A modified formula for defining tissue phantom ratio of photon beams.

Tissue phantom ratio (TPR), for square fields of various dimensions has been determined at varying depths in water. The dose in water has been measured at a fixed source-to-surface distance (SSD) of 100 cm and reference depth of 5 cm for 6 MV photon beam of Siemens Linear Accelerator Primus 11 in German Cancer Research Center (DKFZ), Heidelberg, Germany. A modified formula has been developed to calculate the TPR value for isocentric treatment. The present article describes the conversion of the measured data values into a comprehensive and consistent data set by the modified formula, that gives the TPR from Percentage Depth Dose (PDD) with depth as a function of field sizes from 10 mm x 10 mm upto 300 mm x 300 mm) and depth (from 0 mm to 300 mm).

Pulsed electromagnetic fields for the treatment of bone fractures.

The effectiveness of electrical stimulation and Pulsed Electro Magnetic Field (PEMF) stimulation for enhancement of bone healing has been reported by many workers. The mechanism of osteogenesis is not clear, therefore, studies look for empirical evidence. The present study involved a clinical trial using low amplitude PEMF on 19 patients with non-union or delayed union of the long bones. The pulse system used was similar in shape to Bassett's single pulse system where the electric voltage pulse was 0.3 mSec wide repeating every 12 mSec making a frequency of about 80 Hz. The peak magnetic fields were of the order of 0.01 to 0.1 m Tesla, hundred to thousand times smaller than that of Bassett. Among the 13 who completed this treatment schedule the history of non-union was an average of 41.3 weeks. Within an average treatment period of 14 weeks, 11 of the 13 patients had successful bone healing. The two unsuccessful cases had bone gaps greater than 1 cm following removal of dead bone after infection. However, use of such a low field negates Bassett's claim for a narrow window for shape and amplitude of wave form, and justifies further experimental study and an attempt to understand the underlying mechanism.

Effect of PEMF on fresh fracture-healing in rat tibia.

The present experiment was designed to find out whether PEMF can act as a healing agent on induced fracture of rat tibia. Eighty rats were taken for this experiment. Under general anaesthesia mid-shaft of tibia and fibula of all rats were osteotomied, Intramedullary nailing was done for proper alignment of the fractured fragments. The animals were then divided into two groups: group-1 and Group-II. Each group contained forty animals. Out of these forty animals twenty were treated as experimental and twenty as control. From the third day of osteotomy, PEMF was applied to experimental rats around the osteotomy sites for a period of nine hours a day. PEMF was not applied to the control rats. The animals of group-1 and group-II were sacrificed after applied one week and three weeks of PEMF, respectively. Radiological and microscopical examination of the callus were performed. Gross and microscopic measurements of the callus were statistically analysed. The growth of callus was taken as a criterion of fracture healing. The results of the present experiment revealed significant enhancement of fracture healing in group-I. The results of the radiological evaluation of group-II experimental animals were also consistent with the morphological analysis. It was concluded that healing of fractured rat tibia was enhanced by the application of PEMF and this effect of PEMF was more pronounced at the end of third week.

Effect of pulsed electromagnetic field on healing of experimental nonunion in rat tibiae.

To see the effect of Pulsed Electromagnetic Field (PEMF) on nonunited fracture healing, nonunion was induced in rat tibiae and PEMF was applied on it. Out of five different techniques utilised for inducing nonunion soft tissue interposition was found to be the most suitable and effective method of experimental induction of nonunion. Twenty eight experimental and 15 control rats were finally evaluated for the effect of PEMF applied for up to 8 weeks. After sacrifice of 8 experimental and 4 controls, 6 experimental and 3 controls, again 6 experimental and 3 controls and finally 8 experimental and 5 controls at 2, 4, 6 and 8 weeks respectively of PEMF application no significant difference as to the quality of healing was observed between the experimental and control animals. It was thus concluded that PEMF appeared to have no beneficial effect on the healing of nonunited fractures in experimental set-up.