Individual 3D-printed fixation masks for radiotherapy: first clinical experiences.

PURPOSE: To show the feasibility of 3D-printed fixation masks for whole brain radiation therapy in a clinical setting and perform a first comparison to an established thermoplastic mask system. METHODS: Six patients were irradiated with whole brain radiotherapy using individually 3D-printed masks. Daily image guidance and position correction were performed prior to each irradiation fraction. The vectors of the daily position correction were compared to two collectives of patients, who were irradiated using the standard thermoplastic mask system (one cohort with head masks; one cohort with head and neck masks). RESULTS: The mean systematic errors in the experimental cohort ranged between 0.59 and 2.10 mm which is in a comparable range to the control groups (0.18 mm-0.68 mm and 0.34 mm-2.96 mm, respectively). The 3D-printed masks seem to be an alternative to the established thermoplastic mask systems. Nevertheless, further investigation will need to be performed. CONCLUSION: The prevailing study showed a reliable and reproducible interfractional positioning accuracy using individually 3D-printed masks for whole brain irradiation in a clinical routine. Further investigations, especially concerning smaller target volumes or other areas of the body, need to be performed before using the system on a larger basis.

Four-dimensional visualization of thoracic blood flow by magnetic resonance imaging in a patient following correction of transposition of the great arteries (d-TGA) and uncorrected aortic coarctation.

Recent advances in flow-sensitive magnetic resonance imaging (MRI) and data analysis allow for comprehensive noninvasive three-dimensional (3D) visualization of complex blood flow. Electrocardiogram (ECG)-gated three-directional (3dir) flow measurements were employed to assess and visualize time-resolved 3D blood flow in the pulmonary arteries (PA) and thoracic aorta. We present findings in a juvenile patient with surgically corrected transposition of the great arteries (d-TGA) and aortic coarctation. For the first time, the complex flow patterns in the PA following d-TGA were visualized. Morphologically, a slight asymmetry of the PA was found, with considerable impact on vascular hemodynamics, resulting in diastolic retrograde flow in the larger vessel and diastolic filling of the smaller PA. Additionally, increased flow to the supraaortic vessels was found due to aortic coarctation.

3D printing based on imaging data: review of medical applications.

PURPOSE: Generation of graspable three-dimensional objects applied for surgical planning, prosthetics and related applications using 3D printing or rapid prototyping is summarized and evaluated. MATERIALS AND METHODS: Graspable 3D objects overcome the limitations of 3D visualizations which can only be displayed on flat screens. 3D objects can be produced based on CT or MRI volumetric medical images. Using dedicated post-processing algorithms, a spatial model can be extracted from image data sets and exported to machine-readable data. That spatial model data is utilized by special printers for generating the final rapid prototype model. RESULTS: Patient-clinician interaction, surgical training, medical research and education may require graspable 3D objects. The limitations of rapid prototyping include cost and complexity, as well as the need for specialized equipment and consumables such as photoresist resins. CONCLUSIONS: Medical application of rapid prototyping is feasible for specialized surgical planning and prosthetics applications and has significant potential for development of new medical applications.

[MR-based tridirectional flow imaging. Acquisition and 3D analysis of flows in the thoracic aorta]. / MRT-basierte tridirektionale Flussbildgebung. Aufnahme und 3D-Analyse von Strömungen in der thorakalen Aorta.

Tridirectional MR flow imaging is a novel method that extends the well-established technique of phase-contrast flow measurement by vectorial velocity encoding, i.e., by encoding in all three spatial directions. Modern sequence protocols allow the acquisition of velocity vector fields with high spatial resolutions of 1-3 mm and temporal resolutions of 20-50 ms over the heart cycle. Using navigating techniques, data on the entire thoracic aorta can be acquired within about 20 min in free breathing. The subsequent computer-based data processing includes automatic correction of aliasing effects, eddy currents, gradient field inhomogeneities, and Maxwell terms. The data can be visualized in three dimensions using vector arrows, streamlines, or particle traces. The parallel visualization of morphological slices and of the surface of the vascular lumen in 3D enhances spatial and anatomical orientation. Furthermore, quantitative values such as blood flow velocity and volume, vorticity, and vessel wall shear stress can be determined. Modern software systems support the integrated flow-based analysis of typical aortic pathologies such as aneurysms and aortic insufficiency. To what extent this additional information will help us in making better therapeutic decisions needs to be studied in clinical trials.