Apparatus and method for variable angle slant hole collimator
Inventors
Lee, Seung Joon • Kross, Brian J. • McKisson, John E.
Assignees
Jefferson Science Associates LLC
Publication Number
US-9711251-B2
Publication Date
2017-07-18
Expiration Date
2035-08-05
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Abstract
A variable angle slant hole (VASH) collimator for providing collimation of high energy photons such as gamma rays during radiological imaging of humans. The VASH collimator includes a stack of multiple collimator leaves and a means of quickly aligning each leaf to provide various projection angles. Rather than rotate the detector around the subject, the VASH collimator enables the detector to remain stationary while the projection angle of the collimator is varied for tomographic acquisition. High collimator efficiency is achieved by maintaining the leaves in accurate alignment through the various projection angles. Individual leaves include unique angled cuts to maintain a precise target collimation angle. Matching wedge blocks driven by two actuators with twin-lead screws accurately position each leaf in the stack resulting in the precise target collimation angle. A computer interface with the actuators enables precise control of the projection angle of the collimator.
Core Innovation
The invention is a variable angle slant hole (VASH) collimator designed for collimation of high energy photons such as gamma rays used in radiological imaging of humans. The VASH collimator comprises a stack of multiple collimator leaves, each precisely aligned to provide various projection angles. This configuration enables the detector to remain stationary during tomographic acquisition by varying the projection angle of the collimator rather than rotating the detector around the subject. Accurate alignment of the leaves is essential to maintaining high collimator efficiency and image quality.
Each individual leaf includes unique angled cuts that maintain a precise target collimation angle, and the collimator utilizes matching wedge blocks driven by two actuators with twin-lead screws to accurately position each leaf, resulting in the desired collimation angle. A computer interface controls the actuators to enable precise adjustment of the projection angle. The compact and mechanically efficient design allows quick and accurate adjustment of viewing angles and eliminates mechanisms adjacent to the patient, enhancing safety and patient comfort.
The problem addressed by this invention arises from previous multi-angle collimators that either use multiple detectors or rotate a detector or which have multiple collimators at fixed angles. These methods can physically interfere with the imaging target or do not provide accurate leaf alignment, leading to reduced aperture size and inaccurate collimation angles, which degrade image quality. Thus, there is a need for a variable angle slant hole collimator that can provide accurate leaf alignment, maintain constant collimation angles across multiple projection views, improve image quality, eliminate the need to move the detector, and allow rapid, precise adjustment of viewing angles.
Claims Coverage
The patent includes one independent apparatus claim and one independent method claim. The main inventive features cover the structural elements of the variable angle slant hole collimator and the method steps for aligning the multi-leaf stack.
Variable angle slant hole collimator apparatus
- A frame with opposing sides, opposing ends, and a front panel having an opening. - A plurality of substantially planar leaves stacked against the front panel, each leaf containing an array of apertures arranged identically and capable of axial alignment at initial position. - A means for positioning the leaves within the stack to slide at predetermined rates relative to surrounding leaves to provide variable collimation angles. - The positioning means includes lead screws and two wedge blocks on each end of the frame driven by an actuator.
Unique angled cuts on leaves for precise displacement
- Each leaf end includes an angled cut unique to that leaf, typically with a central apex and two angled surfaces extending to the leaf sides, allowing calculated displacement when wedge blocks move.
Drive mechanism with lead screws and wedge blocks
- Lead screws with screw threads embedded in drive nuts within wedge blocks. - Use of right-hand and left-hand threads on opposing halves of the lead screws. - Wedge blocks have stepped edges matching the leaf thickness for precise leaf displacement. - Pillow blocks support the lead screws to prevent bending.
Computer-controlled motor and gearbox actuation
- Actuators comprising motors and gearboxes controlled via a computer interface to precisely adjust the rotation of the lead screws and thus position the wedge blocks and leaves.
Method for aligning multi-leaf collimator stack
- Providing the frame, twin lead screws, wedge blocks, coupling nuts, and plurality of leaves. - Moving wedge blocks and coupling nuts to side rails and fixing wedge blocks to coupling nuts with set screws. - Stacking leaves and adjusting wedge blocks until contact. - Moving wedge blocks synchronously with controlled speed and distance to set desired slant angle without gaps between leaves and wedges.
The claims collectively disclose an apparatus consisting of a multi-leaf collimator stack with uniquely angled leaf ends, driven by wedge blocks on twin lead screws actuated by motors and gearboxes, controlled via computer, enabling precise and rapid variable angle collimation. The method claims cover the stepwise procedure of assembling and adjusting the wedge blocks and leaves to achieve accurate collimation angle alignment.
Stated Advantages
Enables accurate tomographic acquisition by allowing multiple angle projection with a stationary detector.
Provides multiple viewing angles for body parts such as breast, thyroid, and heart.
Improved actuation device removes mechanisms adjacent to the patient, enhancing safety and patient comfort.
Maintains a constant collimation angle across the multi-leaf stack yielding high output image quality.
Eliminates the need to rotate the detector, simplifying imaging procedures.
Allows rapid and precise adjustment to various viewing angles.
Prevents motor strain when the collimator stack is turned vertically.
Reduces radiation dose to the patient by enabling quick viewing angle changes during tomographic imaging.
Minimizes the time required to acquire multiple angle views for patients administered radioisotopes.
Compact size facilitates easy handling and orientation adjustments relative to the patient.
Documented Applications
Medical radiology and nuclear medicine imaging of humans, specifically for imaging high energy photons such as gamma rays.
Tomographic imaging of body parts including breast, thyroid, and heart.
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