Akke Bakker

Dr. Akke Bakker


Research Focus & Metrics

Academic Career Length

28Years (1999-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 March 2017 in Strahlentherapie und Onkologie
Verified
Journal Article
Open access
PDF file
HTHana Dobsicek Trefna
Hana Dobsicek Trefna
Johannes Hans CrezeeJohannes Hans Crezee
Johannes Hans Crezee
MSManfred Schmidt
Manfred Schmidt
DMDietmar Marder
Dietmar Marder
ULUlf Lamprecht
Ulf Lamprecht
Gerard van RhoonGerard van Rhoon
Gerard van Rhoon
Quality assurance (QA) guidelines are essential to provide uniform execution of clinical trials with uniform quality hyperthermia treatments. This document outlines the requirements for appropriate QA of all current superficial heating equipment including electromagnetic (radiative and capacitive), ultrasound, and infrared heating techniques. Detailed instructions are provided how to characterize and document the performance of these hyperthermia applicators in order to apply reproducible hyperthermia treatments of uniform high quality. Earlier documents used specific absorption rate (SAR) to define and characterize applicator performance. In these QA guidelines, temperature rise is the leading parameter for characterization of applicator performance. The intention of this approach is that characterization can be achieved with affordable equipment and easy-to-implement procedures. These characteristics are essential to establish for each individual applicator the specific maximum size and depth of tumors that can be heated adequately. The guidelines in this document are supplemented with a second set of guidelines focusing on the clinical application. Both sets of guidelines were developed by the European Society for Hyperthermic Oncology (ESHO) Technical Committee with participation of senior Society of Thermal Medicine (STM) members and members of the Atzelsberg Circle. Um eine einheitliche Durchführung klinischer Studien in der Hyperthermie zu gewährleisten, sind Leitlinien zur Qualitätssicherung (QA) unerlässlich. Dieses Dokument enthält die Anforderungen zur QA für alle aktuellen Therapiegeräte zur lokalen Hyperthermie, inklusive elektromagnetischer Systeme (radiativ und kapazitiv), Ultraschall- und Infrarottechnik. In detaillierten Anleitungen wird erklärt, wie die Leistungscharakteristik der Hyperthermieapplikatoren zu beschreiben und zu dokumentieren ist, um reproduzierbare, einheitliche und qualitativ hochwertige Hyperthermiebehandlungen zu gewährleisten. Im Gegensatz zu früheren Leitlinien wird anstelle der spezifischen Absorptionsrate (SAR) jetzt der Temperaturanstieg als maßgeblicher Parameter für die Beschreibung der Leistungscharakteristik von Hyperthermieapplikatoren verwendet. Grund für diesen Ansatz ist eine möglichst einfache und kostengünstige Leistungsbeschreibung. Diese ist notwendig, um für jeden einzelnen Applikator die maximale Tumorgröße und -tiefe zu bestimmen, die adäquat überwärmt werden kann. Dieses Dokument wird durch die Leitlinie zur klinischen Durchführung der lokalen Hyperthermie vervollständigt. Beide Teile der Leitlinie wurden vom Technischen Komitee der European Society for Hyperthermic Oncology (ESHO) in Zusammenarbeit mit leitenden Mitgliedern der Society of Thermal Medicine (STM) und Mitgliedern des Atzelsberger Kreises erarbeitet.

6 December 2016 in International Journal of Hyperthermia
Verified
Journal Article
Closed access
HTHana Dobsicek Trefna
Hana Dobsicek Trefna
HCHans Crezee
Hans Crezee
MSManfred Schmidt
Manfred Schmidt
DMDietmar Marder
Dietmar Marder
ULUlf Lamprecht
Ulf Lamprecht
Gerard van RhoonGerard van Rhoon
Gerard van Rhoon
Quality assurance guidelines are essential to provide uniform execution of clinical trials and treatment in the application of hyperthermia. This document provides definitions for a good hyperthermia treatment and identifies the clinical conditions where a certain hyperthermia system can or cannot adequately heat the tumour volume. It also provides brief description of the characteristics and performance of the current electromagnetic (radiative and capacitive), ultrasound and infra-red heating techniques. This information helps to select the appropriate heating technique for the specific tumour location and size, and appropriate settings of the water bolus and thermometry. Finally, requirements of staff training and documentation are provided. The guidelines in this document focus on the clinical application and are complemented with a second, more technical quality assurance document providing instructions and procedure to determine essential parameters that describe heating properties of the applicator for superficial hyperthermia. Both sets of guidelines were developed by the ESHO Technical Committee with participation of senior STM members and members of the Atzelsberg Circle.

