Background: Articular cartilage lacks a regenerative response. Embryonic stem cells (ESCs) are a source of pluripotent cells for cartilage regeneration. Their use, however, is associated with a risk of teratoma development, which depends on multiple factors including the number of engrafted cells and their degree of histocompatibility with recipients, the immunosuppression of the host and the site of transplantation. Colonies of sheep embryonic stem-like (ES-like) cells from in vitro-produced embryos, positive for stage-specific embryonic antigens (SSEAs), alkaline phosphatase (ALP), Oct 4, Nanog, Sox 2 and Stat 3 gene expression, and forming embryoid bodies, were pooled in groups of two-three, embedded in fibrin glue and engrafted into osteochondral defects in the left medial femoral condyles of 3 allogeneic ewes (ES). Empty defects (ED) and defects filled with cell-free glue (G) in the condyles of the controlateral stifle joint served as controls. After euthanasia at 4 years post-engraftment, the regenerated tissue was evaluated by macroscopic, histological and immunohistochemical (collagen type II) examinations and fluorescent in situ hybridization (FISH) assay to prove the ES-like cells origin of the regenerated tissue. Results: No teratoma occurred in any of the ES samples. No statistically significant macroscopic or histological differences were observed among the 3 treatment groups. FISH was positive in all the 3 ES samples. Conclusions: This in vivo preclinical study allowed a long-term evaluation of the occurrence of teratoma in non-immunosuppressed allogeneic adult sheep engrafted with allogeneic ES-like cells, supporting the safe and reliable application of ES cells in the clinic.

Purpose: the aim of this study was to determine whether local delivery of embryonic stem-like (ESL) cells into osteochondral defects in the femoral condyles of sheep would enhance regeneration of hyaline articular cartilage. Methods: male ESL cells embedded in fibrin glue were engrafted into osteochondral defects in the medial condyles (ESL-M) of the left femur in 22 ewes. An identical defect was created in the medial condyle of the contralateral stifle joint and left untreated as a control (empty defect, ED). The ewes were divided into 5 groups. Four sheep each were euthanized at 1, 2, 6, and 12 months from surgery, and 6 ewes were euthanized 24 months post-implantation. To study the effect of varying loads on the long-term regeneration process, an identical defect was also created and ESL cell engraftment performed in the lateral condyle (ESL-L) of the left stifle joint of the animals in the 12- and 24-month groups. The evaluation of regenerated tissue was performed by biomechanical, macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays. Results: no significant differences were found between treated and control sites in the biomechanical assays at any time point. ESL cell grafts showed significantly greater macroscopic evidence of regeneration as compared to controls at 24 months after surgery; significantly better histological evidence of repair in ESL-M samples versus controls was found throughout the considered period. At 24 months from surgery there was significantly improved integration of graft edges with the host tissue in the ESL-M as compared to the ESL-L samples, demonstrating that load bearing positively affects the long-term regeneration process. Conclusions: ESL cells enhanced the regeneration of hyaline cartilage. FISH confirmed that the regenerative tissue originated from ESL cells. Clinical Relevance: ESL cells are able to self-renew for prolonged periods without differentiation and, most importantly, to differentiate into a large variety of tissues.

BACKGROUND:Articular cartilage has poor intrinsic capacity for regeneration because of its avascularity and very slow cellular turnover. Defects deriving from trauma or joint disease tend to be repaired with fibrocartilage rather than hyaline cartilage. Consequent degenerative processes are related to the width and depth of the defect. Since mesenchymal stem cells (MSCs) deriving from patients affected by osteoarthritis have a lower proliferative and chondrogenic activity, the systemic or local delivery of heterologous cells may enhance regeneration or inhibit the progressive loss of joint tissue. Embryonic stem cells (ESCs) are very promising, since they can self-renew for prolonged periods without differentiation and can differentiate into tissues from all the 3 germ layers. To date only a few experiments have used ESCs for the study of the cartilage regeneration in animal models and most of them used laboratory animals. Sheep, due to their anatomical, physiological and immunological similarity to humans, represent a valid model for translational studies. This experiment aimed to evaluate if the local delivery of male sheep embryonic stem-like (ES-like) cells into osteochondral defects in the femoral condyles of adult sheep can enhance the regeneration of articular cartilage. Twenty-two ewes were divided into 5 groups (1, 2, 6, 12 and 24 months after surgery). Newly formed tissue was evaluated by macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays.RESULTS:Regenerated tissue was ultimately evaluated on 17 sheep. Samples engrafted with ES-like cells had significantly better histologic evidence of regeneration with respect to empty defects, used as controls, at all time periods.CONCLUSIONS:Histological assessments demonstrated that the local delivery of ES-like cells into osteochondral defects in sheep femoral condyles enhances the regeneration of the articular hyaline cartilage, without signs of immune rejection or teratoma for 24 months after engraftment.

