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Review ArticleArtificial Neural Networks in Image Processing forEarly Detection of Breast Cancer
M. M. Mehdy,1 P. Y. Ng,1 E. F. Shair,2 N. I. Md Saleh,3 and C. Gomes2
1Department of Computer and Communication System Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia2Department of Electrical and Electronics Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia3Department of Chemical and Environmental Engineering, Universiti Putra Malaysia, Serdang, Selangor, Malaysia
Correspondence should be addressed to C. Gomes; [email protected]
Received 15 January 2017; Accepted 9 March 2017; Published 3 April 2017
Academic Editor: Po-Hsiang Tsui
Copyright © 2017 M. M. Mehdy et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Medical imaging techniques have widely been in use in the diagnosis and detection of breast cancer.The drawback of applying thesetechniques is the large time consumption in the manual diagnosis of each image pattern by a professional radiologist. Automatedclassifiers could substantially upgrade the diagnosis process, in terms of both accuracy and time requirement by distinguishingbenign and malignant patterns automatically. Neural network (NN) plays an important role in this respect, especially in theapplication of breast cancer detection. Despite the large number of publications that describe the utilization of NN in variousmedical techniques, only a few reviews are available that guide the development of these algorithms to enhance the detectiontechniques with respect to specificity and sensitivity. The purpose of this review is to analyze the contents of recently publishedliterature with special attention to techniques and states of the art of NN in medical imaging. We discuss the usage of NN in fourdifferent medical imaging applications to show that NN is not restricted to few areas of medicine. Types of NN used, along withthe various types of feeding data, have been reviewed. We also address hybrid NN adaptation in breast cancer detection.
1. Introduction
Breast cancer is one of the main causes of death amongwomen and the most frequently diagnosed non-skin cancerin women [1]. Breast cancer occurs when the cell tissuesof the breast become abnormal and uncontrollably divided.These abnormal cells form large lump of tissues, whichconsequently becomes a tumor [2]. Such disorders couldsuccessfully be treated if they are detected early. Thus, it isof importance to have appropriate methods for screening theearliest signs of breast cancer.
Microcalcifications and masses are the earliest signs ofbreast cancer which can only be detected using modern tech-niques. Microcalcifications are clusters of calcium depositswhich are very small in size and present inside the soft breasttissues [2]. Generally, detection of masses in breast tissues ismore challenging compared to the detection of microcalcifi-cations, not only due to the large variation in size and shapebut also because masses often exhibit poor image contrast
when usingmammography [3].The difficulty in classificationof benign and malignant microcalcifications also causes asignificant problem in medical image processing.
Automated classifiers may be useful for radiologists indistinguishing between benign andmalignant patterns.Thus,in this paper, an artificial neural network (ANN) which canbe served as an automated classifier is investigated. Inmedicalimage processing, ANNs have been applied to a variety ofdata-classification and pattern recognition tasks and becomea promising classification tool in breast cancer [4]. ANNapplications in mammography, ultrasound, and MRI and IRimaging for early detection of breast cancer are reviewed inthis paper.
Image features can be distinguished inmany aspects, suchas texture, color, shape, and spatial relations. They can reflectthe subtle variance inmany degrees.Thus, different selectionsof image features will result in different classification deci-sions. These classifications can be divided into three types:first, the method based on statistics, such as Support Vector
HindawiComputational and Mathematical Methods in MedicineVolume 2017, Article ID 2610628, 15 pageshttps://doi.org/10.1155/2017/2610628
2 Computational and Mathematical Methods in Medicine
Machine; second, the method based on rule, such as decisiontree and rough sets; and third, artificial neural network [5].
In the early 1980s, there was an increment in the use ofneural networks in the field of image and signal process-ing. The main benefit was the reduction in manipulationtime due to the parallel-distributed processing behaviorof neural networks [6]. Then the network had been usedwidely in the common image processing methods such asvector quantization, eigenvector extraction, 2D pulse codemodulation, or 2D filtering [7]. The artificial neural networkresembles the function of the biological neuron, and it iscomposed of neurons with different layers and these neuronsare interconnected by numeric weights; these weights canbe changed due to the learning behavior of the network toapproach the optimum result. Usually in image processingapplications, the number of the neurons is directly related tothe number of pixels in the input image [8], and the numberof layers depends on the processing steps.
For cancer detection and classification, image segmen-tation has been widely used. Many image segmentationmethods, based on histogram features, edge detection, regiongrowing, or pixel classification, have been trained usingANNs [9].
Although the technology related to ANN in breast cancerdetection has rapidly moved forward during the last fewyears, there is a dearth of critical literature review on thesubject which is a distinct drawback for further developmentof the technologies. This paper is an attempt to fulfill thatvacuum in the field of image processing in the early detectionof breast cancer.
