Method of and system for destreaking the photoelectric image in multi-energy computed tomography

• US 7,415,147 B2
• Filed: 06/04/2004
• Issued: 08/19/2008
• Est. Priority Date: 06/04/2004
• Status: Expired due to Fees

• Current Assignee: Analogic Corporation
• Original Assignee: Analogic Corporation
• Inventors: Crawford, Carl R., Simanovsky, Sergey, Ying, Zhengrong, Naidu, Ram
• Primary Examiner(s): AZARIAN, SEYED H
• Application Number:
  US10/860,984
• Publication Number:
  US 20050271293A1
• Time in Patent Office: 1,537 Days
• Field of Search: 382/100, 382/128, 382/129, 382/130, 382131-133, 382/168, 382/172, 382/203, 382/254, 382/255, 382/274, 382/275, 382/276, 382288-297, 382/318, 382/154, 382/232, 378/4, 378/21
• US Class Current: 382/132
• CPC Class Codes: G06T 2200/04 involving 3D image data
• CPC Class Codes: G06T 2207/10081 Computed x-ray tomography [CT]
• CPC Class Codes: G06T 2207/30112 Baggage; Luggage; Suitcase
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/77 Retouching; Inpainting; Scratch removal

Abstract

A method of and a system for destreaking the photoelectric image in multi-energy computed tomography are provided, wherein the photoelectric projections are generated from the projection data acquired using at least two x-ray spectra for scanned objects; wherein a neighboring scheme is provided; the method comprises computing the statistics including mean and standard deviation using the neighboring scheme; calculating an upper limit and a lower limit from the computed statistics; detecting outliers in the photoelectric projections using the upper and lower limits; and replacing values of outliers using the upper or lower limit.

Claims

1. A method of destreaking photoelectric images reconstructed from a set of three-dimensional photoelectric projection data points obtained from a two-dimensional detector array at multiple view angles in multi-energy X-ray computed tomography, wherein a neighboring scheme is provided, for each photoelectric projection data point, the method comprising:

A. Computing the mean and the standard deviation of the neighbors defined by the neighboring scheme;

B. Calculating an upper limit and a lower limit from the computed mean and standard deviation as a function of a pre-determined constant, including;

B1. Calculating a product of the standard deviation and the pre-determined constant;

B2. Calculating an upper limit as a function of adding the product calculated in Step B1 to the mean; and

B3. Calculating the lower limit as a function of subtracting the product calculated in Step B1 from the mean;

C. Detecting if said photoelectric projection data point is an outlier using the calculated upper and lower limits; and

D. Replacing the detected outliers with a replacement data point calculated as a function of said mean and standard deviation of said neighboring data points corresponding to the detected outlier.

2. The method of claim 1, wherein the said neighboring scheme includes determining six data points which are on the six surfaces of a three by three cube centered by said photoelectric projection data point.

3. The method of claim 1, wherein said replacements data point is the upper limit if the photoelectric value of the outlier point is greater than the upper limit and is the lower limits if the photoelectric value of the outlier point is less than the lower limit.

4. A system for destreaking photoelectric images reconstructed from a set of three-dimensional photoelectric projection data points obtained from a two-dimensional detector array at multiple view angles in multi-energy X-ray computed tomography, wherein a neighboring scheme is provided, the system comprising:

A. A computation subsystem constructed and arranged so as to compute the mean and the standard deviation of the neighbors defined by the neighboring scheme;

B. A calculation subsystem constructed and arranged so as to calculate an upper limit and a lower limit from the computed mean and standard deviation as a function of a pre-determined constant, the calculation subsystem being constructed and arranged so as to;

B1. Calculate a product of the standard deviation and the pre-determined constant;

B2. Calculate the upper limit by adding the product calculated in Step B1 to the mean; and

B3. Calculate the lower limit by subtracting the product calculated in Step B1 from the mean.

C. A detection subsystem constructed and arranged so as to detect whether said photoelectric projection data point is an outlier using the calculated upper and lower limits; and

D. A replacement subsystem is constructed and arranged so as to replace the detected outlier with a replacement projection data point calculated as a function of the mean and standard deviation of said neighboring data points corresponding to the detected outlier.

5. The system of claim 4, wherein the said neighboring scheme includes six data points which are on the six surfaces of a three by three cube centered by the photoelectric projection data point.

6. The system of claim 4, wherein said replacement projection data points is the upper limit if the photoelectric value of the outlier point is greater than the upper limit, and is the lower limit if the photoelectric value of the outlier point is less than the lower limit.