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SPECT/CT localization of oral radioiodine activity: a retrospective study and in-vitro assessment.

Burlison JS, Hartshorne MF, Voda AM, Cocks FH, Fair JR - Nucl Med Commun (2013)

Bottom Line: Despite subsequent washings with normal saline, significant 131I activity (maximally 12% for amalgam and 68% for Argenco HP 77) was retained by these metals.Subsequent soaking in a saturated solution of potassium iodide partially displaced 131I from amalgam, with near-total displacement of I from Argenco HP 77.Furthermore, in-vitro studies demonstrate partially reversible binding of 131I to common dental metals.

View Article: PubMed Central - PubMed

Affiliation: aDepartment of Radiology, University of New Mexico bPrivate Practice, Albuquerque, New Mexico cDepartment of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina, USA.

ABSTRACT

Purpose: We sought to further localize radioiodine activity in the mouth on post-thyroid cancer therapy imaging using single-photon emission computed tomography/computed tomography (SPECT/CT).

Materials and methods: We retrospectively reviewed all patients (58) who underwent thyroid cancer therapy with iodine-131 (131I) at our institution from August 2009 to March 2011 whose post-therapy radioiodine imaging included neck SPECT/CT. A small group (six) of diagnostic 131I scans including SPECT/CT was also reviewed. Separately, we performed in-vitro 131I (sodium iodide) binding assays with amalgam and Argenco HP 77 (77% dental gold alloy) as proof of principle for these interactions.

Results: Of the 58 post-therapy patients, 45 (78%) had undergone metallic dental restorations, and of them 41 (91%) demonstrated oral 131I activity localizing preferentially to those restorations. It was observed that radioiodine also localized to other dental restorations and to orthodontic hardware. Gum-line activity in edentulous patients suggests radioiodine interaction with denture adhesive. In vitro, dental amalgam and Argenco HP 77 bound 131I in a time-dependent manner over 1-16 days of exposure. Despite subsequent washings with normal saline, significant 131I activity (maximally 12% for amalgam and 68% for Argenco HP 77) was retained by these metals. Subsequent soaking in a saturated solution of potassium iodide partially displaced 131I from amalgam, with near-total displacement of I from Argenco HP 77.

Conclusion: SPECT/CT shows that radioiodine in the oral cavity localizes to metallic dental restorations. Furthermore, in-vitro studies demonstrate partially reversible binding of 131I to common dental metals.

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Post-therapeutic SPECT/CTs of the neck showing 131I localizing to metallic dental restorations. The left column contains axial CT images through the oral cavity; the right column contains the corresponding axial SPECT/CT fused images. (a, b) Bilateral beam hardening artifact associates with bilateral molar metallic dental restorations, localizing symmetric radioiodine activity. (c, d) Bilateral metallic beam hardening artifact associates with bilateral mandibular dental restorations, greater on the left, with asymmetric (left greater than right) radioiodine localization. (e, f) Metallic orthodontic appliances localizing radioiodine activity, most intensely to circumferential metallic molar bands. (g, h) No metallic dental restorations or evidence of prior dental procedures, with nonlocalizing, low-level oral radioiodine uptake. (i, j) Molar restorations without metallic beam hardening artifact demonstrate nonlocalizing, low-level oral radioiodine uptake. SPECT/CT, single-photon emission computed tomography/computed tomography.
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Figure 1: Post-therapeutic SPECT/CTs of the neck showing 131I localizing to metallic dental restorations. The left column contains axial CT images through the oral cavity; the right column contains the corresponding axial SPECT/CT fused images. (a, b) Bilateral beam hardening artifact associates with bilateral molar metallic dental restorations, localizing symmetric radioiodine activity. (c, d) Bilateral metallic beam hardening artifact associates with bilateral mandibular dental restorations, greater on the left, with asymmetric (left greater than right) radioiodine localization. (e, f) Metallic orthodontic appliances localizing radioiodine activity, most intensely to circumferential metallic molar bands. (g, h) No metallic dental restorations or evidence of prior dental procedures, with nonlocalizing, low-level oral radioiodine uptake. (i, j) Molar restorations without metallic beam hardening artifact demonstrate nonlocalizing, low-level oral radioiodine uptake. SPECT/CT, single-photon emission computed tomography/computed tomography.

Mentions: Of the 58 post-therapy patients imaged, 45 (78%) showed metallic dental restorations on CT, typically with a beam hardening artifact, and of them 41 (91%) demonstrated oral 131I activity localized to the restorations. In patients with bilateral restorations, activity was typically bilateral (Fig. 1a and b), although sometimes asymmetric (Fig. 1c and d). In patients with unilateral metallic dental restorations, the 131I activity typically localized to that side. Similar to 131I, 123I localized to metallic dental restorations when present (not shown). Radioiodine (131I and 123I) also localized to other metallic appliances such as braces, palate expanders, and tongue piercings (Fig. 1e and f, and additional data not shown). As alluded to above, four patients with metallic dental restorations did not demonstrate localizing oral radioiodine activity. In our study, which is a retrospective review, the compositions of the patient’s restorations are unknown. It is possible that some dental metals are not radioiodine avid, a hypothesis that could be tested but is beyond the scope of this study.


