New landmarks in endonasal surgery: from nasal bone to anterior cribriform plate including branches of anterior ethmoidal artery and nerve and terminal nerve.

BACKGROUND: Despite the development of anterior skull base surgery, the anatomy of the nasal bone and anterior cribriform plate remains unclear. A recent study confirmed 2 distinct foramina in the anterior part of cribriform plate: the ethmoidal slit (ES) and the cribroethmoidal foramen (CF). The aim of this study was to specify their content, their anatomic relationship to the frontal sinus and skull base, and their potential value in skull base surgery. METHODS: Dissections were performed on 36 cadaver heads. Macro- and microscopic examinations were carried out. Microcomputed tomography scans contrasted with osmium were performed to identify vessels and nerves. Histology with neural, meningeal, or luteinizing hormone-releasing hormone immunomarkers was performed on the content of the foramina. Finally, endonasal surgical dissections were carried out. RESULTS: The ES and the CF were observed in all cases. They measured a mean of 4.2 and 1.6 mm, respectively. The ES contained dura mater, arachnoid tissues, lymphatics, and the terminal nerve. The CF contained the anterior ethmoidal nerve and artery. This foramen continued forward with the cribroethmoidal groove, which measured a mean of 2.5 mm. This groove was under the frontal sinus and in front of the skull base. We also described a "cribroethmoidal canal" and a "nasal bone foramen." CONCLUSION: The clinical applications of this new anatomic description concern both cribriform plate and frontal sinus surgeries. Identifying the terminal nerve passing through the ES is a step forward in understanding pheromone recognition in humans.

Development of a dynamic phantom and investigation of mobile target imaging and irradiation in preclinical small animal research.

OBJECTIVE: Progress made in preclinical radiotherapy makes respiratory gating reachable. Nevertheless, technical means are still needed, as well as accurate investigations of the effect of motion on small animal treatment plans. METHODS: An animal-scaled dynamic phantom (0.3-11.1-mm motion peak-to-peak amplitude, 30-120 cycles per minute) was developed and characterized. It was used to evaluate respiratory monitoring and high resolution imaging (µPET/CT scans). The width and position variations of a fluorine-18 solution were measured for various motions and gating configurations. The phantom was finally used to measure the impact of motion on dose distribution for vertical irradiation using 2.5- and 5-mm collimations. RESULTS: Phantom motions accurately reproduced original waveforms with good rate and amplitude linearity (R2 = 1 and R2 = 0.9995, respectively). µPET/CT acquisitions showed an increase of 92% of the target size caused by a 4.9-mm sine motion and reduced to <12% by gating. Target motion measurements showed consistency better than 18% between modalities. Irradiations showed that motions >0.8 and 1.1 mm (for the 2.5- and 5-mm collimations, respectively) significantly impact dose homogeneity in the target. CONCLUSION: The phantom allowed studying motion in small animal imaging and irradiation. It showed the important impact of motions >2 mm and provided accurate data to improve the management of mobile tumour irradiation. The implementation of gated irradiation, associated with motion-compensated imaging, is currently under progress. Advances in knowledge: Small animal irradiation gating is not yet used in preclinical studies. As few solutions are under development, tools and accurate studies are highly needed.

Prospective versus retrospective ECG-gating for 64-detector computed tomography of the coronary venous system in pigs.

BACKGROUND: Multidetector computed tomography (MDCT) provides a non-invasive anatomic description of the coronary veins that may be useful in patients candidates to cardiac resynchronization. Prospective gating reduces radiation exposure but its impact on image quality is unknown is this setting. AIMS: This study compared image quality and reliability of MDCT angiography of the coronary veins between prospective and retrospective gating. METHODS: Seven anaesthetized pigs underwent 64-detector row MDCT with prospective and retrospective ECG-gating. MDCT scans were evaluated for visibility of the veins, estimated radiation dose and vein characteristics. Inter- and intra-observer reproducibility was calculated. RESULTS: Visibility grades of all veins were significantly decreased in prospective (0.82 ± 0.6) compared to retrospective gating (1.68 ± 0.9; P<0.001), the lateral vein being missed in two cases when using prospective vs. retrospective gating. The maximal vein length was significantly increased when using retrospective gating (P=0.015). Inter-observer but not intra-observer reproducibility was dependent on the gating technique for the maximal length and contrast-to-noise ratio (P=0.003 for both). Heart rate was 82 ± 13 bpm and 86 ± 11 bpm during retrospective and prospective ECG-gating (P=ns) despite full dose of atenolol titration. CONCLUSION: Retrospective gating seems to be superior to prospective gating MDCT to describe the coronary venous system but the conclusions of our study should be confined to high heart rate condition.