1. Computer-aided detection of pulmonary embolism (CAD):
can junior radiologist benefit from consensus with CAD in detecting of segmental and subsegmental pulmonary embolism?
Mr. chairman, ladies and gentlemen. I would like to introduce our work about new software tool for automated detection of pulmonary embolism.
J. Baxa, J. Ferda, A. Bednarova, R. Vondrakova, H. Mirka,
Radiology clinic, University Hospital Plzen, Czech Republic

2. introduction and goals
PE-CAD: new automated software for detection of PE
Syngo Circulation® - Siemens Medical Solutions
 evaluate performance of PE-CAD
 possible benefit for junior radiologist
 compare results with other studies
The pulmonary embolism CAD software is a new part of originally cardiac application distributed on workstations by Siemens Medical. We decided to find out performance of this prototype software, possible benefit for young radiologist and finally compare our results with other available studies.
Zhou C et al. Preliminary investigation of computer.aided detection of pulmonary embolism in three-dimensional computed tomography
pulmonary angiography images, Acad Radiol 2005

3. CT pulmonary angiography
64-slice CT (Somatom Sensation 64, Siemens)
standard protocol: 64x0.6 mm; rotation 0.33 s; pitch 0.95;
120 kV, 140 eff. mAs
contrast: 80 ml i.v. (Iomeron 400, Bracco ALTANA Pharma)
+ 60 ml flush of saline
flow rate: 5 ml/sec + 3 ml/s
bolus tracking: 80 HU at ascending aorta
data set: slice 0.6 mm, increment 0.4 mm,
soft tissue kernel (Siemens B30f – medium smooth)
We reviewed our set of CT pulmonary angiographies performed on 64-slice CT with this standard protocol. We administrated 80 ml of contrast agent with concentration 400 mg of iodine per ml and flush of 60 ml of solution saline. Bolus tracking was placed in ascending aorta with threshold of 80 HU.
Standard data sets used for evaluation of pulmonary vessels were reconstructed with slice 0.6 mm, increment 0.4 mm and soft tissue kernel.

4. patient selection segmental and subsegmental embolism
18 positive (9a 9,  58.1)
18 negative (13a 5,  60.7)
78 emboli (41 seg., 37 subseg.);  4.33; <1;9>
board of 2 certified radiologist with specialisation in thoracic imaging
CAD ………………………… Syngo Circulation® (Siemens)
JR …………………………… junior radiologist (3 years praxis)
JR+CAD …………………… consensus of JR with CAD
SR …………………………… senior radiologist (15 years praxis)
In our study, we concentrated on segmental and subsegmental embolism. So we picked up 18 positive and 18 negative examinations. Total count of emboli by this patients was 78, 41 segmental and 37 subsegmental, it means more than 4 emboli per patient. Minimal count by one patient was 1 embolus and maximum 9 emboli. At first, the data sets of our selection were applied to CAD software. Then same selection had been analyzed by junior radiologist with time limit of 10 minutes and after completing and storing was results compared with results of CAD. For control, we also applied same selection to one of senior radiologist at our clinic.

5. 25 y.o. female false positive
Just one short example of young female 25 years old, using hormonal contraception with short episode of dyspnoea and swelling of right leg. On the first image you can see basic background of PE-CAD application with list of 3 possible emboli offered by software. Here is first one in artery of third segment, a second one in bifurcation of lower lobe artery and third one in segmental branch for tenth segment.
This was ideal example, but often CAD offers false negatives and more often false positives. Most frequent false positives are: pulmonary vein, azygos vein, hilar or intrapulmonary lymph nodes.

6. results – „per embolus“
total segmental subsegmental
CAD Sensitivity % % %
PPV %
JR Sensitivity % % %
PPV % % %
JR+CAD Sensitivity % % %
PPV % % %
SR Sensitivity % % %
PPV % % %
And now results in per embolus analysis. Overall „per embolus“ sensitivity of CAD reached 56%, especially at subsegmental level was sensitivity of CAD very low. Sensitivity of junior radiologist was more than 80% and especially in detection of subsegmental embolisation is evident benefit in sensitivity after confrontation with results of CAD.
Engelke C et al. Computer-assisted detection of pulmonary embolism: performance evaluation in consensus with experienced and
inexperienced chest radiologists. Eur Radiol 2007

7. results – „per patient“
CAD
- sensitivity 83%, specificity 61%
- PPV 68%, NPV 79%
JR + CAD
- sensitivity 95%, specificity 89%,
- PPV 90%, NPV 94% SR
- sensitivity 100%, specificity 94%
- PPV 95%, NPV 100%
In per patient analysis, true positive subject is settled, if at least one embolus is truely found. Young radiologist in cooperation with CAD reached very high sensitivity, 95%.

8. comparison results of CAD in recent studies are different
study
no. emboli
SE_CAD
total
segmental
subsegmental
False positive
Plzen, CZE
(Siemens) 78
57%
73%
38%
 3.1
Würzburg, GER
820
34%
41% 
28% 
 4.1
Munich, GER
147
82%
  3.9
Aachen, GER
(Siemens – new version)
215
83%
87%
77%
 4.0
results of CAD in recent studies are different
all studies proved contribution for young radiologist (4-10%)
new version of PE-CAD is really better in comparison
high average of false positives
Comparison of CAD sensitivity with other studies evaluating same CAD software is shown in this table. As you can see results are a little bit different, but all studies proved significant contribution of CAD to sensitivity of young radiologist. Colleagues from Aachen had possibility to evaluate a new version of CAD from Siemens and their results are very promising. Persisting problem is a high rate of false positive findings.
Das M et al. Computer-aided detection of pulmonary embolism: influence on radiologists´ detection performance,
Eur Radiol 2008

9. conclusions
PIOPED II: pulmonary CTA (pCTA) - first line modality in detection of pulmonary embolism (PE)
PE-CAD: innovation in CAD systems
easy and fast usage x lower sensitivity
great potential as a „second reader“
new development is necessary
In conclusion, according to study PIOPED II, pulmonary CTA is gold standard in detection of pulmonary embolism, so number of pulmonary CTA´s is growing. PE-CAD is innovation in CAD system, which is very simple and fast to use, but has lower sensitivity. According to our and other results has CAD software from Siemens great potential as a „second reader“ for junior radiologist, but new development is neccesary.
Chan HP et al. Computer-aided diagnosis of lung cancer and pulmonary embolism in computed tomography-a review.
Acad Radiol 2008 May;15(5):