2. Applications of ANNs
2.1.Mammogram. Mammography is one of themost effectivemethods used in hospitals and clinics for early detection ofbreast cancer. It has been proven effective to reduce mortalityas much as by 30% [3]. The main objective of screeningmammography is to early detect the cancerous tumor andremove it before the establishment of metastases [3, 10, 11].The early signs for breast cancer are masses and microcal-cification but the abnormalities and normal breast tissuesare often difficult to be differentiated due to their subtleappearance and ambiguous margins [3]. Only about 3% ofthe required information are revealed during a mammogramwhere a part of suspicious region is covered with vesselsand normal tissues. This situation may cause the radiologistsdifficult to identify a cancerous tumor. Thus, computer-aided diagnosis (CAD) has been developed to overcomethe limitation of mammogram and assists the radiologiststo read the mammograms much better [10]. ANN modelis the most commonly used in CAD for mammographyinterpretation and biopsy decision making. There are twoways used in ANN to assist in mammography interpretation:first, applying classifier directly to the region of interest (ROI)image data and second, understanding the situation from thefeatures extracted from the preprocessed image signals [12].Figure 1 shows an example of ANN structure with multi-featured input data and multi-hidden layers [12].
Microcalcification is deposition calcium in the soft breasttissues. They are quite minute in quantity and size. It isfound in a cluster or pattern of circles/lines together withextra cell activity in breast region [2]. Many researchershave developed CAD system using artificial neural networkto detect microcalcification. In early 90’s, research doneby Dhawan et al. [13] has defined image structure featuresusing the second-order grey-level statistics.The classificationwas based on implementing perceptron based 3-layer neuralnetwork and the network uses backpropagation algorithmin training which has been used successfully for a numberof pattern recognition and classification applications [13, 14].The entropy feature has significant discriminating power forclassification [13]. The group of researchers further extendedtheir research in investigating the potential of using second-order histogram textural features for their correlation withmalignancy. Several architectures of neural networks wereproposed to analyze the features extracted from segmentedcalcifications and it shows that the neural network gives goodresults for the classification of hard-to-diagnoses cases ofmammographic microcalcification into benign and malig-nant categories using the selected set of features [15].
Image segmentation is a technique used in image process-ing. Basically, segmentation is performed on the raw image todetect small, local, and bright spots. Research done by Kevinet al. [16] has drawn significant attention on the segmenta-tion process and neural network used. After segmentationprocess, ANN is performed to distinguish the segmentedobjects called candidates, as either microcalcifications ornonmicrocalcifications. The accuracy of the ANN is testedby having a set of labelled test images for determination oftrue positive (TP) and false positive (FP) detection rates.This ANN is using cascade correlation (CC) for patternclassification. It is a self-organizing ANN which runs asupervised learning algorithm.TheCCANNapproach showsa promising result to detect microcalcification [16].
Not only image segmentation but also image registrationtechniques can be used for the breast cancer detection whereANN is performed to enhance the effectiveness of the cancerdetection. In Saini and Vijay [17], Grey-Level CooccurrenceMatrix (GLCM) features are extracted and used as input totrain artificial neural network based breast cancer detectionsystem. After that, the extracted features of known andunknown mammogram images have been compared usingfeed-forward backpropagation and Cascade forward back-propagation ANN to distinguish the malignant and benignimages. Feed-forward backpropagation network has highaccuracy of 87.5% compared to Cascade forward backpropa-gation network with 67.8% after optimizing the number ofneurons and number of layers [17].
In late 90’s, the application of ANN in CADmammogra-phy was found to have limitation in terms of data overfitting.Thus, Bayesian belief network (BBN) was compared withANN classification method to identify the positive massregions based on a set of computed features in CAD. Thesame database was used in ANN and a BNN with topologiesoptimization using a genetic algorithm (GA) to test theperformance and robustness of the ANN and BBN. However,the result shows that there is no significant difference between
Computational and Mathematical Methods in Medicine 3
Input layer(patient’s data)
Hidden layers Output layer(malignancy probability)
Input Node 1:calc.
calc.
distribution
calc. number
distribution
Input Node 2:
Input Node 3:
Input Node 4:
Input Node 5:
mass density
mass margin
age
Transfer function
Transfer function
Transfer function
Hidden layer 1Neuron 1
Hidden layer 2
Neuron 2
Hidden layer 3
Neuron 3
Hidden layer 3
Neuron R
Hidden layer K
Neuron 1
Hidden layer K
Neuron T
Output(probability ofbeing malignant)
···
···
···
∑
∑
∑
Hidden layer K
Neuron 2
∑
∑
∑
∑
Input Node R:
WeightsWeights
Weights
Figure 1: Structure of a typical ANN for classification of breast tumors in mammography [12].
using an ANN and using a BBN in CAD for mass detectionif the network is optimized properly [18]. In Alayliogh andAghdasi [11], wavelet-based image enhancement techniquehas been used to improve the detection of breast cancer. Inputfeature vectors containing spatial and spectral image wereemployed in neural network classifier. Microcalcificationdetection scheme and wavelet image enhancement havebeen investigated. Microcalcification detection has been per-formed by using amultistage algorithm comprising the imagesegmentation and pattern recognition to classify the micro-calcifications whereas biorthogonal spline wavelets have beenused in image enhancement to separate the image intofrequency bands without affecting the spatial locality. Theresult shows that spatial and spectral feature are promisingways to detect microcalcification [11].
