A density assignment method for dose monitoring in head-and-neck radiotherapy

BACKGROUND AND PURPOSE

During head-and-neck (H&N) radiotherapy, the parotid glands (PGs) may be overdosed; thus, a tool is required to monitor the delivered dose. This study aimed to assess the dose accuracy of a patient-specific density assignment method (DAM) for dose calculation to monitor the dose to PGs during treatment.

PATIENTS AND METHODS

Forty patients with H&N cancer received an intensity modulated radiation therapy (IMRT), among whom 15 had weekly CTs. Dose distributions were calculated either on the CTs (CT_ref), on one-class CTs (1C-CT, water), or on three-class CTs (3C-CT, water-air-bone). The inter- and intra-patient DAM uncertainties were evaluated by the difference between doses calculated on CT_ref and 1C-CTs or 3C-CTs. PG mean dose (D_mean) and spinal cord maximum dose (D_2%) were considered. The cumulated dose to the PGs was estimated by the mean D_mean of the weekly CTs.

RESULTS

The mean (maximum) inter-patient DAM dose uncertainties for the PGs (in cGy) were 23 (75) using 1C-CTs and 12 (50) using 3C-CTs (p ≤ 0.001). For the spinal cord, these uncertainties were 118 (245) and 15 (67; p ≤ 0.001). The mean (maximum) DAM dose uncertainty between cumulated doses calculated on CTs and 3C-CTs was 7 cGy (45 cGy) for the PGs. Considering the difference between the planned and cumulated doses, 53% of the ipsilateral and 80% of the contralateral PGs were overdosed by +3.6 Gy (up to 8.2 Gy) and +1.9 Gy (up to 5.2 Gy), respectively.

CONCLUSION

The uncertainty of the three-class DAM appears to be clinically non-significant (<0.5 Gy) compared with the PG overdose (up to 8.2 Gy). This DAM could therefore be used to monitor PG doses and trigger replanning.

Adaptive radiotherapy for head and neck cancer

INTRODUCTION

Large anatomical variations can be observed during the treatment course intensity-modulated radiotherapy (IMRT) for head and neck cancer (HNC), leading to potential dose variations. Adaptive radiotherapy (ART) uses one or several replanning sessions to correct these variations and thus optimize the delivered dose distribution to the daily anatomy of the patient. This review, which is focused on ART in the HNC, aims to identify the various strategies of ART and to estimate the dosimetric and clinical benefits of these strategies.

MATERIAL AND METHODS

We performed an electronic search of articles published in PubMed/MEDLINE and Science Direct from January 2005 to December 2016. Among a total of 134 articles assessed for eligibility, 29 articles were ultimately retained for the review. Eighteen studies evaluated dosimetric variations without ART, and 11 studies reported the benefits of ART.

RESULTS

Eight in silico studies tested a number of replanning sessions, ranging from 1 to 6, aiming primarily to reduce the dose to the parotid glands. The optimal timing for replanning appears to be early during the first two weeks of treatment. Compared to standard IMRT, ART decreases the mean dose to the parotid gland from 0.6 to 6 Gy and the maximum dose to the spinal cord from 0.1 to 4 Gy while improving target coverage and homogeneity in most studies. Only five studies reported the clinical results of ART, and three of those studies included a non-randomized comparison with standard IMRT. These studies suggest a benefit of ART in regard to decreasing xerostomia, increasing quality of life, and increasing local control. Patients with the largest early anatomical and dose variations are the best candidates for ART.

CONCLUSION

ART may decrease toxicity and improve local control for locally advanced HNC. However, randomized trials are necessary to demonstrate the benefit of ART before using the technique in routine practice.

Self-adaptive ultrasonic beam amplifiers: application to transcostal shock wave therapy

Ultrasound shock wave therapy is increasingly used for non-invasive surgery. It requires the focusing of very high pressure amplitude in precisely controlled focal spots. In transcostal therapy of the heart or the liver, the high impedance mismatch between the bones and surrounding tissues gives rise to strong aberrations and attenuation of the therapeutic wavefront, with potential risks of injury at the tissue-bone interface. An adaptive propagation of the ultrasonic beam through the intercostal spaces would be required. Several solutions have been developed so far, but they require a prior knowledge of the patient's anatomy or an invasive calibration process, not applicable in clinic. Here, we develop a non-invasive adaptive focusing method for ultrasound therapy through the ribcage using a time reversal cavity (TRC) acting as an ultrasonic beam amplifier. This method is based on ribcage imaging through the TRC and a projection orthogonally to the strongest identified reflectors. The focal pressure of our device was improved by up to 30% using such self-adaptive processing, without degrading the focal spots size and shape. This improvement allowed lesion formation in an Ultracal^® phantom through a ribcage without invasive calibration of the device. This adaptive method could be particularly interesting to improve the efficiency and the safety of pulsed cavitational therapy of the heart or the liver.

