# US 11,113,814 B2 · Determining respiratory phase from fluoroscopic images

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- Number: US 11,113,814 B2
- Document ID: US11113814B2
- Status: Granted
- Kind: B2
- Application number: 16/693,021
- Filed: 2019-11-22
- Published: 2020-03-19
- Granted: 2021-09-07
- Earliest claimed: 2018-02-08
- Assignees: APN Health, LLC
- Applicants: APN Health, LLC
- Inventors: Donald Brodnick; Shivani Kohut
- Web page: https://patentgrep.com/patent/US11113814B2

## CPC

- A61B 6/12: Arrangements for detecting or locating foreign bodies
- G06T 7/0016: {involving temporal comparison}
- A61B 6/481: {involving the use of contrast agents}
- A61B 6/485: {involving fluorescence X-ray imaging}
- A61B 6/486: {involving generating temporal series of image data}
- A61B 6/487: {involving fluoroscopy}
- A61B 6/503: {for diagnosis of the heart}
- A61B 6/5217: {extracting a diagnostic or physiological parameter from medical diagnostic data}
- A61B 6/541: {involving acquisition triggered by a physiological signal}
- G06T 5/20: using local operators
- G06T 7/254: involving subtraction of images
- G06T 2207/10064: Fluorescence image
- G06T 2207/20021: Dividing image into blocks, subimages or windows
- G06T 2207/20056: Discrete and fast Fourier transform, [DFT, FFT]
- G06T 2207/30101: Blood vessel; Artery; Vein; Vascular
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

A method of determining respiratory phase of a living body from a sequence of digitized fluoroscopic images of a living-body region exhibiting respiratory displacement, the method employing programmable computing apparatus and comprising the steps of: (a) in each living-body-region image in the sequence, defining one or more zones with each image having identical image-to-image zone locations, sizes, and shapes; (b) for each image, computing an average pixel intensity for each zone to form a sequence thereof for each zone; (c) for each zone, modifying the average pixel intensities by (i) computing the mean value of the sequence of average pixel intensities for such zone, and (ii) subtracting the mean from each average pixel intensity in the zone; (d) for each zone sequence, computing a figure-of-merit; (e) selecting the zone having the highest figure-of-merit; and (f) using the sequence of pixel intensities of the selected zone to determine respiratory phase.

## Claims

### Claim 1

A method of determining respiratory phase of a living body from a sequence of digitized fluoroscopic images of a living-body region exhibiting respiratory displacement, the method employing programmable computing apparatus and comprising the steps of:
in each living-body-region image in the sequence, defining one or more zones with each image having identical image-to-image zone locations, sizes, and shapes;
for each image, computing an average pixel intensity for each zone to form a sequence thereof for each zone;
for each zone, modifying the average pixel intensities by:
computing the mean value of the sequence of average pixel intensities for such zone; and
subtracting the mean from each average pixel intensity in the zone;
for each zone sequence, computing a figure-of-merit;
selecting the zone having the highest figure-of-merit; and
using the sequence of pixel intensities of the selected zone to determine respiratory phase.

### Claim 2 (depends on 1)

The method of determining respiratory phase of claim 1 wherein the figure-of-merit for a zone is based on estimates of power spectral density of the sequence of modified average pixel intensities for the zone.

### Claim 3 (depends on 2)

The method of determining respiratory phase of claim 2 wherein the power spectral density estimates are determined using a maximum entropy method.

### Claim 4 (depends on 3)

The method of determining respiratory phase of claim 3 wherein the figure-of-merit is the ratio of power in a predetermined frequency band to the power outside of the predetermined band.

### Claim 5 (depends on 4)

The method of determining respiratory phase of claim 4 wherein the predetermined frequency band is defined by a low frequency f1 and a high frequency f2.

### Claim 6 (depends on 5)

The method of determining respiratory phase of claim 5 wherein f1 is 0.16 Hz and f2 is 0.33 Hz.

### Claim 7 (depends on 5)

The method of determining respiratory phase of claim 5 wherein the predetermined frequency band is centered around a prior estimate of respiratory rate.

### Claim 8 (depends on 6)

The method of determining respiratory phase of claim 6 wherein the prior estimate of respiratory rate is provided by an external signal.

### Claim 9 (depends on 2)

The method of determining respiratory phase of claim 2 wherein the power spectral density estimates are determined using a Fourier transform method.