T 1921/16 27-10-2017

Reasons for the Decision

1. The appeal is admissible.

2. Definition of the invention

2.1 The invention concerns a dental panoramic x-ray imaging system having an x-ray source and an imaging device which move around the patient's head according to a predetermined geometric path and speed profile (paragraph [0010] of the patent; Figure 3). The movement is such that an image of a predetermined layer of interest is formed. The invention allows the x-ray scan to be performed by moving the x-ray source and imaging device in a continuous movement around the patient's head (paragraph [0030]).

2.2 The movement is defined in claim 1 (feature (c)) by specifying a "rotational axis around which at least one of the x-ray source and imaging device rotates along a spline in a scanning direction, ... wherein the spline is a non-circular trajectory". Whilst the patent as granted already defined the motion "... along a spline", the feature "wherein the spline is a non-circular trajectory" was added during opposition proceedings.

It is common general knowledge that a "spline" is a continuous curve having continuous derivatives. This concept corresponds, for example, to the definition in the Shorter Oxford English Dictionary (E1) and the Wikipedia article "Spline (mathematics)" filed with the statement of grounds of appeal. In essence, "spline" designates a smooth curve, without sharp turns or kinks (as in a "V"-shaped curve).

As explained in the patent as granted (page 8, lines 28 to 30, corresponding to page 17, lines 7 to 10 of the application as filed), the movement along a spline can be either a circular or a non-circular trajectory, and in the presently pursued claims 1 the movement of the x-ray source and imaging device is limited to a non-circular trajectory. Hence, the claimed expression of "a spline, which is a non-circular trajectory" can be given no meaningful reading other than that of a non-circular spline trajectory.

3. Main request

3.1 Priority right

3.1.1 It is undisputed by the parties that application US 11/277,530, from which the patent claims its priority, is represented by document D3. It is likewise undisputed that if the claim to priority fails, D3 is comprised in the state of the art within the meaning of Article 54(2) EPC (as it was published on 14 September 2006, before the 10 November 2006 filing date of the application leading to the patent in suit) and that, in that case, D3 is novelty-destroying.

3.1.2 What was disputed, however, is whether priority could be validly claimed from D3, since the same applicant had already disclosed the same invention in the earlier previous application US 60/677,020 (USPRE). USPRE had been filed on 2 May 2005, i.e. before the 27 March 2006 filing date of D3 and about 18 months before the 10 November 2006 filing date of the parent of the divisional application leading to the patent in suit.

3.1.3 According to Article 87(1) EPC, only the first application filed in a state party to the Paris Convention or a member of the WTO can form the basis for a priority right. Therefore, if apart from the application whose priority is being claimed in the patent (in this case D3), an earlier previous application had also been filed (in this case USPRE), in order to check the validity of the priority claim it must be established whether the invention claimed in the patent was already disclosed in the earlier previous application (USPRE).

To establish whether the invention claimed in the patent was already disclosed in the earlier previous application, USPRE, the same principles have to be applied as when establishing identity of invention between the application forming the basis for priority and the application claiming priority. The question is whether the person skilled in the art could derive the subject-matter of the claim of the patent directly and unambiguously, using common general knowledge, from the earlier previous application USPRE (G 2/98, OJ 2001, 413). As confirmed in G 1/03, point 4 of the Reasons, the disclosure as the basis for the right to priority under Article 87(1) EPC and as the basis for amendments in an application under Article 123(2) EPC has to be interpreted in the same way.

3.1.4 The respondent contested that USPRE directly and unambiguously disclosed that:

(a) the trajectory of the x-ray source and imaging device was a non-circular spline trajectory,

(b) the CMOS of the imaging device had an active area with a ratio of the long dimension m to the short dimension n of m/n > 5, and

(c) the frame rate was at least 50 frames per second.

3.1.5 In the Board's view, these features are disclosed in USPRE for the following reasons.

3.1.6 Non-circular spline trajectory

USPRE discloses in claim 1 that the x-ray source and imaging device rotate on a circular or non-circular trajectory. USPRE does not explicitly mention that the trajectory is a spline, i.e. essentially a smooth curve without sharp turns or kinks, as explained under point 2.2 above.

However, the Board considers that from what is disclosed on page 16, paragraphs 4 and 5 in connection with Figure 7, such a trajectory inevitably occurs in USPRE as well. This passage explains that a transversal layer is obtained, the layer being transversal to the panoramic images which follow the contour of the jaw and parallel to the direction of radiation. Thus, the direction of radiation will be perpendicular to the panoramic images or layers which are illustrated in Figure 7. This is what Figure 3 illustrates too, albeit with reference to prior-art orthopantomographs (OPG), in which the perpendicularity of the center of the x-ray beam to the panoramic layer is expressly indicated by a graphical symbol denoting perpendicularity. Moreover, in the description of Figure 3, on page 3, paragraphs 4 and 5, it is mentioned that the movement of the x-ray source and imaging device is synchronised so that the imaging device surface normal is perpendicular to the layer of interest, i.e. the panoramic layer.

The respondent held the view that USPRE disclosed on page 16, paragraph 5, that the transversal layer did not have to be strictly parallel to the direction of radiation, but could be just "close to parallel". In the Board's view, this possibility (mentioned in parentheses after the feature "parallel") addresses the fact that for a fan-type x-ray beam, as depicted in Figure 3, only the center ray will be strictly perpendicular to the panoramic layer, while the rays of the periphery of the beam will be only substantially perpendicular to it.

