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Rectal dosimetry in intracavitary brachytherapy by HDR at rural center of Maharashtra: Comparison of two methods.

Shrivastava R, Umbarkar RB, Sarje MB, Singh KK - J Med Phys (2009)

Bottom Line: The rectal doses at each complementary pair were compared with each other.The rectal dose obtained by the intrarectal wire method underestimates the actual dose to the rectum when compared to the ICRU-38 method.Thus ICRU-38 recommendations should be strictly adhered to, to reduce late complications.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiotherapy and Oncology, Rural Medical College, Loni, Ahmednagar, Maharashtra, India.

ABSTRACT
The purpose of this study was to calculate the radiation dose at the anterior rectal wall as per the International Commission on Radiation Units and Measurements (ICRU 38) recommendations and compare it with the dose calculated by the commonly used intrarectal catheter. Dose delivery by brachytherapy to the cervix is limited by the critical structure of the bladder and rectum. In this study the ICRU-38 rectal point was derived by using a radio-opaque gauze piece on the posterior vaginal wall, and the intrarectal point was derived by inserting a rubber catheter with a wire, inside the rectum. A total of 146 applications were performed in 81 patients. Rectal doses were compared for complementary rectal points R1 and R5, R2 and R6, R3 and R7, and R4 and R8, obtained by both methods. The rectal doses at each complementary pair were compared with each other. The average dose at R1 was 5% higher than at R5 (60.57% vs. 55.57%). The average dose at R2 was 1% higher than at R6 (58% vs. 57%). The average dose at R3 was 1.29% higher than at R7 (52.71% vs. 51.42%), and the average dose at R4 was 1.15% higher than at R8 (43% vs. 41.85%). There were many instances where the rectal dose exceeded by more than 15%, from the R1 to R4 points (43, 22, 21, and 11 times, respectively, for R1-R5, R2-R6, R3-R7, and R4-R8 pairs). The difference in dose between R1 and R5 was significant as seen on the statistical tests, i.e., Pair T test, Wilcoxan Signed Ranks test, and Sign test (p value 0.002). The rectal dose obtained by the intrarectal wire method underestimates the actual dose to the rectum when compared to the ICRU-38 method. Thus ICRU-38 recommendations should be strictly adhered to, to reduce late complications.

No MeSH data available.


Lateral film with ICRU-38 as well as intrarectal points marked
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Figure 0001: Lateral film with ICRU-38 as well as intrarectal points marked

Mentions: This study was undertaken in a prospective way from October 2006 to January 2008. Eighty-one patients of proven carcinoma cervix, stage IIB to IIIB, were taken for the study. All the patients received EBRT at the dose of 50 Gy/25#/5 weeks. All the patients were planned for three to four fractions of ICRT via the High Dose Rate Brachytherapy machine (HDR), as per the stage. During each application, an intrauterine tandem (4-6 cm) was placed into the uterine cavity, with ovoids (1.5-2.5 cm) in the vagina, at the level of the fornices. A radio-opaque gauze (barium soaked) was placed on the posterior vagina followed by proper packing with a povidine iodine-soaked gauze piece to further displace the bladder anteriorly and rectum posteriorly. A rectum marker, using a radio-opaque metallic wire inside the hollow rubber catheter of 1 cm diameter, was also placed inside the rectum. Orthogonal films were taken and rectal points were marked on the lateral x-ray film as R1-R4, 0.5 cm behind the posterior most visualized portion of the barium-soaked gauge, with R1 at the level of the cervical os, i.e., on the lower end of intrauterine source. Similarly points R5-R8 were marked 0.5 cm anterior to the rectal catheter with R5 at the level of the cervical os [Figure 1]. The distance between each point in both sets was taken as 1 cm. The points were selected symmetrically in relation to the anteroposterior line passing through the middle of the intravaginal sources. In all insertions a dose of 7 Gy was given at point A. Planning and dose distribution were calculated using the Abacus treatment planning software for each complementary rectal point, i.e., R1 and R5, R2 and R6, R3 and R7, and R4 and R8.


