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Pinhole micro-SPECT/CT for noninvasive monitoring and quantitation of oncolytic virus dispersion and percent infection in solid tumors.

Penheiter AR, Griesmann GE, Federspiel MJ, Dingli D, Russell SJ, Carlson SK - Gene Ther. (2011)

Bottom Line: The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS).We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions.Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS). Sodium iodide symporter (NIS) RNA level and dispersion pattern were determined in control and MV-NIS-infected BxPC-3 pancreatic tumor cells and mouse xenografts using quantitative, real-time, reverse transcriptase, polymerase chain reaction, autoradiography and immunohistochemistry (IHC). Mice with BxPC-3 xenografts were imaged with (123)I or (99)TcO(4) micro-SPECT/CT. Tumor dimensions and radionuclide localization were determined with imaging software. Linear regression and correlation analyses were performed to determine the relationship between tumor infection percentage and radionuclide uptake (% injected dose per gram) above background and a highly significant correlation was observed (r(2)=0.947). A detection threshold of 1.5-fold above the control tumor uptake (background) yielded a sensitivity of 2.7% MV-NIS-infected tumor cells. We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions. Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

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Comparison of Manual Region-of-Interest Analysis and Automated Threshold Pixel Analysis. Images of immunohistochemically stained sections of 5 MV-NIS–infected tumors were quantified manually with region-of-interest analysis (A) or automated threshold pixel analysis (B). The mean recovery coefficient of the automated analysis for 10 randomly selected images (mean 0.396 ± 0.09 × the manual ROI) was used to correct for nonuniformity of staining within MV-NIS–infected syncytia. Black arrows show nucleoli used to establish the image threshold; the white arrow denotes a region in the center of a syncytium that is weakly stained and below the designated threshold. MV-NIS denotes measles virus expressing sodium iodide symporter.
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Figure 3: Comparison of Manual Region-of-Interest Analysis and Automated Threshold Pixel Analysis. Images of immunohistochemically stained sections of 5 MV-NIS–infected tumors were quantified manually with region-of-interest analysis (A) or automated threshold pixel analysis (B). The mean recovery coefficient of the automated analysis for 10 randomly selected images (mean 0.396 ± 0.09 × the manual ROI) was used to correct for nonuniformity of staining within MV-NIS–infected syncytia. Black arrows show nucleoli used to establish the image threshold; the white arrow denotes a region in the center of a syncytium that is weakly stained and below the designated threshold. MV-NIS denotes measles virus expressing sodium iodide symporter.

Mentions: Next, we compared manually determined volumes with a quantitative technique that applied automated threshold pixel analysis (Figure 3). For consistency, the image threshold was set such that the nucleoli (stained only with hematoxylin) were just below the threshold. Immunohistochemical (IHC) staining of individual syncytium on frozen sections showed a patchy distribution of colorimetric precipitate. This nonuniform staining caused the image analysis software to underestimate the syncytial area. Fortunately, the underestimate was very consistent among syncytia; the true infected area could be approximated by applying a recovery coefficient to the software measurement. After evaluating 10 representative automated threshold images, we determined the mean ± SD recovery coefficient was 0.396 ± 0.09.


Pinhole micro-SPECT/CT for noninvasive monitoring and quantitation of oncolytic virus dispersion and percent infection in solid tumors.

Penheiter AR, Griesmann GE, Federspiel MJ, Dingli D, Russell SJ, Carlson SK - Gene Ther. (2011)

Comparison of Manual Region-of-Interest Analysis and Automated Threshold Pixel Analysis. Images of immunohistochemically stained sections of 5 MV-NIS–infected tumors were quantified manually with region-of-interest analysis (A) or automated threshold pixel analysis (B). The mean recovery coefficient of the automated analysis for 10 randomly selected images (mean 0.396 ± 0.09 × the manual ROI) was used to correct for nonuniformity of staining within MV-NIS–infected syncytia. Black arrows show nucleoli used to establish the image threshold; the white arrow denotes a region in the center of a syncytium that is weakly stained and below the designated threshold. MV-NIS denotes measles virus expressing sodium iodide symporter.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198860&req=5

Figure 3: Comparison of Manual Region-of-Interest Analysis and Automated Threshold Pixel Analysis. Images of immunohistochemically stained sections of 5 MV-NIS–infected tumors were quantified manually with region-of-interest analysis (A) or automated threshold pixel analysis (B). The mean recovery coefficient of the automated analysis for 10 randomly selected images (mean 0.396 ± 0.09 × the manual ROI) was used to correct for nonuniformity of staining within MV-NIS–infected syncytia. Black arrows show nucleoli used to establish the image threshold; the white arrow denotes a region in the center of a syncytium that is weakly stained and below the designated threshold. MV-NIS denotes measles virus expressing sodium iodide symporter.
Mentions: Next, we compared manually determined volumes with a quantitative technique that applied automated threshold pixel analysis (Figure 3). For consistency, the image threshold was set such that the nucleoli (stained only with hematoxylin) were just below the threshold. Immunohistochemical (IHC) staining of individual syncytium on frozen sections showed a patchy distribution of colorimetric precipitate. This nonuniform staining caused the image analysis software to underestimate the syncytial area. Fortunately, the underestimate was very consistent among syncytia; the true infected area could be approximated by applying a recovery coefficient to the software measurement. After evaluating 10 representative automated threshold images, we determined the mean ± SD recovery coefficient was 0.396 ± 0.09.

Bottom Line: The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS).We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions.Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine, Mayo Clinic, Rochester, MN 55905, USA.

ABSTRACT
The purpose of our study was to validate the ability of pinhole micro-single-photon emission computed tomography/computed tomography (SPECT/CT) to: 1) accurately resolve the intratumoral dispersion pattern and 2) quantify the infection percentage in solid tumors of an oncolytic measles virus encoding the human sodium iodide symporter (MV-NIS). Sodium iodide symporter (NIS) RNA level and dispersion pattern were determined in control and MV-NIS-infected BxPC-3 pancreatic tumor cells and mouse xenografts using quantitative, real-time, reverse transcriptase, polymerase chain reaction, autoradiography and immunohistochemistry (IHC). Mice with BxPC-3 xenografts were imaged with (123)I or (99)TcO(4) micro-SPECT/CT. Tumor dimensions and radionuclide localization were determined with imaging software. Linear regression and correlation analyses were performed to determine the relationship between tumor infection percentage and radionuclide uptake (% injected dose per gram) above background and a highly significant correlation was observed (r(2)=0.947). A detection threshold of 1.5-fold above the control tumor uptake (background) yielded a sensitivity of 2.7% MV-NIS-infected tumor cells. We reliably resolved multiple distinct intratumoral zones of infection from non-infected regions. Pinhole micro-SPECT/CT imaging using the NIS reporter demonstrated precise localization and quantitation of oncolytic MV-NIS infection, and can replace more time-consuming and expensive analyses (for example, autoradiography and IHC) that require animal killing.

Show MeSH
Related in: MedlinePlus