Besides microcalcification, masses are the most impor-tant symptoms which are difficult to be detected and distin-guished accurately. A new algorithm based on two ANNs
(artificial neural networks) was proposed to detect thesemasses automatically. ANFIS and multilayer perceptron(MLP) classifier have been used for adjustment and filtration.Suitable methods and parameters should be applied to gethigh detection precision and low false positive (FP) [10]. Thedetection process was well adjusted and improved with thisproposed algorithm and the final diagnosis result showedthat the CAD scheme could simultaneously achieve compar-atively high detection precision and low false positive rate,even when the special masses are dealt with [10].
In mammography equipped with CAD system, the majorproblems developed are inconsistency and low classificationaccuracy. The accuracy can be improved by introducing anovel intelligent classifier which used texture information asinput for the classification of normal and abnormal tissues inmammograms. Dheeba et al. [3] used neutral network as anew artificial intelligent technique for the tissue classification.CAD system based on the optimized wavelet neural network
4 Computational and Mathematical Methods in Medicine
(a) (b) (c)
Figure 2: Results (from (a)–(c)): original image, image after first stage of NN processing, and image at second stage of NN processing usingGabor wavelets as input for mammogram image [20].
was designed and evaluated using Particle Swarm Opti-mization approach (PSOWNN). Optimization using heuris-tic algorithm is done to find appropriate hidden neurons,momentum constant, and learning rate during the trainingprocess. Thus, it will improve the classification accuracy inbreast cancer detection by reducing the misclassification rate[3]. In Zhang et al. [19], backpropagation neural network(BPNN) is introduced for the classification of benign andmalignant. The digitized mammogram used fuzzy detectionalgorithm to detect the microcalcification and suspiciousarea. BPNN gives a very promising result with 83.3% for theclassification [19].
Any defect in breast image obtained frommammogram ishighly advantageous to be detected automatically. In Lashkari[20], Gabor wavelets and ANN are used to classify normaland abnormal tissues which could increase the accuracy andsave radiologist’s time (Figure 2). Gabor wavelets transformshave a good attribute in image processing and computervision. The result shows that this combination of neural net-works has a good potential with 97% accuracy on unknowncases [20].
2.2. Ultrasound. Neural network (NN) also plays its rolein ultrasound images in detecting breast cancer. We willfirst look into the capability of NN in determining andrecognizing a region wheremalignant and benign lesions canbe found. Buller [21] was one of the first who used neuralnetwork in breast cancer detection for ultrasound images.In his work, he separated the training process for benignand malignant cases by feeding the first system only withimages containing benign lesion and the other with imagescontaining only malignant lesion. He also introduces “spiderweb” topology which are able to produce two vectors thatare further used in the classification process. The first vector
represent the localized effects in a defined neighborhoodand the other represents the global attributes. The techniquebrings high advantages as the spider web topology is sensitiveto small area and hence provides better results in smallarea by putting more weights on the localized effects. Thistechnique can actually be improved taking into account theextra parameters of texture and shape. As we know, malignand benign lesion has slightly different texture and shape. InRuggierol et al. [22], the researchers implement the NN usingboth texture and shape parameters. Transition probabilitymatrix and Run length matrix on the texture parameterhave been used to quantify the homogeneity of images whileshape parameter shows the irregularity of border of lesion.Besides, three-layer NN consisting of input, output, andhidden neurons was used. They also execute the trainingprocess by leaving one out before training and use the left outas tester. From the result, texture implementation achieved avery good result on both solid and liquid lesion.
Classification is an important technique used widely todifferentiate cancerous and noncancerous breasts. Denserbreast has higher risk in having cancer. Knowing this, Sahineret al. [23] in their paper describe the importance of textureimages in classification of dense breast tissue. They alsointroduce convolution neural network classifier to replacethe backpropagation methods where the images are feddirectly into the network. To measure the coarseness oftexture, grey-level difference statistics and features are used,whereas spatial grey-level dependence features will be show-ing the element distribution. The strength of this methodis that no image of tumor is fed into the network. Besides,segmentation does not need to be performed beforehand;instead a threshold value will be used. The drawback is thehigh computational cost which in turn makes the techniqueprobably unsuitable for real-time operation.
Computational and Mathematical Methods in Medicine 5
As early as 1999,NN classifier has been usedwith autocor-relation features to classify the breast cancer as benign ormalignant. Chen et al. [24] introduced a 25-input node mul-tilayer feed-forward NN which consists of 24-dimensionalimage feature vector from the ultrasound image, togetherwith a predefined threshold of the input layer to classifythe cancer. The introduced system has a relatively highaccuracy in classifying malignancies and thus could helpinexperienced operators to diagnose complicated ultrasoundimages. One of the striking advantages of NN is that it couldbe further optimized by supplying larger set of ultrasoundimages as the NN is well-trainable.