1 January 2019 in International Journal of Hyperthermia
Verified
Journal Article
Open access
ABAkke Bakker
Akke Bakker
JZJacoba van der Zee
Jacoba van der Zee
GTGeertjan van Tienhoven
Geertjan van Tienhoven
H.P. KokH.P. Kok
H.P. Kok
CRCoen R. N. Rasch
Coen R. N. Rasch
HCHans Crezee
Hans Crezee
Objective: Hyperthermia therapy (HT), heating tumors to 40–45 °C, is a known radiotherapy (RT) and chemotherapy sensitizer. The additional benefit of HT to RT for recurrent breast cancer has been proven in multiple randomized trials. However, published outcome after RT + HT varies widely. We performed a systematic review to investigate whether there is a relationship between achieved HT dose and clinical outcome and thermal toxicity for patients with recurrent breast cancer treated with RT + HT. Method: Four databases, EMBASE, PubMed, Cochrane library and clinicaltrials.gov, were searched with the terms breast, radiotherapy, hyperthermia therapy and their synonyms. Final search was performed on 3 April 2019. Twenty-two articles were included in the systematic review, reporting on 2330 patients with breast cancer treated with RT + HT. Results: Thirty-two HT parameters were tested for a relationship with clinical outcome. In studies reporting a relationship, the relationship was significant for complete response in 10/15 studies, in 10/13 studies for duration of local control, in 2/2 studies for overall survival and in 7/11 studies for thermal toxicity. Patients who received high thermal dose had on average 34% (range 27%–53%) more complete responses than patients who received low thermal dose. Patients who achieved higher HT parameters had increased odds/probability on improved clinical outcome and on thermal toxicity. Conclusion: Temperature and thermal dose during HT had significant influence on complete response, duration of local control, overall survival and thermal toxicity of patients with recurrent breast cancer treated with RT + HT. Higher temperature and thermal dose improved outcome, while higher maximum temperature increased incidence of thermal toxicity.

1 April 2014 in Journal of Applied Physiology
Verified
Journal Article
Open access
PDF file
CWC. K. Willie
C. K. Willie
KSK. J. Smith
K. J. Smith
TDT. A. Day
T. A. Day
LRL. A. Ray
L. A. Ray
NLN. C. S. Lewis
N. C. S. Lewis
PAP. N. Ainslie
P. N. Ainslie
The interindividual variation in ventilatory acclimatization to high altitude is likely reflected in variability in the cerebrovascular responses to high altitude, particularly between brain regions displaying disparate hypoxic sensitivity. We assessed regional differences in cerebral blood flow (CBF) measured with Duplex ultrasound of the left internal carotid and vertebral arteries. End-tidal Pco2, oxyhemoglobin saturation (SpO2), blood pressure, and heart rate were measured during a trekking ascent to, and during the first 2 wk at, 5,050 m. Transcranial color-coded Duplex ultrasound (TCCD) was employed to measure flow and diameter of the middle cerebral artery (MCA). Measures were collected at 344 m (TCCD-baseline), 1,338 m (CBF-baseline), 3,440 m, and 4,371 m. Following arrival to 5,050 m, regional CBF was measured every 12 h during the first 3 days, once at 5–9 days, and once at 12–16 days. Total CBF was calculated as twice the sum of internal carotid and vertebral flow and increased steadily with ascent, reaching a maximum of 842 ± 110 ml/min (+53 ± 7.6% vs. 1,338 m; mean ± SE) at ∼60 h after arrival at 5,050 m. These changes returned to +15 ± 12% after 12–16 days at 5,050 m and were related to changes in SpO2( R2= 0.36; P < 0.0001). TCCD-measured MCA flow paralleled the temporal changes in total CBF. Dilation of the MCA was sustained on days 2 (+12.6 ± 4.6%) and 8 (+12.9 ± 2.9%) after arrival at 5,050 m. We observed no significant differences in regional CBF at any time point. In conclusion, the variability in CBF during ascent and acclimatization is related to ventilatory acclimatization, as reflected in changes in SpO2.

1 November 2017 in International Journal of Radiation Oncology, Biology, Physics
Verified
Journal Article
Closed access
H.P. KokH.P. Kok
H.P. Kok
LSLinda Korshuize- van Straten
Linda Korshuize- van Straten
ABAkke Bakker
Akke Bakker
RORianne de Kroon- Oldenhof
Rianne de Kroon- Oldenhof
EGElisabeth D. Geijsen
Elisabeth D. Geijsen
Johannes Hans CrezeeJohannes Hans Crezee
Johannes Hans Crezee

15 November 2015 in Journal of Applied Physiology
Verified
Journal Article
Closed access
PDF file
MSMike Stembridge
Mike Stembridge
PAPhilip N. Ainslie
Philip N. Ainslie
MHMichael G. Hughes
Michael G. Hughes
ESEric J. Stöhr
Eric J. Stöhr
JCJames D. Cotter
James D. Cotter
RSRob Shave
Rob Shave
Impaired myocardial systolic contraction and diastolic relaxation have been suggested as possible mechanisms contributing to the decreased stroke volume (SV) observed at high altitude (HA). To determine whether intrinsic myocardial performance is a limiting factor in the generation of SV at HA, we assessed left ventricular (LV) systolic and diastolic mechanics and volumes in 10 healthy participants (aged 32 ± 7; mean ± SD) at rest and during exercise at sea level (SL; 344 m) and after 10 days at 5,050 m. In contrast to SL, LV end-diastolic volume was ∼19% lower at rest (P = 0.004) and did not increase during exercise despite a greater untwisting velocity. Furthermore, resting SV was lower at HA (∼17%; 60 ± 10 vs. 70 ± 8 ml) despite higher LV twist (43%), apical rotation (115%), and circumferential strain (17%). With exercise at HA, the increase in SV was limited (12 vs. 22 ml at SL), and LV apical rotation failed to augment. For the first time, we have demonstrated that EDV does not increase upon exercise at high altitude despite enhanced in vivo diastolic relaxation. The increase in LV mechanics at rest may represent a mechanism by which SV is defended in the presence of a reduced EDV. However, likely because of the higher LV mechanics at rest, no further increase was observed up to 50% peak power. Consequently, although hypoxia does not suppress systolic function per se, the capacity to increase SV through greater deformation during submaximal exercise at HA is restricted.