SPECT/CT localization of oral radioiodine activity: a retrospective study and in-vitro assessment.

Burlison JS, Hartshorne MF, Voda AM, Cocks FH, Fair JR - Nucl Med Commun (2013)

Post-therapeutic SPECT/CTs of the neck showing 131I localizing to metallic dental restorations. The left column contains axial CT images through the oral cavity; the right column contains the corresponding axial SPECT/CT fused images. (a, b) Bilateral beam hardening artifact associates with bilateral molar metallic dental restorations, localizing symmetric radioiodine activity. (c, d) Bilateral metallic beam hardening artifact associates with bilateral mandibular dental restorations, greater on the left, with asymmetric (left greater than right) radioiodine localization. (e, f) Metallic orthodontic appliances localizing radioiodine activity, most intensely to circumferential metallic molar bands. (g, h) No metallic dental restorations or evidence of prior dental procedures, with nonlocalizing, low-level oral radioiodine uptake. (i, j) Molar restorations without metallic beam hardening artifact demonstrate nonlocalizing, low-level oral radioiodine uptake. SPECT/CT, single-photon emission computed tomography/computed tomography.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3815121&req=5

Figure 1: Post-therapeutic SPECT/CTs of the neck showing 131I localizing to metallic dental restorations. The left column contains axial CT images through the oral cavity; the right column contains the corresponding axial SPECT/CT fused images. (a, b) Bilateral beam hardening artifact associates with bilateral molar metallic dental restorations, localizing symmetric radioiodine activity. (c, d) Bilateral metallic beam hardening artifact associates with bilateral mandibular dental restorations, greater on the left, with asymmetric (left greater than right) radioiodine localization. (e, f) Metallic orthodontic appliances localizing radioiodine activity, most intensely to circumferential metallic molar bands. (g, h) No metallic dental restorations or evidence of prior dental procedures, with nonlocalizing, low-level oral radioiodine uptake. (i, j) Molar restorations without metallic beam hardening artifact demonstrate nonlocalizing, low-level oral radioiodine uptake. SPECT/CT, single-photon emission computed tomography/computed tomography.
Mentions: Of the 58 post-therapy patients imaged, 45 (78%) showed metallic dental restorations on CT, typically with a beam hardening artifact, and of them 41 (91%) demonstrated oral 131I activity localized to the restorations. In patients with bilateral restorations, activity was typically bilateral (Fig. 1a and b), although sometimes asymmetric (Fig. 1c and d). In patients with unilateral metallic dental restorations, the 131I activity typically localized to that side. Similar to 131I, 123I localized to metallic dental restorations when present (not shown). Radioiodine (131I and 123I) also localized to other metallic appliances such as braces, palate expanders, and tongue piercings (Fig. 1e and f, and additional data not shown). As alluded to above, four patients with metallic dental restorations did not demonstrate localizing oral radioiodine activity. In our study, which is a retrospective review, the compositions of the patient’s restorations are unknown. It is possible that some dental metals are not radioiodine avid, a hypothesis that could be tested but is beyond the scope of this study.

Bottom Line: Despite subsequent washings with normal saline, significant 131I activity (maximally 12% for amalgam and 68% for Argenco HP 77) was retained by these metals.Subsequent soaking in a saturated solution of potassium iodide partially displaced 131I from amalgam, with near-total displacement of I from Argenco HP 77.Furthermore, in-vitro studies demonstrate partially reversible binding of 131I to common dental metals.

View Article: PubMed Central - PubMed

Affiliation: aDepartment of Radiology, University of New Mexico bPrivate Practice, Albuquerque, New Mexico cDepartment of Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina, USA.

ABSTRACT

Purpose: We sought to further localize radioiodine activity in the mouth on post-thyroid cancer therapy imaging using single-photon emission computed tomography/computed tomography (SPECT/CT).

Materials and methods: We retrospectively reviewed all patients (58) who underwent thyroid cancer therapy with iodine-131 (131I) at our institution from August 2009 to March 2011 whose post-therapy radioiodine imaging included neck SPECT/CT. A small group (six) of diagnostic 131I scans including SPECT/CT was also reviewed. Separately, we performed in-vitro 131I (sodium iodide) binding assays with amalgam and Argenco HP 77 (77% dental gold alloy) as proof of principle for these interactions.

Results: Of the 58 post-therapy patients, 45 (78%) had undergone metallic dental restorations, and of them 41 (91%) demonstrated oral 131I activity localizing preferentially to those restorations. It was observed that radioiodine also localized to other dental restorations and to orthodontic hardware. Gum-line activity in edentulous patients suggests radioiodine interaction with denture adhesive. In vitro, dental amalgam and Argenco HP 77 bound 131I in a time-dependent manner over 1-16 days of exposure. Despite subsequent washings with normal saline, significant 131I activity (maximally 12% for amalgam and 68% for Argenco HP 77) was retained by these metals. Subsequent soaking in a saturated solution of potassium iodide partially displaced 131I from amalgam, with near-total displacement of I from Argenco HP 77.

Conclusion: SPECT/CT shows that radioiodine in the oral cavity localizes to metallic dental restorations. Furthermore, in-vitro studies demonstrate partially reversible binding of 131I to common dental metals.

Show MeSH
Related in: MedlinePlus