Self-organizing map (SOM) model is one type of neuralnetworks that can be trained without supervision; it iswidely used as a classifier in recent years. It expresses lowerdimensional data in a simple geometry compared with thecomplex high dimensional data such as that in Chen et al.[25]. SOM training is fairly easy as a desired output is notnecessary. SOM will automatically choose the closest inputvector. The classification of benign and malignant lesion isautomated.The only training needed is the data from textureanalysis. However, its accuracy is slightly lower than that ofthe multilayer feed-forward NN introduced by Chen et al.[24] previously. With a high negative predictive value of 98%,this CAD technique of SOM could potentially avoid benignbiopsies. In the same year, Chen et al. [26] came out with aHNN diagnostic system.The texture information features areextracted from four ultrasound images. The 2D normalizedautocorrelation matrix for the input is modified and 2-phaseHNN was used to combine the texture information from allof the ultrasound images.This study proves that the use of all4 images leads to amore promising result than the case whereimages are used separately.
Bootstrap is a statistical measure that relies on randomsampling with replacement. Combination of bootstrap tech-nique with neural network helps improve the accuracy. Chenet al. [27] implement bootstrap to perform random sampling;the observation was then recomputed. This technique isuseful where large amount of training data is not available, asit does not require much training data. However, the reducedamount of data should be compensated by adding imageanalysis component, in the bootstrap method.
The research done in 2002 used error backpropagationalgorithm to train the multilayer perceptron neural network(MLPNN) and resulted in an area index of the receiver oper-ating curve (ROC) of 0.9396 ± 0.0183 [28]. Seven morpho-logical features have been introduced to differentiate benignfrom malignant breast lesions with the use of MPNN [29].The morphological features were named as lobulation index(LI), elliptic-normalized skeleton (ENS), elliptic-normalizedcircumference (ENC), depth to width ratio (D :W), long axisto short axis (L : S), number of substantial protuberances anddepressions (NSPD), and the size of lesion. The MPLNNis also tested with different number of hidden neurons butall results lead to a similar performance. Accuracy of thetraining set and test set is better than SOM and MLP NNwith three inputs but on par with the accuracy of NN with25 autocorrelation features as inputs. Different inputs selected
and number of inputs may have an impact on the accuracy ofthe NN itself regardless of any types of NN techniques.
A year later, a research tested the NN by using only5 morphological features which are the spiculation, branchpattern, ellipsoid shape, brightness of nodule, and the numberof lobulations [30, 31]. Based on thesemorphological features,the difference of characteristics between the benign andmalignant could be seen as follows:
(i) Spiculation (benign: larger; malignant: smaller)(ii) Branch pattern (benign: fewer; malignant: more)(iii) Ellipsoid shape (benign: smaller; malignant: larger)(iv) Brightness of nodule (benign: larger; malignant:
smaller)(v) Number of lobulations (benign: fewer; malignant:
more)Latest research implements the hybrid method to
improve the conventional neural network method to detectthe malignancies of breast cancer. Combination of thek-means cluster algorithm with the backpropagation neuralnetwork (BPNN) is proven to provide an impressive perform-ance [32]. Figure 3 shows the result of image segmentationusing ANN to extract cysts from an ultrasound breast image[32].
2.3. Thermal Imaging. Thermal imaging has been used forearly identification of breast tumor and risk prediction sincethe 60s [33].Thermogram is a promising cutting edge screen-ing instrument as it can caution ladies of breast malignancyup to 10 years ahead of time [34]. Some studies have utilizedseveral types of ANNs to manipulate and classify IR images,by taking the IR image as an input to the ANN [35]. In2003, multispectral IR images were classified using LagrangeConstraint Neural Network (LCNN) which provides a betterdiagnosis for the physician [36]. Wavelet transformation isalso useful with ANN for multidimensional features of the IRimage, especially when it was found that the temperature ofthe breast is affected by many pathological factors includingthemental state [37]. Asymmetry discrimination between leftand right breasts can be done to produce statistical featuressuch as mean temperature and standard deviation that couldbe utilized as info parameters to a backpropagation ANN[33]. In 2007, thermographic image analysis was done byimplementing a special neural network that utilizes somefuzzy logic principles, called Complementary Learning FuzzyNeural Network (CLFNN). CLFNN takes many factors intoaccount such as family history and temperature difference ofthe statistical features between contralateral breasts [34]. Thesystem is widely used in several countries at present.
2.4. MRI. MRI technique has been used widely in medicalexaminations, especially for cancer investigation for fewdecades [38]. For the diagnosis to be done properly, breastregion should be extracted from other surrounding regionsand tissues using image segmentation methods [39]. Figure 4depicts such case as it was reported in the study [39].
Many neural networks models were utilized to aid MRIfor enhancing the detection and the classification of the
6 Computational and Mathematical Methods in Medicine
Figure 3: Segmentations of cysts for breast ultrasound image using ANN [32].
Figure 4: Multistate CNN used to segment small fatty breast and medium dense breast for MRI image [39].
breast tumors, which can be trained with previous casesthat are diagnosed by the clinicians correctly [40], or canmanipulate the signal intensity or the mass characteristics(margins, shape, size, and granularity) [41]. In 2012,multistatecellular neural networks (CNN) have been used inMR imagesegmentation to estimate the density of the breast regionsfor evaluation of the fat contents [39]. Hassanien et al.[38] introduced a hybrid model consisting of Pulse CoupleNeural Network (PCNN) and Support Vector Machines(SVM) to identify breast cancer from MR images. Anotherhybrid algorithm was presented by ElNawasany et al. in 2014by combining perceptron with the Scale Invariant FeatureTransform (SIFT) for the same purpose [42].
