As discussed in past posts, teaching away is a tough row to hoe at the USPTO. So it comes as a bit of a shock when the PTAB offers it up in a decision where the applicant did not even raise it. The case is Appeal 2020-004944, Application 13/902,224.

The application relates to measuring fluid flow through a blood vessel using imaging techniques. The case illustrates the classic unreasonable examiner where the applicant is forced to deal with piece-meal examination and multiple RCEs until they realize there is no way forward other than to appeal. The applicant even tried the pre-appeal conference - but with an examiner supported by their supervisor, such an effort unfortunately falls on deaf ears.

Turning back to the case, the technology involves to systems that utilize a bolus of a flushing agent and observe the fluid via ultrasound. By determining a travel distance of the bolus within the vessel and/or an elapsed time during which the bolus traveled the distance, it is possible measure the flow rate through the vessel. The particular invention utilizes a flushing agent bolus that can be distinguished from blood via intravascular ultrasound (IVUS) by observing changes in speckle densities. The speckle density is used to detect a position of the quantity of fluid within the vessel to determine a start time and/or an end time.

As explained in the Applicant’s specification, speckles are “an image artifact that commonly appears as specks in ultrasound images that are caused when structure in an object is on a scale too small to be resolved by an imaging system. A density of speckle (e.g., the density of specks in the ultrasound image) is directly correlated to the concentration of unresolvable structure in an object. Blood may be a cause of speckle in an ultrasound image as the content of blood (e.g., red blood cells, white blood cells, platelets) is too small to be resolved by an ultrasound transducer. Generally, [a] speckle is considered an undesirable image artifact as it can mask small but potentially diagnostically significant imaging features. To avoid speckle caused by blood, many imaging systems (e.g., IVUS, OCT) can be configured to use a flushing agent (e.g., saline, contrast, Ringer’s solution, dextran, lactate solution) to clear blood out of an area of interest within a vessel before imaging the vessel.”

Claim 1 of the application on appeal is reproduced below:

1. A system comprising:
a catheter assembly including an intravascular measuring device comprising an intravascular ultrasound imaging probe having a measurement module configured to emit and receive energy and generate ultrasound measurement data, the catheter assembly configured to introduce a quantity of fluid into a vessel of a patient; and
a measurement engine in communication with the intravascular measuring device comprising at least one processor, the measurement engine configured to:
receive the ultrasound measurement data from the intravascular measuring device;
generate, using the at least one processor, a speckle density value based on the ultrasound measurement data, the speckle density value corresponding to a concentration of structure in the vessel that is too small to be resolved by the intravascular ultrasound imaging probe, wherein when the quantity of fluid is introduced into the vessel the speckle density value is relatively high compared to the speckle density value when the intravascular ultrasound imaging probe is surrounded by the quantity of fluid;
determine a fluid flow travel start time associated with an introduction of the quantity of fluid into a predetermined portion of the vessel;
determine a fluid flow travel end time as being when the speckle density crosses a first predetermined speckle density threshold using the at least one processor;
calculate, using the at least one processor, an elapsed fluid flow travel time based on the fluid flow travel start time and the fluid flow travel end time; and
calculate, using the at least one processor, a flow rate of the quantity of fluid through the vessel based on the elapsed fluid flow travel time and a travel distance of the quantity of fluid during the elapsed fluid flow travel time.

The Examiner’s Rejections relied on various different combinations of references. The applicant asserted two common propositions to attack obviousness: that the combination was based on unsound rationale, and that even if combined, limitations were missing. The PTAB decided the case on the first point. The PTAB’s reasoning is below (in some detail) (internal citations omitted, emphasis added):

The Examiner found that Kemp discloses a method for intravascular imaging and flushing that includes much of the subject matter of claims 1 and 35. However, the Examiner conceded that Kemp does not explicitly teach the last two “calculat[ing]” steps of claims 1 and 35. Id. at 8. The Examiner found that Knight discloses an “imaging catheter with integrated contrast agent injector,” in which the fluid flow travel and end times are used to calculate an elapsed time for fluid flow (i.e., the first calculating step). Id.8 Based on these findings, the Examiner determined … “it would have been obvious … to have utilized calculating the fluid flow travel and end time, and calculating an elapsed time from the fluid low travel and end time in the invention of Kemp, as taught by Knight, to be able to know the exact timing when the flushing fluid has arrived in the predetermined portion of the vessel for more accurate start timing of the imaging.”

Appellant argues that the Examiner’s rationale is deficient. Appellant points out—correctly—that “Kemp determines the exact timing of when the flushing fluid has arrived at the location of interest based on the backscattering signal change and then begins image data collection that instant.” Appellant adds: As soon as that backscattering signal change is received, Kemp begins image data collection. The backscattering signal change triggers image data collection without regard for any time measurement. The amount of time from when the flushing fluid is first introduced into the vessel to when the flushing fluid causes the backscattering signal change would have had no effect on the accuracy of when Kemp begins image data collection. This is because information relating to flushing fluid flow preceding its arrival at the imaging unit, as in Knight, is irrelevant to Kemp. Thus, contrary to the Final Office Action’s assertion, one of ordinary skill in the art would have had no motivation to have combined Knight’s measurement techniques with Kemp’s system because it would have been clear that such a combination would have provided no benefit. Appellant’s argument is factually correct and its conclusion about a lack of motivation is persuasive. In fact, as discussed below, Kemp may even teach away from the proposed modification. Kemp “relates to methods for determining when to initiate an imaging procedure inside a lumen of a vessel.” Kemp explains that “blood interferes” with imaging of a blood vessel. “Successful imaging of the inside of the vessel . . . requires temporarily displacing the blood from the portion of the vessel that will be imaged.” However, “the blood cannot be displaced for an extended period of time without resulting in harm to a patient.” Thus, “displacement of the blood must be coordinated with initiation of the imaging procedure so that the imaging procedure may be accomplished in an accurate and timely manner without harming the patient.” Kemp accomplishes its objective by measuring changes in red blood cell “backscattering,” using this as a trigger for turning imaging (or image capturing) on and off. For example, after the flush bolus is introduced and backscattering is no longer detected, “step 688 starts the image acquisition and saving of the image frames to a memory device operably coupled to the imaging system or computer system.”

The Examiner does not explain how the proposed modification could improve Kemp. In fact, the Examiner does not even explain how the proposed modification would operate. …

It is good to see the PTAB get into the technical arguments and understand the problem with the examiner’s hindsight reconstruction. And we see that even when the board members themselves raise teaching away, they cannot even commit to it (“… Kemp may even teach away…”). This just confirms that an applicant should first focus on the technical arguments as to why the combination is not properly established by the examiner before worrying about teaching away.