Quantification of Nuclear Medicine Image Data

Abstract

A novel technique of quantifying nuclear medicine data is provided. The novel technique is characterized in that information acquired from nuclear medicine image data is normalized with bone mineral content (BMC) or bone mineral density (BMD). Some embodiments use, instead of the conventional SUV, the SUVbone that has been invented by the inventors of the present application such as the following: SUVbone={Amount of attenuation-corrected radioactivity in region of interest (kBq)÷Volume of region of interest (ml)}/{Administered radioactivity dose (kBq)÷Bone mineral content (g)} or SUVbone={Amount of attenuation-corrected radioactivity in region of interest (kBq)÷Volume of region of interest (ml)}/{Administered radioactivity dose (kBq)÷Bone mineral density (g/m.sup.2)}. BMC or BMD may be estimated from sex, age, height, or weight of a subject.

Claims

1-7. (canceled)

8. A computer program on a non-transitory medium comprising a program instruction that causes, when executed by processing means of a system, the system to perform: loading nuclear medicine image data acquired using a bone disease diagnostic agent; loading information on a radioactivity dose administered to a subject of the nuclear medicine image data; loading information on bone mineral content or bone mineral density of the subject; acquiring certain information from the nuclear medicine image data; normalizing the certain information based on the information on the administered radioactivity dose, and the bone mineral content or the bone mineral density; and outputting the normalized information, the certain information being a value obtained by dividing an amount of attenuation-corrected radioactivity in a region of interest by a volume of the region of interest.

9. A method comprising: loading nuclear medicine image data acquired using a bone disease diagnostic agent; loading sex information on a subject of the nuclear medicine image data; loading age information on the subject; loading height information on the subject; loading weight information on the subject; loading information on a radioactivity dose administered to the subject; acquiring certain information from the nuclear medicine image data; calculating bone mineral content or bone mineral density based on at least one of the sex information, the age information, the height information, or the weight information; normalizing the certain information based on the information on the administered radioactivity dose, and the bone mineral content or the bone mineral density; and outputting the normalized information, the certain information being a value obtained by dividing an amount of attenuation-corrected radioactivity in a region of interest by a volume of the region of interest.

10. The method according to claim 9, wherein the region of interest is a region corresponding to one pixel in the nuclear medicine image data.

11. The method according to claim 9, further comprising integrating the normalized information and outputting an integrated value based upon the integrated normalized information.

12. The method according to claim 9, wherein the normalized information is SUVbone that is a value defined by the following:
SUVbone={Amount of attenuation-corrected radioactivity in region of interest÷Volume of region of interest}/{Administered radioactivity dose÷Bone mineral content},
or
SUVbone={Amount of attenuation-corrected radioactivity in region of interest÷Volume of region of interest}/{Administered radioactivity dose÷Bone mineral density}.

13. A non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: loading nuclear medicine image data acquired using a bone disease diagnostic agent; loading sex information on a subject of the nuclear medicine image data; loading age information on the subject; loading height information on the subject; loading weight information on the subject; loading information on a radioactivity dose administered to the subject; acquiring certain information from the nuclear medicine image data; calculating bone mineral content or bone mineral density based on at least one of the sex information, the age information, the height information, or the weight information; normalizing the certain information based on the information on the administered radioactivity dose, and the bone mineral content or the bone mineral density; and outputting the normalized information, the certain information being a value obtained by dividing an amount of attenuation-corrected radioactivity in a region of interest by a volume of the region of interest.

14. The non-transitory program storage device as in claim 13 where the region of interest is a region corresponding to one pixel in the nuclear medicine image data.

15. The non-transitory program storage device as in claim 13 where the operations comprise integrating the normalized information and outputting an integrated value corresponding to the integrated normalized information.

16. The non-transitory program storage device as in claim 13 where the normalized information is SUVbone that is a value defined by the following:
SUVbone={Amount of attenuation-corrected radioactivity in region of interest÷Volume of region of interest}/{Administered radioactivity dose÷Bone mineral content}, or
SUVbone={Amount of attenuation-corrected radioactivity in region of interest±Volume of region of interest}/{Administered radioactivity dose±Bone mineral density}.

