Experimental investigation and histopathological identification of acute thermal damage in skeletal porcine muscle in relation to whole-body SAR, maximum temperature, and CEM43 °C due to RF irradiation in an MR body coil of birdcage type at 123 MHz

Nadobny, Jacek; Klopfleisch, Robert; Brinker, Gerhard; Stoltenburg‐Didinger, Gisela

doi:10.3109/02656736.2015.1007537

Cited by 19 publications

(23 citation statements)

References 21 publications

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“…However, the magnitude of which is not known and may be scanner specific. The association of full exposure exploitation of the standard with potentially significantly elevated temperatures of > 42.5 C has been documented in earlier studies already (7,9), as well as in recent animal studies (49,50).…”

Section: Discussionmentioning

confidence: 62%

Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B₁+ uniformity

Murbach

Neufeld

Cabot

et al. 2015

Magnetic Resonance in Med

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Purpose: To assess the effect of radiofrequency (RF) shimming of a 3 Tesla (T) two-port body coil on B 1 þ uniformity, the local specific absorption rate (SAR), and the local temperature increase as a function of the thermoregulatory response. Methods: RF shimming alters induced current distribution, which may result in large changes in the level and location of absorbed RF energy. We investigated this effect with six anatomical human models from the Virtual Population in 10 imaging landmarks and four RF coils. Three thermoregulation models were applied to estimate potential local temperature increases, including a newly proposed model for impaired thermoregulation. Results: Two-port RF shimming, compared to circular polarization mode, can increase the B 1 þ uniformity on average by þ32%. Worst-case SAR excitations increase the local RF power deposition on average by þ39%. In the first level controlled operating mode, induced peak temperatures reach 42.5 C and 45.6 C in patients with normal and impaired thermoregulation, respectively. Conclusion: Image quality with 3T body coils can be significantly increased by RF shimming. Exposure in realistic scan scenarios within guideline limits can be considered safe for a broad patient population with normal thermoregulation. Patients with impaired thermoregulation should not be scanned outside of the normal operating mode. Magn Reson Med 76:986-997, 2016. V C 2015 Wiley Periodicals, Inc.

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Section: Discussionmentioning

confidence: 62%

Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B₁+ uniformity

Murbach

Neufeld

Cabot

et al. 2015

Magnetic Resonance in Med

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“…Pearce [47] discusses mathematical modelling of the underlying molecular damage processes. The thermal damage threshold concept has been validated in many animal studies [48]. A review given by Yarmolenko et al [49] lists thermal damage thresholds showing that exposure to 43 C for 1 h causes no major damage for many relevant normal tissue types.…”

Section: Normal Tissue Thresholdsmentioning

confidence: 99%

Thermoradiotherapy planning: Integration in routine clinical practice

Crezee

Leeuwen

Oei

et al. 2015

International Journal of Hyperthermia

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Planning of combined radiotherapy and hyperthermia treatments should be performed taking the synergistic action between the two modalities into account. This work evaluates the available experimental data on cytotoxicity of combined radiotherapy and hyperthermia treatment and the requirements for integration of hyperthermia and radiotherapy treatment planning into a single planning platform. The underlying synergistic mechanisms of hyperthermia include inhibiting DNA repair, selective killing of radioresistant hypoxic tumour tissue and increased radiosensitivity by enhanced tissue perfusion. Each of these mechanisms displays different dose-effect relations, different optimal time intervals and different optimal sequences between radiotherapy and hyperthermia. Radiosensitisation can be modelled using the linear-quadratic (LQ) model to account for DNA repair inhibition by hyperthermia. In a recent study, an LQ model-based thermoradiotherapy planning (TRTP) system was used to demonstrate that dose escalation by hyperthermia is equivalent to $10 Gy for prostate cancer patients treated with radiotherapy. The first step for more reliable TRTP is further expansion of the data set of LQ parameters for normally oxygenated normal and tumour tissue valid over the temperature range used clinically and for the relevant time intervals between radiotherapy and hyperthermia. The next step is to model the effect of hyperthermia in hypoxic tumour cells including the physiological response to hyperthermia and the resulting reoxygenation. Thermoradiotherapy planning is feasible and a necessity for an optimal clinical application of hyperthermia combined with radiotherapy in individual patients.

