Method and apparatus for adjusting technical exposure factors during radiographic acquisition

1. An apparatus for panoramic radiography comprising:

an X-ray source projecting a collimated X-ray bundle through a patient;

a bi-dimensional X-ray detector positioned to measure intensity of radiation after the radiation has crossed the patient;

a C-arm on which said X-ray source and X-ray detector are fixed at opposed ends, a position of the C-arm being adjusted according to patient height with a mobile post;

a mechanical system providing rotation and translation of the C-arm around the patient, such to acquire radiographic images from different positions;

a device for positioning the patient; and

an electronic system to control and synchronize operation of apparatus components, wherein the apparatus is configured to perform a method of patient specific, real time automatic adjustment of a technical exposure factor selected from the group consisting of X-ray tube power (kV), X-ray tube current (mA), exposure duration (sec), and film speed to acquire a radiographic image, the method comprising the following steps:

performing a first (scout) acquisition in a specific anatomical area of a patient using pre defined parameters;

extracting a region of interest (ROI) from the scout acquisition;

developing a grey level histogram of image pixels from the ROI,

segmenting the grey level histogram into a plurality of sectors, each sector corresponding to a gray level of a tissue typically found in a panoramic radiographic image;

assigning a coefficient to each sector;

assigning a weight to each coefficient;

computing an exposure parameter according to the weight assigned to each sector; and

performing an exposure of a real acquisition using the exposure parameters.

2. The apparatus according to claim 1 , wherein the plurality of sectors are five sectors, and wherein the exposure of the real acquisition is computed as follows:

[kV, mA, sec, filmspeed]=f(K 1 *W 1 , K 2 *W 2 , K 3 *W 3 , K 4 *W 4 , K 5 *W 5 ), and wherein:

K =the coefficient of each sector

W =the weight of each coefficient.

3. The apparatus according to claim 2 , wherein:

W 1 =Num(Seg/Num(totROI), and wherein:

Num(Segi) =number of pixels in sector i

Num(totRoI) =number of pixels in the region of interest.

4. A method of acquiring a radiographic image of a patient with an apparatus comprising a X-ray source and a X-ray detector, the X-ray source and the detector being disposes disposed in opposed positions, a region of interest of the patient being positioned in an intermediate position between the X-ray source and the detector and within a propagation bundle of a radiation emitted by the X-ray source, wherein the X-ray source and the detector are movable along a pre-set trajectory due to at least two movements:

a rotational movement of the X-ray source and the detector around a rotation axis, and

a translational movement of the rotation axis along a Y-direction in a horizontal plane perpendicular to the rotation axis, or a rotatory movement of the rotation axis around a second axis of rotation perpendicular to a plane parallel to the rotation axis, wherein, due to a combination of the at least two movements, a virtual rotation center which is an instant rotation center of the X-ray source and the detector moves during each acquisition, the method comprising:

acquiring a scout image by acquiring a pre-exam image; and

subsequently acquiring a real image, wherein, for acquiring the scout image, the rotational movement of the X-ray source and the detector around the rotation axis occurs in opposite directions with respect to a rotation direction of the X-ray source and the detector around the rotation axis during exposure for acquiring the real image.

5. The method according to claim 4 , wherein the X-ray source and the detector perform three combined movements, namely, the rotational movement around the rotation axis, a translational movement in the plane perpendicular to the rotation axis along an X-direction, the translational movement in the plane perpendicular to the rotation axis along the Y-direction different from the X-direction, or a combined translational movement according to two different directions along a curved line due to a rotational movement of the rotation axis around the second axis of rotation parallel to the rotation axis.

6. The method according to claim 4 , wherein the step of acquiring the real image occurs immediately after the step of acquiring the scout image without repositioning of the patient.

7. The method according to claim 4 , wherein image acquisition utilizes full-frame technology.

8. The method according to claim 4 , wherein image acquisition utilizes Time-Delay Integration (TDI) technology.

9. The method according to claim 4 , wherein the real image is a bi-dimensional image or a volumetric three-dimensional image of a patient's maxilla and mandible.

10. The method according to claim 4 , wherein:

the step of acquiring a scout image comprises,

using pre-defined parameters;

extracting a region of interest (ROI) from the scout image;

developing a grey level histogram of image pixels from the ROI,

segmenting the grey level histogram into a plurality of sectors;

assigning a coefficient to each sector;

assigning a weight to each coefficient;

computing an exposure parameter according to the weight assigned to each sector; and

the step of acquiring the real image is performed using the exposure parameters.

11. A method of acquiring a radiographic image of a patient with an apparatus comprising a X-ray source and a X-ray detector, the X-ray source and the detector being disposes in opposed positions, a region of interest of the patient being positioned in an intermediate position between the X-ray source and the detector and within a propagation bundle of a radiation emitted by the X-ray source, wherein the X-ray source and the detector are movable along a pre-set trajectory due to at least two movements:

a rotational movement of the X-ray source and the detector around a rotation axis, and

a translational movement of the rotation axis along a Y-direction in a horizontal plane perpendicular to the rotation axis, or a rotatory movement of the rotation axis around a second axis of rotation perpendicular to a plane parallel to the rotation axis, wherein, due to a combination of the at least two movements, a virtual rotation center which is an instant rotation center of the X-ray source and the detector moves during each acquisition, the method comprising:

acquiring a scout image by acquiring pre-exam image; and

subsequently acquiring a real image,

wherein, for acquiring the scout image, the rotational movement of the X-ray source and the detector around the rotation axis occurs in opposite directions with respect to a rotation direction of the X-ray source and the detector around the rotation axis during exposure for acquiring the real image, and

wherein the steps of acquiring a scout image and a real image are each performed with the virtual rotation center) in a different position with respect to the X-ray source, the detector, and the patient under investigation.

12. The method according to claim 11 , wherein, during the step of acquiring a scout image, the virtual rotation center is beyond the detector on a side opposed to the X-ray source.