The number of citations a scientific paper receives is seen as a measure of its importance. Lots of citations mean not only that many people have read the paper, but also that it has influenced their research. According to Physics in Medicine and Biology publisher Simon Harris, a typical paper might get a handful of citations over a five-year period, while some get none at all. "More than a hundred citations is an extremely high number," he said.

The winning paper is entitled "Acquiring a four-dimensional computed tomography dataset using an external respiratory signal". It reports a method to acquire 4D images of the lungs from a spiral CT scan, as well as examining the potential utility of 4D CT imaging for radiation-therapy treatment planning (Phys. Med. Biol. 48 45). "This was one of the first papers to describe the inclusion of respiratory motion during CT imaging," said Keall, who is now an associate professor of radiation physics at Stanford University (Stanford, CA).

The researchers explained how an ordinary spiral CT scanner could be used to acquire artefact-free images of the lungs in the presence of respiratory motion. Their method involved taking an over-sampled CT scan and then assigning each slice to one of eight bins, corresponding to the different phases of the breathing cycle. As well as being considerably less distorted, images obtained in this way contain respiratory-motion information not available in 3D CT images.

Keall's team was one of three groups to pioneer the technique. Since the publication of this early work (as represented by the paper in Phys. Med. Biol.), the technique has been incorporated into most commercial CT machines. "Currently all major CT vendors offer 4D CT technology, and it's widely used in radiation oncology," Keall told medicalphysicsweb.

But research into 4D CT is far from done and dusted, says Keall. The early work, as described in the paper, assumed that respiratory motion was regular. Researchers now know that this is not the case.

"Our method was developed based on cardiac imaging protocols, and the cardiac signal is quite regular," Keall explained. "What we're finding now is that though the 4D CT can help us describe respiratory motion, where irregularities exist we are still getting artefacts in the images."

Dealing with tumour motion during imaging and radiation therapy is still one of the hottest topics in medical physics, and the runner-up paper in the Phys. Med. Biol. awards also dealt with this complex problem. In 2002, Thomas Bortfeld and colleagues presented a statistical analysis of the effects of intrafraction motion on IMRT dose delivery (Phys. Med. Biol. 47 2203).

The authors of the winning paper received prize money of $450.

The top 10 most cited papers published in Physics in Medicine and Biology over the last five years are:

  1. S S Vedam, P J Keall, V R Kini, H Mostafavi, H P Shukla and R Mohan 2003 Acquiring a four-dimensional computed tomography dataset using an external respiratory signal Phys. Med. Biol. 48 45.
  2. T Bortfeld et al. 2002 Effects of intra-fraction motion on IMRT dose delivery: statistical analysis and simulation Phys. Med. Biol. 47 2203.
  3. T Durduran et al. 2002 Bulk optical properties of healthy female breast tissue Phys. Med. Biol. 47 2847.
  4. Y C Tai et al. 2003 MicroPET II: design, development and initial performance of an improved microPET scanner for small animal imaging Phys. Med. Biol. 48 1519.
  5. B M Fischer et al. 2002 Far-infrared vibrational modes of DNA components studied by terahertz time-domain spectroscopy Phys. Med. Biol. 47 3807.
  6. T Neicu et al. 2003 Synchronized moving aperture radiation therapy (SMART): average tumour trajectory for lung patients Phys. Med. Biol. 48 587.
  7. P J Keall et al. 2004 Acquiring 4D thoracic CT scans using a multislice helical method Phys. Med. Biol. 49 2053.
  8. A P Gibson et al. 2005 Recent advances in diffuse optical imaging 2005 Phys. Med. Biol. 50 R1.
  9. A Katsevich 2002 Analysis of an exact inversion algorithm for spiral cone-beam CT Phys. Med. Biol. 47 2583.
  10. S Jan et al. 2004 GATE: a simulation toolkit for PET and SPECT Phys. Med. Biol. 49 4543.