17. An apparatus comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: load nuclear medicine image data acquired using a bone disease diagnostic agent; load sex information on a subject of the nuclear medicine image data; load age information on the subject; load height information on the subject; load weight information on the subject; load information on a radioactivity dose administered to the subject; acquire certain information from the nuclear medicine image data; calculate bone mineral content or bone mineral density based on at least one of the sex information, the age information, the height information, or the weight information; normalize the certain information based on the information on the administered radioactivity dose, and the bone mineral content or the bone mineral density; and output the normalized information, the certain information being a value obtained by dividing an amount of attenuation-corrected radioactivity in a region of interest by a volume of the region of interest.

18. The apparatus as in claim 17 where the region of interest is a region corresponding to one pixel in the nuclear medicine image data.

19. The apparatus as in claim 17 where the apparatus is configured to integrate the normalized information and outputting an integrated value corresponding to the integrated normalized information.

20. The apparatus as in claim 17 where the normalized information is SUVbone that is a value defined by the following:
SUVbone={Amount of attenuation-corrected radioactivity in region of interest÷Volume of region of interest}/{Administered radioactivity dose÷Bone mineral content}, or
SUVbone={Amount of attenuation-corrected radioactivity in region of interest÷Volume of region of interest}/{Administered radioactivity dose÷Bone mineral density}.

21. An apparatus for outputting a quantitative value of nuclear medicine image data acquired using a bone disease diagnostic agent, the apparatus comprising: at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: load the nuclear medicine image data; load information on a radioactivity dose administered to a subject of the nuclear medicine image data; load information on bone mineral content or bone mineral density of the subject; acquire certain information from the nuclear medicine image data; normalize the certain information based on the information on the radioactivity dose administered to the subject and the bone mineral content or the bone mineral density; and output one or more values corresponding to the normalized certain information, where the certain information is a value obtained by dividing an amount of attenuation-corrected radioactivity in a region of interest by a volume of the region of interest.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0063] FIG. 1 is a graph illustrating that the SUV has age dependency in diagnosis of bone metastases using a nuclear medicine technique.

[0064] FIG. 2A is a graph illustrating that the SUVbone (using BMC) developed by the inventors of the present application indicates no age dependency.

[0065] FIG. 2B is a graph illustrating that the SUVbone (using BMD) developed by the inventors of the present application indicates no age dependency.

[0066] FIG. 3 is an explanatory diagram of a system configuration that can embody the present invention.

[0067] FIG. 4 is an explanatory diagram of exemplary processing according to the present invention.

DESCRIPTION OF EMBODIMENTS

[0068] FIG. 3 is a diagram illustrating a main configuration of an apparatus or a system 100, which is exemplary hardware capable of executing various processes disclosed in the present description. As illustrated in FIG. 3, the system 100 is similar to a general-purpose computer in terms of hardware, and may include a central processing unit (CPU) 102, a main memory 104, an auxiliary storage unit 106, a display interface 107, a peripheral device interface 108, and a network interface 109, for example. Similarly to a general-purpose computer, a high-speed random access memory (RAM) may be used as the main memory 104, and an inexpensive, large-capacity hard disk or a solid state disk (SSD) may be used as the auxiliary storage unit 106. To the system 100, a display for displaying information may be connected through the display interface 107. Also to the system 100, a user interface such as a keyboard, a mouse, or a touch panel may be connected through the peripheral device interface 108. The network interface 109 may be used to connect the system 100 to another computer or the Internet via a network.

[0069] The auxiliary storage unit 106 may store therein, for example, an operating system (OS) 110 and an analysis program 120 for providing characteristic processes disclosed in the present description. The most basic functions of the system 100 are provided when the CPU 102 executes the OS 110.

