Dose perturbation effects in prostate seed implant brachytherapy with I-125

Mobit, Paul N; Badragan, Iulian

doi:10.1088/0031-9155/49/14/011

Cited by 25 publications

(27 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This inter-seed attenuation (ISA) effect depends on radionuclide ( i.e ., photon energy), source encapsulation, seed spacing, or equivalently seed density, which in turn depends on prostate size and seed air-kerma strength. Initial studies using MC simulations of a number of seeds with different spacing [21] or idealized implants [22] reported an effect on conformity and homogeneity indices that becomes negligible for 125 I seeds spaced >0.5 cm apart. Subsequent studies of the ISA effect were performed using MC simulations in clinical, CT-based, pre- or post-implant geometries with results reported in CTV and OAR DVH parameters employed for treatment plan evaluation [23–26].…”

Section: Sources Of Uncertaintymentioning

confidence: 99%

Review of clinical brachytherapy uncertainties: Analysis guidelines of GEC-ESTRO and the AAPM

Kirisits

Rivard

Baltas

et al. 2014

Radiotherapy and Oncology

258

210

View full text Add to dashboard Cite

Background and purposeA substantial reduction of uncertainties in clinical brachytherapy should result in improved outcome in terms of increased local control and reduced side effects. Types of uncertainties have to be identified, grouped, and quantified.MethodsA detailed literature review was performed to identify uncertainty components and their relative importance to the combined overall uncertainty.ResultsVery few components (e.g., source strength and afterloader timer) are independent of clinical disease site and location of administered dose. While the influence of medium on dose calculation can be substantial for low energy sources or non-deeply seated implants, the influence of medium is of minor importance for high-energy sources in the pelvic region. The level of uncertainties due to target, organ, applicator, and/or source movement in relation to the geometry assumed for treatment planning is highly dependent on fractionation and the level of image guided adaptive treatment. Most studies to date report the results in a manner that allows no direct reproduction and further comparison with other studies. Often, no distinction is made between variations, uncertainties, and errors or mistakes. The literature review facilitated the drafting of recommendations for uniform uncertainty reporting in clinical BT, which are also provided. The recommended comprehensive uncertainty investigations are key to obtain a general impression of uncertainties, and may help to identify elements of the brachytherapy treatment process that need improvement in terms of diminishing their dosimetric uncertainties. It is recommended to present data on the analyzed parameters (distance shifts, volume changes, source or applicator position, etc.), and also their influence on absorbed dose for clinically-relevant dose parameters (e.g., target parameters such as D90 or OAR doses). Publications on brachytherapy should include a statement of total dose uncertainty for the entire treatment course, taking into account the fractionation schedule and level of image guidance for adaptation.ConclusionsThis report on brachytherapy clinical uncertainties represents a working project developed by the Brachytherapy Physics Quality Assurances System (BRAPHYQS) subcommittee to the Physics Committee within GEC-ESTRO. Further, this report has been reviewed and approved by the American Association of Physicists in Medicine.

show abstract

Section: Sources Of Uncertaintymentioning

confidence: 99%

Review of clinical brachytherapy uncertainties: Analysis guidelines of GEC-ESTRO and the AAPM

Kirisits

Rivard

Baltas

et al. 2014

Radiotherapy and Oncology

258

210

View full text Add to dashboard Cite

show abstract

“…The TG-43u1 calculations overestimate the D 90 values calculated with MCP by 5.8%-12.8%, depending on the seed density and prostate size. This difference corresponds to [13][14][15][16][17][18][19][20][21][22][23][24][25][26] Gy. This is illustrating the systematic effect when taking into account the interseed attenuation and prostate composition corrections in the dosimetry.…”

Section: Overall Comparisonmentioning

confidence: 99%

“…Similar works have been recently published about dosimetric perturbation effects calculated using Monte Carlo methods. Mobit and Badragan 17 have studied the interseed attenuation in a water cube with 27 uniformly distributed seeds. Chibani et al 18 have evaluated the interseed attenuation for idealized and clinical prostate implants.…”

