| 1. |
- Ardenfors, Oscar, et al.
(author)
-
Are IMRT treatments in the head and neck region increasing the risk of secondary cancers?
- 2014
-
In: Acta Oncologica. - : Informa Healthcare. - 0284-186X .- 1651-226X. ; 53:8, s. 1041-1047
-
Journal article (peer-reviewed)abstract
- Background. Intensity-modulated radiation therapy (IMRT) has been increasingly employed for treating head and neck (H&N) tumours due to its ability to produce isodoses suitable for the complex anatomy of the region. The aim of this study was to assess possible differences between IMRT and conformal radiation therapy (CRT) with regard to risk of radiation-induced secondary malignancies for H&N tumours. Material and methods. IMRT and CRT plans were made for 10 H&N adult patients and the resulting treatment planning data were used to calculate the risk of radiation-induced malignancies in four different tissues. Three risk models with biologically relevant parameters were used for calculations. The influence of scatter radiation and repeated imaging sessions has also been investigated. Results. The results showed that the total lifetime risks of developing radiation-induced secondary malignancies from the two treatment techniques, CRT and IMRT, were comparable and in the interval 0.9-2.5%. The risk contributions from the primary beam and scatter radiation were comparable, whereas the contribution from repeated diagnostic imaging was considerably smaller. Conclusion. The results indicated that the redistribution of the dose characteristic to IMRT leads to a redistribution of the risks in individual tissues. However, the total levels of risk were similar between the two irradiation techniques considered.
|
|
| 2. |
|
|
| 3. |
- Ardenfors, Oscar, et al.
(author)
-
IMPACT OF IRRADIATION SETUP IN PROTON SPOT SCANNING BRAIN THERAPY ON ORGAN DOSES FROM SECONDARY RADIATION
- 2018
-
In: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 180:1-4, s. 261-266
-
Journal article (peer-reviewed)abstract
- A Monte Carlo model of a proton spot scanning pencil beam was used to simulate organ doses from secondary radiation produced from brain tumour treatments delivered with either a lateral field or a vertex field to one adult and one paediatric patient. Absorbed doses from secondary neutrons, photons and protons and neutron equivalent doses were higher for the vertex field in both patients, but the differences were low in absolute terms. Absorbed doses ranged between 0.1 and 43 mu Gy. Gy(-1) in both patients with the paediatric patient receiving higher doses. The neutron equivalent doses to the organs ranged between 0.5 and 141 mu Sv. Gy(-1) for the paediatric patient and between 0.2 and 134 mu Sv. Gy(-1) for the adult. The highest neutron equivalent dose from the entire treatment was 7 mSv regardless of field setup and patient size. The results indicate that different field setups do not introduce large absolute variations in out-of-field doses produced in patients undergoing proton pencil beam scanning of centrally located brain tumours.
|
|
| 4. |
- Ardenfors, Oscar, et al.
(author)
-
Modelling of a proton spot scanning system using MCNP6
- 2017
-
In: International Nuclear Science and Technology Conference. - : Institute of Physics (IOP). ; 860, s. 012025-
-
Conference paper (peer-reviewed)abstract
- The aim of this work was to model the characteristics of a clinical proton spot scanning beam using Monte Carlo simulations with the code MCNP6. The proton beam was defined using parameters obtained from beam commissioning at the Skandion Clinic, Uppsala, Sweden. Simulations were evaluated against measurements for proton energies between 60 and 226 MeV with regard to range in water, lateral spot sizes in air and absorbed dose depth profiles in water. The model was also used to evaluate the experimental impact of lateral signal losses in an ionization chamber through simulations using different detector radii. Simulated and measured distal ranges agreed within 0.1 mm for R90 and R80 , and within 0.2 mm for R50 . The average absolute difference of all spot sizes was 0.1 mm. The average agreement of absorbed dose integrals and Bragg-peak heights was 0.9%. Lateral signal losses increased with incident proton energy with a maximum signal loss of 7% for 226 MeV protons. The good agreement between simulations and measurements supports the assumptions and parameters employed in the presented Monte Carlo model. The characteristics of the proton spot scanning beam were accurately reproduced and the model will prove useful in future studies on secondary neutrons.
|
|
| 5. |
- Ardenfors, Oscar, et al.
