We developed a new approach to produce individual immobilization devices for the head based on MRI data and 3D printing technologies. The purpose of this study was to determine positioning accuracy ...with healthy volunteers. 3D MRI data of the head were acquired for 8 volunteers. In-house developed software processed the image data to generate a surface mesh model of the immobilization mask. After adding an interface for the couch, the fixation setup was materialized using a 3D printer with acrylonitrile butadiene styrene (ABS). Repeated MRI datasets (n=10) were acquired for all volunteers wearing their masks thus simulating a setup for multiple fractions. Using automatic image-to-image registration, displacements of the head were calculated relative to the first dataset (6 degrees of freedom). The production process has been described in detail. The absolute lateral (x), vertical (y) and longitudinal (z) translations ranged between -0.7 and 0.5 mm, -1.8 and 1.4 mm, and -1.6 and 2.4 mm, respectively. The absolute rotations for pitch (x), yaw (y) and roll (z) ranged between -0.9 and 0.8°, -0.5 and 1.1°, and -0.6 and 0.8°, respectively. The mean 3D displacement was 0.9 mm with a standard deviation (SD) of the systematic and random error of 0.2 mm and 0.5 mm, respectively. In conclusion, an almost entirely automated production process of 3D printed immobilization masks for the head derived from MRI data was established. A high level of setup accuracy was demonstrated in a volunteer cohort. Future research will have to focus on workflow optimization and clinical evaluation.
Crowd counting is a challenging problem due to the diverse crowd distribution and background interference. In this paper, we propose a new approach for head size estimation to reduce the impact of ...different crowd scale and background noise. Different from just using local information of distance between human heads, the global information of the people distribution in the whole image is also under consideration. We obey the order of far- to near-region (small to large) to spread head size, and ensure that the propagation is uninterrupted by inserting dummy head points. The estimated head size is further exploited, such as dividing the crowd into parts of different densities and generating a high-fidelity head mask. On the other hand, we design three different head mask usage mechanisms and the corresponding head masks to analyze where and which mask could lead to better background filtering. Based on the learned masks, two competitive models are proposed which can perform robust crowd estimation against background noise and diverse crowd scale. We evaluate the proposed method on three public crowd counting datasets of ShanghaiTech, UCF QNRF and UCF CC_50 . Experimental results demonstrate that the proposed algorithm performs favorably against the state-of-the-art crowd counting approaches.
The warp-knitted fully formed products are widely popular because of their fast production speed, seamless, beautiful patterns, and wearing comfort. The structure and performance of the warp-knitted ...head mask influence the wearer's physiological and psychological state. In this article, according to the structure of the human head, a warp-knitted fully formed head mask technology model was established. Afterward, the article designed nine kinds of jacquard stitches and tested heat-moisture performance. A comprehensive evaluation system for the heat-moisture performance of jacquard stitches was installed based on a fuzzy matter-element analysis model. The all-around heat-moisture performance of nine kinds of jacquard stitches was evaluated, and the factors affecting the heat-moisture performance of jacquard stitches were analyzed. The research aims to provide a reference for the structure optimization and performance research of warp-knitted fully formed head masks.
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.
To provide an alternative device for immobilization of the head while easing claustrophobia and improving comfort, an “open‐face” thermoplastic mask was evaluated using video‐based optical surface ...imaging (OSI) and kilovoltage (kV) X‐ray radiography. A three‐point thermoplastic head mask with a precut opening and reinforced strips was developed. After molding, it provided sufficient visible facial area as the region of interest for OSI. Using real‐time OSI, the head motion of ten volunteers in the new mask was evaluated during mask locking and 15 minutes lying on the treatment couch. Using a nose mark with reference to room lasers, forced head movement in open‐face and full‐head masks (with a nose hole) was compared. Five patients with claustrophobia were immobilized with open‐face masks, set up using OSI and kV, and treated in 121 fractions, in which 61 fractions were monitored during treatment using real‐time OSI. With the open‐face mask, head motion was found to be 1.0 ± 0.6 mm and 0.4° ± 0.2° in volunteers during the experiment, and 0.8 ± 0.3 mm and 0.4° ± 0.2° in patients during treatment. These agree with patient motion calculated from pre‐/post‐treatment OSI and kV data using different anatomical landmarks. In volunteers, the head shift induced by mask‐locking was 2.3 ± 1.7 mm and 1.8° ± 0.6°, and the range of forced movements in the open‐face and full‐head masks were found to be similar. Most (80%) of the volunteers preferred the open‐face mask to the full‐head mask, while claustrophobic patients could only tolerate the open‐face mask. The open‐face mask is characterized for its immobilization capability and can immobilize patients sufficiently (< 2 mm) during radiotherapy. It provides a clinical solution to the immobilization of patients with head and neck (HN) cancer undergoing radiotherapy, and is particularly beneficial for claustrophobic patients. This new open‐face mask is readily adopted in radiotherapy clinic as a superior alternative to the standard full‐head mask.
