Technical improvement of Brachytherapy

1964 radiumimplantaat recontructie.jpg 

In 1959 radiologist Breur and physicist Kaalen in the Rotterdam Radiotherapy institute (RRTI) designed a reconstruction method for radium needle implants. In 1964 the engineer Joop Wijnen in the NKI made some adjustments to this, and made the method suitable for clinical practice. [47] 

In a radium needle implant, hollow needles of a few centimeters in length, containing radium salt, are inserted into the tissue in or around the zone to be treated. A spatial distribution according to the Parker Paterson system is pursued to achieve the correct dose distribution. However, the needles in Amsterdam are not completely compatible with the Manchester system, and the position of the needles varies because of complications during their insertion. Based on the mapping of the positions of the needles, the dose distribution and the exposure time are calculated. To find the exact positions of the inserted needles, a reconstruction method has been developed. 

It is a 3-dimensional reconstruction, starting from two X-ray pictures taken  of the implant at beam angles 90 degrees apart.  In the reconstruction, two light sources are positioned to simulate the two positions of the X-ray tube focus, and the two X-ray pictures are positioned in the path of the resulting light beams. Dummy needles are placed in the light beams at the positions in which the shadow of each needle coincides with the needle images on each of the two films. This is repeated for all the needles and the resulting reconstructed implant is fixed by casting the  base ends of the dummy-needles in plaster. In the resulting dummy model the needle positions are measured and used to calculate the dose distribution and the required exposure time. 

In 1968 radiation oncologist Marion Burgers, physicist Herbert Marcuse and others design a computer program for the reconstruction and for the dose calculations. The two X-ray images are no longer exposed separately, instead they are projected next to each other on one X-ray film at tube angles 30 degrees apart. The two tips of the shadow image of each of the needles are measured manually on the film and entered into the computer program. In 1981 physicist Rob van der Laarse developes an improved program for the reconstruction and the dose calculations. 

The radium is replaced by Caesium-137. In 1965 radiation physicist Herbert Marcuse is appointed by Breur in the Netherlands Cancer Institute. Marcuse quickly notes that the old radium stocks have become unreliable. Many radium capsules and needles are found to leak radium salt and decay products. Radioactive contamination is found in equipment and in the building. The radium stocks are cleaned up and partly replaced. An improved radium safe is constructed, and caesium is introduced as a safe radiation source for brachytherapy. Also small tubes loaded with Cobalt-60 are introduced. 

Bronnen & Publicaties

  • [47] “Dose, time and volume effects in interstitial radiation therapy” by J. Marion V. Burgers. Doctoral thesis, University of Amsterdam 1982, supervisor Prof. Dr. G. W. Barendsen. ,