3. Discussion
For the last few decades, several computer-aided diagnosis(CAD) techniques have been developed in mammographicexamination of breast cancer to assist radiologist in overallimage analysis and to highlight suspicious areas that needfurther attention. It can help radiologist to find a tumorwhich cannot be spotted using naked eye. As technologieskeep growing, many researchers are concerned about thedevelopment of intelligent techniques which can be used inmammography to improve the classification accuracy. Thisartificial intelligence makes use of human skills in a moreefficient manner than the conventional mathematical modelsdo. Based on the research outcomes, ANN is proved to be agood classifier in mammography for classification of massesand microcalcifications. Implementation perceptron basedthree-layer neural network using backpropagation algorithmbecomes a pioneer in ANN mammography. Various ANNsdeveloped are based on the concept of increasing the truepositive (TP) detection rate and decreasing the false positive
(FP) and false negative (FN) detection rate for the optimumresult. Implementation of wavelet in ANNs such as ParticleSwarm Optimized Wavelet Neural Network (PSOWNN),biorthogonal spline wavelet ANN, second-order grey-levelANN, and Gabor wavelets ANN can improve the sensitivityand specificity which are acquired in masses and microcalci-fication detection.
For ultrasound applications, in the field of determiningbreast cancer malignancy, CAD frameworks utilizing ultra-sound images are widely used due to their nonradiationproperties, low cost, high availability, speedier results, andhigher accuracy. An improved version of the breast cancerdetection using ultrasound images has been introduced,whichworks on a three-dimensional ultrasound imaging thatcan give more in-depth information on the breast lesioncompared to the conventional two-dimensional imaging.This three-dimensional imaging joins each of the two-dimensional characteristics. Furthermore, in order to handlethe vulnerability nature of the ultrasound images, somemethods and methodologies based on ANN have also beenintroduced.Amajority of the researchworks that utilizeANNhave acquired noteworthy results. Hybrid methods, whichcombine two ANN techniques, have recently been developedfor the detection and classification of breast cancer. A two-phase hierarchical NN is also found to be promising ratherthan using the image analysis separately. It can also be seenthat the larger the number of inputs to theANN, the better theaccuracy of the output in identification and classification ofbreast cancer. However, the number of hidden neurons doesnot seem to have a big impact on the accuracy of the system.To state which individual ANN is the best is quite subjectivedepending on the application and various variables to beconsidered. Most of the ANN techniques for the ultrasoundapplication give good results in terms of accuracy, sensitivity,
Computational and Mathematical Methods in Medicine 7
Table1:Summaryof
metho
dswith
NNin
breastcancer
detection.
Stud
yMetho
dsInpu
tPu
rpose
Dataset
Classifi
erRe
sults
Dheebae
tal.
[3]
ParticleSw
arm
Optim
ized
Wavelet
NeuralN
etwork
(PSO
WNN)
Mam
mogram
Improvec
lassificatio
naccuracy
inbreastcancer
detectionandredu
cing
misc
lassificatio
nrate
216mam
mograms
PSOWNN
(i)Sensitivity94.16
7%(ii)S
pecificity
92.10
5%(iii)AU
C0.96853
(iv)Y
ouden’s
index0.86272
(v)M
isclassificatio
nrate0.063291
Xuetal.[10]
New
algorithm
basedon
two
ANNs
Mam
mogram
Classifi
catio
nof
masses
30casesa
nd60
mam
mograms
(con
taining78
masses)
ANFISandMLP
(i)True
positive(TP
)rate9
3.6%
(73/78),
(ii)N
umbero
fthe
FPsp
erim
age
0.63
(38/60).
Alay
liogh
andAgh
dasi
[11]
ANNand
biorthogon
alsplin
ewavele
tMam
mogram
Classifi
catio
nof
microcalcificatio
nclu
ster(MCC
)and
imagee
nhancement
40digitized
mam
mogram
ANN
(i)Sensitivity93%,
(ii)F
Prate(M
CC/im
age)0.82
Dhawan
etal.
[13]
(i)ANN
(ii)secon
d-order
gray-le
velstatistic
sMam
mogram
Classifi
catio
nof
significantand
benign
microcalcificatio
ns5im
ages
tructure
features
(i)Th
ree-lay
erperceptro
nbased
ANN
Thee
ntropy
featureh
assig
nificantd
iscrim
inatingpo
wer
forc
lassificatio
n
Chitree
tal.
[15]
ANN
Mam
mogram
Classifi
catio
nof
microcalcificatio
ninto
benign
andmalignant
(i)40
,60,and80
training
cases
(ii)151,131,and
111testcases
ANN
Neuraln
etworkisar
obust
classifier
ofac
ombinatio
nof
images
tructure
andbinary
features
into
benign
and
malignant
8 Computational and Mathematical Methods in Medicine
Table1:Con
tinued.
Stud
yMetho
dsInpu
tPu
rpose
Dataset
Classifi
erRe
sults
Kevinetal.