PACS numbers: 87.19.xj, 87.63.L‐, 87.59.‐e, 87.55.tg, 87.55.‐x
The repositioning accuracy of mask-based fixation systems has been assessed with two-dimensional/two-dimensional or two-dimensional/three-dimensional (3D) matching. We analyzed the accuracy of ...commercially available head mask systems, using true 3D/3D matching, with X-ray volume imaging and cone-beam CT.
Twenty-one patients receiving radiotherapy (intracranial/head-and-neck tumors) were evaluated (14 patients with rigid and 7 with thermoplastic masks). X-ray volume imaging was analyzed online and offline separately for the skull and neck regions. Translation/rotation errors of the target isocenter were analyzed. Four patients were treated to neck sites. For these patients, repositioning was aided by additional body tattoos. A separate analysis of the setup error on the basis of the registration of the cervical vertebra was performed. The residual error after correction and intrafractional motility were calculated.
The mean length of the displacement vector for rigid masks was 0.312 +/- 0.152 cm (intracranial) and 0.586 +/- 0.294 cm (neck). For the thermoplastic masks, the value was 0.472 +/- 0.174 cm (intracranial) and 0.726 +/- 0.445 cm (neck). Rigid masks with body tattoos had a displacement vector length in the neck region of 0.35 +/- 0.197 cm. The intracranial residual error and intrafractional motility after X-ray volume imaging correction for rigid masks was 0.188 +/- 0.074 cm, and was 0.134 +/- 0.14 cm for thermoplastic masks.
The results of our study have demonstrated that rigid masks have a high intracranial repositioning accuracy per se. Given the small residual error and intrafractional movement, thermoplastic masks may also be used for high-precision treatments when combined with cone-beam CT. The neck region repositioning accuracy was worse than the intracranial accuracy in both cases. However, body tattoos and image guidance improved the accuracy. Finally, the combination of both mask systems with 3D image guidance has the potential to replace therapy simulation and intracranial stereotaxy.
Purpose: Conformal radiotherapy in the head and neck region requires precise and reproducible patient setup. The definition of safety margins around the clinical target volume has to take into ...account uncertainties of fixation and positioning. Data are presented to quantify the involved uncertainties for the system used.
Methods and Materials: Interfractional reproducibility of fixation and positioning of a target point in the brain was evaluated by biplanar films. 118 film pairs obtained at 52 fractions in 4 patients were analyzed. The setup was verified at the actual treatment table position by diagnostic X-ray units aligned to the isocenter and by a stereotactic X-ray localization technique. The stereotactic coordinates of the treated isocenter, of fiducials on the mask, and of implanted internal markers within the patient were measured to determine systematic and random errors. The data are corrected for uncertainty of the localization method.
Results: Displacements in target point positioning were 0.35 ± 0.41 mm, 1.22 ± 0.25 mm, and −0.74 ± 0.32 mm in the
x,
y, and
z direction, respectively. The reproducibility of the fixation of the patient’s head within the mask was 0.48 mm (
x), 0.67 mm (
y), and 0.72 mm (
z). Rotational uncertainties around an axis parallel to the
x,
y, and
z axis were 0.72°, 0.43°, and 0.70°, respectively. A simulation, based on the acquired data, yields a typical radial overall uncertainty for positioning and fixation of 1.80 ± 0.60 mm.
Conclusions: The applied setup technique showed to be highly reproducible. The data suggest that for the applied technique, a safety margin between clinical and planning target volume of 1–2 mm along one axis is sufficient for a target at the base of skull.
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