We investigated the clinical impact of breast scintigraphy acquired with a breast specific γ-camera (BSGC) in the diagnosis of breast cancer (BC) and assessed its incremental value over mammography (Mx). A consecutive series of 467 patients underwent BSGC scintigraphy for different indications: suspicious lesions on physical examination and/or on US/MRI negative at Mx (BI-RADS 1 or 3), characterization of lesions suspicious at Mx (BI-RADS 4), preoperative staging in lesions highly suggestive of malignancy at Mx (BI-RADS 5). Definitive histopathological findings were obtained in all cases after scintigraphy: 420/467 patients had BC, while 47/467 patients had benign lesions. The scintigraphic data were correlated to Mx BI-RADS category findings and to histology. The incremental value of scintigraphy over Mx was calculated. Scintigraphy was true-positive in 97.1% BC patients, detecting 96.2% of overall tumor foci, including 91.5% of carcinomas ≤10 mm, and it was true-negative in 85.1% of patients with benign lesions. Scintigraphy gave an additional value over Mx in 141/467 cases (30.2%). In particular, scintigraphy ascertained BC missed at Mx in 31 patients with BI-RADS 1 or 3, including 26 patients with heterogeneously/high dense breast (19/26 with tumors ≤10 mm) and detected additional clinically occult ipsilateral or controlateral tumor foci (all <10 mm) or the in situ component sited around invasive tumors in 77 BC patients with BI-RADS 4 or 5, changing surgical management in 18.2% of these cases; moreover, scintigraphy ruled out malignancy in 33 patients with BI-RADS 4. BSGC scintigraphy proved a highly sensitive diagnostic tool, even in small size carcinoma detection, while maintaining a high specificity. The procedure increased both the sensitivity of Mx, especially in dense breast and in multifocal/multicentric disease, and the specificity as well as it better defined local tumor extension, thus guiding the surgeon to a more appropriate surgical treatment.

1287 Objectives To assess the usefulness of BSGC breast scintigraphy in comparison with MRI in the detection of primary BC. Methods We retrospectively studied 51 patients (36-74 yrs) with surgically proven primary BC that was invasive in 39/51 cases (IDCa in 36 cases, ILCa in 2 cases and medullary in 1 case) and in situ (DCIS) in 12/51 cases. The invasive carcinomas were ≤10 mm in 14/39 cases (4 T1a and 10 T1b) and >10 mm in 25/39 cases (19 T1c and 6 T2). All patients preoperatively underwent both breast scintigraphy, using 99mTc-tetrofosmin as radiotracer and a high resolution BSGC (cranio-caudal and medio-lateral oblique views, 600 sec./view), and contrast material-enhanced breast MRI. Scintigraphy and MRI data were compared each other and correlated with histopathological findings in all cases. Results BSGC scintigraphy was true positive in 50/51 BC patients, while MRI in 48/51 cases (overall sensitivity: 98% and 94.1%, respectively; p>0.05). Both procedures were true positive in 38/39 (97.4%) patients with invasive tumors, including 13 of the 14 patients with lesions ≤10 mm, and false negative in the remaining patient who had a 8 mm IDCa. Moreover, scintigraphy was true positive in 12/12 (100%) patients with DCIS, while MRI in 10/12 (83.3%). Furthermore, breast cancer extent was correctly assessed by scintigraphy in 48/50 (96%) positive cases, while MRI in 41/48 (85.4%) cases. In particular, scintigraphy, concordantly with MRI, overstaged local disease extent in 2 patients with invasive tumors, while MRI overstaged disease in 3 further patients with invasive tumors and downstaged disease in 2 patients with tumors in situ. Conclusions Both BSGC scintigraphy and MRI proved highly sensitive diagnostic tools in the detection of primary breast carcinomas, even when small in size and in situ, without any evident statistically significant difference. However, scintigraphy appeared more suitable than MRI in the detection of DCIS and in the assessment of local tumor extent. Research Support Fondazione Banco di Sardegna. Regione Sardegna (Legge n.7/2007)

