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Reduced dose to urethra and rectum with the use of variable needle spacing in prostate brachytherapy: a potential role for robotic technology.

Vyas S, Le Y, Zhang Z, Armour W, Song DY - J Contemp Brachytherapy (2015)

Bottom Line: We sought to quantify potential reductions in the dose to urethra and rectum by utilizing variable needle spacing, as compared to fixed needle spacing.Combined results for all plans show statistically significant improvements in all assessed dosimetric variables for urethra (Umax, Umean, D30, D5) and rectum (Rmax, Rmean, RV100) when using variable spacing.Similarly dose reductions for mean and maximum rectal dose using variable spacing had p values of 0.007 and 0.052 with (103)Pd, and 0.012 and 0.037 with (125)I plans.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Baylor Scott & White Health/Texas A&M College of Medicine, Temple, Texas.

ABSTRACT

Purpose: Several robotic delivery systems for prostate brachytherapy are under development or in pre-clinical testing. One of the features of robotic brachytherapy is the ability to vary spacing of needles at non-fixed intervals. This feature may play an important role in prostate brachytherapy, which is traditionally template-based with fixed needle spacing of 0.5 cm. We sought to quantify potential reductions in the dose to urethra and rectum by utilizing variable needle spacing, as compared to fixed needle spacing.

Material and methods: Transrectal ultrasound images from 10 patients were used by 3 experienced planners to create 120 treatment plans. Each planner created 4 plan variations per patient with respect to needle positions: (125)I fixed spacing, (125)I variable spacing, (103)Pd fixed spacing, and (103)Pd variable spacing. The primary planning objective was to achieve a prostate V100 of 100% while minimizing dose to urethra and rectum.

Results: All plans met the objective of achieving prostate V100 of 100%. Combined results for all plans show statistically significant improvements in all assessed dosimetric variables for urethra (Umax, Umean, D30, D5) and rectum (Rmax, Rmean, RV100) when using variable spacing. The dose reductions for mean and maximum urethra dose using variable spacing had p values of 0.011 and 0.024 with (103)Pd, and 0.007 and 0.029 with (125)I plans. Similarly dose reductions for mean and maximum rectal dose using variable spacing had p values of 0.007 and 0.052 with (103)Pd, and 0.012 and 0.037 with (125)I plans.

Conclusions: The variable needle spacing achievable by the use of robotics in prostate brachytherapy allows for reductions in both urethral and rectal planned doses while maintaining prostate dose coverage. Such dosimetric advantages have the potential in translating to significant clinical benefits with the use of robotic brachytherapy.

No MeSH data available.


Depiction of dose distribution in fixed needle spacing and variable needle spacing plans. Transverse section of ultrasound image at mid-prostate level planned with 103Pd seeds using fixed needle spacing plan (left) and variable needle spacing plan (right). The urethral sparing is well visualized with the variable spacing plan by assessing the distance between the urethra and the 150% isodose line.Key: prostate gland – green; urethra – magenta; 100% isodose line – red; 150% isodose line – turquoise; needle/source positions (sources within currently visualized axial plane) – blue; other needle positions (sources not in currently visualized axial plane) – empty circles.
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Figure 0001: Depiction of dose distribution in fixed needle spacing and variable needle spacing plans. Transverse section of ultrasound image at mid-prostate level planned with 103Pd seeds using fixed needle spacing plan (left) and variable needle spacing plan (right). The urethral sparing is well visualized with the variable spacing plan by assessing the distance between the urethra and the 150% isodose line.Key: prostate gland – green; urethra – magenta; 100% isodose line – red; 150% isodose line – turquoise; needle/source positions (sources within currently visualized axial plane) – blue; other needle positions (sources not in currently visualized axial plane) – empty circles.

Mentions: The mean numbers of needles with 103Pd plans were 33 (± 9) and 35 (± 8) for variable and fixed spacing, respectively, which were found to be significantly different despite the differences being only 1-2 needles (Table 1). Similarly, the mean difference in number of sources with 125I plans was clinically trivial although statistically significant (Table 1). Figure 1 shows the pictorial depiction of the urethral sparing with variable-spacing plans using 103Pd.


