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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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Correlation of In Vivo Micro-CT and Micro-SPECT Tumor Measurements with Ex Vivo Analysis. Mice with MV-NIS-injected BxPC-3 flank tumors (n=12) were imaged with 99mTcO4 pinhole micro-SPECT/CT. Immediately after imaging, mice were euthanized and tumors were excised, weighed, and counted in a dose calibrator. A, CT volume measured with region-of-interest software image analysis was highly correlated with ex vivo tumor mass (r2 = 0.977, p<0.0001). B, Micro-SPECT quantitation of tumor activity was highly correlated with ex vivo tumor activity (r2 = 0.966, p<0.0001).
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Figure 5: Correlation of In Vivo Micro-CT and Micro-SPECT Tumor Measurements with Ex Vivo Analysis. Mice with MV-NIS-injected BxPC-3 flank tumors (n=12) were imaged with 99mTcO4 pinhole micro-SPECT/CT. Immediately after imaging, mice were euthanized and tumors were excised, weighed, and counted in a dose calibrator. A, CT volume measured with region-of-interest software image analysis was highly correlated with ex vivo tumor mass (r2 = 0.977, p<0.0001). B, Micro-SPECT quantitation of tumor activity was highly correlated with ex vivo tumor activity (r2 = 0.966, p<0.0001).

Mentions: Up to this point, all experiments used 123I as the imaging isotope. In all subsequent imaging experiments with pinhole collimation, we used pertechnetate 99m (99mTcO4). Advantages of 99mTcO4 include 1) higher-resolution images due to lower scattering; 2) no special aerosol precautions for handling animals, cages, or ex vivo 99mTc-containing tissues (in contrast, iodide can be oxidized to volatile iodine); and 3) 99mTcO4 is less than 10% of the cost of 123I. In addition, the combination of 99mTc04 with pinhole collimation minimizes partial volume losses, which greatly simplifies in vivo quantitation of small tumors by pinhole micro-SPECT volume of interest (VOI) analysis. A strong correlation (p<0.0001) was observed for both micro-CT and pinhole-micro-SPECT VOI analysis in comparison to ex vivo measurements in a group of mice bearing BxPC-3 tumors ranging in size from 0.1 to 0.6 ccm (Figure 5).


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)

Correlation of In Vivo Micro-CT and Micro-SPECT Tumor Measurements with Ex Vivo Analysis. Mice with MV-NIS-injected BxPC-3 flank tumors (n=12) were imaged with 99mTcO4 pinhole micro-SPECT/CT. Immediately after imaging, mice were euthanized and tumors were excised, weighed, and counted in a dose calibrator. A, CT volume measured with region-of-interest software image analysis was highly correlated with ex vivo tumor mass (r2 = 0.977, p<0.0001). B, Micro-SPECT quantitation of tumor activity was highly correlated with ex vivo tumor activity (r2 = 0.966, p<0.0001).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3198860&req=5

Figure 5: Correlation of In Vivo Micro-CT and Micro-SPECT Tumor Measurements with Ex Vivo Analysis. Mice with MV-NIS-injected BxPC-3 flank tumors (n=12) were imaged with 99mTcO4 pinhole micro-SPECT/CT. Immediately after imaging, mice were euthanized and tumors were excised, weighed, and counted in a dose calibrator. A, CT volume measured with region-of-interest software image analysis was highly correlated with ex vivo tumor mass (r2 = 0.977, p<0.0001). B, Micro-SPECT quantitation of tumor activity was highly correlated with ex vivo tumor activity (r2 = 0.966, p<0.0001).
Mentions: Up to this point, all experiments used 123I as the imaging isotope. In all subsequent imaging experiments with pinhole collimation, we used pertechnetate 99m (99mTcO4). Advantages of 99mTcO4 include 1) higher-resolution images due to lower scattering; 2) no special aerosol precautions for handling animals, cages, or ex vivo 99mTc-containing tissues (in contrast, iodide can be oxidized to volatile iodine); and 3) 99mTcO4 is less than 10% of the cost of 123I. In addition, the combination of 99mTc04 with pinhole collimation minimizes partial volume losses, which greatly simplifies in vivo quantitation of small tumors by pinhole micro-SPECT volume of interest (VOI) analysis. A strong correlation (p<0.0001) was observed for both micro-CT and pinhole-micro-SPECT VOI analysis in comparison to ex vivo measurements in a group of mice bearing BxPC-3 tumors ranging in size from 0.1 to 0.6 ccm (Figure 5).

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