Ductal carcinoma in situ (DCIS) is a subtype of breast cancer encountered increasingly in clinical practice because of the widespread use of screening mammography. In the present study, we evaluated the usefulness of breast-specific γ-camera (BSGC) scintigraphy in DCIS identification, describing the scintigraphic findings and their correlation with mammography and histologic subtype. Methods: Thirty-three women, aged 41–81 y, with surgically proven DCIS were retrospectively reviewed. Before surgery, all patients underwent breast scintigraphy using a high-resolution semiconductor-based BSGC, starting 10 min after intravenous injection of 740 MBq of 99mTc-tetrofosmin. All patients had previously undergone mammography. A definitive histologic diagnosis was obtained in all cases after scintigraphy, and the scintigraphic findings were correlated with mammography and histologic subtype. Results: Mammography was positive in 30 of 33 patients (sensitivity, 90.9%), showing calcifications in 22 of 30 (73.3%), masses in 3 of 30 (10%), and masses plus calcifications in the remaining 5 of 30 (16.7%). Scintigraphy was positive in 31 of 33 patients (sensitivity, 93.9%), showing patchy irregular uptake in patients with calcifications and focal uptake in masses; sensitivity was higher in low- to intermediate-grade DCIS than in intermediate/high- and high-grade DCIS (100% vs. 91.3%), but the difference was not statistically significant. Two comedo-type DCIS (one 20-mm intermediate/high-grade and one 15-mm high-grade) with heterogeneously or highly dense breasts at mammography and one papillary low/intermediate-grade DCIS associated with Paget disease were true positive only at scintigraphy. Moreover, scintigraphy better assessed disease extent than did mammography in 5 additional patients. Two comedo-type DCIS (one 6-mm intermediate/high-grade and one 15-mm high-grade) were true positive only at mammography. The difference in sensitivity between scintigraphy and mammography was not statistically significant. The combined use of mammography and scintigraphy achieved 100% sensitivity. Conclusion: BSGC scintigraphy proved to be a highly sensitive diagnostic tool in the detection of DCIS, irrespective of histologic subtype, and with a scintigraphic pattern of uptake that correlated well with mammography findings. In our series, BSGC scintigraphy demonstrated a slightly higher sensitivity than mammography and a better assessment of local disease extent. Thus, BSGC scintigraphy should represent a useful adjunctive tool in breast cancer diagnosis.

245 Objectives Breast DCIS is a non-invasive malignancy encountered increasingly at screening mammography.Early detection is important because high grade and comedo type DCIS can progress to invasive carcinoma.We retrospectively investigated the role of SM acquired with a BSGC in the detection of DCIS and examined possible associations between scintigraphic features and both mammographic and histopathological findings. Methods Thirty-three women (41-81 yrs) underwent SM in both cranio-caudal and mediolateral oblique views (600 sec/view) using a high resolution BSGC, starting ten min after i.v. injection of 740 MBq of 99mTc-tetrofosmin.Definitive histological diagnosis was obtained after SM.Scintigraphic features were correlated with Mx and surgical findings; 23/33 patients had a high-grade DCIS, while 10/33 patients had an intermediate or a low grade DCIS.A comedo-type DCIS was present in 27/33 cases.The tumor extension was ≤1 cm in 17/33 cases. Results SM was positive in 31/33 patients (sens.: 93.9%), including 3 negative at Mx (2 high-grade multifocal comedo DCIS >1 cm and 1 Paget’s disease), and false negative in the remaining 2/33 cases (2 high-grade comedo DCIS of 0.6 and 1.5 cm in size) that were positive at Mx which showed a pattern of microcalcifications.Scintigraphic pattern tended to be patchy, irregular or linear in patients with calcifications at Mx, matching their distribution, while focal uptake with well-delineated contours were seen in patients with masses, opacities or distortions.No differences in scintigraphic features were observed between high-grade and non high-grade DCIS or between comedo and non comedo type DCIS. Conclusions SM acquired with a high resolution BSGC proved a highly sensitive diagnostic tool in DCIS detection, even in subcentimetric lesions, irrespective of the different histopathological subtype, and with a scintigraphic uptake pattern well correlated with Mx findings. Research Support 1)Fondazione Banco di Sardegna (Prot.1294/2010.1164). 2)PO Sardegna FSE 2007-2013 L.R.7/200

