Open Journal of Clinical Diagnostics, 2011, 1, 9-14
doi:10.4236/ojcd.2011.13003 Published Online December 2011 ( OJCD
Published Online December 2011 in SciRes.
Training benefits of virtual bronchoscopy prior to
endobronchial ultrasound guide sheath
D. Fielding, F. Bashirzadeh, P. Nguyen
Depart ment of Thoracic Medicine , Royal Brisbane an d Womens Hospital, Herst o n, Australia.
Received 4 August 2011; revised 6 September 2011; accepted 16 September 2011.
Research questions: How does a virtual broncho-
scopy navigation system (VBNS) improve prediction
of candidate bronchus across a range of doctors in-
vestigating a range of lesions with endobronchial ul-
trasound (EBUS) guide sheath? To what extent do
benefits of virtual bronchoscopic pre-procedure
navigation apply to experienced versus inexperienced
bronchoscopists? Methods: Using archived EBUS
Guide sheath cases, a comparison was made between
identified candidate 4th order bronchus by Comput-
erised tomography (CT) evaluation versus that iden-
tified after virtual path creation. Results: From 7
archived cases, 14 doctors identified the correct
bronchus in 94 of 98 assessments (95%). Percentage
of cases where there was an improvement in localisa-
tion by 2 or more 4th order bronchi was 39.8% over-
all (28.6% - 51.0%), 26.6 for experienced and 53.1 for
inexperienced bronchoscopists (p < 0.02). The abso-
lute mean number of 4th order bronchi different be-
tween CT and VBNS was 2.0 ± 2.6 overall, 1.2 (range
0 - 6) for experienced, and 2.8 (range 0 - 11) for inex-
perienced bronchoscopists. Virtual Path software
calculation time was 8.1 ± 2.7 minutes, compared to
3.6 ± 2.1 minutes by CT. Conclusion: VBNS allowed
rapid accurate assessment with minimal software
training. Greatest benefits in reduction of procedure
time were obtained in inexperienced bronchoscopists,
and VBNS could allow more rapid skill development
in EBUS GS in these doctors.
Keywords: Virtual Bronchoscopy; Lung Neoplasms and
Solitary Pulmonary Nodule/Diagnosis; Transbronchial Bi-
opsy; Three-Dimensional Imaging; Endobronchial Ultra-
Endobronchial Ultrasound Guide sheath (EBUS GS)
sampling of peripheral lung nodules is an accepted
method in bronchoscopy [1,2]. Finding small peripheral
lesions is difficult [3] and EBUS GS has substantially
improved procedural yields [4]. It involves pre proce-
dure scrutiny of the CT chest to predict which bronchus
is likely to harbour the lesion into which the probe is
passed. However due to a number of factors the selection
of the correct bronchus can be difficult. These include
the presence of endobronchial variations, difficulty in
interpreting segmental pulmonary anatomy on CT, and
the experience of the operator [5,6]. In recent years a
number of virtual navigation tools have improved the
ability to extract info rmation from a CT scan which pre-
viously would only have been used for axial and coronal
imaging [7,8]. Now CT reconstruction is used to create
“fly through” images showing endobronchial appear-
ances [9,10]. Some systems have enough definition to
enable correct path tracking in up to 14 branches from
the trachea out to a peripheral lesion [11]. The majority
identify 5 - 8 branches [9]. This information is particu-
larly useful when combined with EBUS GS because the
selection of the bronchus is so critical, thereby reducing
procedure time. This has been demonstrated in a limited
number of centres, usually by operators highly experi-
enced in the field [12,13]. In Asano’s series combining
EBUS GS with a CT virtual bronchoscopy navigation
system (VBNS) the system automatically produced vir-
tual images to a median of fifth- (third- to seventh-) or-
der bronchi [12]. In all patients, the thin bronchoscope
could be guided along the planned route, and observa-
tion to a median of fifth- (third- to seventh-) order bron-
chi was possible. Thirty lesions (93.8%) were success-
fully visualized by EBUS, and 27 (84.4%) could be
pathologically diagnosed. In lesions < or =30 mm in size,
the EBUS visualization yield was 91.7% (22/24), and the
diagnostic yield was 79.2% (19/24). Shinagawa com-
pared use of VBNS with real time in-procedure tracking
