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The Jacobian of the deformation field of elastic registration between images taken during radiotherapy is a measure of inter-fraction local deformation. The histogram of the Jacobian values (Jac) within an organ was introduced (JVH-Jacobian-volume-histogram) and first applied in quantifying parotid shrinkage. MVCTs of 32 patients previously treated with helical tomotherapy for head-neck cancers were collected. Parotid deformation was evaluated through elastic registration between MVCTs taken at the first and last fractions. Jac was calculated for each voxel of all parotids, and integral JVHs were calculated for each parotid; the correlation between the JVH and the planning dose-volume histogram (DVH) was investigated. On average, 82% (±17%) of the voxels shrinks (Jac < 1) and 14% (±17%) shows a local compression >50% (Jac < 0.5). The best correlation between the DVH and the JVH was found between V10 and V15, and Jac < 0.4-0.6 (p < 0.01). The best constraint predicting a higher number of largely compressing voxels (Jac0.5

Objective. The diagnosis of follicular tumors of the thyroid mainly rests on the examination of peri-lesional capsule. Lesions with an intact shell are labeled as adenoma, those with capsular invasion are considered carcinoma and those with doubtful aspects are regarded as tumors of uncertain malignant potential. Aim. To better understand the biology of capsular invasion and its practical implication by applying a peculiar three dimension (3-D) reconstruction. Method. Two follicular carcinoma (FC) and one follicular tumour of uncertain malignant potential (FT-UMP) were considered. Areas of true/doubtful capsular invasion were labeled using Tissue Micro Array technology and the corresponding paraffin blocks underwent serial sectioning. H&E slides (range 30-100, mean 70) were captured as pictures, aligned using automated method based on the maximization of mutual information and imported into a 3-D image processing software (AMIRA). Results. The 3-D reconstruction revealed that capsular openings were oval shaped and sized E100-200 ¼m. In one FC the hole was entirely engaged by a tumor mass. In the remaining cases (1 FC and 1 FT-UMP) the 3-D reconstruction showed a small feeding vessel (E 50 ¼m) passing through the capsule together with the bulge of the lesion [see 3-D reconstruction at http://www.ibfm. cnr.it/ricerca/inv_cap.php]. Conclusions. Our approach allows a better spatial reconstruction of the exact point of capsular interruption; the results obtained suggest that capsular invasion can be due either by abruptly interruption of the shell or by a protrusion along the path of a small feeding vessels

Local hemodynamics plays a key role in the onset of vessel wall pathophysiology, with peculiar blood flow structures (i.e. spatial velocity profiles, vortices, re-circulating zones, helical patterns and so on) characterizing the behavior of specific vascular districts. Thanks to the evolving technologies on computer sciences, mathematical modeling and hardware performances, the study of local hemodynamics can today afford also the use of a virtual environment to perform hypothesis testing, product development, protocol design and methods validation that just a couple of decades ago would have not been thinkable. Computational fluid dynamics (CFD) appears to be more than a complementary partner to in vitro modeling and a possible substitute to animal models, furnishing a privileged environment for cheap fast and reproducible data generation.

Aim To evaluate the use of peripheral quantitative computed tomography (pQCT) for qualitative and quantitative analysis of root canal anatomy and for assessing the extent of canal enlargement during root canal instrumentation. Summary The volume variation achieved by S1 ProTaper instruments in the coronal third of the root canals was analysed using peripheral computed tomography. The tooth was scanned in the horizontal plane producing 36 consecutive cross-sectional images. All images were the result of 360 projections with a section thickness of 250 mum, a distance between slices of 0.5 mm and an in-plane pixel size of 70 x 70 mum. The evaluation was completed before and after S1 ProTaper instrumentation (with or without circumferential filing) of one root canal of a freshly extracted maxillary first premolar tooth. The acquired images were realigned geometrically and processed using a 3D visualization software. pQCT scanning allowed 3D reconstruction of the root canal anatomy and the assessment of the extent of canal enlargement during root canal instrumentation with lateral displacement of canal walls and hence volume change being greater than the coefficient of variation. The densitometry evaluation showed uniform density along the root canal wall. Key learning points * pQCT scanning allowed 3D reconstruction of the root canal anatomy and the assessment of the extent of canal enlargement during root canal instrumentation. * pQCT shows promise for allowing qualitative and quantitative analysis of endodontic procedures.

AIM: To prospectively evaluate the impact of coregistered positron emission tomography (PET) and computed tomography (CT) in 3D conformal radiotherapy (3D-CRT) planning in patients with non-small lung cancer (NSCLC). METHODS: Twenty-one patients (median age: 57 years; range: 42-80 years) referred to 3D-CRT for NSCLC were recruited. Positron emission tomography with 18F-fluorodeoxyglucose ([18F]FDG-PET) and conventional CT images were coregistered (PET/CT images) using a commercial software package based on surface matching technique. Neoplastic areas were contoured on [18F]FDG-PET images with the aid of the correspondent CT image by a nuclear medicine physician. CT images and their relative PET contours were then transferred to treatment planning system. A radiation oncologist firstly contoured clinical target volumes (CTV) on CT scan alone (CTV-CT), and then on coregistered PET/CT images (CTV-PET/CT). CTV-CT and CTV-PET/CT were compared for each patient; a difference higher than 25% was considered of clinical relevance. RESULTS: Three patients were shifted to palliative radiotherapy for metastatic disease or very large tumor size, showed by [18F]FDG-PET. Of the remaining 18 patients a CTV change, after inclusion of PET/CT data, was observed in 10/18 cases (55%): larger in 7/18 (range 33-279%) and smaller in 3/18 patients (range 26-34%), mainly due to inclusion or exclusion of lymph-nodal disease and to better definition of tumor extent. CTV changes smaller than 25% occurred in the remaining 8/18 patients. CONCLUSIONS: [18F]FDG-PET and CT images co-registration in radiotherapy treatment planning led to a change in CTV definition in the majority of our patients, which may significantly modify management and radiation treatment modality in these patients.