[0070] In addition, novel processes disclosed in the present description are provided when the CPU 102 executes the analysis program 120. A program instruction group constructing the analysis program 120 may be programmed in any of existing computer program languages such as C++ and JAVA (registered trademark). The program instruction group may be converted to an executable format by a preferred compiler and stored in the auxiliary storage unit 106.

[0071] The auxiliary storage unit 106 may store therein, for example, nuclear medicine image data 132 subject to an analysis by the analysis program 120, measurement condition data 134 containing various measurement conditions of the nuclear medicine image data 132, data 136 containing information calculated during processes, and data 138 containing results of the processes.

[0072] Other than the components illustrated in FIG. 3, the system 100 may include the same units as those of a general computer system, such as a power source and a cooling unit. Various embodiments of a computer system employing various techniques have been known, such as distributed, redundant, or virtualized storage units, use of multiple CPUs, CPU virtualization, use of a processor suitable for a specific process such as digital signal processing (DSP), and implementation of a specific process as hardware to be used with a CPU. The matters disclosed in the present description may be implemented in any form of computer system. The form of computer system does not limit the scope of the present invention. The matters disclosed in the present description may generally be embodied as: (1) a computer program containing an instruction configured to cause, when executed by processing means, an apparatus or a system including the processing means to execute various processes described in the present description; (2) a method for operating the apparatus or the system, the method being performed when the processing means executes the computer program; and (3) the apparatus or the system including the computer program and the processing means configured to execute the computer program.

[0073] Note that the pieces of data 132 to 138 are not stored in the auxiliary storage unit 106 in many cases at the time of manufacture, sales, and initial start-up of the system 100. These pieces of data may be transferred from an external apparatus to the system 100 through the network interface 109, for example. In some embodiments, the pieces of data 136 and 138 may be generated and stored when the CPU 102 executes the computer program 120 or other computer programs. In some embodiments of the computer program 120 or the OS 110, the pieces of data 136 and 138 are stored only in the main memory 104 instead of being stored in the auxiliary storage unit 106. In some cases, the data 134 is combined with the data 132, so that the data 134 does not exist as an individual data file. Note that the scope of the present invention is not limited by the existence of the pieces of data 132 to 138.

[0074] The following describes the nuclear medicine image data 132 subject to an analysis in an example. The nuclear medicine image data 132 may be image data acquired by PET measurement for diagnosis of bone metastases or other purposes. For example, the nuclear medicine image data 132 may be image data generated on the basis of radiation count values acquired by administering .sup.18F-NaF as a radiopharmaceutical to a subject, and detecting radiation emitted from within the subject's body with a PET apparatus. In general, each pixel has a value corresponding to a radioactivity count value; that is, each pixel value indicates the intensity of radioactivity. Note that possible nuclear medicine image data subject to an analysis according to the present invention is not limited to PET images acquired using .sup.18F-NaF. Various nuclear medicine images (PET images, SPECT images, and scintigraphy images) acquired using other radiopharmaceuticals (e.g., Technetium (.sup.99mTc) Hydroxymethylenediphosphonate Injection, Technetium (.sup.99mTc) Methylenediphosphonate Injection) may be subject to an analysis according to the present invention.

[0075] The measurement condition data 134 contains various conditions regarding PET measurement on the basis of which PET images contained in the nuclear medicine image data 132 have been created. The conditions contained in the measurement condition data 134 preferably include at least sex, age, height, and weight of a subject, and also the amount of administered radiopharmaceutical. In some cases, the content of the measurement condition data 134 is contained in the nuclear medicine image data 132, so that the measurement condition data 134 does not exist as an individual data file. In some embodiments, at least one of the conditions contained in the measurement condition data 134 may be input by a user with a keyboard or other devices connected to the peripheral device interface 108. In some embodiments, the measurement condition data 134 may be stored on the main memory 104 instead of the auxiliary storage unit 106.

[0076] The following describes characteristic processes in a preferred example with reference to FIG. 4. These processes may be performed by the system 100 when the CPU 102 executes the analysis program 120.

[0077] Step 200 indicates the start of processing. In step 202, at least part of the nuclear medicine image data 132 is copied to the main memory 104 for preparation of an analysis process to be performed by the analysis program 120.