[16]
ANN
Mam
mogram
Classifi
catio
nof
microcalcificatio
nsand
nonm
icrocalcificatio
ns
24mam
mogramsw
itheach
containing
atleasto
neclu
stero
fmicrocalcificatio
ns
Cascadec
orrelatio
nANN
(CCANN)
(i)TP
detectionratefor
individu
almicrocalcificatio
nsis73%and
92%forn
onmicrocalcificatio
ns
Zhengetal.
[18]
ANNandBB
NMam
mogram
Com
pare
perfo
rmances
ofANNandBB
N3independ
entimaged
atabases
and38
features
ANNandBB
N
Perfo
rmance
level(𝐴𝑧value)
(i)ANN𝐴𝑧value
0.847±0.014(ii)B
BN𝐴𝑧value
0.845±0.011
(iii)Hybrid
classifier
(ANNand
BBN)
A zvalueincreased
to0.859±0.01
Zhangetal.
[19]
Digitize
mod
ule,
detectionmod
ule,
featuree
xtraction
mod
ule,neural
networkmod
ule,
andcla
ssificatio
nmod
ule
Mam
mogram
Classifi
catio
nof
microcalcificatio
nclu
sters/suspiciou
sareas
Fuzzydetectionalgorithm
(i)30
digitalimages
(15contain
benign
casesa
nd15
contain
malignant
cases)
Backprop
agationneuralnetwork
(BPN
N)
(i)Fu
zzydetectionrate(benign
84.10
%and80.30%
)(ii)C
lassificatio
nrates(feature
vector,𝑛=10is83.8%),(fe
ature
vector𝑛=14is72.2%)
Lashkari[20]
ANNandGabor
wavele
tsMam
mogram
Classifi
catio
nof
breast
tissues
tono
rmaland
abno
rmalcla
sses
automatically
(i)Im
ages
of50
norm
aland50
abno
rmalbreasttissues
(ii)6
5casesfor
training
setand
35casesfor
testing
set
ANNandGabor
wavelets
(i)Classifi
catio
nrate(te
sting
perfo
rmance
96.3%andtraining
perfo
rmance
97.5%)
Sainiand
Vijay[17]
Imager
egistratio
ntechniqu
eand
ANN
Mam
mogram
Classifi
catio
nof
benign
andmalignant
42mam
mogram
images
(30
benign
and12
malignant
images)
Feed-fo
rwardbackprop
agation
andCa
scadeforward
backprop
agationartifi
cialneural
network
Percentage
accuracy
(feed-fo
rward
backprop
agationnetworkis
87.5%andCascade
forw
ard
backprop
agationnetworkis
67.8%)
Computational and Mathematical Methods in Medicine 9
Table1:Con
tinued.
Stud
yMetho
dsInpu
tPu
rpose
Dataset
Classifi
erRe
sults
Bullere
tal.
[21]
Spider
web
topo
logy
with
NN
Ultrasou
ndClassifyandseparate
benign
andmalignant
lesio
n25
sono
gram
s(i)
NNcla
ssifier
(i)69%accuracy
inmalignant
(ii)6
6%accuracy
inbenign
(iii)66%accuracy
inno
lesio
ns
Ruggierolet
al.[22]
Texturea
ndshape
parameter
feeds
into
NN
Ultrasou
ndAu
tomated
recogn
ition
ofmalignant
lesio
n
(i)41
carcinom
as(ii)4
1fibroadeno
mas
(iii)41
cysts
(i)NNcla
ssifier
(i)95%accuracy
insolid
lesio
ns(ii)9
2.7%
accuracy
inliq
uid
lesio
ns
Sahinere
tal.
[23]
Con
volutio
nalN
Nwith
spatialand
textureimage
Mam
mogram
Classifi
catio
nof
mass
andno
rmalbreast
168mam
mograms
(i)Con
volutio
nNNcla
ssifier
(i)Av
eragetruep
ositive
fractio
nof
90%atfalse
positivefraction
of31%
Chen
etal.
[24]
Multilayer
feed-fo
rward
neuralnetwork
(MFN
N)
Ultrasou
ndClassifybenign
and
malignant
lesio
n140pathologicalproved
tumors
(52malignant,88benign
)MFN
N
(i)95%accuracy,98%
sensitivity
(ii)9
3%specificity
(iii)89%po
sitivep
redictivev
alue
(iv)9
9%negativ
epredictive
value
Chen
etal.
[25]
Self-organizing
map
(SOM)
Ultrasou
ndClassifi
catio
nof
benign
andmalignant
lesio
ns243tumors(82
malignant,161
benign
)SO
M
(i)Ac
curacy
of85.6,sensitivity
97.6%
(ii)S
pecificity
79.5%
(iii)Po
sitivep
redictivev
alue
70.8%
(iv)N
egativep
redictivev
alue
98.5%
10 Computational and Mathematical Methods in Medicine
Table1:Con
tinued.
Stud
yMetho
dsInpu
tPu
rpose
Dataset
Classifi
erRe
sults
Chen
etal.
[27]
Bootstrapwith
NN
Ultrasou
ndcla
ssificatio
nof
tumor
263sono
graphicimages
olid
breastno
dules
NN
(i)Ac
curacy
87.07%
,sensitivity
98.35%
(ii)S
pecificity
79.10
%(iii)Po
sitivep
redictivev
alue
81.46%
(iv)N
egativep
redictivev
alue
94.64%
Chen
etal.
