their
● best long-term results (2, 7),
● good bony foundation (5)
– for esthetic projection as well as
– for functional dental retention by
implants.
The deep circumflex iliac artery flap (so
called from its feeding vessel of the bone
graft) is difficult to harvest and has variable
anatomy with the need of precise planning
for optimal results (1). To assure good
Fig. 3
The bone graft with
preserved vascular
pedicle shows homo-
geneous perfusion
after osteotomy.
Fig. 4 Scintigraphy with declipseSPECT reveals a somewhat inhomogenous re-perfusion after trans-
plantation of the bone graft to the mandibula (left). The finding is confirmed by Sentinella (right). For
orientation, an anatomical image of a skull is inserted where the scintigraphic finding is marked.
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4. 204 T. Krohn et al.: Intraoperative bone perfusion scintigraphy
Nuklearmedizin 5/2012 © Schattauer 2012
long-term results, adequate perfusion as-
sessment during surgery is essential in
order to investigate whether the planned
bone graft is sufficiently perfused by the
dissected vascular pedicle.
Furthermore, it is beneficial to find out
immediately, if the re-perfusion of the
transplanted bone graft is sufficient. In
cases of inadequate re-perfusion (e.g. be-
cause of inaccurate vascular anastomosis)
an immediate revision would be possible
within the same procedure. A diagnostic
possibilityforthispurposehasnotbeende-
scribed so far. Generally, the viability of the
bone graft is usually investigated after sur-
gery, e. g. by 99mTc-diphosphonate bone
scintigraphy (3).
Portable camera systems
Intraoperative imaging with 99mTc tracers
and the portable camera systems Sentinella
(9, 10) and declipseSPECT has been shown
as advantageous (8, 11) especially for the
sentinel node biopsy. DeclipseSPECT sup-
ports an easy correlation between the
scintigraphic finding and the intraoper-
ative situs: Both images are continuously
displayed as an intuitively comprehensive
fusion. However, the practical use of
declipseSPECT is more complex due to the
scanning procedure.
For imaging with Sentinella, the cor-
relation between scintigraphic finding and
anatomy requires a gadolinium point
source. The situs needs to be scanned with
the pointer to find out how the coordinates
within the scintigram fit with anatomical
positions. Nevertheless, image acquisition
itself is easier with Sentinella: The camera
head just needs to be placed over the pa-
tient and acquisition can start.
Limitation
Onlyqualitativeresultsof graftperfusionare
obtainedbyournewmethod.Thisisapoten-
tial limitation. Exact quantification of blood
flow in ml/min×g could give further infor-
mation. This requires kinetic modelling.
As far as we know, no validated model
for quantification of blood flow in planar
bone scintigraphy with pertechnetate as
tracer is known.In order to turn intraoper-
ative bone perfusion scintigraphy more
quantitative, the validation of a compart-
ment model is necessary (e. g. by using
microspheres in animals). This is far
beyond the scope of this pilot study.
Conclusion
Theearlyknowledgeof graftperfusionpre-
dicts the success of surgical outcome (4).
Our study demonstrates
● how intraoperative perfusion assess-
ment of bone grafts is clinically feasible
with continuous intra-arterial infusion
of 99mTc-pertechnetate by the imaging
systems Sentinella and declipseSPECT,
● that perfusion of bone graft can be in-
vestigated easily before osteotomy and
after transplantation.
The advantage of our novel scintigraphic
method: Adequate re-perfusion of the
transplanted graft is assured before surgery
is finished. This enables an early revision if
necessary. Based on our results, further as-
sessment of bone perfusion scintigraphy in
a large patient group appears promising.
Conflict of interest
The authors declare, that there is no
conflict of interest.
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