The jaw of a patient has a roughly horseshoe-shaped contour, which is clearly non-circular, particularly in its lateral portions. Hence, if a circular trajectory of the x-ray source and imaging device were used, as suggested by the respondent, the direction of the x-rays would not be perpendicular to the panoramic layers which follow the contour of the jaw. Moreover, the panoramic layers shown in Figure 7 of USPRE, as well as in Figure 3, are undoubtedly smooth curves without sharp turns or kinks, thus having continuous derivatives. Hence, since the x-rays are emitted perpendicularly to these curves, the x-ray source and imaging device will likewise move along a smooth trajectory.

The Board therefore finds that from the explicit direct and unambiguous disclosure of the movement of the x-ray source and imaging device in USPRE, the skilled person would conclude that the movement inevitably occurs along a non-circular spline. This is consequently no new information over what is explicitly disclosed.

3.1.7 m/n > 5

In USPRE, the imaging device is disclosed as a slot-shaped CMOS sensor having dimensions of 150 mm x 6,4 mm (page 13, paragraph 4). The ratio of these dimensions is thus 23,4, which falls within the claimed range m/n > 5.

3.1.8 At least 50 frames per second

The CMOS sensor disclosed on page 13, paragraph 4 of USPRE is specified as producing a frame rate of 200 to 300 frames per second. These frame rates fall within the claimed range of at least 50 frames per second.

3.1.9 Apart from the aforementioned features the respondent identified no further ones in claim 1 of the main request which goes beyond the subject-matter disclosed in USPRE.

3.1.10 As the person skilled in the art derives the subject-matter of claim 1 of the main request directly and unambiguously, using common general knowledge, from the earlier previous application USPRE, D3 is not the first application within the meaning of Article 87(1) EPC and thus does not form the basis for a priority right.

Consequently, D3 is comprised in the state of the art within the meaning of Article 54(2) EPC.

3.2 Novelty

As it is undisputed that D3 discloses the subject-matter of claim 1 of the main request, the novelty requirement of Article 54(1) EPC is not fulfilled.

4. Auxiliary request E

4.1 Article 123(2) EPC

Contrary to the appellant's view, the Board finds that the following features are indeed directly and unambiguously derivable from the application as filed.

4.1.1 "Wherein the spline is a non-circular trajectory"

As already explained under point 2.2 above, page 17, lines 7 to 10 of the application as filed discloses that the movement along a spline can be either a circular or a non-circular trajectory. In claim 1, the movement of the x-ray source and imaging device is limited to one of these disclosed alternatives in which "the spline is a non-circular trajectory".

4.1.2 Fast memory

Claim 11 as originally filed defines "a fast memory having sufficient speed for storing the multiple frames substantially concurrently with the exposure" [emphasis added]. The appellant pointed out that the underlined terms were omitted from the definition of the memory in feature (d) of claim 1. It argued that this omission led to an unallowable intermediate generalisation.

The Board does not share this view. The claim defines the storing of frames within a certain time period, namely "substantially concurrently with the (x-ray) exposure". It is thus implicit that the memory speed needs to be "sufficient" to do so. Also, the omitted specification of the memory as a "fast" one is devoid of any precise additional content. It is incidentally noted that the last sentence of the paragraph bridging pages 8 and 9 of the application as filed actually omits to mention this attribute.

4.1.3 Random access memory

The last paragraph on page 8 is also the basis for the further definition in claim 1 (first paragraph of the characterising portion) of the memory being adapted for storing and accessing the multiple overlapping frames in any order and having storage locations that are all equally accessible. The last full sentence on page 8 makes reference to the memory allowing "information" to be stored and accessed in any order, and the next sentence explains that the multiple frames stored in the memory are retrieved in real time. Hence, in the terminology of the claim, the "information" which is stored and accessed in any order is clearly that of the multiple frames.

4.1.4 The Board thus concludes that claim 1 of auxiliary request E satisfies the requirements of Article 123(2) EPC.

4.2 Priority right

The range of frame rates of at least 50 frames per second (fps) as defined in claim 1 of the main request has been replaced in claim 1 of auxiliary request E by the more limited one of more than 300 fps.

This range lies outside the range of 200 to 300 fps disclosed for the specific slot-shaped CMOS sensor with dimensions of 150 mm x 6,4 mm mentioned on page 13, paragraph 4 of USPRE. Therefore, the claimed range of more than 300 fps is not disclosed in USPRE in this context.

The appellant pointed out that claim 16 of USPRE defined an imaging device capable of producing at least 300 fps, including, inter alia, more than 300 fps. The Board considers that this range of frame rates is not directly and unambiguously disclosed in conjunction with the aforementioned particular sensor of page 13, having dimensions of 150 mm x 6,4 mm and producing frame rates from 200 to 300 fps.

The Board therefore comes to the conclusion that the subject-matter of claim 1 of auxiliary request E is novel over USPRE and that for this subject-matter D3 is the first application within the meaning of Article 87(1) EPC, thereby conferring a right to priority.

4.3 Novelty

As a consequence, D3 is not comprised in the state of the art under Article 54(2) EPC. The appellant's novelty objection based on D3 therefore fails.

4.4 The appellant explicitly stated during the oral proceedings that, apart from the objection based on D3, there were no objections concerning the novelty and inventive step of the subject-matter of claim 1 of auxiliary request E. The Board saw none either.