[0078] In step 204, information on measurement conditions on the nuclear medicine image data 132, such as an administered radioactivity dose, is acquired. In one example, this step is performed by loading the measurement condition data 134. In another example, this step is performed by loading information on various conditions contained in the nuclear medicine image data 132. In still another example, various conditions may be input with a keyboard or other devices connected through the peripheral device interface 108. In this case, according to an instruction from the analysis program 120, the CPU 102 may cause, through the display interface 107, a display connected to the display interface 107 to display a message for prompting input of a measurement condition. In some embodiments, the information on measurement conditions acquired in step 204 may include information on a subject (sex, age, weight, height, or other attributes) of the nuclear medicine image data 132.

[0079] In step 206, bone mineral content (BMC) or bone mineral density (BMD) is calculated. BMC or BMD can be estimated from sex, age, height, or weight of a subject. A prior research has been conducted specifically on Japanese people using databases (for example, European Journal of Clinical Nutrition (2001) 55, pp. 462-470). According to this document, BMC and BMD can be estimated by the following formulas:

Bone mineral content (Male: kg)=−1.81−0.0015×Age+1.89×Height+0.017×Weight

Bone mineral content (Female: kg)=−1.05−0.009×Age+1.57×Height+0.017×Weight

Bone mineral density (Male: g/m.sup.2)=0.934−0.00081×Age+0.003×Weight

Bone mineral density (Female: g/m.sup.2)=0.824−0.00368×Age+0.137×Height+0.0026×Weight

[0080] In these formulas, the unit of age is year, the unit of weight is kilogram (kg), and the unit of height is meter (m).

[0081] In the present example, the analysis program 120 contains therein these formulas and is configured to control the CPU 102 to substitute, into these formulas, the information on the sex, age, height, and weight of a subject acquired in step 204 and to calculate the bone mineral content BMC and the bone mineral density BMD. In some embodiments, the calculated BMC and/or BMD may be stored, as the data 136 for example, on the auxiliary storage unit 106 or the main memory 104 for example.

[0082] Step 208 indicates a phase at which certain information is obtained from the nuclear medicine image data 132. In later steps, this information is normalized with the BMC or the BMD (step 210), and output as a map or a numeric value (step 214). The information acquired in step 208 may vary depending on embodiments. In one embodiment, the information is the pixel value of each pixel. In this case, the data has already been loaded in step 202, and thus step 208 is unnecessary. In some embodiments, the information acquired in step 208 may be the radioactivity concentration of each pixel. In this case, in step 208, each pixel value in the image data 132 may be multiplied by a certain factor, such as the reciprocal of the volume of the pixel, in order to convert the pixel value of each pixel to radioactivity concentration.

[0083] In some embodiments, in step 208, correction may be performed to correct the pixel value (count) of each pixel in the nuclear medicine image data 132. This correction may correct the effect of absorption or scatter of radiation within the body, and the attenuation of radioactivity due to the decay of radionuclide. These corrections have generally been performed in nuclear medicine techniques, and thus the detail of the corrections is not described here. In some embodiments, the nuclear medicine image data 132 may have been subjected to such corrections.

[0084] In some embodiments, in step 208, calculation may be performed on the radioactivity count value of a region including a plurality of pixels, or the radioactivity concentration of a region including a plurality of pixels (that is, a value obtained by dividing the radioactivity dose in a region including a plurality of pixels by the volume of the region). These values may be subjected to the attenuation correction described above.

[0085] In some embodiments, in step 208, a plurality of pieces of information may be calculated. For example, two or more types of information (values) may be calculated out of the radioactivity count value of each pixel, the radioactivity concentration of each pixel, the radioactivity count value of a region including a plurality of pixels, and the radioactivity concentration of a region including a plurality of pixels. These value's may be subjected to the attenuation correction described above.

