Impact of edema and seed movement on the dosimetry of prostate seed implants

Sloboda, Ron S.; Usmani, Nawaid; Monajemi, T; Liu, Dm-C

doi:10.4103/0971-6203.94742

Cited by 5 publications

(7 citation statements)

References 26 publications

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“…Our appreciation that a clinically significant extent of seed migration was occurring with this new product stems from our previous experience in studying seed migration [ 9 ]. Although this previous experience was from a different institution, the products and techniques were similar to our current methods and included one common physician.…”

Section: Discussionmentioning

confidence: 99%

“…While using this new product, routine quality assurance revealed qualitatively significant migration of strands in six of the 26 patients, often to bizarre locations, such as the ischiorectal fossa. This migration was particularly unusual for our institution, as we have previous experience in patients with serial imaging and no such significant migration [9]. We initiated an additional Day 30 CT scan in these patients to analyze seed fixity.…”

Section: Methodsmentioning

confidence: 97%

“…Leading and trailing half spacers were present. A description of our planning algorithm has been described previously [ 9 ]. Source strength was 0.395 mCi per seed.…”

Section: Methodsmentioning

confidence: 99%

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Unexpected Seed Migration in Prostate Brachytherapy Implants Coincident with Change in Seed Stranding Product

Rose¹,

Liu²,

Boychak³

et al. 2017

Cureus

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Purpose: This study was undertaken to determine if significant seed migration occurred when our institution changed seed products by comparing patterns of seed migration in implants containing different stranding material.Methods and Materials: Day 0 and Day 30 CT scans were registered by the contoured prostate center of mass. An implant reconstruction program identified seeds on CT according to the pre-plan, enabling one-to-one correspondence between Day 0 and Day 30 seeds. Significant seed migration was defined by review of seeds that migrated > 2 cm outside the prostate or appearance in unexpected locations. Results: Twenty-five (149, 16.8%) new strands displayed movement > 2 cm between Day 0 and Day 30 compared with just 2/118 (1.7%) of the standard strands. Six out of 26 (23%) patients with new strands displayed significant migration compared with 2/13 (14%) of patients with standard strands. In the six patients with new strands and significant migration, a mean of four strands (17%, range: 2-8 per patient) migrated significantly with 65% due to whole strand migration, 25% due to strand breakage, and 10% strand clumping. In the control group, only two strands (2%) migrated significantly, both due to strand breakage. Despite the greater seed movement with the new strands, Day 0 and Day 30 dosimetry was acceptable.Conclusion: In this short report, we identified that a change to a new strand type was associated with unexpected significant seed movement compared to our typical strands. Since seed movement can arise from unexpected causes, it is important to maintain quality assurance practices when a change in technique or infrastructure is instituted.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 97%

See 1 more Smart Citation

Unexpected Seed Migration in Prostate Brachytherapy Implants Coincident with Change in Seed Stranding Product

Rose¹,

Liu²,

Boychak³

et al. 2017

Cureus

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“…To determine the quality of the implantation, we perform a CT scan immediately following the implantation and use it to generate a second treatment plan, called the Day 0 treatment plan. After the prostate edema has resolved in approximately a month, another CT scan is performed to generate the Day 30 treatment plan (16‐19) …”

Section: Methodsmentioning

confidence: 99%

Evaluation of the MIM Symphony treatment planning system for low‐dose‐rate‐ prostate brachytherapy