[26]
2-ph
ase
Hierarchical
NeuralN
etwork
(HNN)
Ultrasou
ndDifferentiatebetween
benign
andmalignant
tumors
1020
images
(4different
rectangu
larregions
from
the2
orthogon
alplanes
ofeach
tumor)
HNN
4im
agea
nalyseso
feachtumor
appear
togive
morep
romising
resultthan
ifthey
areu
sed
separately
Chen
etal.
[28]
Wavele
ttransform
andneural
network
Ultrasou
ndDifferentia
ldiagn
osisof
breasttumorso
nsono
gram
s
242cases(161b
enign,
82malignant)
Multilayer
perceptro
nneural
network(M
LPNN)
(i)Re
ceiver
operating
characteris
tic(ROC)
area
index
is0.9396±0.0183
(ii)9
8.77%sensitivity,81.3
7%specificity
(iii)72.73%
positivep
redictive
value
(iv)9
9.24%
negativ
epredictive
value
Chen
etal.
[29]
Multilayer
feed-fo
rward
neuralnetwork
(MFN
N)
Ultrasou
ndDifferentiatebenign
from
malignant
breast
lesio
ns
1stset:160
lesio
ns2n
dset:111lesions
MFN
N(i)
98.2%training
accuracy
(ii)9
5.5%
testingaccuracy
Jooetal.[30]Artificialneural
network(A
NN)
Ultrasou
ndDeterminingwhether
abreastno
duleisbenign
ormalignant
584histo
logically
confi
rmed
cases(300benign
,284
malignant)
ANN
(i)100%
training
accuracy
(ii)9
1.4%testingset
(iii)92.3%sensitivity,90.7%
specificity
Computational and Mathematical Methods in Medicine 11
Table1:Con
tinued.
Stud
yMetho
dsInpu
tPu
rpose
Dataset
Classifi
erRe
sults
Jooetal.[31]
Digita
limage
processin
gand
artifi
cialneural
network
Ultrasou
ndDetermineb
reastn
odule
malignancy
584histo
logically
confi
rmed
cases(300benign
,284
malignant)
ANN
(i)91.4%accuracy,92.3%
sensitivity
(ii)9
0.7%
specificity
Zhengetal.
[32]
Hybrid
metho
d(unsup
ervised
k-means
cluste
r,supervise
dbackprop
agation
neuralnetwork
(BPN
N))
Ultrasou
ndClassifi
catio
nof
breast
tumorsa
sbenignor
malignant
125benign
tumors,110malignant
tumors
Com
binatio
nof
k-means
with
BPNN
(i)Re
cogn
ition
rate(94.5%
for
benign
,93.6%
form
alignant)
(ii)9
4%accuracy,94.5%
sensitivity
(iii)93.6%specificity
Foketal.[35]ANNwith
3Dfin
iteelem
ent
analysis
IRTu
mor
predictio
n200patie
nts
ANN
Goo
ddetection,
poor
sensitivity
Szuetal.[36]
Unsup
ervised
classificatio
nusing
Lagrange
Con
straint
Neural
Network(LCN
N)
Mid
andlong
IRim
ages
Early
detectionof
breast
cancer
One
patie
ntwith
DCI
SLC
NN
Bette
rsensitivity
Jaku
bowska
etal.[37]
ANNwith
wavelet
transfo
rmIR
Disc
riminationof
healthyandpathological
cases
30healthy
ANN
Accuracy
(%)
(fron
tal/side)
Raw:90/93,P
CA:90/93
LDA:93/97,N
DA:93/93
10with
recogn
ized
tumors
Accuracy
(%)
(fron
tal/side)
Raw:80/90,P
CA:80/90
LDA:90/90,N
DA:80/100
12 Computational and Mathematical Methods in Medicine
Table1:Con
tinued.
Stud
yMetho
dsInpu
tPu
rpose
Dataset
Classifi
erRe
sults
Koay
etal.
[33]
Backprop
agation
NN
IREa
rlydetectionof
breast
cancer
19patie
nts
Levenb
erg-Marqu
ardt
(LM)a
ndRe
silient
Backprop
agation(RP)
Accuracy
(%)
(RP/LM
)Who
le:
95/95
Quadrants:
95/10
0
Tanetal.[34]
Fuzzyadaptiv
elearning
control
networkfuzzy
neuralnetwork
IREa
rlydetectionof
breast
cancer
andtumor
classificatio
n
28healthy,43
benign
tumors,7
cancer
patie
nts
FALC
ON-AART
Cancer
detection(%
)(TH
/TDF)
Predicted:95,sensitivity
:100,
specificity:60
Breasttumor
detection(%
)(TH/TDF)
Predicted:84/71,sensitivity:
33/76,
specificity:91/6
2Breasttumor
classificatio
n(%
)(TH/TDF)
Predicted:88/84,sensitivity:
33/33,
specificity:95.5/91
Cardilloetal.