Single photon emission computed tomography (SPECT)/CT is emerging as a useful diagnostic tool in several oncological fields. In this prospective study, we assessed the usefulness of Tc-99m-tetrofosmin SPECT/CT in the detection of both residual breast tumors and axillary lymph node metastases following neoadjuvant therapy. Thirty-seven consecutive breast cancer patients scheduled to surgery following neoadjuvant therapy preoperatively underwent a Tc-99m-tetrofosmin SPECT/CT study, using a dual head gamma camera integrated with a x-ray tube for low-dose CT, including both breasts and axillary regions in the field of view. Within 1 week of SPECT/CT, all 37 patients had breast surgery with associated axillary lymph node dissection in 33/37 cases. At surgery, 31/37 patients had breast residues (microscopic in 4/31 cases and macroscopic in 27/31 cases). Axillary lymph node metastases were ascertained in 19/33 cases (N1mi: 2 cases, N1a: 8 cases, N2a: 6 cases, N2b: 3 cases). SPECT/CT sensitivity, specificity, and accuracy in detecting residual tumors were 87%, 100%, and 89.2%, respectively; the corresponding values in detecting axillary lymph node metastases were 36.8%, 92.8%, and 60.6%. SPECT/CT missed breast cancer residues in 4/31 patients, including 2 cases with microscopic residual disease. Moreover, lymph node metastases were missed in 12/19 patients (10/12 with pN1mi or pN1a metastases), all with lymph nodes with post-therapy fibrotic changes and small deposits of metastases. Tc-99m-tetrofosmin SPECT/CT proved a useful diagnostic tool in the detection and in the localization of residual breast tumors following neoadjuvant therapy. The procedure lacked in sensitivity in identifying axillary lymph node metastases, especially in patients with a limited lymph node involvement. According to our data, SPECT/CT may guide the surgeon to the most appropriate breast surgical treatment and to eventually select the most suitable axillary lymph node sampling (axillary lymph node dissection or sentinel node biopsy).

Pediatric fungal infections are associated with significant morbidity and mortality. Few adequately powered antifungal trials have been performed in neonates and children. Neonatologists and peditricians are reliant on adult trials when managing candidemia. Recent guidelines from the Infectious Diseases Society of America recommend fluconazole or an echinocandin for empiric therapy in suitable candidates, with a preference for an echinocandin in patients with moderate-to severe disease, recent azole exposure, or high risk of C. glabrata or C. krusei infection.

Background In this study we aimed to assess lipid peroxidation during carotid endarterectomy by the formation of PUFA hydroperoxides (PUFAHP) and isoprostanes (IP) and concomitant peroxisomal beta-oxidation as a physiological mechanism to limit their concentration. Two markers of peroxisomal beta oxidation have been evaluated, formation of 2,3 dinor from IP and conjugated esadecadienoic acid (CD 16:2) from peroxisomal beta-oxidation of conjugated linoleic acid (CLA), an unusual fatty acid present in small concentration in our diet and preferentially beta-oxidised in peroxisomes. The study was conducted on 30 patients undergoing carotid endarterectomy. Blood samplings were performed before, during endarterectomy in the "ischemic phase", and 30 seconds, 30 minutes and 2 hours after reperfusion. Results The results showed that PUFAHP increased significantly after 30 min of reperfusion in patients with controlateral stenosis > 50%, and steeply decreased after 2 hour of reperfusion. Interestingly, IP increased in a similar fashion of PUFAHP but never significantly. Both ratios CD16:2/CLA and DIN/IP also increased significantly after 30 min of reperfusion to decrease thereafter. Conclusions Our data show that lipid peroxidation takes place only in patients with high controlateral stenosis and within 2 hours occurs a physiological response aimed to decrease IP and PUFAHP by increasing their catabolism in peroxisomes.

Background: In this study we aimed to assess lipid peroxidation during carotid endarterectomy by the formation of PUFA hydroperoxides (PUFAHP) and isoprostanes (IP) and concomitant peroxisomal beta-oxidation as a physiological mechanism to limit their concentration. Two markers of peroxisomal beta oxidation have been evaluated, formation of 2,3 dinor from IP and conjugated esadecadienoic acid (CD 16:2) from peroxisomal beta-oxidation of conjugated linoleic acid (CLA), an unusual fatty acid present in small concentration in our diet and preferentially beta-oxidised in peroxisomes. The study was conducted on 30 patients undergoing carotid endarterectomy. Blood samplings were performed before, during endarterectomy in the ischemic phase, and 30 seconds, 30 minutes and 2 hours after reperfusion. Results: The results showed that PUFAHP increased significantly after 30 min of reperfusion in patients with controlateral stenosis > 50%, and steeply decreased after 2 hour of reperfusion. Interestingly, IP increased in a similar fashion of PUFAHP but never significantly. Both ratios CD16:2/CLA and DIN/IP also increased significantly after 30 min of reperfusion to decrease thereafter. Conclusions: Our data show that lipid peroxidation takes place only in patients with high controlateral stenosis and within 2 hours occurs a physiological response aimed to decrease IP and PUFAHP by increasing their catabolism in peroxisomes.

