The potential impact of High Intensity Focused Ultrasound (HIFU) into General Medicine and Oncolo... more The potential impact of High Intensity Focused Ultrasound (HIFU) into General Medicine and Oncology seems very high. But, while in the research area, the development of this technique is very rapid and unchallenged, the direct application of HIFU to the human tumour therapy it's hampered by various technical difficulties, which may confine its role to a marginal device in the surgery armamentarium. To deploy the full potential of Focused Ultrasound in Oncology, it seems necessary to review the basic relationship between HIFU and External Beam Radiotherapy (EBRT). This is the aim of the present work.
Urethral NTCP has been determined for three prostates implanted with seeds based on (125)I (145 G... more Urethral NTCP has been determined for three prostates implanted with seeds based on (125)I (145 Gy), (103)Pd (125 Gy), (131)Cs (115 Gy), (103)Pd-(125)I (145 Gy), or (103)Pd-(131)Cs (115 Gy or 130 Gy). First, DU(20), meaning that 20% of the urhral volume receive a dose of at least DU(20), is converted into an I-125 LDR equivalent DU(20) in order to use the urethral NTCP model. Second, the propagation of uncertainties through the steps in the NTCP calculation was assessed in order to identify the parameters responsible for large data uncertainties. Two sets of radiobiological parameters were studied. The NTCP results all fall in the 19%-23% range and are associated with large uncertainties, making the comparison difficult. Depending on the dataset chosen, the ranking of NTCP values among the six seed implants studied changes. Moreover, the large uncertainties on the fitting parameters of the urethral NTCP model result in large uncertainty on the NTCP value. In conclusion, the use of N...
Monte Carlo simulations with the EGS4 code system have been performed to determine the quality de... more Monte Carlo simulations with the EGS4 code system have been performed to determine the quality dependence of diamond TLDs in photon beams ranging from 25 kV to 25 MV x-rays and also in megavoltage electron beams. It has been shown that diamond TLDs in the form of discs of thickness 0.3 mm and diameter 5.64 mm show no significant dependence on the incident energy in clinical electron beams when irradiated close to <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img6.gif" ALIGN="TOP"/>, but require an energy correction factor of <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img7.gif" ALIGN="TOP"/> compared with diamond TLDs irradiated in <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img8.gif" ALIGN="TOP"/>-rays. The correction factor increases with depth of irradiation and this effect is greater for thicker detectors. The Monte Carlo predicted sensitivity in x-ray beams is constant within 2.5% over the energy range 250 kV to 25 MV. However the sensitivity decreases by about 60% for 25 kV x-rays compared with <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img8.gif" ALIGN="TOP"/>-rays.
... photon and electron beams Chang-ming Ma and A E Nahum Joint Department of Physics, Institute ... more ... photon and electron beams Chang-ming Ma and A E Nahum Joint Department of Physics, Institute of Cancer Reseamh and Royal Marsden Hospital, Sutton, Surrey SM2 5PT UK Received 19 June 1992 Abstract. ... Chang-ming Ma and A E Nahum bY ...
Clinical oncology (Royal College of Radiologists (Great Britain)), 2015
If the α/β ratio is high (e.g. 10 Gy) for tumour clonogen killing, but low (e.g. 3 Gy) for late n... more If the α/β ratio is high (e.g. 10 Gy) for tumour clonogen killing, but low (e.g. 3 Gy) for late normal tissue complications, then delivering external beam radiotherapy in a large number (20-30) of small (≈2 Gy) dose fractions should yield the highest 'therapeutic ratio'; this is demonstrated via the linear-quadratic model of cell killing. However, this 'conventional wisdom' is increasingly being challenged, partly by the success of stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR) extreme hypofractionation regimens of three to five large fractions for early stage non-small cell lung cancer and partly by indications that for certain tumours (prostate, breast) the α/β ratio may be of the same order or even lower than that characterising late complications. It is shown how highly conformal dose delivery combined with quasi-parallel normal tissue behaviour (n close to 1) enables 'safe' hypofractionation; this can be predicted by t...
