Device for positioning a patient during acquisition of volumetric CBCT radiographs

Abstract

A radiographic apparatus includes a gantry and a table supporting a patient and having a device that immobilizes the head of the patient lying on the table. Such device includes a dome configured to support the head of the patient; a basal plate; one or more junctions provided at a first end of the basal plate; two uprights provided at a second end of the basal plate opposed to the first end, two slits being defined in the two uprights, a slide being disposed within each slit; and a cursor sliding in the two slits and configured to be blocked in position by a bushing, wherein the basal plate, the one or more junctions, the two uprights, the cursor, and the bushing are all radio-transparent and non-metallic.

Claims

1. A radiographic apparatus comprising a gantry and a table for supporting a patient, the table comprising a device configured to immobilize a head of the patient lying on the table, wherein the device configured to immobilize a head of the patient comprises: a dome configured to support the head of the patient therein; a basal plate; at least one junction provided at a first end of the basal plate; two uprights provided at a second end of the basal plate opposed to the first end, two slits being defined in the two uprights, a slide being disposed within each slit; and a cursor sliding in the two slits and configured to be blocked in position by a bushing, and wherein the basal plate, the at least one junction, the two uprights, the cursor, and the bushing are all radio-transparent and non-metallic.

2. The radiographic apparatus according to claim 1, wherein the device configured to immobilize the head of the patient is provided with a coupling and releasing system to the table, the coupling and releasing system comprising a plurality of pins disposed under the basal plate, a plurality of bushings being provided on the table at mating points, so as to enable an insertion of the plurality of pins into the plurality of bushings with hand pressure.

3. The radiographic apparatus according to claim 1, wherein the sliding of the cursor the two slits provides for a tilting of the dome around the at least one junction, between two positions: a first extreme position wherein the dome is parallel to the table; and a second extreme position wherein the dome is tilted 45° with respect to the table.

4. The radiographic apparatus according to claim 3, wherein the cursor is adapted to stop at pre-set intermediate positions between the first and the second extreme positions.

5. The radiographic apparatus according to claim 3, wherein the cursor is adapted to stop at any intermediate position between the first and the second extreme positions.

6. The radiographic apparatus according to claim 1, wherein the dome comprises a plurality of protuberances protruding from a border of the dome at a distal end proximal tod the two uprights.

7. The radiographic apparatus according to claim 1, further comprising members coupled to the dome to immobilize the patient, the members being selected from the group consisting of a removable cushion, a wedge, and a band.

8. The radiographic apparatus according to claim 1, wherein the gantry is provided with a through hole, an X-ray source, and a sensor panel, the table comprising a gurney movably being mounted on a base in relation to the gantry with at least one degree of freedom, and wherein the gurney is movably supported along three spatial axes so as to acquire the patient's anatomical area of interest, a field of view being always concentric to the through hole of the gantry.

9. The radiographic apparatus according to claim 8, wherein positioning the gurney (6) supporting the patient (80) occurs in two successive steps: (a) a first rough positioning through laser indicators; and (b) a second fine positioning through scout acquisitions; patient positioning occurring due to a moving of the gurney in the three spatial axes.

10. The radiographic apparatus according to claim 8, wherein the radiographic apparatus is configured to provide a radiograph having dimensions bigger than dimensions of the sensor panel by performing at least two sub-acquisitions which are then summed with a stitching procedure of the at least two sub-acquisitions; the gurney being re-positioned between a first sub-acquisition and a following sub-acquisition, so as to cover an entirety of the anatomical area of interest.

11. The radiographic apparatus according to claim 8, wherein a movement of the gurney along the a first one of the three spatial axes occurs through a moto-reducer system with a rack-and-pinion transmission, so as to actuate a cart on which the gurney is fixed.

12. The radiographic apparatus according to claim 8, wherein the gurney is provided with: a longitudinal stroke of 150 cm; a lateral stroke up to 21 cm; and a height stroke of about 40 cm.

13. The radiographic apparatus according to claim 1, wherein the gantry is provided with a through hole, an X-ray source, and a sensor panel; and further comprising a patient support comprising a gurney movably mounted on a base in relation to the gantry, the gurney being movable with at least one degree of freedom, wherein the gurney is movably supported along three spatial axes to acquire an anatomical area of interest of a patient, a field of view being always concentric to the through hole of the gantry.

14. A method of positioning a patient in a radiographic apparatus according to claim 8, wherein the positioning of the patient comprises: positioning the gurney supporting the patient in two successive steps: (a) a first rough positioning through laser indicators, and (b) a second fine positioning through scout acquisitions; wherein the positioning of the patient is achieved by moving the gurney along the three spatial axes.

