Toward adaptive radiotherapy for head and neck patients: Uncertainties in dose warping due to the choice of deformable registration algorithm.

The aims of this work were to evaluate the performance of several deformable image registration (DIR) algorithms implemented in our in-house software (NiftyReg) and the uncertainties inherent to using different algorithms for dose warping

The potential impact of CT-MRI matching on tumor volume delineation in advanced head and neck cancer

To study the potential impact of the combined use of CT and MRI scans on the Gross Tumor Volume (GTV) estimation and interobserver variation. Four observers outlined the GTV in six patients with advanced head and neck cancer on CT, axial MRI, and coronal or sagittal MRI. The MRI scans were subsequently matched to the CT scan. The interobserver and interscan set variation were assessed in three dimensions. The mean CT derived volume was a factor of 1.3 larger than the mean axial MRI volume. The range in volumes was larger for the CT than for the axial MRI volumes in five of the six cases. The ratio of the scan set common (i.e., the volume common to all GTVs) and the scan set encompassing volume (i.e., the smallest volume encompassing all GTVs) was closer to one in MRI (0.3-0.6) than in CT (0.1-0.5). The rest volumes (i.e., the volume defined by one observer as GTV in one data set but not in the other data set) were never zero for CT vs. MRI nor for MRI vs. CT. In two cases the craniocaudal border was poorly recognized on the axial MRI but could be delineated with a good agreement between the observers in the coronal/sagittal MRI. MRI-derived GTVs are smaller and have less interobserver variation than CT-derived GTVs. CT and MRI are complementary in delineating the GTV. A coronal or sagittal MRI adds to a better GTV definition in the craniocaudal directio

Artsen onder druk: Het kwaliteitsbeleid van de medische beroepen in Groot-Brittannië, Nederland en België tussen 1970 en 1996, als gevolg van de interne en externe druk op de zelfregulering van artsen.

Tot in de jaren zeventig werd de medische professie gezien als een beroepsgroep met een grote mate van gezag en professionele vrijheid, die haar kennis in dienst stelde van de belangen van patiënten en samenleving. Omdat de samenleving vanouds een groot belang aan gezondheid hecht, maar geen zicht heeft op de kwaliteit en prijs van het medisch handelen, kwamen West-Europese overheden en de medische beroepen al rond de eeuwwisseling tot een vergelijk over de 'aanbodregulering' van de zorg. In ruil voor een redelijk inkomen en bescherming tegen concurrentie, reguleert het medisch beroep zichzelf in dienst van het algemeen belang door haar bepalende invloed op zaken zoals de medische opleidingen en het medisch tuchtrecht. Een belangrijk kenmerk van de aldus totstandgekomen zelfregulering is de klinische autonomie, waarvan de kern zich bevindt in de diagnostische en therapeutische vrijheid in het handelen van de individuele arts. Essentieel voor de werkzaamheid van de zelfregulering is dat burgers erop vertrouwen dat artsen de verkregen privileges, met name de klinische autonomie, niet zullen misbruiken,l Dit vertrouwen in het altruïsme van artsen is nooit een algemeen goed geweest. In 1 911 schreef de Britse schrijver Bernard Shaw bijvoorbeeld: 'That any sane nation, having observed that you could provide for the supply of bread by giving bakers a pecuniary interest in baking for you, should go on to give a surgeon a pecuniary interest in cutting of your leg, is enough to make one despair of political humanity." Sedert de jaren zeventig kreeg dit wantrouwen in de sociaal-wetenschappelijke literatuur hernieuwde aandacht. Binnen de machts- en beheersingsbenadering worden professies door sociologen, zoals Freidson, beschouwd als kartels gericht op het eigen belang.' Tegelijkertijd stelde een economische recessie grenzen aan de alsmaar stijgende kosten van de gezondheidszorg. Tot die tijd waren de aanvallen van niet-medische partijen op de zelfregulering van het medisch beroep succesvol door de artsen gepareerd. Sindsdien blijken de tijden voor de Britse, Nederlandse en Belgische artsen, gesitueerd in drie verschillende gezondheidszorgsystemen, drastisch te zijn veranderd

Pulsed-laser studies on the free-radical polymerization kinetics of styrene in microemulsion

A mean value of 339 L mol-1 s-1 was obtained for the propagation const. derived from pulsed-laser polymn. (PLP) of styrene in aq. AOT microemulsions. For accurate detns., simulations accounting for the esp. high radical concn. after the laser pulse in microemulsions were recommended. PLP with microemulsions apparently permitted specific kinetic aspects such as transfer to monomer and influence of droplet size on bimol. termination to be studied in detai

99mTc Hynic-rh-Annexin V scintigraphy for in vivo imaging of apoptosis in patients with head and neck cancer treated with chemoradiotherapy

PURPOSE: The purpose of this study was to determine the value of (99m)Tc Hynic-rh-Annexin-V-Scintigraphy (TAVS), a non-invasive in vivo technique to demonstrate apoptosis in patients with head and neck squamous cell carcinoma. METHODS: TAVS were performed before and within 48 h after the first course of cisplatin-based chemoradiation. Radiation dose given to the tumour at the time of post-treatment TAVS was 6-8 Gy. Single-photon emission tomography data were co-registered to planning CT scan. Complete sets of these data were available for 13 patients. The radiation dose at post-treatment TAVS was calculated for several regions of interest (ROI): primary tumour, involved lymph nodes and salivary glands. Annexin uptake was determined in each ROI, and the difference between post-treatment and baseline TAVS represented the absolute Annexin uptake: Delta uptake (DeltaU). RESULTS: In 24 of 26 parotid glands, treatment-induced Annexin uptake was observed. Mean DeltaU was significantly correlated with the mean radiation dose given to the parotid glands (r = 0.59, p = 0.002): Glands that received higher doses showed more Annexin uptake. DeltaU in primary tumour and pathological lymph nodes showed large inter-patient differences. A high correlation was observed on an inter-patient level (r = 0.71, p = 0.006) between the maximum DeltaU in primary tumour and in the lymph nodes. CONCLUSIONS: Within the dose range of 0-8 Gy, Annexin-V-scintigraphy showed a radiation-dose-dependent uptake in parotid glands, indicative of early apoptosis during treatment. The inter-individual spread in Annexin uptake in primary tumours could not be related to differences in dose or tumour volume, but the Annexin uptake in tumour and lymph nodes were closely correlated. This effect might represent a tumour-specific apoptotic respons

Effects of anatomical changes on pencil beam scanning proton plans in locally advanced NSCLC patients

Daily anatomical variations can cause considerable differences between delivered and planned dose. This study simulates and evaluates these effects in spot-scanning proton therapy for lung cancer patients. Robust intensity modulated treatment plans were designed on the mid-position CT scan for sixteen locally advanced lung cancer patients. To estimate dosimetric uncertainty, deformable registration was performed on their daily CBCTs to generate 4DCT equivalent scans for each fraction and to map recomputed dose to a common frame. Without adaptive planning, eight patients had an undercoverage of the targets of more than 2GyE (maximum of 14.1GyE) on the recalculated treatment dose from the daily anatomy variations including respiration. In organs at risk, a maximum increase of 4.7GyE in the D1 was found in the mediastinal structures. The effect of respiratory motion alone is smaller: 1.4GyE undercoverage for targets and less than 1GyE for organs at risk. Daily anatomical variations over the course of treatment can cause considerable dose differences in the robust planned dose distribution. An advanced planning strategy including knowledge of anatomical uncertainties would be recommended to improve plan robustness against interfractional variations. For large anatomical changes, adaptive therapy is mandator