Influence of differently processed yeast (Kluyveromyces fragilis) on feed intake and gut physiology in weaned pigs

Two feeding trials were conducted to investigate the effects of hydrolyzed (HY) or non-hydrolyzed (NHY) yeast (Kluyveromyces fragilis) in isoenergetic and isonitrogeneous diets in the postweaning period. In experiment 1, a total of 550 unsexed pigs (6.5 ± 0.5 kg BW), weaned at 24 ± 2 d of age, were allocated to five treatment groups, receiving either a control diet (CON) or diets with 1%, 3%, and 5% HY (groups HY1, HY3, and HY5, respectively), or a diet with 3% NHY (group NHY3). In experiment 2, a total of 48 male and female pigs (6.2 ± 0.3 kg BW, weaned at d 25) were allocated to three dietary groups (n = 8 replicates with two pigs) receiving a control diet (CON) or diets with 1% NHY or 1% HY. Eight animals were sacrificed 2 wk after weaning for histological investigations in the jejunum and colon, determination of apparent ileal digestibility (AID) of CP and ether extract (EE), and electrophysiological measurements in the jejunal tissue after addition of carbachol or l-glutamine using Ussing chambers. In experiment 1, different treatments had no significant effect on pig performance, but diet HY1 tended to increase ADG and G:F in wk 2 after weaning (P < 0.1). In experiment 2, diet HY1 increased feed intake in wk 2 (P < 0.05), whereas NHY yeast had no effect on feed intake. Villus height, villus/crypt ratio in jejunum (P < 0.05), and crypt depth in colon (P < 0.01) were increased in group HY1. Crypt depth in jejunum and small intestinal length were not affected by different treatments. The AID of CP and EE tended to increase in group HY1 (P < 0.1) compared with groups CON and NHY. In the Ussing chamber experiments, no changes in basal electrophysiological parameters were observed, and the reactions of the treatment groups to carbachol and l-glutamine were comparable. ADFI was positively correlated with different parameters of intestinal morphology (villus height, villus/crypt ratio, crypt depth in colon, length of small intestine), AID of CP, EE, and performance. The results suggest that a supplementation of 1% HY based on K. fragilis to pig diets may positively influence ADFI and intestinal morphology in pig in the early postweaning period (d 1 to 14).

Influence of Sialic Acid on Erythrocyte Aggregation in Hypercholesterolemi

The respective role of adhesive forces induced by fibrinogen and repulsive forces induced by erythrocyte sialic acid content on erythrocyte aggregation, was investigated in hypercholesterolemic and control subjects. Aggregation index (AI) and disaggregation shear rate threshold (³t) were determined in the presence of either autologous plasma or dextran. Compared with controls, fibrinogen (p <0.001) and aggregation parameters (AI p <0.01; ³t p <0.01) were higher in hypercholester-olemics while erythrocyte sialic acid content (p <0.001) was lower; in addition total serum sialic acid was increased (p <0.01). The aggregation properties of erythrocytes, independent of plasma environment using dextran as a bridging macromolecule, showed an enhanced disaggregation shear rate threshold and an inverse relationship with erythrocyte sialic acid content. We conclude that decreased erythrocyte sialic acid content may intensify the effect of fibrinogen on aggregation and disaggregation of erythrocytes and participate in the development of atherothrombotic complications.

Men from Sub-Saharan Africa Living in Worker Hostels in France: A Hidden Population with Poor Access to HIV Testing

Delayed presentation to care among HIV-infected individuals continued to be frequent in France. Migrants are at high risk for late presentation. This cross-sectional study investigated barriers to HIV testing in the specific population of men from sub-Saharan Africa living in four migrant worker hostels in Paris, France. Factors associated with never having been tested for HIV were examined using logistic regression. In all, 550 men participated, coming mainly from Mali and Senegal, with 31 % having lived in France for less than 5 years, and 25 % without any health insurance. Only 37 % have ever been tested for HIV. Not having health insurance was the main risk factor for never-testing [adjusted odds ratio (aOR) 2.4; 95 % confidence interval (CI) 1.4-4.0]. Despite free and anonymous HIV testing available at dedicated public screening centers, 63 % of men living in migrant worker hostels had never been tested for HIV.

Referral of patients with fever of unknown origin to an expertise center has high diagnostic and therapeutic value

BACKGROUND

up to 50% of patients with fever of unknown origin (FUO) remain undiagnosed despite extensive evaluation. In expertise centers, at least 25-63% of these patients are referred after evaluation in another hospital. The diagnostic and therapeutic yields of referral to an expertise center are currently unknown.

AIM

To determine the diagnostic and therapeutic yield of referral of patients with fever of unknown origin (FUO) that remain undiagnosed in non-expertise hospitals.

DESIGN

Data on workup, outcome, treatment and prognosis were extracted from medical records of all 236 patients referred to the Radboud university medical center's department of internal medicine because of FUO between January 2005 and June 2014.

RESULTS

A final diagnosis could be made in 110 of 192 tertiary referred FUO patients. The rate of diagnosis did not differ between patients referred for first opinion or after tertiary referral (68.2 vs. 57.3%, P = 0.234). Over half of undiagnosed tertiary referred patients were treated, and fever resolved in half of these patients. Of 96 undiagnosed patients, two died (2.1)% and in both death was considered unrelated to the febrile disease.

CONCLUSION

The diagnostic rate in patients with FUO does not differ between patients that are tertiary referred and patients that have not been previously evaluated in another hospital. With a total diagnostic value of 57.3% and an additional therapeutic yield of 10.9% in undiagnosed patients, tertiary referral should therefore be considered in patients that remain undiagnosed in a non-expertise center.