Time Modulated Apertures for Tomography in Nuclear Medicine
TL;DR: In this paper, a general theory for increasing the efficiency of such multiple view systems is presented, in which a particular modulating function is chosen according to the characteristics of the source being imaged.
Abstract: This paper presents techniques for overcoming the shortcomings inherent in known methods for imaging three-dimensional ?-ray sources as encountered in nuclear medicine. Conventional pinhole and collimator cameras have low efficiency and do not display depth information. Coded aperture systems have high photon collection efficiencies, but their noise performance is worse than that of conventional apertures for sources of interest. Multiple view systems, with either cone beam or transverse axial geometries, have low efficiencies. This paper presents a general theory for increasing the efficiency of such multiple view systems. Source dependent time-modulated apertures are used. In other words, a particular modulating function is chosen according to the characteristics of the source being imaged. A statistically optimal demodulating method is used. The final image is that of a chosen source plane, without the out-of-focus background produced by other imaging methods.
Citations
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01 Nov 1975
TL;DR: In this paper, a method is described for three dimensional reconstruction of axial tomographic images which removes the blurred off-plane activity from a number of transverse planes simultaneously, which can be applied to any tomographic camera, such as the multiple single-pinhole camera, the rotating slanted-hole collimator, the Anger focussing tomographic scanner, and the positron camera.
Abstract: A number of existing $gamma$ cameras for imaging of radioisotope distributions give depth information about the distribution. These devices have in common that they provide tomographic images of the object, that is, that images of a given object plane have that plane in focus and all other object planes contribute an out-of-focus background superimposed on the in-focus image. A method is described for three dimensional reconstruction of these axial tomographic images which removes the blurred off-plane activity from a number of transverse planes simultaneously. The method is applicable to a number of tomographic cameras, such as the multiple single-pinhole camera, the rotating slanted-hole collimator, the Anger focussing tomographic scanner, and the positron camera. The method can be implemented on a small computer having a disc system. (auth)
41 citations
TL;DR: The concept of alignment is introduced in which the aperture parameters are adjusted until the system is tuned to measure the given object class well, and may be applied to any linear imaging system.
Abstract: A strategy is given for the design of coded apertures with respect to a given class of objects that are to be imaged. Previous knowledge of the first- and second-order statistics for the object class is assumed. The object class is characterized by its Karhunen–Loeve eigenvectors and eigenvalues, whereas the imaging system is characterized by its singular-value decomposition. We introduce the concept of alignment in which the aperture parameters are adjusted until the system is tuned to measure the given object class well. A mean-square-error figure of merit that indicates degree of alignment is given, and alignment is performed by standard optimization techniques. We illustrate this technique with a simple proof-of-principle experiment. These concepts are general and may be applied to any linear imaging system.
29 citations
Dissertation•
01 Jan 2017
TL;DR: In this paper, the authors propose a method to improve the quality of the data collected by the data collection system. But the method is not suitable for large-scale data collection.
Abstract: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
15 citations
Cites background from "Time Modulated Apertures for Tomogr..."
...However, some improvement may be achieved by optimizing the mask design when the source extent is known [78, 79, 80]....
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01 Jan 1988
TL;DR: In this paper, the Begriff Emissions-Tomographie bedarf einer Erlauterung, da nicht eindeutig festliegt, where die flachige Szintigraphie aufhort and the Tomographie beginnt.
Abstract: Der Begriff Emissions-Tomographie bedarf einer Erlauterung, da nicht eindeutig festliegt, wo die flachige Szintigraphie aufhort und die Tomographie beginnt. Man konnte annehmen, das mit Einfuhrung des fokussierenden Vielloch-Kollimators beim szintigraphischen Scanner durch Newell et al. (1952) die Tomographie ihren Anfang genommen hat, denn in der Tat hat dieser Kollimator tomographische Eigenschaften. Er bildet eine bestimmte Objektschicht (Fokusebene) scharf ab, wahrend die davor und dahinter liegenden Schichten mehr oder weniger unscharf abgebildet werden. Dieser Effekt war anfanglich bei den damals ublichen NaJ(Tl)-Szintillationskristallen mit 2 Zoll Durchmesser relativ gering, wurde dann aber bei den gebrauchlichen 5 Zoll Kristallen und besonders bei kurzeren Fokusabstanden doch merklich. Trotzdem mochte ich diesen Scannern keine tomographischen Eigenschaften zuerkennen, denn diese Kollimatoren wurden entwickelt, um die Ausbeute gegenuber der einzelnen zylindrischen Bohrung ganz erheblich zu erhohen und nicht, um damit Tomographie zu betreiben. Im Gegenteil, diese fokussierende Eigenschaft storte eher bei der flachigen Szintigraphie, da sie dazu zwang, den Kollimator-Objekt-Abstand moglichst exakt zu wahlen. Auch wurde die raumliche Auflosung in den nicht fokussierten Schichten unnotigerweise schlecht.
