Tuberculosis Screening

Nodule DetectionThe current issue of the SPIE Newsletter features an article about our image-processing software for chest x-ray examination. The article gives a short overview of our TB screening project and highlights some of the processing steps, such as nodule detection. Here is the link to the article: SPIE Newsroom

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The Butterfly Dream

The butterfly dream is one of the most well-known text passages of Chinese Philosophy. It was written (dreamed) by Chuang Tzu, who lived around the 4th century BCE and who was, together with Lao Tzu, one of the great Taoist philosophers. The dream goes as follows:

One night, Chuang Tzu dreamed of being a butterfly — a happy butterfly, showing off and doing things as he pleased, unaware of being Chuang Tzu. Suddenly he awoke, drowsily, Chuang Tzu again. And he could not tell whether it was Chuang Tzu who had dreamt the butterfly or the butterfly dreaming Chuang Tzu. But there must be some difference between them! This is called ‘the transformation of things.’

As probably many before me, I have wondered about its meaning. In my humble opinion, the dream exemplifies the distinction between existence and non-existence. We would typically think of the person having the dream as an existing entity, and the world he is living in as reality, while the dream world would be fiction and thus non-existing. However, Chuang Tzu’s butterfly dream tells us that we do not know which is which; meaning we cannot distinguish between the existing and non-existing worlds. Actually, in some sense, both worlds are existing (or non-existing). In our effort to identify one of both worlds as ultimate reality, which the dream tells us is not possible, we are constantly switching between both worlds, living in either one and taking it for real.

This difference between existence and non-existence is a classical Yin-Yang opposite. And yet, because existence is regarded as so fundamental, many would rather abandon the concept of Yin and Yang than to give up their sense of reality. Too strong is our desire to identify the real world and to classify Chuang Tzu as being part of reality. Only few dare to accept the fact that our dreams are as real as our bodies, although this is exactly what Chunag Tzu’s dream tells us in my opinion. Scientists, and mathematicians in particular, are no exception to this. Mathematicians would shudder with horror at the mere thought of performing calculations on objects (sets) that do not exist. In mathematics, everything needs to exist. On the most fundamental level of mathematics, where formal proofs are a rare guest, mathematicians have introduced a plethora of axioms to guarantee the existence of sets, numbers, etc. This clearly shows their ignorance about non-existing things, which are not worth to be considered simply because they do not exist. However, I think that Chuang Tzu’s butterfly dream tells us to incorporate non-existing objects into our formal considerations; and that mathematics needs to embrace the intrinsic uncertainty between existence and non-existence.

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P/NP Problem

I posted a paper about my solution to the P/NP problem on arXiv this week: arXiv:1104.2538v1 The key idea making this paper different from other approaches is that the relationship between the complexity classes P and NP depends on the definition of the natural numbers. In other words, there is no clear answer to the P/NP problem. The paper claims that for the traditional encoding of the natural numbers, which is based on the Peano axioms, the complexity hierarchy collapses and P becomes equal to NP. On the other hand, if we remove the first Peano axiom, P becomes a proper subset of NP.

The removal of the first Peano axiom introduces intrinsic uncertainty into the encodings of natural numbers, which obviously has drastic consequences on computability and computational complexity. Every computation, and every proof, is uncertain under this relaxed set of Peano axioms. However, the first Peano axiom cannot remove this uncertainty, it can merely subsume it into one statement. I think this fact and the consequences it has on computational complexity has been underestimated in the literature so far. I’m going to elaborate more on this here in the coming months.

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Budget Deal

Phew. The budget deal seems to be home and dry. Unbelievable isn’t it? Can someone take away this toy from the politicians, please? Using the government and its research to blackmail political opponents sounds insane to me. The National Library of Medicine, for example, delivers trillions of bytes every day to people around the globe. Do we really want to jeopardize this service that is crucial to the lives of so many people in this world? Instead of celebrating a last-minute agreement, should we not take preventive measures so that this can never happen again?

Anyway, looks like we have some work to do until the end of the year.

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World Tuberculosis Day

Today is World TB Day, commemorating the discovery of the TB bacillus by Robert Koch in 1882. The web portal of the National Institute of Allergy and Infectious Diseases (NIAID) has more information on tuberculosis (see also the TB web site of the Department of Health & Human Services).

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After the last tree has been cut down

After the last tree has been cut down,
after the last river has been poisoned,
after the last fish has been caught …

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My New Project: Computer-aided Diagnosis on Radiographs

My new project is computer-aided diagnosis on radiographs. The goal of this project is to be able to capture and process digital radiographs in remote and difficult to access areas using a portable x-ray machine, and to assist local doctors with various degrees of experience in their diagnosis. Special emphasis lies in the development of a reliable system to automatically differentiate normal from pathologic chest x-rays to screen for the presence of tuberculosis or other lung disease. Despite some preliminary work published in the last ten years, computer-aided diagnosis in chest radiography can be considered a largely unsolved problem. To solve this problem, and to reach a performance relevant to clinical practice, extensive research is required to develop new image processing techniques that can cope with the low-contrast and noisy images encountered in practice. Other problems that need to be addressed include, but are not limited to segmentation and feature computation. The textural abnormalities in chest radiographs, in particular those associated with pulmonary tuberculosis, need to be quantified in a way that allows reliable discrimination between normal and abnormal cases. Typical abnormal findings in chest radiographs, in particular findings associated with pulmonary tuberculosis, are for instance, nodules, pleural effusions, or cavitations. It is very unlikely that a single feature type will be powerful enough to capture all the abnormal findings encountered in clinical practice. Different feature sets need to be experimented with, including features already proposed for computer-aided medical diagnosis, as well as features from other image processing domains and entirely new features yet to be developed.

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Happy New Year!

I wish all my friends and colleagues, wherever they may be in the world, a Happy New Year and all the best for 2011!

I am now working for the National Library of Medicine at the National Institutes of Health in Washington DC.

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