Reduced dose to urethra and rectum with the use of variable needle spacing in prostate brachytherapy: a potential role for robotic technology.

Vyas S, Le Y, Zhang Z, Armour W, Song DY - J Contemp Brachytherapy (2015)

Depiction of dose distribution in fixed needle spacing and variable needle spacing plans. Transverse section of ultrasound image at mid-prostate level planned with 103Pd seeds using fixed needle spacing plan (left) and variable needle spacing plan (right). The urethral sparing is well visualized with the variable spacing plan by assessing the distance between the urethra and the 150% isodose line.Key: prostate gland – green; urethra – magenta; 100% isodose line – red; 150% isodose line – turquoise; needle/source positions (sources within currently visualized axial plane) – blue; other needle positions (sources not in currently visualized axial plane) – empty circles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643728&req=5

Figure 0001: Depiction of dose distribution in fixed needle spacing and variable needle spacing plans. Transverse section of ultrasound image at mid-prostate level planned with 103Pd seeds using fixed needle spacing plan (left) and variable needle spacing plan (right). The urethral sparing is well visualized with the variable spacing plan by assessing the distance between the urethra and the 150% isodose line.Key: prostate gland – green; urethra – magenta; 100% isodose line – red; 150% isodose line – turquoise; needle/source positions (sources within currently visualized axial plane) – blue; other needle positions (sources not in currently visualized axial plane) – empty circles.
Mentions: The mean numbers of needles with 103Pd plans were 33 (± 9) and 35 (± 8) for variable and fixed spacing, respectively, which were found to be significantly different despite the differences being only 1-2 needles (Table 1). Similarly, the mean difference in number of sources with 125I plans was clinically trivial although statistically significant (Table 1). Figure 1 shows the pictorial depiction of the urethral sparing with variable-spacing plans using 103Pd.

Bottom Line: We sought to quantify potential reductions in the dose to urethra and rectum by utilizing variable needle spacing, as compared to fixed needle spacing.Combined results for all plans show statistically significant improvements in all assessed dosimetric variables for urethra (Umax, Umean, D30, D5) and rectum (Rmax, Rmean, RV100) when using variable spacing.Similarly dose reductions for mean and maximum rectal dose using variable spacing had p values of 0.007 and 0.052 with (103)Pd, and 0.012 and 0.037 with (125)I plans.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Baylor Scott & White Health/Texas A&M College of Medicine, Temple, Texas.

ABSTRACT

Purpose: Several robotic delivery systems for prostate brachytherapy are under development or in pre-clinical testing. One of the features of robotic brachytherapy is the ability to vary spacing of needles at non-fixed intervals. This feature may play an important role in prostate brachytherapy, which is traditionally template-based with fixed needle spacing of 0.5 cm. We sought to quantify potential reductions in the dose to urethra and rectum by utilizing variable needle spacing, as compared to fixed needle spacing.

Material and methods: Transrectal ultrasound images from 10 patients were used by 3 experienced planners to create 120 treatment plans. Each planner created 4 plan variations per patient with respect to needle positions: (125)I fixed spacing, (125)I variable spacing, (103)Pd fixed spacing, and (103)Pd variable spacing. The primary planning objective was to achieve a prostate V100 of 100% while minimizing dose to urethra and rectum.

Results: All plans met the objective of achieving prostate V100 of 100%. Combined results for all plans show statistically significant improvements in all assessed dosimetric variables for urethra (Umax, Umean, D30, D5) and rectum (Rmax, Rmean, RV100) when using variable spacing. The dose reductions for mean and maximum urethra dose using variable spacing had p values of 0.011 and 0.024 with (103)Pd, and 0.007 and 0.029 with (125)I plans. Similarly dose reductions for mean and maximum rectal dose using variable spacing had p values of 0.007 and 0.052 with (103)Pd, and 0.012 and 0.037 with (125)I plans.

Conclusions: The variable needle spacing achievable by the use of robotics in prostate brachytherapy allows for reductions in both urethral and rectal planned doses while maintaining prostate dose coverage. Such dosimetric advantages have the potential in translating to significant clinical benefits with the use of robotic brachytherapy.

No MeSH data available.