15. The method according to claim 14, further comprising: acquiring a radiograph with dimensions larger than dimensions of the sensor panel by performing at least a first and a second sub-acquisition, which are then summed using a stitching procedure of the first and the second sub-acquisitions, the gurney being re-positioned between the first sub-acquisition and the second sub-acquisition, so as to cover an entirety of the anatomical area of interest.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and properties of the present invention are disclosed in the following description, in which exemplary embodiments of the present invention are explained in detail based on the drawings:

(2) FIG. 1 is an axonometric view of a radiographic apparatus according to the present invention, with the gurney in its extracted position (first extreme position);

(3) FIG. 2 is an axonometric view of a detail of the headrest;

(4) FIG. 3 is an axonometric view of the detail of the fixing of the headrest to the gurney;

(5) FIG. 4 is a lateral view of a patient having her/his head parallel to the gurney;

(6) FIG. 5 is a lateral view of a patient having her/his head tilted with respect to the gurney.

(7) FIG. 6 is an axonometric view of the radiographic apparatus according to the present invention, with the gurney in its end of stroke inserted position (second extreme position);

(8) FIG. 7 is a schematic view of a patient; his left shoulder is under acquisition;

(9) FIG. 8 is a schematic view of a patient; his vertebral column is under acquisition.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(10) FIG. 1 shows an extraoral radiographic apparatus 1, comprising a table 2 for positioning a (not shown) patient in a lying position, and a gantry 3, in its turn comprising a not shown X-ray source and detector.

(11) Said table 2 comprises a relocatable, adjustable device 4 for immobilizing patient's head.

(12) Said apparatus 1 comprises a screen 5 to visualize the images of the patient, or an instruction panel.

(13) FIG. 2 shows a detail of the device 4 for immobilizing the head of a not shown patient. Said device 4 is provided with a headrest dome 7, tilting from a first extreme planar position that is parallel to the plane of the gurney 6 and adjacent to it (visible in FIG. 4), to a tilted position which can reach up to 45° in its second extreme position. Said dome 7 can be blocked in intermediate positions between 0° and 45°.

(14) Said dome 7 is provided with the shape of a cradle, consisting in a plane having ends raised with respect to said plane. In its distal portion, nearer to uprights 10, said dome is provided with two protuberances 27 protruding from the border of said plane, aiming at further holding patient's head.

(15) Said device 4 for immobilizing patient's head comprises a basal plate 8, made of radio-transparent material and hollowed out, which is in contact with said gurney 6. Partially said plate 8 can be focused inside the FOV.

(16) On said plate 8, on the side opposed to the gantry 3, there are provided two junctions 9 made of radio-transparent material, allowing a tilting movement of the dome 7.

(17) At the end opposed to the junctions 9 (i.e. oriented toward said gantry 3), on the plate 8 there are provided two uprights 10, which are radio-transparent, too. Said uprights have a guiding function, while at the same time create a rigid structural element aiming at correctly immobilizing the head of the patient. Said two uprights 10 are placed so as not to be irradiated, in order to generate no artefact. Each upright 10 comprises a slit 11, inside which a cursor 12 slides, which is fixed to the end of said dome 7. The cursor 12 can be blocked in pre-set positions through a radio-transparent nut 13. E.g. the device 4 is provided with a blocked position every e.g. 5° of tilting.

(18) In an alternative embodiment, the fixing of the dome 7 on the uprights 10 is continuous, without pre-set positions.

(19) FIG. 3 shows a detail of the fixing system of said device 4. Said system comprises two centering pins 14 placed in the lower portion of the plate 8, at the opposed end of the junctions 9 of said plate, under said uprights 10. Due to the image prospective, only a pin 14 is visible in FIG. 3.

(20) The fixing system further comprises two radio-transparent bushing 15, which are inserted at the end of the gurney 6 oriented toward said gantry 3. Obviously, said two pins 14 and bushing 15 are placed in corresponding portions.

(21) Like the structural portions, said pins 14 and bushing 15 are provided outside the area focused by the FOV, always with the aim of minimizing the generation of artefacts.

(22) The fixing system allows to reduce to a minimum the mechanical parts for the fixing (no screws or blocking systems). Thanks to the weight of the patient, the fixing system allows to obtain a good blocking system, easy and fast to fix/remove without the use of tools. A human operator inserts or removes said pins 14 into or from said bushings 15; with a slight pressure the device 4 becomes integral with the gurney 6.

(23) FIG. 4 shows a detail of an acquisition of the head 16 of a patient, of whom the ear has to be acquired. If her/his head is kept at 0° with respect to the gurney 6 (i.e. the head is co-planar to the gurney), an X-ray beam 17 impinges on both the eyes 18 and the pituitary gland (not shown) of the patient, with ensuing useless irradiation of organs which are particularly sensitive to X-rays, without acquiring portions that are useful for the investigation under way.