(author)
-
Organ doses from a proton gantry-mounted cone-beam computed tomography system characterized with MCNP6 and GATE
- 2018
-
In: Physica medica (Testo stampato). - : Elsevier BV. - 1120-1797 .- 1724-191X. ; 53, s. 56-61
-
Journal article (peer-reviewed)abstract
- PurposeTo determine organ doses from a proton gantry-mounted cone-beam computed tomography (CBCT) system using two Monte Carlo codes and to study the influence on organ doses from different acquisition modes and repeated imaging.MethodsThe CBCT system was characterized with MCNP6 and GATE using measurements of depth doses in water and spatial profiles in air. The beam models were validated against absolute dose measurements and used to simulate organ doses from CBCT imaging with head, thorax and pelvis protocols. Anterior and posterior 190° scans were simulated and the resulting organ doses per mAs were compared to those from 360° scans. The influence on organ doses from repeated imaging with different imaging schedules was also investigated.ResultsThe agreement between MCNP6, GATE and measurements with regard to depth doses and beam profiles was within 4% for all protocols and the corresponding average agreement in absolute dose validation was 4%. Absorbed doses for in-field organs from 360° scans ranged between 6 and 8 mGy, 15–17 mGy and 24–54 mGy for the head, thorax and pelvis protocols, respectively. Cumulative organ doses from repeated CBCT imaging ranged between 0.04 and 0.32 Gy for weekly imaging and 0.2–1.6 Gy for daily imaging. The anterior scans resulted in an average increase in dose per mAs of 24% to the organs of interest relative to the 360° scan, while the posterior scan showed a 37% decrease.ConclusionsA proton gantry-mounted CBCT system was accurately characterized with MCNP6 and GATE. Organ doses varied greatly depending on acquisition mode, favoring posterior scans.
|
|
| 6. |
- Ardenfors, Oscar, 1985-
(author)
-
Out-of-field doses from proton therapy and doses from CBCT imaging : Risk of radiation-induced second cancer from modern radiotherapy
- 2018
-
Doctoral thesis (other academic/artistic)abstract
- The use of ionizing radiation for treatment of cancer diseases is continuously increasing as patient survival is improving and new treatment techniques are emerging. While this development is beneficial for curing primary tumors, concerns have been raised regarding the unwanted dose contribution to healthy tissues of patients and the associated risk of radiation-induced second cancer (RISC). This is especially important for younger patients receiving radiotherapy more often than before and for whom the risk of developing RISC is elevated in comparison to the typical adult radiotherapy patient. In order to estimate the risk of RISC associated with modern radiotherapy and imaging, the associated radiation doses must be determined.Patients undergoing radiotherapy receive in-field doses from the primary beam but also out-of-field doses originating from secondary radiation produced in the beamline and within the patient. Over the last years, the use of proton pencil beam scanning (PBS) therapy has rapidly increased due to its potential to reduce the in-field doses to healthy tissues in comparison to photon therapy. One of the drawbacks with proton therapy is the production of neutrons capable of travelling large distances and depositing out-of-field doses to organs located far from the primary treatment field. The dose reduction associated with proton PBS therapy could consequently be affected by the out-of-field doses originating from secondary radiation.The sharp dose gradients associated with modern treatment techniques, such as photon intensity-modulated radiotherapy (IMRT) and proton PBS therapy require more frequent and accurate patient imaging in comparison to conventional treatment techniques such as three-dimensional conformal radiotherapy (CRT). Setup verification images could be acquired with cone-beam computed tomography (CBCT) producing three-dimensional patient images at the cost of an increased patient dose in comparison to planar x-ray imaging. Concerns have been raised regarding the cumulative patient doses from repeated CBCT imaging versus the dose-saving benefits associated with modern radiotherapy techniques like IMRT and proton PBS.In this thesis, a study on the in-field and out-of-field doses to healthy tissues from photon IMRT and CRT treatments of head and neck tumors showed that the risk of RISC was unaffected by the employed treatment technique and indicated that the lifetime risk of cancer induction was of the order of 1-2%.Results from measurements and Monte Carlo simulations showed that the out-of-field absorbed doses and equivalent doses associated with proton PBS treatments of brain tumors were up to 60 µGy/Gy and 150 µSv/Gy, respectively. The risk of RISC associated with these out-of-field doses was in the range of approximately one induced cancer in ten thousand treated patients. A simulation study on the doses from a proton gantry-mounted CBCT system showed that repeated CBCT imaging could result in cumulative organ doses of almost 2 Gy. The conclusion from these studies is that the dose-sparing effects of proton PBS therapy are not overshadowed by the out-of-field doses originating from secondary radiation for brain tumor treatments, but that the cumulative doses from repeated CBCT imaging could have a relevant impact on the overall dose reduction.
