Master in Medical Physics 2015 to 2016

Imaging Instrumentation (SPECT) QC

Francisco J. Hernandez Flores

International Centre for Theoretical Physics

franciscohernandez_f2010@hotmail.com

December 25, 2015

Abstract

This task is relation to visit the Cattinara Hospital nuclear medicine area,the mean part of this practice was to now the layout of the nuclear medicine thestructure of the all room and your respective equipment used in cuality control ofimage. and discuses about which parameter affect the quality of image such as:differential and integral uniformity, spatial resolution, energy resolution, pixeldimension, intrinsic spatial resolution, intrinsic spatial linearity, intrinsic countrate, system sensitivity, system spatial resolution etc. are all calculated withreproducible methodology that allows the user reliable technique for creation ofthese standards to avoid any lack of clinical service that may violate the ethics ofpatient care. Because Tc-99m is the most frequently used radionuclide in nuclearmedicine, many clinics perform the daily uniformity and weekly resolution checksusing this radionuclide.

I. Introduction

The objective of this practice based in nuclear medicine layout and instrumenta-tion is to give basic knowledge at student based in nuclear medicine detailedquality control test procedures for the camera and computer system. Duringthe practice were described in detail: acceptance, reference and routine testsfor the camera, both in single and multiple head configurations, for obtainingimages and quantitative data in planar imaging mode; whole body imagingmode; and single-photon emission computed tomography (SPECT).

II. Theory

I. PLANAR INTRINSIC UNIFORMITY

Uniformity is a measure of a camera’s response to uniform irradiation of detec-tor surface; the ideal response is a perfectly uniform image (all pixels have thesame counts). [2]

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Master in Medical Physics 2015 to 2016

II. PIXEL DIMENSION.

Definition: The actual physical dimension of pixels.Evaluation of pixel dimension. draw on the image two profiles (along X andY directions) and evaluate the central position of the point sources. Evaluatethe distance (in pixel) along the x and y direction. [2]

Pixeldimension =200mm

Numbero f pixel(1)

Figure 1: Three sources (drops) of about 25 MBq. for evaluate pixel dimension

III. INTRINSIC SPATIAL RESOLUTION

Definition. The ability to accurately distinguish as separate two close radioac-tive (point or linear) sources. The pixel dimension is the physical size of thesmallest element in the image obtained by a specific sampling frequency (ma-trix). The spatial resolution is never < pixel dimension. [2]Evaluation. the calculated average values of FWHM and FWTM for both axes,lying within UFOV and CFOV.

IV. INTRINSIC SPATIAL LINEARITY

Definition. The ability to portray the shape of objects accurately, i.e. the amountof positional distortion or displacement of the measured position of a sourcerelative to the actual position. [2]Evaluation.

• Differential linearity: Standard deviation of the distance of peaks of thefitted LSF (Line Spread Function) from the straight line fitting the slitimage.

• Integral Linearity: maximum distance of peaks of the fitted LSF (LineSpread Function) from the straight line fitting the slit image.

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Master in Medical Physics 2015 to 2016

III. Materials and Methods

During this practice were discuses two point patient management and qualityassurance of gamma cameras.

1. Patient management.The layout of the department of Nuclear medicine.

• Different rooms, patient path, staff path, radiation protection criteria.

Radio pharmaceutical preparation room.

• The manipulation cell, the activity calibrator.

• Calibration quality control.

2. Quality assurance of gamma cameras.Scintigraphic examination room

• Acquisition console, gamma camera, collimator.

• Test objects and phantom.

Practice gamma camera quality control.

• Intrinsic and system test.

• Intrinsic uniformity and sensitivity according to NEMA protocol

(a) Gamma camera (b) Phantom

(c) ionization camera (d) Phantom pixel dimension

Figure 2: Instrument used for quality control in Gamma Camera

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Master in Medical Physics 2015 to 2016

Figure 3: layout nuclear medicine of the Catinara Hospital [1]

IV. discussion and results

This practice was qualitative not quantitative. The discussion during this prac-tice was about how to use adequate instrumentation, and different equipmentthat to use for quality control of gamma camera.

And during the practice talked about each test for quality control of imagehow we can measure or obtaine each parameter in quality control of image suchas: Pixel dimension, Uniformity, intrinsic spatial resolution, intrinsic spatiallinearity and intrinsic counter rate.

The count density (counts per pixel) has a significant impact on image qual-ity. Spatial resolution and lesion detectability are reduced in low-count densityimages.

In the case of Pixel dimension they use a sheet of plexiglass with three holes

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Master in Medical Physics 2015 to 2016

in the edges of a square of 200 mm they obtain pixel dimension see fig.1 andthis image obtained is processed with software osiris or imagej the pixcel sizecan calculate using the equation 1

V. Conclusion

• This report has briefly commentary the the practical in Cattinara Hospitalin nuclear medicine department about routine QC procedures of currentnuclear medicine instrumentation, including dose calibrator, well counter,SPECT and SPECT/CT scanner, this training practice is very useful forour knowledge like medical physicist.

References

[1] Dedenaro, Lecture Radiation protection Italian law , Mageore Hospital TriesteItaly, 3rd trimester 2015.

[2] Formasier M.R, Lecture Nuclear Medicine , ICTP, Trieste Italy, 3rd trimester2015.

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