Section: Introductionmentioning

confidence: 99%

Impact of interseed attenuation and tissue composition for permanent prostate implants

et al. 2006

View full text Add to dashboard Cite

The purpose is to evaluate the impact of interseed attenuation and prostate composition for prostate treatment plans with 125I permanent seed implants using the Monte Carlo (MC) method. The effect of seed density (number of seeds per prostate unit volume) is specifically investigated. The study focuses on treatment plans that were generated for clinical cases. For each plan, four different dose calculation techniques are compared: TG-43 based calculation, superposition MC, full MC with water prostate, and full MC with realistic prostate tissue. The prostate tissue description is from the ICRP report 23 (W. S. Snyer, M. J. Cook, E. S. Nasset, L. R. Karkhausen, G. P. Howells, and I. H. Tipton, "Report of the task group on reference man," Technical Report 23, International Commission on Radiological Protection, 1974). According to the comparisons, the seed density has an influence on interseed attenuation. A plan with a typical low seed density (42 0.6 mCi seeds in a 26 cm3 prostate) suffers a 1.2% drop in the CTV D90 value due to interseed attenuation. A drop of 3.0% is calculated for a higher seed density (75 0.3 mCi seeds, same prostate). The influence of the prostate composition is similar for all seed densities and prostate sizes. The difference between MC simulations in water and MC simulations in prostate tissue is between 4.4% and 4.8% for the D90 parameter. Overall, the effect on D90 is ranging from 5.8% to 12.8% when comparing clinically approved TG-43 and MC simulations in prostate tissue. The impact varies from one patient to the other and depends on the prostate size and the number of seeds. This effect can reach a significant level when reporting correlations between clinical effect and deposited dose.

show abstract

“…That study reported a reduction of 6% of the peripheral dose due to the mutual attenuation by neighboring seeds. Mobit et al 34 studied the interseed effect for an array of 27 125 I seeds in a 20 ϫ 20ϫ 20 cm 3 cube of water deposited at 1, 0.75, and 0.5 cm apart. They reported no significant change in dose volume histograms due to the interseed effect provided that the seeds are separated by more than 0.5 cm.…”

Section: Discussionmentioning

confidence: 99%

A Monte Carlo study on the effect of seed design on the interseed attenuation in permanent prostate implants

et al. 2008

View full text Add to dashboard Cite

Standard algorithms for postimplant analysis of transperineal interstitial permanent prostate brachytherapy (TIPPB) are based on AAPM Task Group 43 formalism (TG-43), which makes use of a world entirely made of water. This entails an assignment of the prostate, surrounding organs at risk, as well as all brachytherapy seeds present in a permanent prostate implant to water. Brachytherapy seeds are generally made from high atomic number materials. Because of the simultaneous presence of many brachytherapy seeds in a TIPPB, there is a shielding effect causing an attenuation of energy of the emitted photons generally called the "interseed attenuation" (ISA). This study investigates the impact of seed designs and compositions on the interseed attenuation. For this purpose, six brachytherapy seeds covering a wide variety of seed design and composition were modeled with the GEANT4 Monte Carlo (MC) toolkit. MC has allowed calculation of the contribution of each major component (encapsulation and internal components) of a given seed model to ISA separately. The impact of ISA on real clinical implant configurations was also explored. Two clinical postimplant geometries with different brachytherapy seeds were studied with MC simulations. The change in the clinical parameter D90 was observed. This study shows that Nucletron SelectSeed (similar to the Oncura model 6711), ProstaSeed, and Best Medical model 2335 are the most attenuating designs with 4.8%, 3.9%, and 4.6% of D90 reduction, respectively. The least attenuating seed is a 103Pd seed encapsulated in a polymer shell, the IBt OptiSeed with 1.5%. Finally, based on this systematic study, a new seed design is proposed that is predicted to be the most waterlike brachytherapy seed and thus TG-43 compatible.

show abstract

Dose perturbation effects in prostate seed implant brachytherapy with I-125

Cited by 25 publications

References 6 publications

Review of clinical brachytherapy uncertainties: Analysis guidelines of GEC-ESTRO and the AAPM

Review of clinical brachytherapy uncertainties: Analysis guidelines of GEC-ESTRO and the AAPM

Impact of interseed attenuation and tissue composition for permanent prostate implants

A Monte Carlo study on the effect of seed design on the interseed attenuation in permanent prostate implants

Contact Info

Product

Resources

About