The potential impact of High Intensity Focused Ultrasound (HIFU) into General Medicine and Oncolo... more The potential impact of High Intensity Focused Ultrasound (HIFU) into General Medicine and Oncology seems very high. But, while in the research area, the development of this technique is very rapid and unchallenged, the direct application of HIFU to the human tumour therapy it's hampered by various technical difficulties, which may confine its role to a marginal device in the surgery armamentarium. To deploy the full potential of Focused Ultrasound in Oncology, it seems necessary to review the basic relationship between HIFU and External Beam Radiotherapy (EBRT). This is the aim of the present work.
Urethral NTCP has been determined for three prostates implanted with seeds based on (125)I (145 G... more Urethral NTCP has been determined for three prostates implanted with seeds based on (125)I (145 Gy), (103)Pd (125 Gy), (131)Cs (115 Gy), (103)Pd-(125)I (145 Gy), or (103)Pd-(131)Cs (115 Gy or 130 Gy). First, DU(20), meaning that 20% of the urhral volume receive a dose of at least DU(20), is converted into an I-125 LDR equivalent DU(20) in order to use the urethral NTCP model. Second, the propagation of uncertainties through the steps in the NTCP calculation was assessed in order to identify the parameters responsible for large data uncertainties. Two sets of radiobiological parameters were studied. The NTCP results all fall in the 19%-23% range and are associated with large uncertainties, making the comparison difficult. Depending on the dataset chosen, the ranking of NTCP values among the six seed implants studied changes. Moreover, the large uncertainties on the fitting parameters of the urethral NTCP model result in large uncertainty on the NTCP value. In conclusion, the use of N...
Monte Carlo simulations with the EGS4 code system have been performed to determine the quality de... more Monte Carlo simulations with the EGS4 code system have been performed to determine the quality dependence of diamond TLDs in photon beams ranging from 25 kV to 25 MV x-rays and also in megavoltage electron beams. It has been shown that diamond TLDs in the form of discs of thickness 0.3 mm and diameter 5.64 mm show no significant dependence on the incident energy in clinical electron beams when irradiated close to <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img6.gif" ALIGN="TOP"/>, but require an energy correction factor of <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img7.gif" ALIGN="TOP"/> compared with diamond TLDs irradiated in <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img8.gif" ALIGN="TOP"/>-rays. The correction factor increases with depth of irradiation and this effect is greater for thicker detectors. The Monte Carlo predicted sensitivity in x-ray beams is constant within 2.5% over the energy range 250 kV to 25 MV. However the sensitivity decreases by about 60% for 25 kV x-rays compared with <IMG SRC="http://ej.iop.org/images/0031-9155/42/10/005/img8.gif" ALIGN="TOP"/>-rays.
... photon and electron beams Chang-ming Ma and A E Nahum Joint Department of Physics, Institute ... more ... photon and electron beams Chang-ming Ma and A E Nahum Joint Department of Physics, Institute of Cancer Reseamh and Royal Marsden Hospital, Sutton, Surrey SM2 5PT UK Received 19 June 1992 Abstract. ... Chang-ming Ma and A E Nahum bY ...
Clinical oncology (Royal College of Radiologists (Great Britain)), 2015
If the α/β ratio is high (e.g. 10 Gy) for tumour clonogen killing, but low (e.g. 3 Gy) for late n... more If the α/β ratio is high (e.g. 10 Gy) for tumour clonogen killing, but low (e.g. 3 Gy) for late normal tissue complications, then delivering external beam radiotherapy in a large number (20-30) of small (≈2 Gy) dose fractions should yield the highest 'therapeutic ratio'; this is demonstrated via the linear-quadratic model of cell killing. However, this 'conventional wisdom' is increasingly being challenged, partly by the success of stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR) extreme hypofractionation regimens of three to five large fractions for early stage non-small cell lung cancer and partly by indications that for certain tumours (prostate, breast) the α/β ratio may be of the same order or even lower than that characterising late complications. It is shown how highly conformal dose delivery combined with quasi-parallel normal tissue behaviour (n close to 1) enables 'safe' hypofractionation; this can be predicted by t...
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