with EBUS GS to a historical series of VBNS assisted
biopsies where the bronchoscopist had to remember the
D. Fielding et al. / Open Journal of Clinical Diagnostics 1 (2011) 9-14
images [10]. Here there were slight improvements in
diagnostic sensitivity for a similar sized cohort of lesions,
as well as a 5 minute reduction in the overall procedure
time. This was attributed to the benefits of the VBNS in
quickly identifying the correct bronchus. In a recent
multicentre study by Asan o comparing CT to VB guided
EBUS GS there were significant improvements in diag-
nostic yield (81% for VB versus 67% for CT) and reduc-
tions in examination times [14]. VBNS is not a real time
tracking device in itself, that is it does not track the ac-
tual bronchoscope; however it has the advantage of sim-
plicity in that it is not directly connected to the patient
and does not require additional bronch oscopic hardware.
It is almost real time in the sense that the proceduralist
can easily progress the stored virtual images ahead of the
actual bronchoscopic images to allow the correct path to
be followed. It utilises existing CT imaging.
Learning endobronchial anatomy is difficult, particu-
larly when combined with the challeng e of matching CT
segmental anatomy to endobronchial appearances [9].
Sakurada et al have noted great inter-individual differ-
ences in subsegmental bronchial angulation, and diffi-
culties due to bronchial movement during respiration [5].
Conversely actually doing the biopsies and manipulation
of the EBUS miniprobe in EBUS GS is no different to a
standard transbronchial biopsy, and this part of the pro-
cedure does not require any real new skills [4]. There-
fore for doctors starting out in EBUS GS assistance in
obtaining the correct bronchial anatomy would greatly
enhance their results, and indeed possibly their overall
motivation to learn the technique.
We wanted to determine the practical aspects of a vir-
tual bronchoscopic navigation system- how easy was it
to use, how much time does it take to learn to use it, and
how much longer preparation time is involved. We also
wanted to know to what extent it could quickly bring
inexperienced bronchoscopists up to the level of their
more experienced colleagues in finding the correct
bronchus into which they might pass the EBUS GS
2.1. Subjects
Subjects were bronchoscopists with an interest in EBUS
guide sheath TBLB. There were seven experienced and
seven inexperienced in EBUS GS. In the experienced
group all were at consultant level and the mean number
EBUS GS cases was 100, range 10 - 250. Inexperienced
bronchoscopists had a year of standard bronchoscopy
training during which they had observed EBUS GS pro-
cedures and were about to start their own procedural
learning of this. All had received endobronchial anatomy
tuition as part of their standard bronchoscopy training.
2.2. Study Design
A prospective single blind crossover study. Only ar-
chived de-identified bronchoscopy data and CT images
were used from procedures which were part of a normal
patient workup and as such no ethics committee submis-
sion was made. A prospective single blind crossover
study. Only archived de-identified bronchoscopy data
and CT images were used from procedures which were
part of a normal patient workup and as such no ethics
committee submission was made.
2.3. Methods
See Figure 1 for a flow diagram of the study design.
There were 7 cases for the doctors to review. Each case
had previously had an EBUS GS procedure so the cor-
rect bronchus was known from that. The task for each
doctor look at the CT scan with the lesion and nominate
the correct bronchus they thought would reach that le-
sion. Then they would use the VBNS software with the
same CT images and use that to nominate the correct
bronchus. They did not use the name of the bronchus,
rather just indicate on a picture of an endobronchial view
which bronchus they had chosen. (The endobronchial
pictures were prepared for each case from fly through
images obtained from the CT of each case. Therefore it
was more of a real life situation, rather than just having
the doctors mark a single standard anatomical chart.)
