Published in 2004, Keall's paper describes the implementation of multislice helical CT for acquiring 4D thoracic CT scans. Such scans can be employed to create 4D treatment plans that explicitly account for respiratory motion during radiation delivery. The work builds on Keall's previous publication (and the winner of the 2007 PMB Citations Prize), which described a method to acquire 4D lung images from a spiral CT scan and was one of the first to report on the inclusion of respiratory-motion information during CT imaging.
"The earlier published works on respiratory correlated CT for helical acquisition used single-slice scanners," explained Keall. "Given the technology used for these studies, the acquisition was limited to 8 cm of coverage. Using a multislice scanner allowed the acquisition of the entire thorax and/or abdomen with 4D CT."
Keall, who was with the Virginia Commonwealth University (Richmond, VA) at the time of this publication, explained that the work was performed during a month-long visiting professorship at the M D Anderson Cancer Center (Houston, TX). The goal of the visit was to develop and clinically implement 4D thoracic CT using a helical method on a multislice scanner.
"There were many technological barriers to overcome," Keall explained. "Such as the need to shorten the pulse width from the respiratory monitoring system (Varian RPM) that communicated with the scanner and 'trick' the scanner by initializing it with a 1 Hz cardiac input and then switching to the respiratory signal once initialized."
The researchers tested the 4D CT scanning method on a phantom under various conditions (stationary, periodic motion and non-periodic motion). They also implemented the technique for a lung cancer patient using audio-visual breathing coaching. This represented the first published instance of a multislice helical method being used for 4D CT imaging of a patient. "On the last day of my visit, the first patient scan was successfully acquired; it was an intense and exhilarating month," Keall told medicalphysicsweb.
Since first reported upon in 2003, 4D CT has been embraced by the radiation oncology community for patient care and research. In fact, says Keall, a technique similar to the one that he published is now offered by Philips Medical Systems on its CT scanners and is in routine use in many centres. "There has been a large and continuing growth in the studies and applications of 4D CT for tumour-motion measurement, motion-inclusive, gated and 4D planning, as well as functional investigations such as ventilation assessment," he added.
From this year onwards, the primary contributing author of the winning paper is presented with a medal, named in honour of Professor Sir Joseph Rotblat, who was the PMB's second, and longest serving, editor (the winning co-authors each receive a certificate). It is somewhat fitting that the first recipient of the Rotblat Medal is Paul Keall, as he was also an author on the papers that won in 2007 and 2006. In fact, Keall et al. have the top two entries in this year's top 10 (see full list below), but the first of these was last year's winner, and thus ineligible for the 2008 prize.
The top 10 most cited papers published in Physics in Medicine and Biology over the last five years are:
1a. 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. (last year's winner)
1b. P J Keall, G Starkschall, H Shukla, K M Forster, V Ortiz, C W Stevens, S S Vedam, R George, T Guerrero and R Mohan 2004 Acquiring 4D thoracic CT scans using a multislice helical method Phys. Med. Biol. 49 2053. (this year's winner)
2. Y Zou and XC Pan 2004 Exact image reconstruction on PI-lines from minimum data in helical cone-beam CT Phys. Med. Biol. 49 941.
3. T Neicu et al. 2003 Synchronized moving aperture radiation therapy (SMART): average tumour trajectory for lung patients Phys. Med. Biol. 48 587.
=4. S Jan et al. 2004 GATE: a simulation toolkit for PET and SPECT Phys. Med. Biol. 49 4543.
=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.
6. S B Jiang et al. 2003 An experimental investigation on intra-fractional organ motion effects in lung IMRT treatments Phys. Med. Biol. 48 1773.
7. G C Sharp et al. 2004 Prediction of respiratory tumour motion for real-time image-guided radiotherapy Phys. Med. Biol. 49 425.
8. F Noo et al. 2003 Exact helical reconstruction using native cone-beam geometries Phys. Med. Biol. 48 3787.
9. X Ma et al. 2003 Determination of complex refractive index of polystyrene microspheres from 370 to 1610 nm Phys. Med. Biol. 48 4165.
10. W Lu et al. 2004 Fast free-form deformable registration via calculus of variations Phys. Med. Biol. 49 3067.