Applications of diffusion-weighted magnetic resonance imaging in head and neck squamous cell carcinoma

In the head and neck, squamous cell carcinoma is one of the most common tumour types. Currently, the primary imaging modalities for initial locoregional staging are computed tomography and—to a lesser extent—magnetic resonance imaging, whilst [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography has additional value in the detection of subcentimetric metastatic lymph nodes and of tumour recurrence after chemoradiotherapy (CRT). However, dependency on the morphological and size-related criteria of anatomical imaging and the limited spatial resolution and FDG avidity of inflammation in metabolic imaging may reduce diagnostic accuracy in the head and neck. Diffusion-weighted magnetic resonance imaging (DWI) is a noninvasive imaging technique that measures the differences in water mobility in different tissue microstructures. Water mobility is likely influenced by cell size, density, and cellular membrane integrity and is quantified by means of the apparent diffusion coefficient. As such, the technique is able to differentiate tumoural tissue from normal tissue, inflammatory tissue and necrosis. In this article, we examine the use of DWI in head and neck cancer, focussing on technique optimization and image interpretation. Afterwards, the value of DWI will be outlined for clinical questions regarding nodal staging, lesion characterization, differentiation of post-CRT tumour recurrence from necrosis and inflammation, and predictive imaging towards treatment outcome. The possible consequences of adding DWI towards therapeutic management are outlined.     

Flow cytometric assay for the simultaneous determination of residual white blood cells, red blood cells, and platelets in fresh-frozen plasma: validation and two years' experience

BACKGROUND: A fully automated single‐tube assay with tubes (BD TruCOUNT, BD Biosciences) for absolute counting of residual cells in freshly prepared plasma by flow cytometry was developed (BD Plasma Count). STUDY DESIGN AND METHODS: The nucleic acid dye thiazole orange stains white blood cells (WBCs). The monoclonal antibodies anti‐CD41a–peridinin chlorophyll protein–Cy5.5 and anti‐glycophorin A–fluorescein isothiocyanate label platelets (PLTs) and red blood cells (RBCs), respectively. No fixation, permeabilization, or washing steps were required. Validation was done according to guidelines of the International Conference on Harmonization and the National Committee for Clinical Laboratory Standards. Cell‐free plasma was spiked with each cell type for accuracy, reproducibility, and linearity measurements. RESULTS: Results showed no carryover or drift under automated sample acquisition conditions. Nonspecific background was fewer than 0.3 cells per µL for residual WBCs (rWBCs), fewer than 2.7 cells per µL for rRBCs, and fewer than 85 cells per µL for rPLTs. Determinations of rWBC and rPLT counts were linear with a coefficient of variation of less than 12 percent for the imprecision. Owing to cross‐linking of the anti‐glycophorin A antibody, linearity and precision for rRBCs diverged up to 21 percent at a count of 6000 rRBCs per µL. In a 2‐year period, five operators investigated 2666 quality control (QC) samples of fresh‐frozen plasma on 108 working days. Maximum cell numbers found were 196 for rWBCs, 3960 for rRBCs, and 28,952 for rPLTs per µL. In 31 cases (1.2%) rWBCs were out of specification. No outlier was observed for rRBCs and rPLTs. Residual RBC cell numbers determined were always within the acceptable concentration range of the assay. CONCLUSION: These data demonstrate that the single‐tube test is suitable for routine QC assessment of the cellular contaminants of therapeutic plasma according to the European recommendations.     

Intraosseous temperature changes during the use of piezosurgical inserts in vitro

This study concerns intraosseous temperature changes during the use of piezosurgical inserts. On six fresh pig jaws heated to body temperature (36 °C), osteotomies and osteoplasties were performed in vitro with the Piezosurgery^® 3 device (Mectron, Carasco, Italy) and various inserts. The intraosseous temperature increases were measured at a depth of 3 mm and at a distance of 1 mm from the working site using nickel–chromium/nickel temperature sensors. 20 °C Ringer's solution was used for cooling in an initial test series and 10 °C Ringer's in a second series. The processed bone was examined using digital volume tomography images to determine the ratio of cortical to cancellous bone thickness. Mean temperature increases of 4.4–10.9 °C were found; maximum temperature peaks were over 47 °C for an average of only 8.5 s. The type of piezosurgical insert had a marked influence on intraosseous temperature generation (p = 0.026); the thickness of the cortical bone and the temperature of the coolant did not. Coolant temperature had an influence on the bone cooling time (p = 0.013). The results show that correct use of the piezosurgery device does not give rise to prolonged temperature increases over 47 °C and hence does not cause any irreversible thermal damage in the bone.     

The focus of attention at the virtual cocktail party—Electrophysiological evidence

The width of the attentional focus during the selection of one of two concurrent normal human participants was investigated using event-related potentials. Two stories were presented from virtual locations located 15° to the left and right azimuth by convolving the speech message by the appropriate head-related transfer function determined for each individual participant. Task irrelevant probe stimuli (phoneme/da/uttered by the same speaker as the story) were presented in rapid sequence from the same virtual locations. Occasionally, probes were presented at locations 15 or 30° lateral of the standard probes. Probes coinciding with the attended message gave rise to a fronto-central negativity relative to the phoneme probes coinciding with the unattended speech message. This was similar to the typical ERP attention effect. On the attended side probes deviating from the standard location by 30° elicited a different type of negative response, tentatively identified as a reorienting negativity, whereas probes deviating by 15° did not. These results are taken to suggest that spatial information is used for message selection in a cocktail-party situation but that the focus of spatial attention is relatively wide.     

Predictors for occlusion of cerebral AVMs following radiation therapy

Background

Intracranial arteriovenous malformations (AVMs) may show a harmful development. AVMs are treated by surgery, embolization, or radiation therapy.

Objective

This study investigated obliteration rates and side effects in patients with AVMs treated by radiation therapy.

Methods

A total of 40 cases treated between 2005 and 2013 were analyzed. Single-dose stereotactic radiosurgery (SRS) was received by 13 patients and 27 received hypofractionated stereotactic radiation therapy (HSRT). In 20 patients, endovascular embolization had been performed prior to irradiation and 24 patients (60?%) had a history of previous intracranial hemorrhage.

Results

Treatment resulted in complete obliteration (CO) in 23/40 cases and partial obliteration in 8/40. CO was achieved in 85?% of patients receiving SRS compared to 44?% of those receiving HSRT. In the HSRT group, a first indication of an influence of AVM volume on obliteration rate was found. Equivalent 2 Gy fraction doses (EQD2) >70 Gy showed an obliteration rate of 50?%. Prior embolization was significantly associated with a higher portion of CO (p = 0.032). Median latency period (24.2 vs. 26 months) until CO was similar in both groups (SRS vs. HSRT). The rate of intracranial hemorrhage in patients with no prior bleeding events was 0?%.

Conclusion

Excellent obliteration rates were achieved by SRS. Consistent with the literature, this data analysis suggests that the results of HSRT are volume-dependent. Furthermore, regimens with EQD2 doses >70 Gy appear more likely to achieve obliteration than schemes with lower doses. The findings indicate that radiation therapy does not increase the risk of bleeding. Prior embolization may have a good prognostic impact.