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“…This modeling approach has been validated with measurements in RF hyperthermia [101], for local exposure at 7T [102], and in (anesthetized) pigs where severe muscle damage was observed for >4 W/kg and SA of 8-15 kJ/kg [103]. The observed damage in [103] points to the usefulness of applying the thermal dose concept, or CEM43, from hyperthermia to assess potential risks associated with long-term high-SAR MRI examinations. CEM43, or cumulative equivalent minutes at 43 ∘ C, is a local thermal dose "iso-effect" metric [3], representing the duration of exposure at a reference temperature of 43 ∘ C, associated with the magnitude of a thermally induced bioeffect observed or predicted to occur at a different temperature T for duration t exam .…”

Section: Thermal Dose and Its Proposed Used In Mrimentioning

confidence: 90%

“…A critical review of the merits and implications of the use of PBE concludes that it is adequate in the context of RF-induced heating simulations [100]. This modeling approach has been validated with measurements in RF hyperthermia [101], for local exposure at 7T [102], and in (anesthetized) pigs where severe muscle damage was observed for >4 W/kg and SA of 8-15 kJ/kg [103]. The observed damage in [103] points to the usefulness of applying the thermal dose concept, or CEM43, from hyperthermia to assess potential risks associated with long-term high-SAR MRI examinations.…”

Section: Thermal Dose and Its Proposed Used In Mrimentioning

confidence: 97%

Thermal Effects Associated with RF Exposures in Diagnostic MRI: Overview of Existing and Emerging Concepts of Protection

Brink

Stender²

2019

Concepts in Magnetic Resonance Part B

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Apart from magnetic attraction risks, the primary biophysical concern associated with MRI is radiofrequency heating of the human body and associated discomfort, health deterioration, or potential burns. This paper reviews experimental data and numerical modeling of systemic (core and brain) temperature and local thermal effects associated with diagnostic MRI exposures at 1.5T (64 MHz) and 3.0T (128 MHz). Allowable temperatures and duration of systemic exposure are established based on knowledge of (short-term) human thermobiology. Longer term effects related to DNA damage or altered cellular pathways are not covered in this review. Updated limits are proposed for core temperature increase (≤1.3°C) and for Specific Absorption (<4 kJ/kg). The potential use of thermal dose (CEM43) for local thermal protection is described, and previously proposed exposure limit values are evaluated against available data from current MRI practice. Gaps in knowledge are identified, and recommendations for additional research are provided.

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Experimental investigation and histopathological identification of acute thermal damage in skeletal porcine muscle in relation to whole-body SAR, maximum temperature, and CEM43 °C due to RF irradiation in an MR body coil of birdcage type at 123 MHz

Abstract: Both T-max and CEM43, are able to predict thermal damage in porcine muscle. However, CEM43 is the less ambiguous parameter. The reasons for the occurrence of the aforementioned damage at low local temperatures at the animals' periphery remain unclear and further investigations are needed.

Cited by 19 publications

References 21 publications

Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B₁+ uniformity

Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B₁+ uniformity

Thermoradiotherapy planning: Integration in routine clinical practice

Thermal Effects Associated with RF Exposures in Diagnostic MRI: Overview of Existing and Emerging Concepts of Protection

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Experimental investigation and histopathological identification of acute thermal damage in skeletal porcine muscle in relation to whole-body SAR, maximum temperature, and CEM43 °C due to RF irradiation in an MR body coil of birdcage type at 123 MHz

Abstract: Both T-max and CEM43, are able to predict thermal damage in porcine muscle. However, CEM43 is the less ambiguous parameter. The reasons for the occurrence of the aforementioned damage at low local temperatures at the animals' periphery remain unclear and further investigations are needed.

Cited by 19 publications

References 21 publications

Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B1+ uniformity

Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B1+ uniformity

Thermoradiotherapy planning: Integration in routine clinical practice

Thermal Effects Associated with RF Exposures in Diagnostic MRI: Overview of Existing and Emerging Concepts of Protection

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Product

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Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B₁+ uniformity

Virtual population‐based assessment of the impact of 3 Tesla radiofrequency shimming and thermoregulation on safety and B₁+ uniformity