Each doctor received 45 minutes of tuition in the use of
the VBNS system. Each doctor therefore placed 2 points
on the same bronchial picture for each case—one for the
estimate by CT viewing, the other from viewing the
VBNS fly-through path leading to th e lesion. Th e pictur e
was of all bronchi within the bronchial tree, not just the
likely candidate lobe. Doctors were asked to mark the
bronchus at the 4th order level. Each doctor therefore
marked 7 pictures. These pictures were scored by com-
paring the two marked bronchi to the actual known cor-
rect bronchus—were they the same or different, and if
different by how many 4th order bronchi were they in-
correct? An integer for each doctor for each of the 7
cases was therefore derived. This was 0 if they were
correct and 1, 2 or 3 and so on depending on how many
4th order bronchi they were incorrect by. Within a lobe
the number of bronchi different was counted directly
back towards the nearest correct bronchus. For example
marks on RB1a for CT and RB1b for VBNS would be a
score of 1. Where the identified bronchus was in a dif-
ferent lobe from the correct one then all of the 4 th order
bronchi in that lobe were counted in addition to co unting
the number in the correct lobe. Figure 2 gives an exam-
ple of creation of a path for 1 lesion. A supplemental
video shows the fly through for that case. Figure 3 gives
an example of a score sheet for 1 case for 1 doctor. To
opyright © 2011 SciRes. OJCD
D. Fielding et al. / Open Journal of Clinical Diagnostics 1 (2011) 9-14 11
Figure 1. Study design.
Figure 2. Example of a path created to a lesion in RML using
VBNS software. The CT panels ((a) Axial, (b) Coronal, (c)
Sagittal) show the blue “bronchogram” which shows a bron-
chus leading to the lesion. This blue bronchus is clicked by the
operator which then leads to the creation of the virtual path
down which the operator can scroll ((d) still image from the
flythough). The green dot seen in the still example in lower
right panel indicated the direction of the lesion.
estimate the added time of missing the correct bronchus
by only using CT we timed how long it took to unsuc-
cessfully interrogate a 4th order bronchus in 6 conven-
tional EBUS GS cases, not used in the localisation part
of this study.
2.4. Equipment
CTs were viewed on Osirix free ware, with both axial
and coronal images available. The virtual bronchoscopy
system was Olympus VBNS system (Olympus Tokyo
2008). This system inputs Diagnostic Imaging and Com-
miunication in Medicine (DICOM) CT images of 1mm
thickness overlapping at 0.5 mm intervals. The method
is as described in Asano, but briefly the operator identi-
fies the lower trachea as the start point, then identifies
Figure 3. Figure 2 Example of a score sheet of one doctor for
one case. The marked bronchus by CT (*) is RB3B. The
marked bronchus by VBNS (**) is RB1b. This is a difference
of 4 4th order bronchi and a score of 4 is given.
Table 1. Details of archived cases.
Case numberLesion size, mmLobe 4thorder bronchus
1 70 RLL Rb6a
2 18 Lingula LB4a
3 23 LUL LB 1&2c
4 11 LLL LB 9a
5 20 RML RB4a
6 10 RUL Rb1a
7 29 RUL RB1b
Mean 25.9 ± 20.6
the pulmonary nodule in question, then identifies the
closest bronchus leading to the lesion. The pathway so
derived is then presented as a fly through or as a series
of thumbnail images at branch points. Archived EBUS
GS cases had been performed with Olympus 20 - 20 or
20 - 17 EBUS mini-probes with 4.9 or 6.4 mm diameter
2.5. Analysis
Standard statistical comparison of CT versus VBNS
such as t tests could not be applied because the data were
clumped at zero and skewed above zero.