[0086] In step 210, the information acquired in step 208 is normalized. Specifically, the information (value) acquired in step 208 is subjected to division, that is, (Administered radioactivity dose BMC) or (Administered radioactivity dose BMD), where the administered radioactivity dose is the value acquired in step 204, and the BMC or the BMD is the value acquired in step 206. In some embodiments, the units of the administered radioactivity dose, the BMC, and the BMD may be changed as appropriate.

[0087] When the information acquired in step 208 is attenuation-corrected radioactivity concentration for example, then a value obtained by the normalization process in step 210 is the SUVbone defined by formula 2 or 3.

[0088] The value normalized in step 210 is output in step 214. In some embodiments, an additional process may be performed before the output. FIG. 4 illustrates such an optional process in step 212. For example, when the information acquired in step 208 is the attenuation-corrected radioactivity concentration of each pixel, which is normalized in step 210 (that is, SUVbones are calculated in step 210), SUVbones in a region of interest including a plurality of pixels may be integrated in step 212.

[0089] In step 214, the values calculated in step 210 and/or 212 are output. The output may include visualizing and displaying the values calculated in step 210 and/or 212, and/or displaying the values as numeric values. Alternatively, the output may include storing the values as the data 138 on the auxiliary storage unit 106.

[0090] When the values calculated in step 210 are the normalized radioactivity concentration of respective pixels (that is, SUVbones of respective pixels), these values can be displayed as an image in a map view similarly to a tomogram. When the normalized attenuation-corrected radioactivity concentration of a region including a plurality of pixels is calculated in step 210 or 212, it may be displayed as a value. In some embodiments, a map of normalized values of respective pixels and a normalized value of a region of interest may be displayed together. The display may be performed on, for example, a display connected to the display interface 107.

[0091] Step 220 indicates the end of the processing.

[0092] Embodiments of the present invention have been described with reference to preferred examples; however, the description of these examples are not intended to limit the scope of the present invention, but intended to satisfy the requirements of the Patent Law and to contribute to the understanding of the present invention. The present invention can be embodied in various forms, and embodiments of the present invention include a number of variations other than the embodiments exemplified herein. The present invention is applicable to nuclear medicine images (PET images, SPECT images, and scintigraphy images) acquired using various radiopharmaceuticals other than the PET images acquired using .sup.18F-NaF described above.

[0093] Individual features included in various examples that have been described in the description are not limited to usage with examples in which these features are explicitly explained to be included, but may be used in combination with other examples that have been described herein or various specific embodiments that have not been described. In particular, the processes presented in the flowchart do not necessarily need to be performed in the described order. According to the preference of an executor, the processes may be performed in a changed order or in parallel, as a plurality of blocks integrally implemented or in a manner divided to a plurality of sub-blocks, or in a loop as appropriate. In some embodiments, some of the blocks in the flowchart may be omitted. For example, step 212 may be unnecessary for some embodiments as described above. In other cases, BMC or BMD has already been calculated for some embodiments, and thus recalculation of the BMC or the BMD in step 206 may be unnecessary. The BMC and the BMD may be values separately measured by known methods. Quantification of BMC and BMD may be performed by various known methods (for example, the method described in “SHIKAHOUSHASEN (Dental Radiology), Volume 18 (1978) pp. 278 to 295”) other than generally known methods using bone mineral quantification devices. In this case, step 206 can be replaced with a loading process of BMC or BMD. These variations are all included in the scope of the present invention. The order of the description of the processes defined in the claims does not necessarily specify the mandatory order of the processes. For example, an embodiment specifying a different order of the processes and an embodiment that executes the processes in a loop are also included in the scope of the present invention according to the claims. It should be noted that the applicants claim to possess the right to have a patent granted on all the embodiments not deviating from the spirit of the present invention regardless of whether a patent is claimed in the current set of attached claims.

REFERENCE SIGNS LIST

[0094] 100 system [0095] 102 CPU [0096] 104 main memory [0097] 106 auxiliary storage unit [0098] 107 display interface [0099] 108 peripheral device interface [0100] 109 network interface [0101] 110 OS [0102] 120 analysis program