|
|
| 7. |
- Ardenfors, Oscar, et al.
(author)
-
Out-of-field doses from secondary radiation produced in proton therapy and the associated risk of radiation-induced cancer from a brain tumor treatment
- 2018
-
In: Physica medica (Testo stampato). - : Elsevier BV. - 1120-1797 .- 1724-191X. ; 53, s. 129-136
-
Journal article (peer-reviewed)abstract
- PurposeTo determine out-of-field doses produced in proton pencil beam scanning (PBS) therapy using Monte Carlo simulations and to estimate the associated risk of radiation-induced second cancer from a brain tumor treatment.MethodsSimulations of out-of-field absorbed doses were performed with MCNP6 and benchmarked against measurements with tissue-equivalent proportional counters (TEPC) for three irradiation setups: two irradiations of a water phantom using proton energies of 78-147 MeV and 177-223 MeV, and one brain tumor irradiation of a whole-body phantom. Out-of-field absorbed and equivalent doses to organs in a whole-body phantom following a brain tumor treatment were subsequently simulated and used to estimate the risk of radiation-induced cancer. Additionally, the contribution of absorbed dose originating from radiation produced in the nozzle was calculated from simulations.ResultsOut-of-field absorbed doses to the TEPC ranged from 0.4 to 135 mu Gy/Gy. The average deviation between simulations and measurements of the water phantom irradiations was about 17%. The absorbed dose contribution from radiation produced in the nozzle ranged between 0 and 70% of the total dose; the contribution was however small in absolute terms. The absorbed and equivalent doses to the organs ranged between 0.2 and 60 mu Gy/Gy and 0.5-151 mu Sv/Gy. The estimated lifetime risk of radiation-induced second cancer was approximately 0.01%.ConclusionsThe agreement of out-of-field absorbed doses between measurements and simulations was good given the sources of uncertainties. Calculations of out-of-field organ doses following a brain tumor treatment indicated that proton PBS therapy of brain tumors is associated with a low risk of radiation-induced cancer.
|
|
| 8. |
- Ardenfors, Oscar
(author)
-
Secondary doses to healthy tissues from radiotherapy and modern imaging techniques
- 2017
-
Licentiate thesis (other academic/artistic)abstract
- The use of ionizing radiation for treatment of cancer diseases is continuously increasing giving rise to several new questions and concerns. One of the most important aspects of this is the associated dose imparted to healthy tissues. This unwanted dose contribution is a result of both radiotherapy procedures and diagnostic imaging. The dose deposition in healthy tissues from external radiotherapy mainly originates from the incident primary beam. However, the patient also receives non-negligible organ doses originating from secondary radiation produced in the treatment machine and within the patient. This secondary radiation, especially neutrons, can travel large distances and consequently deposit doses to organs located far from the primary treatment field. The dose contribution to healthy organs from diagnostic procedures is growing due to the increase in repeated imaging performed in conjunction with radiotherapy. Also, patients undergoing both external radiotherapy and radionuclide therapy with radioactive isotopes could receive a high combined dose burden to healthy tissues.The need to quantify the secondary dose contribution and the associated risk of radiation-induced cancer is a relevant matter as new techniques are continuously emerging both in the field of radiotherapy and imaging. The technical advances in modern treatment techniques such as intensity modulated radiotherapy, rotational therapy and ion therapy have contributed to the overall increase in patient survival. A parallel development in medical imaging has caused an increase in the use of cone-beam computed tomography for repeated image-guidance imaging providing better tumor localization and a reduction in high doses deposited in adjacent healthy tissues.The most accurate way of estimating the risk of radiation-induced secondary cancers is to conduct comprehensive epidemiological studies on an exposed population stretching over several decades. This has been done in the past using cohorts of survivors of the atomic bombings and other nuclear accidents and medical exposures. However, the implementation of these epidemiological data is complex as the types of exposure differ greatly