Fourteen doctors examined 7 cases, giving a total of 98
sets of data for comparison between CT and VNBS pre-
dicted bronchus. Table 2 shows the times taken to re-
view CT data and then create a VBNS path. Overall
opyright © 2011 SciRes. OJCD
D. Fielding et al. / Open Journal of Clinical Diagnostics 1 (2011) 9-14
Table 2. Times (in minutes) for review of CT and creation of
VBNS path.
bronchoscopist Inexperienced
CT 3.6 ± 2.1 4.2 ± 2.5 2.9 ± 1.4
VBNS 8.1 ± 2.7 8.8 ± 2.9 7.4 ± 2.4
VBNS added approximately 4 minutes of procedure
preparation time. On average experienced broncho-
scopists spent a minute long er on reviewing the CT scan ,
whereas inexperienced bronchoscopists were on average
a minute faster in deriving the virtual path candidate
bronchus. Overall from the 98, 94 (95%) correctly iden-
tified the candidate bronchus by VBNS. Of the 4 where
this was incorrect there was only a single 4th order
bronchus different. Figure 1 gives an example of the
data sheet for one doctor for one case, with the points for
CT and VBNS identification of the candidate bronchus.
Video 1 (supplemental data) is an attachment of a typical
virtual bronchoscopic path and bronchus identification.
The mean number of 4th order bronchi different between
CT and VBNS was as follows: for all cases it was 1.98 ±
2.6, for experienced bronchoscopists it was 1.2 ± 1.7,
range 0 - 6, and fo r inex p erien ced br onch osco p ists it was
2.8 ± 3.1, range 0 - 11. In a series of 6 cases where ac-
tual EBUS GS was done and a 4th order bronchus was
unsuccessfully interrogated we timed that interrogation
to take 96 seconds ± 62. Using this figure, and applying
it to cases where an incorrect candidate bronchus was
identified, the approximate maximum time difference at
a potential bronchoscopy before the lesion was correctly
found would be 9 minutes (6 × 90 seconds) for experi-
enced bronchoscopists, and potentially 15 minutes (11 ×
90 seconds) for an experienced bronchoscopist. No sig-
nificant differences in improvement were noted when
comparing improvements in localisation of upper lobe
lesions versus middle and lower lobe lesions. From the
98 sets of data, the percentage of cases where there was
an improvement in localisation by 2 or more 4th order
bronchi was a follows: All cases 39.8, experienced
bronchoscopists 26.6 and inexperienced 53.1 (p < 0.02
for experienced versus inexperienced). Using McNemars
test, confidence intervals for all cases showed a range of
28.6% to 51.0%. Therefore it is likely to be a minimum
30% of procedures in a wider population where some
benefit would accrue from using VBNS, in the form of a
change of candidate bronchus of 2 or more 4th order
The main result of this study was that after a single brief
tuition session with the software the correct candidate
bronchus could be defined by VBNS in 95% of cases.