1623 Objectives We investigated the usefulness of MBI in the diagnosis of BC and assessed its incremental value over mammography (Mx). Methods A consecutive series of 353 patients with suspicious clinical examination and/or conventional imaging procedures (Mx/US) scheduled for biopsy were studied. Starting 10 min. after 99mTc-tetrofosmin injection, MBI was acquired in both cranio-caudal and medio-lateral oblique views using a CZT high resolution dedicated breast camera. Scintigraphic data were correlated to Mx BI-RADS findings and both of these to histology in all cases. The incremental value of MBI over Mx was calculated. Results MBI was positive in 96.8% BC patients and detected 95.5% of overall tumor foci; sensitivity value in carcinomas ≤10 mm was 90.5%. MBI assessed multifocal/multicentric disease in 87.5% of cases and bilateral disease in 100% of cases. MBI was true negative in 88.6% of patients with benign disease and in 88.2% of the lesions. MBI gave an additional value over Mx in 126/353 cases (35.7%), ascertaining primary BC missed at Mx in 26 patients with BI-RADS 1 or 3, including 22 with dense breast (16/22 with tumors ≤10 mm), and additional clinically occult ipsilateral or controlateral tumor foci (all Conclusions MBI proved a highly accurate diagnostic tool in breast cancer. In our series, MBI increased both the sensitivity of Mx, especially in dense breast and in multifocal/multicentric disease, and specificity as well as it better defined local tumor extension, thus guiding the surgeon to a more appropriate surgical treatment. MBI employment could also be suggested for a more appropriate selection of patients to submit to biopsy

1609 Objectives We assessed SPECT/CT usefulness in diagnosing lung lesions and correlated scintigraphic data with those of diagnostic CT. Methods Ninety consecutive patients (50-84 yrs), 51 with nodules (0.9-3 cm) and 39 with masses (>3 cm) at diagnostic CT were studied. Within 1 week of CT scan, all patients underwent SPECT/CT following 740 MBq of 99mTc-tetrofosmin i.v. injection, using a rectangular dual head gamma camera integrated with a X-ray tube for low dose CT. SPECT/CT images were analysed qualitatively and correlated with diagnostic CT findings. Definitive diagnosis after scintigraphy: 70/90 patients had malignancy (60 primary carcinomas, 8 metastases, 2 recurrences) and 20/90 had benign lesions. Results SPECT/CT was true positive in 66/70 (94.3%) patients with malignancy, detecting 30/34 (88.2%) nodules and 36/36 (100%) masses, while CT was positive in 53/70 (75.7%) patients. SPECT/CT was false negative in 4 patients, 1 with a metastasis (size: 12 mm) positive at CT and 3 with an adenocarcinoma each (size: 10-15 mm) indeterminate at CT; the latter was also indeterminate in the remaining 14 SPECT/CT positive patients, 12 with nodules (3 adenocarcinomas, 2 bronchioalveolar carcinomas, 2 carcinoids, 2 recurrences, 3 metastases) and 2 with masses (1 adenocarcinoma, 1 spinocellular carcinoma). SPECT/CT was true negative in 17/20 (85%) patients with benign lesions, while CT in 11/20 (55%); SPECT/CT was false positive, concordantly with CT, in 3 cases, 2 of whom with aspecific inflammation and 1 with Wegner’s granuloma. CT was indeterminate in the remaining 6 patients with benign lesions (2 idiopatic fibrosis, 2 chronic alveolitis, 1 antracosis, 1 hamartoma) negative at SPECT/CT. Conclusions 99mTc-tetrofosmin SPECT/CT proved highly accurate in lung lesion diagnosis, playing an important complementary role to diagnostic CT in respect of which it showed a better performance in 22.2% of our cases. The procedure also detected carcinoids and bronchioalveolar carcinomas which can often result negative at FDG-PET. A wider SPECT/CT use is suggested in patients with lung lesions, especially with indeterminate CT

