1. AIME'05 1 Learning rules from multisource data for cardiac monitoring Elisa Fromont*, René Quiniou, Marie-Odile Cordier DREAM, IRISA, France * work supported by the French National Net for Health Technologies as a member of the Cepica project

2. AIME'052 Context (ICCU/ [Calicot03]) Cardiac Arrhythmias Learning for Intelligent Classification of On-line Tracks 0 1000200030004000 Signal abstraction: raw data (ECG)  symbolic descriptions Chronicle recognition t P(normal) P(normal) t 0 t 1 t 2 t 3 t 4 QRS(normal) Arrhythmia QRS(abnormal) On line Chronicle base Inductive learning Symbolic transformation Off line Rule base Signal data base [Moody96]

3. AIME'053 Motivations Why learning rules ? A knowledge acquisition module can relieve experts of that time- consuming task [Morik00] Why using Inductive Logic Programming (ILP) ? –First order rules are easily understandable by doctors –Relational learning allows to take into account temporal constraints (  chronicles) Why using multiple sources ? Information from a single source is not always sufficient to give a precise diagnosis (noise, complementary information, etc.) Update Calicot for multisource management

4. AIME'054 Multisource data 2 ECG channels, 1 hemodynamical channel: 3 views of the same phenomenon ECG Chan II : (P, QRS) ECG Chan V : (QRS) ABP Chan Sensor 1 Sensor 2 Sensor 3

5. AIME'055 Monosource learning with ILP From –A set of examples E defined on L E labeled by a class c  C –For each class c, E+ = {(e k,c)| k = 1,m} are the positive examples and E- = {(e k,c’)| k = 1,m, c  c’} are the negative examples –A bias B that defines the language L H of the hypotheses looked for –A Background knowledge BK defined on L = L H  L E Find for each class, a set of hypotheses H such that : 1.H  BK  E+ (H covers all the positive examples) 2.H  BK  E - (H covers no negative example) * * in practice this property is loosen

6. AIME'056 Declarative bias [Bias96] Grammar to define : – the language (specify the vocabulary to use) – the length of the hypotheses looked for – the order in with consider literals Mandatory for ILP system such ICL[ICL95]

7. AIME'057 Example of learned monosource rule rule(bigeminy) :- qrs(R0, anormal), p_wav(P1, normal), suc(P1,R0), qrs(R1, normal), suc(R1,P1), qrs(R2, anormal, R1), suc(R2,R1), rr1(R1, R2, short). R0 R1 R2 P1 Example bigeminy e21 Example bigeminy e31 Example X* e41 Example Z* en1 … Example bigeminy e11 *X…Z  bigeminy Induction +B +BK

8. AIME'058 Multisource learning : 2 approaches (example on two sources for one class) Consistency :  i  j ( e k,i, c)  ( e k,j, c’)  c = c’ Example bigeminy e12 Example bigeminy e13 Example X* e14 Example Z* e1n … Example bigeminy e11 Induction +B1 +BK1 Example bigeminy e22 Example bigeminy e23 Example X* e24 Example Z* e2n … Example bigeminy e21 Induction +B2 +BK2 H1H1 H2H2 H Example bigeminy e12 Example X* e14 Example Z* e1n … Example bigeminy e11 Example Z* e2n Example X* e24 Example bigeminy e13 Example bigeminy e23 Example bigeminy e22 Example bigeminy e21 Induction +B +BK aggregated examples Naive multisource learning monosource learning on source 1 monosource learning on source 2 Vote between H 1 and H 2 ?

9. AIME'059 Naive multisource learning problems When number of sources increases  –volume of data increases (aggregation of examples) – expressiveness of language increases  the size of the hypothesis search defined by B is bigger than both search spaces defined by B1 and B2  too much computation time bad results due to important pruning when looking for hypotheses in the search space

10. AIME'0510 Idea : biased multisource learning Bias efficiently the multisource learning by using : –monosource learned rules –aggregated examples Difficult to define without background knowledge on the problem  create a multisource bias automatically !

11. AIME'0511 Algorithm (on two sources) Resulting search space L : naive multisource language H2H2 L L2L2 H1H1 L1L1 LbLb bt 1 bt 2 bt 3 bt 4 bt 5 Lb : biased multisource language Li : langage of source i

12. AIME'0512 How to construct bt i ? (toy example) H1: class(x):- p_wave(P0,normal), qrs(R0,normal), pr1(P0,R0, normal), suc(R0,P0). H2: class(x):- diastole(D0,normal), systole(S0,normal), suc(S0,D0). … class(x):- p_wave(P0,normal), diastole(D0,normal), suci(D0,P0),qrs(R0,normal), systole(S0,normal), suci(S0,R0), pr1(P0,R0,normal), suc(R0,P0), suc(S0,D0). class(x):- p_wave(P0,normal), qrs(R0,normal), pr1(P0,R0,normal), suc(R0,P0), diastole(D0,normal), suci(D0,R0),systole(S0,normal), suc(S0,D0). Rule fusion + new relational literals