[40]
NNfora
utom
atic
analysisof
image
statistics
MRI
Early
detectionand
classificatio
n150exam
ssub
dividedinto
6grou
psby
contrast
NN
Bette
rinspecificity
Tzacheva
etal.[41]
Evaluatio
nof
signalintensityand
massp
ropertiesb
yNN
MRI
Automaticdiagno
sisof
tumors
14patie
nts
Feed-fo
rwardBP
NN
90%–100%sensitivity,91%
–100%
specificity,and
91%–100%
accuracy
Ertase
tal.
[39]
Extractio
nof
breastregion
sby
conventio
naland
multistateCN
Ns
MRI
Breastdensity
evaluatio
nandabno
rmality
localization
23wom
enCN
N
Averagep
recisio
n99.3±1.8
%True
positivev
olum
efraction
99.5±1.3
%False
positivev
olum
efraction0.1
±0.2%
Hassanien
etal.[38]
Image
classificatio
nusing
PCNNandSV
Mandusingwavele
tandfuzzysetsfor
enhancem
ent
MRI
Breastcancer
detection
70no
rmalcases,50
benign
and
maligncases
Hybrid
schemeo
fPCN
Nand
SVM
Accuracy
SVM:98%
Roug
hsets:
92%
ElNaw
asany
etal.[42]
Classifying
MR
images
byhybrid
perceptro
nNN
MRI
Early
detectionof
breast
cancer
138abno
rmaland143no
rmal
Perceptro
nwith
SIFT
Accuracy
86.74
%
Computational and Mathematical Methods in Medicine 13
specificity, positive predictive value, and negative predictivevalue. Another advantage of using the ANN in determiningbreast lesion is that the ANN can be trained to producebetter accuracy. Besides that, this ANN can be combinedtogether with not only another ANN technique but alsoother signal processing techniques such as wavelet to producebetter results.
For different techniques that have been utilized forthe breast cancer imaging, there are different methods ofdetection and classification according to the input parametersof that technique. For the IR imaging, it has been shownthat the detection of the breast cancer depends mainly onthe statistical features of the thermal behavior of the tissues(mean, standard deviation, etc.), as well as the asymmetrydifferentiation of the contralateral breasts. Therefore, imageclassification methods based on ANN are quite fruitful inthermography.
The MRI imaging is highly recognized as a reliabletechnique for tumor localization as well as early detectionand classification of cancer, as it is generally recommendedfor soft tissue recognition. Many image segmentation and 3Dextraction algorithms are applied in MRI applications, andrecently, many ANN classification types have been designedwith many fine specifications for MRI breast imaging.
A summary of methods with NN in breast cancer detec-tion has been given in tabulated form in Table 1.
4. Conclusion
Neural network plays an important role in detection ofcarcinogenic conditions in the breast. The technique acts asa stepping stone in the detection of cancer. In this review,we show that NN can be used in many medical applicationswhich we categorized into four main medical applicationsthat are widely used in breast cancer detection. These fourmedical applications include mammogram, ultrasound, andthermal and MRI imaging. This shows that NN is notrestricted by the application.
In all applications, NN’s main purposes were automatedclassification and segmentation. The types of data that needto be classified include calcification and noncalcification,benign and malignant, dense and normal breast, and tumor-ous and nontumorous. Neural network needs training data.Different types of data are fed into NN for training purposes.In early adaptation of NN, images of breast are being feddirectly into the NN. This method will perform well onlyif very large databases are available. In the case of usingsuch huge data, the concern was the storage, the time ofperformance, and the data availability. This flaw was realizedand being improved by taking the ROI into account, whichlowered the amount of dataset requirement tremendously.Researcher were then able to come out with better ideaswhere they now train the NN with feature vectors. In ourfindings, the features that can be used as training data includespiculation, branch pattern, shape, brightness of nodule,number of lobulations, margin, size of nodule, granularity,and texture.These features can be extractedmanually or usingimage analysis technique. Introducing of features did improve
the performance of NN in terms of size of training data andaccuracy.
Different variation of NN can be applied as classifier.Feed-forward backpropagation NN is by far the simplestform of NN, as the name suggest, the input nodes do nothave interrelation between each other, andmore importantly,the units do not form a repetitive cycle or loops. Feed-forward backpropagation can only pass data from currentlayer to subsequent layer; hence the data is moving inone fix direction from input to output. Cascade forwardNNs are somehow similar to feed-forward NNs; the onlydifference is that they include connections from not onlythe input, but also every previous layer to the subsequentlayers. ConvolutionNN is considered as a special type of feed-forward neural network where there are multiple layers ofsmall neuron collections that are able to process the portionsof input image.
The trend now is going towards hybrid NN like SOMmodel. Combination of statistical methods such as bootstrapis being used together with NN too. SOM and bootstrapmethods require lesser training data and hence are usefulwhen we do not have many training data. Besides, peopleutilize SVM with NN in order to achieve a better perfor-mance. In conclusion, NN is widely used in medical imageapplications, creatively combined with other methods inorder to achieve better accuracy, sensitivity, and also positivepredictive value.
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper.
Acknowledgments
This study has been supported by the Departments ofComputer and Communication Engineering, Electrical andElectronics Engineering and Chemical and EnvironmentalEngineering at Universiti Putra Malaysia (UPM).
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