1 Department of Human, Environmental and Natural Sciences, University of Urbino “Carlo Bo”, Italy 2 INFN Gran Sasso National Laboratories, Assergi (AQ), Italy 3 Laboratory and Image Diagnostic Department, San Salvatore Hospital, Pesaro, Italy 4 Agris-Sardegna, DIRPA (Agricultural Research Agency of Sardinia, Department of Animal Science) Reproduction Division, Sassari, Italy 5 ASLEM (Associazione Sammarinese Leucemie ed Emopatie Maligne), San Marino 6 Experimental Zooprophylactic Institute of Sardinia, Sassari, Italy 7 Health Physics Department, San Salvatore Hospital, Pesaro, Italy

1696 Objectives To assess the role of 99mTc-tetrofosmin MBI in addition to mammography (Mx) in patients with breast lesions. Methods 321 consecutive patients (26-81 yrs) with breast lesions scheduled for biopsy underwent 99mTc-tetrofosmin MBI using a high resolution dedicated breast camera. MBI and Mx data were compared and correlated to histology. Results 277/321 patients had BC and 44/321 had benign disease. MBI was positive in 267/277 (96.4%) BC patients detecting 95.6% of carcinomas. Sensitivity was 90.4% in carcinomas ≤10 mm and 99% in those >10 mm. The smallest detected carcinoma measured 1.8 mm. MBI assessed multifocal/multicentric disease in 88.9% of cases and bilateral disease in 100%. MBI was positive in 20 patients with an invasive carcinoma (≤10 mm in 16 cases) each in dense breast and in 5 patients with a carcinoma in situ, all negative at Mx. Moreover, MBI was more accurate than Mx in 41.7% of patients with multifocal/multicentric disease, changing the surgical management in 25% of cases. MBI modified the local staging in further 44 BC patients with a unifocal invasive tumor each in whom it also identified the associated intraductal component missed at Mx. MBI also identified a contralateral tumor missed at Mx. MBI was negative in 38/44 (86.4%) patients with benign disease, most of whom with suspicious findings at Mx. Conclusions 99mTc-tetrofosmin MBI proved a highly sensitive diagnostic tool, even in the detection of small size BC, while maintaining a high specificity. A wider employment of MBI in patients with breast lesions is thus suggested to increase Mx sensitivity and specificity as well as to better define tumor disease extension, thus guiding the surgeon to a more appropriate surgical treatment.

Planar 131I scintigraphy is routinely used to detect radioiodine-avid metastases of differentiated thyroid carcinoma (DTC). However, the modality has limitations, such as low sensitivity and lack of anatomic landmarks. We investigated whether SPECT with integrated low-dose CT may have additional value over planar imaging in detecting residue and metastases in DTC patients. Methods: We studied 117 consecutive thyroidectomized DTC patients. On 2 different hybrid dual-head γ-cameras (55 patients on one camera and 62 on the other), 108 patients underwent 131I diagnostic imaging and SPECT/CT, and 9 underwent posttherapeutic 131I planar imaging and SPECT/CT. We assigned an incremental value to SPECT/CT when it provided better identification and interpretation of the foci of radioiodine uptake, more correct anatomic localization and characterization, and precise differentiation between tumor lesions and physiologic uptake. Results: Planar imaging showed 116 foci of uptake in 52 of 117 patients, and SPECT/CT showed 158 foci in 59 of 117 patients, confirming all foci seen on planar imaging but identifying an additional 28 occult foci in 10 of 52 patients. Fourteen occult foci were shown on SPECT/CT in 7 further patients whose planar imaging findings were negative. SPECT/CT correctly characterized 48 foci unclear on planar imaging, also defining location and extent. SPECT/CT was a determinant in classifying as neoplastic those foci for which planar imaging seemed to exclude malignancy, discriminating between residue and lymph node metastases in the neck, some of which were adjacent to salivary glands and had been missed on planar imaging. SPECT/CT also showed occult lesions in the mediastinum, abdomen, and pelvis and identified small bone metastases unsuspected on planar imaging. Globally, SPECT/CT had an incremental value over planar imaging in 67.8% of patients, modified therapeutic management in 35.6% of positive cases, and avoided unnecessary treatment in 20.3% of patients with only single benign lesions or physiologic uptake. Conclusion: 131I SPECT/CT improved planar data interpretation, showing a higher number of DTC lesions, more precisely localizing and characterizing DTC foci, and more correctly differentiating between physiologic uptake and metastases, thus permitting the most appropriate therapeutic approach to be chosen. A wider use of this method is suggested complementary to planar imaging in selected DTC patients.