Dhanesar

Lim²,

et al. 2015

J Applied Clin Med Phys

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MIM Symphony is a recently introduced low‐dose‐rate prostate brachytherapy treatment planning system (TPS). We evaluated the dosimetric and planning accuracy of this new TPS compared to the universally used VariSeed TPS. For dosimetric evaluation of the MIM Symphony version 5.4 TPS, we compared dose calculations from the MIM Symphony TPS with the formalism recommended by the American Association of Physicists in Medicine Task Group 43 report (TG‐43) and those generated by the VariSeed version 8.0 TPS for iodine‐125 (I‐125; Models 6711 and IAI‐125A), palladium‐103 (Pd‐103; Model 200), and cesium‐131 (Cs‐131; Model Cs‐1). Validation was performed for both line source and point source approximations. As part of the treatment planning validation, first a QA phantom (CIRS Brachytherapy QA Phantom Model 045 SN#D7210‐3) containing three ellipsoid objects with certified volumes was scanned in order to check the volume accuracy of the contoured structures in MIM Symphony. Then the DICOM data containing 100 patient plans from the VariSeed TPS were imported into the MIM Symphony TPS. The 100 plans included 25 each of I‐125 pre‐implant plans, Pd‐103 pre‐implant plans, I‐125 Day 30 plans (i.e., from 1 month after implantation), and Pd‐103 Day 30 plans. The dosimetric parameters (including prostate volume, prostate D90 values, and rectum V100 values) of the 100 plans were calculated independently on the two TPSs. Other TPS tests that were done included verification of source input and geometrical accuracy, data transfer between different planning systems, text printout, 2D dose plots, DVH printout, and template grid accuracy. According to the line source formalism, the dosimetric results between the MIM Symphony TPS and TG‐43 were within 0.5% (0.02 Gy) for r>1 cm. In the line source approximation validation, MIM Symphony TPS values agreed with VariSeed TPS values to within 0.5% (0.09 Gy) for r>1 cm. Similarly, in point source approximation validation, the MIM Symphony values agreed to within 1% of the TG‐43 and VariSeed values for r>1 cm. The volume calculations obtained from the MIM Symphony TPS for the CIRS Brachytherapy QA Phantom were within 1% of the actual volume of the phantom. For the clinical cases, the volume and dosimetric parameter calculations for the prostate and rectum did not differ substantially between the pre‐implant and Day 30 plans. Overall, our investigations showed negligible differences in dosimetry calculations and planning parameters between the two TPSs. The tests done to check the performance of the MIM Symphony TPS, such as the library data, data transfer, isodose and DVH printout, were found to be satisfactory. On the basis of these results, we conclude that the MIM Symphony TPS can be used as an alternative to the VariSeed TPS for low‐dose‐rate prostate brachytherapy.PACS numbers: 87.53.Jw; 87.55.D‐, 87.55.Qr

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“…Several studies have investigated the influence of edema on post-implant dosimetry (Chira et al 2013, Tejwani et al 2012, Waterman et al 1998, Sloboda et al 2012, Yue et al 2006, Sloboda et al 2010, Chen et al 2000and Dogan et al 2002. Chira et al (2013) have shown that a prostate volume increase of 10% during brachytherapy can lead to an increase in D90 (dose coverage of 90% of the prostate volume) at Day30 of approximately 11.7% in comparison to the D90 measured at Day1.…”

Section: Introductionmentioning

confidence: 99%

Modeling the impact of prostate edema on LDR brachytherapy: a Monte Carlo dosimetry study based on a 3D biphasic finite element biomechanical model

Mountris¹,

Bert²,

Noailly³

et al. 2017

Phys. Med. Biol.

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Prostate volume changes due to edema occurrence during transperineal permanent brachytherapy should be taken under consideration to ensure optimal dose delivery. Available edema models, based on prostate volume observations, face several limitations. Therefore, patient-specific models need to be developed to accurately account for the impact of edema. In this study we present a biomechanical model developed to reproduce edema resolution patterns documented in the literature. Using the biphasic mixture theory and finite element analysis, the proposed model takes into consideration the mechanical properties of the pubic area tissues in the evolution of prostate edema. The model's computed deformations are incorporated in a Monte Carlo simulation to investigate their effect on post-operative dosimetry. The comparison of Day1 and Day30 dosimetry results demonstrates the capability of the proposed model for patient-specific dosimetry improvements, considering the edema dynamics. The proposed model shows excellent ability to reproduce previously described edema resolution patterns and was validated based on previous findings. According to our results, for a prostate volume increase of 10-20% the Day30 urethra D10 dose metric is higher by 4.2%-10.5% compared to the Day1 value. The introduction of the edema dynamics in Day30 dosimetry shows a significant global dose overestimation identified on the conventional static Day30 dosimetry. In conclusion, the proposed edema biomechanical model can improve the treatment planning of transperineal permanent brachytherapy accounting for post-implant dose alterations during the planning procedure.

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Impact of edema and seed movement on the dosimetry of prostate seed implants

Cited by 5 publications

References 26 publications

Unexpected Seed Migration in Prostate Brachytherapy Implants Coincident with Change in Seed Stranding Product

Unexpected Seed Migration in Prostate Brachytherapy Implants Coincident with Change in Seed Stranding Product

Evaluation of the MIM Symphony treatment planning system for low‐dose‐rate‐ prostate brachytherapy

Modeling the impact of prostate edema on LDR brachytherapy: a Monte Carlo dosimetry study based on a 3D biphasic finite element biomechanical model

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