Rectal dosimetry in intracavitary brachytherapy by HDR at rural center of Maharashtra: Comparison of two methods.

Shrivastava R, Umbarkar RB, Sarje MB, Singh KK - J Med Phys (2009)

Lateral film with ICRU-38 as well as intrarectal points marked
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2805896&req=5

Figure 0001: Lateral film with ICRU-38 as well as intrarectal points marked
Mentions: This study was undertaken in a prospective way from October 2006 to January 2008. Eighty-one patients of proven carcinoma cervix, stage IIB to IIIB, were taken for the study. All the patients received EBRT at the dose of 50 Gy/25#/5 weeks. All the patients were planned for three to four fractions of ICRT via the High Dose Rate Brachytherapy machine (HDR), as per the stage. During each application, an intrauterine tandem (4-6 cm) was placed into the uterine cavity, with ovoids (1.5-2.5 cm) in the vagina, at the level of the fornices. A radio-opaque gauze (barium soaked) was placed on the posterior vagina followed by proper packing with a povidine iodine-soaked gauze piece to further displace the bladder anteriorly and rectum posteriorly. A rectum marker, using a radio-opaque metallic wire inside the hollow rubber catheter of 1 cm diameter, was also placed inside the rectum. Orthogonal films were taken and rectal points were marked on the lateral x-ray film as R1-R4, 0.5 cm behind the posterior most visualized portion of the barium-soaked gauge, with R1 at the level of the cervical os, i.e., on the lower end of intrauterine source. Similarly points R5-R8 were marked 0.5 cm anterior to the rectal catheter with R5 at the level of the cervical os [Figure 1]. The distance between each point in both sets was taken as 1 cm. The points were selected symmetrically in relation to the anteroposterior line passing through the middle of the intravaginal sources. In all insertions a dose of 7 Gy was given at point A. Planning and dose distribution were calculated using the Abacus treatment planning software for each complementary rectal point, i.e., R1 and R5, R2 and R6, R3 and R7, and R4 and R8.

Bottom Line: The rectal doses at each complementary pair were compared with each other.The rectal dose obtained by the intrarectal wire method underestimates the actual dose to the rectum when compared to the ICRU-38 method.Thus ICRU-38 recommendations should be strictly adhered to, to reduce late complications.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiotherapy and Oncology, Rural Medical College, Loni, Ahmednagar, Maharashtra, India.

ABSTRACT
The purpose of this study was to calculate the radiation dose at the anterior rectal wall as per the International Commission on Radiation Units and Measurements (ICRU 38) recommendations and compare it with the dose calculated by the commonly used intrarectal catheter. Dose delivery by brachytherapy to the cervix is limited by the critical structure of the bladder and rectum. In this study the ICRU-38 rectal point was derived by using a radio-opaque gauze piece on the posterior vaginal wall, and the intrarectal point was derived by inserting a rubber catheter with a wire, inside the rectum. A total of 146 applications were performed in 81 patients. Rectal doses were compared for complementary rectal points R1 and R5, R2 and R6, R3 and R7, and R4 and R8, obtained by both methods. The rectal doses at each complementary pair were compared with each other. The average dose at R1 was 5% higher than at R5 (60.57% vs. 55.57%). The average dose at R2 was 1% higher than at R6 (58% vs. 57%). The average dose at R3 was 1.29% higher than at R7 (52.71% vs. 51.42%), and the average dose at R4 was 1.15% higher than at R8 (43% vs. 41.85%). There were many instances where the rectal dose exceeded by more than 15%, from the R1 to R4 points (43, 22, 21, and 11 times, respectively, for R1-R5, R2-R6, R3-R7, and R4-R8 pairs). The difference in dose between R1 and R5 was significant as seen on the statistical tests, i.e., Pair T test, Wilcoxan Signed Ranks test, and Sign test (p value 0.002). The rectal dose obtained by the intrarectal wire method underestimates the actual dose to the rectum when compared to the ICRU-38 method. Thus ICRU-38 recommendations should be strictly adhered to, to reduce late complications.

No MeSH data available.