13. AIME'0513 Properties of the biased multisource search space 1.rules learned with the biased multisource method have an equal or higher accuracy than the monosource rules learned for the same class (in the worst case: vote) 2.the biased multisource search space is smaller than the naive multisource search space (  DLAB [DLAB97]) 3.there is no guaranty to find the best multisource solution with the biased multisource learning

14. 14 Examples of learned rules class(svt):- %ECG qrs(R0),qrs(R1),suc(R1,R0), qrs(R2),suc(R2,R1),rr1(R1,R2,short), rythm(R,R1,R2,regular), qrs(R3), suc(R3,R2),rr1(R2,R3,short), qrs(R4),suc(R4,R3),rr1(R3,R4, short). (covers 2 neg) class(svt):- %ABP systole(S0),systole(S1),suc(S1,S0), amp_ss(S0,S1,normal), systole(S2),suc(S2,S1), amp_ss(S1,S2,normal),ss1(S1,S2,short). (covers 1 neg, does not cover 1 pos) class(svt):- %biased multi qrs(R0),qrs(R1),suc(R1,R0), qrs(R2), suc(R2,R1),rr1(R1,R2,short), rythm(R,R1,R2,regular), qrs(R3), suc(R3,R2),rr1(R2;R3,short), systole(S0), suci(S0,R3), qrs(R4), suci(R4,S0),suc(R4,R3), systole(S1),suc(S1,S0), suci(S1,R4), amp_ss(S0,S1,normal). class(svt):- %naive multi qrs(R0), systole(S0), suc(S0,R0), qrs(R1), suc(R1,S0), systole(S1), suc(S1,R1),suc(R1,R0),rr1(R1,R2,short). (covers 12 neg)

15. AIME'0515 Results on the whole database 6572273510231063Nb Nodes 54/23/25 Cardiac cycles 1221Nb Rules 10.70.841TestACC 10.9160.9981ACC arrhyt1 bigeminy BiasedNaive Source 2 (ABP) Source 1 (ECG) Multi sourceMono source 363.86*310014.2726.99CPU time *include monosource computation times Biased multisource much more efficient than naive multisource No significant improvement from monosource to biased multisource Database : small(50) not noisy sources are redundant for the studied arrhythmias

16. AIME'0516 Less informative database (new results without multisource cross validation problems and new constraint on ABP monosource learning) 8/54/4/654 Cardiac cycles 2311Rules(H) 0.90.640.860.4TestACC 0.980.9450.940.44ACC arrhyt1 ves BiasedNaive Source 2 (ABP) Source 1 (ECG) Multi sourceMono source 5235 Cardiac cycles 1111Rules(H) 0.920.760.840.94TestACC 0.990.760.9620.96ACC arrhyt2 svt BiasedNaive Source 2 (ABP) Source 1 (ECG) Multi sourceMono source

17. AIME'0517 Conclusion Biased multisource vs monosource: better or equal accuracy less complex rules (less rules or less literals) Biased multisource method vs naive method: better accuracy narrower search space reduced computation time Multisource learning can improve the reliability of diagnosis (particularly on complementary data) The biased method allows scalability

18. AIME'0518 References [Calicot03] : Temporal abstraction and inductive logic programming for arrhythmia recognition from ECG. G. Carrault, M-O. Cordier, R. Quiniou, F. Wang, AIMed 2003 [Moody96] : A database to support development and evaluation of intensive care monitoring. G.B. Moody et al. Computer in Cardiology 96 [ICL95] : Inductive Constraint Logic (ILP). L. De Raedt et W. Van Laer, Inductive Logic Programming 95 [Bias96] : Declarative bias in ILP. Nedellec et al. Advances in ILP 96 [DLAB97] : Clausal discovery. L. De Raedt, L. Dehaspe, Machine Learning 97 [Morik00] : Knowledge discovery and knowledge validation in intensive care. K. Morik et al. AIMed 2000

19. AIME'0519 Property on aggregated examples Let H ic a hypothesis induced by learning from source i, i  [1,s] and the class c  C For all k  [1,p], if H ic covers (e i,k, c) then it also covers the aggregated example (e k,c) For all k  [1,n], for all c’  {C-c}, if H ic does not cover (e i,k, c ’ ) and if for all j  i, L i  L j =  then H ic does not cover the aggregated negative example (e k,c ’ )

20. AIME'0520 Activité électrique du cœur : les éléments de l’apprentissage (voies II et V)

21. AIME'0521 Voie hémodynamique Attributs : - amplitude diastole/systole - différence d’amplitude entre diastole et systole - intervalle de temps entre diastole et systole (sd, ds, dd, ss, ….)