Conventional conformal radiotherapy vs intracavitary brachytherapy for the adjuvant postoperative treatment of cervical cancer: a comparative dosimetric study.

OBJECTIVES: The aim of this pilot study is to evaluate the feasibility of 3D-conformal radiotherapy (3D-CRT) in the adjuvant postoperative radiotherapy of the vaginal cuff and upper third of present vaginal tissue. METHODS: The representative patient (FIGO IB; PH: squamous cell carcinoma) was referred for adjuvant post-hysterectomy radiotherapy. A whole pelvis irradiation with concomitant high-dose-rate intracavitary brachytherapy (HDR-ICBT) was applied. HDR-ICBT total dose of 24 Gy in four fractions/one fraction per week was delivered to the vaginal cuff using two Fletcher-Suit ovoids. The feasibility of change from HDR-ICBT to CRT was evaluated by generating of three different plans using 10 MV photon beams shaped by multileaf collimator. RESULTS AND DISCUSSION: The referent volume received HDR-ICBT prescribed dose. The maximum ICBT percentage dose to the rectum and urinary bladder was 101% and 106% respectively. In all 3D-CRT plans almost 100% of planning target volume (PTV) was covered by 95% therapy isodose surface. From 12 - 13% of the rectum and 1-3% urinary bladder volume were covered by 100% isodose surface, with the highest maximum dose of 104% and 101%, respectively. Comparison of the PTV dose coverage and the maximum dose to the rectum and urinary bladder for HDR-ICBT and 3D-CRT plans showed no major difference. CONCLUSION; 3D-CRT could be considered as adequate replacement for ICBT in the adjuvant postoperative treatment of the vaginal cuff and upper thi-rd of present vaginal tissue. Time-dose-fractionation pattern for HDR-ICBT may be safely applied for 3D-CRT.

Fractal and nonfractal analysis of cell images: comparison and application to neuronal dendritic arborization.

Neurons of the rat spinal cord were stained using the Golgi impregnation method. Successfully impregnated neurons from laminae II, III, and VI were subjected to fractal and nonfractal analyses. Fractal analysis was performed using length-related techniques. Since an application of fractal methods to the analysis of dendrite arbor structures requires caution, we adopted as appropriate a nonfractal method proposing a generalized power-law model with two main nonfractal parameters: (i) the anfractuosity, characterizing the degree of dendritic deviation from straight lines; and (ii) an estimate of the total length of arbor dendrites. The anfractuosity can distinguish between two sets of drawings where the fractal methods failed. We also redefine some basic concepts of fractal geometry, present the ruler-counting method, and propose a new definition of fractal dimension.

Development of a national protocol for a high activity (192)Ir brachytherapy source calibration.

PURPOSE: Determination of the air kinetic energy released in material (KERMA) rate (commonly named source strength) or a brachytherapy source activity represents one of the first steps in the acceptance, as well as in the periodic Quality Assurance (QA) testing procedures. In this paper, calibration of an (192)Ir high-dose rate (HDR) brachytherapy source is presented. MATERIALS AND METHODS: An (192)Ir HDR brachytherapy source calibration was carried out, with two independent procedures - calibration in water and in free air. The dosimeter used consisted of a thimble ionization chamber (NE 2571) and an electrometer (NE 2670). The reference air KERMA rate was calculated according to the International Atomic Energy Agency (IAEA) and the International Commission for Radiation Units and Measurements (ICRU) protocols. All physical quantities and correction factors used were determined, calculated, and re-checked for particular chamber and source type. RESULTS: In water, the reference air KERMA rate, determined by the IAEA protocol differed by +1.0% from the manufacturer's declared value and was measured with a relative error of 1%. The reference air KERMA rate, calculated by the ICRU protocol differed by -0.4% from the manufacturer's declared value and was measured with a relative error of 1.1%. In air, the value of the reference air KERMA rate, calculated by the IAEA protocol, differed by +1.6% from the manufacturer's declared value and was measured with a relative error of 1%. The value of the reference air KERMA rate for the same source, calculated by the ICRU protocol, differed by +1.1% from the manufacturer's declared value and was measured with a relative error of 0.9%. The results showed that application of the IAEA protocol gave higher values than the application of the ICRU protocol. It stands for both calibration methods. The difference between calibration protocols was not higher than 2% (in the water 1.4% and in the air 0.5%). Finally, calibration results showed that the difference between the calibration methods (in water and in air), for both calibration protocols, was not higher than 2%. For the IAEA protocol the difference was -0.6% and for the ICRU protocol it was -1.5%. We believe that benefits can be derived from the simultaneous application of both methods. CONCLUSION: A proposal of a national protocol represents an attempt to formulate a unique protocol for brachytherapy sources calibration in Serbia. The comparison of "in water" and "in free air" calibration has shown systematic differences of in-source strength of about 2%, respectively. It would be worth suggesting to radiotherapy centres to adopt the most optimal calibration method, based on well-known international protocols.