This was true for both experienced and inexperienced
bronchoscopists and represents quickly acquired accu-
rate information prior to a procedure. In fact inexperi-
enced bronchoscopists on average took a minute less to
gain the information, demonstrating quicker uptake of
use of the software in this group. The degree of im-
provement is modest and as expected there was greater
benefit for inexperienced bronchoscopists. However in
calculating the improvement and a potential time saving
we assume that the bronchoscopist would move towards
rather than away from the correct bronchus, so poten-
tially the improvements could be an underestimate of
benefit. We estimated using the VBNS saves on average
around 2 to 3 minutes. This is in keeping with recently
published data from a group experienced in VB assisted
EBUS GS [10,18]. In the ore recent Shinagawa study
virtual planning did in fact reduce EBUS GS procedure
time by approximately 2 minutes- that study was done
by 3 experienced bronchoscopists and our study pro-
vides unique information about the potential benefit to
trainees as well. As such there would be definite benefits
to patient comfort when the predicted bronchus could be
improved by up to 6 bronchi in experienced and up to 11
bronchi in inexperienced proceduralists. The strength of
our study is the use of actual cases where the gold stan-
dard of comparison was the candidate bronchus which
had localised the lesion in a real bronchoscopy. Other
studies have repeatedly used one endobronchial model
simulation for all cases, only varying the target lesion
[15]. Merritt et al reported a series of image guided
bronchoscopy where lesions had been artificially created
on CT. Having created the lesions the 10 broncho-
scopists then used the same phantom to reach each of the
10 lesions. Our cases had real lesions which were obvi-
ously matched to the real bron chial tree leading to them,
and therefore a fully new virtual bronchial path had to be
created each time. Nonetheless this group still demon-
strated benefits with VB improving overall localisation
from 43% to 94 % for 10 lesions. Interestingly there was
no difference between their inexperienced and experi-
enced group in terms of improvement with addition of
virtual bronchoscopy. What is the trade off for reducing
the procedure time overall by approximately 3 minutes
compared to approximately 8 minutes of VBNS prepara-
tion beforehand? At least part of the preparation time
could be deducted if we subtract the time normally taken
for reading the CT, which here was 4 minutes. In addi-
tion we believe any time saved with the bronchoscop e in
situ constitutes a benefit for a patient, although this of
course is difficult to quantitate. A procedure shortened
by 2 - 3 minutes would likely constitute a comfort bene-
fit to patients, particularly given less manipulation of the
opyright © 2011 SciRes. OJCD
D. Fielding et al. / Open Journal of Clinical Diagnostics 1 (2011) 9-14 13
EBUS GS probe in the bronchus searching for the cor-
rect bronchus.
Overall our inexperienced candidates scored very well
on their knowledge of CT and endobronchial anatomy
before applying VBNS. This may in part reflect their
exposure to others performing the procedure and better
learning tools now available for training bronchoscopists
[16]. In one other series of both experienced and inexpe-
rienced bronchoscopists Dolina reported a simulation
study where 10 lesions were artificially created at endo-
bronchial sites between 3rd and 5th order bronchi [17].
These lesions were therefore considerably easier to iden-
tify and locate than the lesions in this study which were
placed at non bronchoscopically visible locations typi-
cally at 8th order bronchus level. Similar to our study
bronchoscopists recorded their results on a paper deci-
sion sheet in this case it was the bronchoscope path to
the lesion. Results were that without VB assistance the
correct path was only found in 14%, which improved to
49% with the addition of VB assistance. With a com-
puter tracking tool, perhaps more accurate in terms of
the subjects’ decisions, there was an improvement from
40% to 96% in reaching the target. With either method
the basic results for their subjects withou t the aid of vir-
tual bronchoscopy were therefore lower than our group.
A limitations of our study was that only two of the
cases had endobronchial variations, and cases where
more variations had been present may well have shown a
bigger improvement with VBNS. Also we were not test-
ing manipulation of a bronchoscope to arrive at a certain
bronchus as has been done in other mannequin studies.
Sakurada et al. [5] noted that some bronchi are more
difficult to gain access to such as RB3a and LB 1 & 2c,
however we did not include manual dexterity for access
in this study. In terms of the input of CT data into the
VBNS system a significant number of cases could not be
performed because the CT had not been acquired with
thin enough slices, thereby severely reducing definition
of virtual images.
In summary we have showed virtual bronchoscopy is
an easily aquired skill which improves bronchial local-
isation, even with a high baseline knowledge of anatomy.
Inexperienced bronchoscopists quickly acquire the skill
and this affords them greater potential in-procedure
benefit. This is in line with the use of virtual tools for a
range of bronchoscopic skills [18]. We believe this sim-
ple method should be available to all proceduralists do-
ing EBUS GS, but particularly inexperienced broncho-
scopists as a compliment to their learning of the EBUS
GS method.
Supply of VNS software prototype by Olympus Medical Systems
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