12 citations
TL;DR: In this paper, the optimal values of the mean transmission of encoders as a function of the ratio of the statistical characteristics of the particular distribution of radiation sources under study and of the interference superimposed on the measurement are obtained.
Abstract: Encoders constructed on the base of (0, 1)-, (−1, 1)-, and (−1, 0, 1)-codes, tables, and matrices are compared on the basis of the general metrological criteria of A-, D-, and E-optimality taken from the mathematical theory of experimental design and the statistical properties of the sources under study. Optimal values of the mean transmission of encoders as a function of the ratio of the statistical characteristics of the particular distribution of radiation sources under study and of the interference superimposed on the measurement are obtained.
7 citations
References
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Book•
01 Jan 1968
TL;DR: This book shows engineers how to use optimization theory to solve complex problems with a minimum of mathematics and unifies the large field of optimization with a few geometric principles.
Abstract: From the Publisher:
Engineers must make decisions regarding the distribution of expensive resources in a manner that will be economically beneficial. This problem can be realistically formulated and logically analyzed with optimization theory. This book shows engineers how to use optimization theory to solve complex problems. Unifies the large field of optimization with a few geometric principles. Covers functional analysis with a minimum of mathematics. Contains problems that relate to the applications in the book.
5,667 citations
"Time Modulated Apertures for Tomogr..." refers methods in this paper
...This decoding can be represented by a real N X M matrix G so that (5)...
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01 Nov 1975
TL;DR: In this paper, a method is described for three dimensional reconstruction of axial tomographic images which removes the blurred off-plane activity from a number of transverse planes simultaneously, which can be applied to any tomographic camera, such as the multiple single-pinhole camera, the rotating slanted-hole collimator, the Anger focussing tomographic scanner, and the positron camera.
Abstract: A number of existing $gamma$ cameras for imaging of radioisotope distributions give depth information about the distribution. These devices have in common that they provide tomographic images of the object, that is, that images of a given object plane have that plane in focus and all other object planes contribute an out-of-focus background superimposed on the in-focus image. A method is described for three dimensional reconstruction of these axial tomographic images which removes the blurred off-plane activity from a number of transverse planes simultaneously. The method is applicable to a number of tomographic cameras, such as the multiple single-pinhole camera, the rotating slanted-hole collimator, the Anger focussing tomographic scanner, and the positron camera. The method can be implemented on a small computer having a disc system. (auth)
41 citations
TL;DR: In this article, a method for three dimensional reconstruction of axial tomographic images which removes the blurred off-plane activity from a number of transverse planes simultaneously is presented, which can be implemented on a small computer having a disc system.
Abstract: A number of existing cameras for Nuclear Medicine imaging of radio-isotope distributions give depth information about the distribution. These devices have in common that they provide tomographic images of the object, that is, that images of a given object plane have that plane in focus and all other object planes contribute an out-of-focus background superimposed on the in-focus image. We present here a method for three dimensional reconstruction of these axial tomographic images which removes the blurred off-plane activity from a number of transverse planes simultaneously. The method is applicable to a number of tomographic cameras, such as the multiple single-pinhole camera, the rotating slanted-hole collimator, the Anger focussing tomographic scanner, and the positron camera. The method can be implemented on a small computer having a disc system.
38 citations
TL;DR: A method is proposed and analyzed for gamma-ray imaging by stochastic time modulation and cross-correlation and it is seen to provide a theoretical basis for obtaining a smooth three-dimensional point response.
Abstract: The spatial distribution of a radioactive fluid can be measured indirectly by observing the emerging gamma rays. A method is proposed and analyzed for gamma-ray imaging by stochastic time modulation and cross-correlation. Theoretical comparison is made to collimation and coded aperture techniques in gamma-ray image formation. Computed results are presented that illustrate the mean response and statistical error characteristics of this technique. Monte Carlo simulations are performed as a further verification. Because it relies upon a point-by-point reconstruction, rather than upon the integral properties of any particular aperture, the time modulation approach is seen to provide a theoretical basis for obtaining a smooth three-dimensional point response.
27 citations
TL;DR: In this article, the length of the pseudorandom code is matched to the cylinder circumference so that its rotation provides a complete pseudorefandom time modulation for each source-detector combination.
Abstract: Tomographic images of gamma ray sources have been obtained by the use of a one-dimensional pseudorandom aperture and computerized digital reconstruction. The binary code is laid out on the surface of a cylinder. The source to be imaged must be located within the cylinder and detectors are placed outside and facing inward. The length of the code is matched to the cylinder circumference so that its rotation provides a complete pseudorandom time modulation for each source-detector combination. Counts from each detector are separately stored as a function of the rotation phase angle. Subsequent correlation computations give the reconstructed source intensity along any angle within the fan for each detector. Experimentally measured variances confirm the predictions of a theoretical analysis of the statistics of pseudorandom imaging given elsewhere. We have used only three detectors to date, but the scheme will easily accommodate a complete detector ring to maximize the photon counting efficiency and permit a full tomographic reconstruction of the section.
15 citations