from modern radiotherapy procedures. Also, the long latency associated with radiation-induced secondary cancers further complicate the use of epidemiological data.Thus, the goal of achieving a dose-response relationship for secondary cancers is not only a matter of assessing the dose to the patient but also on how this data should be analyzed. Today, the most popular way of achieving this is through theoretical risk models using patient-specific parameters including dose distributions and risk coefficients obtained for populations from epidemiological studies.Due to the difficulties associated with performing measurements of radiation-induced organ doses from treatment and imaging, the dose is often calculated either analytically using an algorithm employed in the clinical treatment planning system or through Monte Carlo simulations that offer the most accurate tool for such calculations. To allow for accurate Monte Carlo simulations of secondary radiation from external radiotherapy the beam model should be validated against measurements with regard to both the primary beam and the out-of-field secondary radiation.These aspects have been investigated in individual studies that make the object of the articles included in this thesis. Paper I presents a literature review of secondary doses from different treatment and imaging modalities. Paper II shows a comparison between the risks of radiation-induced cancer for patients treated for head and neck cancer using two different treatment techniques. Paper III deals with Monte Carlo simulations of doses to healthy tissues from radionuclide therapy given in conjunction with external radiotherapy. Paper IV presents the validation of a proton spot scanning Monte Carlo model.
|
|
| 9. |
- Grzanka, Leszek, et al.
(author)
-
MONTE CARLO SIMULATIONS OF SPATIAL LET DISTRIBUTIONS IN CLINICAL PROTON BEAMS
- 2018
-
In: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 180:1-4, s. 296-299
-
Journal article (peer-reviewed)abstract
- The linear energy transfer (LET) is commonly used as a parameter which describes the quality of the radiation applied in radiation therapy with fast ions. In particular in proton therapy, most models which predict the radiobiological properties of the applied beam, are fitted to the dose-averaged LET, LETd. The related parameter called the fluence-or track-averaged LET, LETt, is less frequently used. Both LETt and in particular LETd depends profoundly on the encountered secondary particle spectrum. For proton beams including all secondary particles, LETd may reach more than 3 keV/um in the entry channel of the proton field. However, typically the charged particle spectrum is only averaged over the primary and secondary protons, which is in the order of 0.5 keV/um for the same region. This is equal to assuming that the secondary particle spectrum from heavier ions is irrelevant for the resulting radiobiology, which is an assertion in the need of closer investigation. Models which rely on LETd should also be clear on what type of LETd is used, which is not always the case. Within this work, we have extended the Monte Carlo particle transport code SHIELD-HIT12A to provide dose-and track-average LET-maps for ion radiation therapy treatment plans.
|
|
| 10. |
- Gudowska, Irena, et al.
(author)
-
Radiation burden from secondary doses to patients undergoing radiation therapy with photons and light ions and radiation doses from imaging modalities
- 2014
-
In: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 161:1-4, s. 357-362
-
Journal article (peer-reviewed)abstract
- Ionising radiation is increasingly used for the treatment of cancer, being the source of a considerable fraction of the medical irradiation to patients. With the increasing success rate of cancer treatments and longer life expectancy of the treated patients, the issue of secondary cancer incidence is of growing concern, especially for paediatric patients who may live long after the treatment and be more susceptible to carcinogenesis. Also, additional imaging procedures like CT, kV and MV imaging and PET, alone or in conjunction with radiation therapy, may add to the radiation burden associated with the risk of occurrence of secondary cancers. This work has been based on literature studies and is focussed on the assessment of secondary doses to healthy tissues that are delivered by the use of modern radiation therapy and diagnostic imaging modalities in the clinical environment.
|
|