(24) FIG. 5 shows a detail of the acquisition of the head 16 of a patient of whom the ear has to be acquired. If her/his head is kept at 45° with respect to the gurney 6 (i.e. tilted with respect to the gurney), the X-ray beam 17 irradiates the ear area only, without impinging on the eyes 18 nor the pituitary gland (not shown) of the patient.

(25) It is worth noting that to said dome 7 special cushions, wedges and removable bands (not shown) can be added, aiming at further immobilizing the patient's head; such devices are known in the art. Said protuberances 27 are provided for fixing said further blocking elements.

(26) Moreover, FIG. 1 shows three double arrows (X, Y, and Z) showing the movement of a gurney 6 in the three space axes. The longitudinal axis Y is the direction for extracting the gurney out of the gantry 3 or inserting the gurney inside the gantry 3; the lateral axis X (right/left) allows the movement of the gurney in a direction orthogonal to the longitudinal direction; while the vertical axis Z allows the raising/lowering of said gurney with respect to the floor plane.

(27) Said patient support 2 comprises a base 71 lying on the floor and integral to said gantry 3; and a gurney 6 mobile with respect to the floor. The patient lays on said gurney 6. Optionally the adjustable device 4 is provided for immobilizing the patient's head, which is fixed to said gurney 6.

(28) FIG. 6 shows the same elements shown in FIG. 1.

(29) In FIGS. 1 and 6, the gurney 6 is shown in its two extreme positions: in FIG. 1, the gurney 6 is shown in its completely extracted position, while in FIG. 6 the gurney 6 is shown in its position inserted in the gantry 3 up to its end of stroke. The comparison between FIG. 1 and FIG. 6 shows the longitudinal movement along the Y axis of the gurney 6 itself, sliding inside the through hole 103 of the gantry.

(30) FIG. 7 and FIG. 8 show the advantages of the present invention.

(31) FIG. 7 shows an area 90 to be acquired consisting in the left shoulder of a patient 80 lying on the gurney 6, which in this case is translated laterally (along the X axis) of about 20 cm with respect to the gurney centered position with respect to the through hole 103 of said gantry.

(32) It is worth noting that the FOV is always generated in a way concentric to the rotation axis of the X-ray source-detector system, independently of the diameter of the volume to be acquired. Therefore, the said FOV is co-axial to the through hole 103 of said gantry 3.

(33) According to the present invention, just the area 90 to be acquired indicated in grey in the image is irradiated, therefore saving the adjacent anatomical structures.

(34) Instead, in a spiral CT radiographic apparatus, this is not possible. In order to focus offset fields of view, big X-ray sensor panels are used, irradiating patient's portions that are not to be acquired. In the example of FIG. 7, both shoulders of the patient 80 would be irradiated and acquired, administering a partially useless X-ray dose to said patient.

(35) On the other hand, FIG. 8 shows the principle of multiple acquisitions. The applicant filed the application EP2868275A1, teaching to perform a stitching procedure of radiographic images acquired in at least two sub-acquisitions of smaller volumes, which are then summed so as to acquire a bigger radiograph.

(36) In the example of FIG. 8, multiple sub-acquisitions were summed, by translating said gurney 6 in the longitudinal direction for a number of times equal to the length of the anatomical portion to be acquired divided by the 17 cm of the FOV height. In practice, in order to acquire the vertebral column of an adult patient in its entirety, at least four-five successive sub-acquisitions are necessary, which are then summed post-acquisition.

(37) The lateral movement (right/left) of said gurney 6 is obtained by implementing a motoreducer system with a rack-and-pinion transmission, so as to actuate a cart on which the gurney is fixed. Said mechanical system, laying outside the irradiated area, does not require special cautions to improve the radiotransparency of the components.

(38) In practice, the patient lays on the gurney 6 and is inserted into the gantry 3, roughly centering the desired anatomic area through laser indicators. Then some scout images are acquired (typically a frontal and a lateral image), allowing to understand whether the desired anatomical area is correctly focused inside said FOV. According to said scout images the fine centering of the patient is performed, making small, even remote, adjustments in the three space axes (X, Y and Z), without the need to repeat the scout acquisitions. Then the real acquisition/s can take place.

REFERENCE NUMBERS

(39) 1 Extraoral radiographic apparatus 2 Table 3 Gantry 4 Device for immobilizing patient's head 5 Screen 6 Gurney 7 Headrest dome 8 Basal plate 9 Junction 10 Upright 11 Slit 12 Cursor 13 Nut 14 Pin 15 Bushing 16 Head 17 X-ray beam 18 Eyes 27 Protuberance 71 Base 80 Patient 90 Area to be acquired 103 Gantry passing hole