Insufficient hepatic uptake in pediatric patients on lymphoscintigraphy.

BACKGROUND: To demonstrate the association between pediatric outcomes and tracer hepatic uptake as a marker of systemic circulation in lymphoscintigraphy. METHODS: We included 31 initial lymphoscintigraphic studies. We compared the presence or absence of hepatic uptake between deceased and survived patients in both early and delayed images using Fisher's exact test. Kaplan-Meier survival analysis was performed based on imaging results, and these curves were compared using the log-rank test. The primary endpoint was death and the survival period was defined from the day of examination to the day of the last visit or death. RESULTS: Of 31 patients, six died. Hepatic uptake was significantly different in both early and delayed images (early images, died [with/without visualization] vs. survived [with/without visualization], 0/6 vs. 13/12, P = 0.028; delayed images, died [with/without visualization] vs. survived [with/without visualization], 2/4 vs. 22/3, P = 0.014) between deceased and survived patients. Survival periods were significantly different between the two groups with and without hepatic uptake in early and delayed images (with/without visualization in early imags = 1,177.1 ± 773.8 days/426.7 ± 419.8 days, P = 0.008 and with/without visualization in delayed images = 821.3 ± 738.0 days/467.4 ± 452.4 days, P = 0.003). CONCLUSIONS: Visualization of hepatic uptake in both early and delayed lymphoscintigraphy is associated with patient outcomes. Hepatic uptake could represent tracer inflow into the systemic circulation, indicating preservation of the connection between the lymphatic system and the systemic circulation. Physicians should evaluate these findings carefully on lymphoscintigraphy.

Radioisotope Therapy of Japan: Future Perspective and Recommendations.

In Japan, because of the rapid increase in the number of thyroid cancer patients and the recent severe shortage of radioisotope therapy wards, the prolonged waiting time for the admission to the radioisotope therapy wards has become a social problem. This situation is against one of the main purposes of the Cancer Control Promotion Plan of our nation, which is advocating an equal accessibility of medical care for the Japanese citizens. In 2015, diet discussions about the problems of radioisotope therapy took place and the prime minister stated that the promotion of radioisotope therapy is one of the most important issues in Japan, therefore further promotion of research and development is anticipated in this field. In this article, we have summarized the problems during radioisotope therapy, and have added our recommendations in the social and medical realizable countermeasures in future, according to the deep considerations of medical economy in Japan, an assumption of disease prevalence of thyroid cancer in the future, and the situations of foreign countries.

Brain perfusion and upper limb motor function: a pilot study on the correlation between evolution of asymmetry in cerebral blood flow and improvement in Fugl-Meyer Assessment score after rTMS in chronic post-stroke patients.

BACKGROUND AND PURPOSE: Few studies have explored the refinement of asymmetry in regional cerebral blood flow in relation to behavioral improvement after treatment. The purpose of this retrospective pilot study was to identify cerebral cortical regions with improved perfusion that correlated with improvement of upper limb motor function after repetitive transcranial magnetic stimulation (rTMS). MATERIALS AND METHODS: The study subjects were 33 post-stroke patients with upper limb hemiparesis who underwent rTMS combined with intensive occupational therapy (mean ± SD age: 64.9 ± 11.2 years; time since onset of stroke: 57.3 ± 45.9 months). Fugl-Meyer Assessment (FMA) and the Wolf Motor Function Test (WMFT) were applied before and after treatment to evaluate motor function in the affected upper limb. Regional brain perfusion was measured by single-photon emission computed tomography, and the percentages of asymmetry values (asymmetry index [AI]) for 52 bilateral regions of interest were calculated. The change in AI was calculated as the post-intervention minus pre-intervention values. RESULTS: Changes in AI in the superior and middle frontal areas correlated significantly and negatively with changes in FMA score (superior: r = -0.406, P = 0.03, R(2) = 0.251; middle: r = -0.437, P < 0.001, R(2) = 0.306), but not with changes in WMFT log performance time. CONCLUSION: Changes in AI less than zero reflect improved perfusion, suggesting that upper limb motor function improvement in post-stroke patients reflects evolution of brain perfusion in the superior and middle frontal areas.

Correction: Investigation of the new non-invasive semi-quantitative method of 123I-IMP pediatric cerebral perfusion SPECT.

[This corrects the article DOI: 10.1371/journal.pone.0241987.].

Retrospective case-control study examining the relationship between recurrence-free survival and changes in pre- and post-radioiodine therapy serum thyroglobulin levels in patients with differentiated thyroid cancer.

PURPOSE: Thyroglobulin assay is important to assess the residual or recurrence of differentiated thyroid cancer (DTC). Patients with positive serum thyroglobulin levels after radioactive iodine (RAI) adjuvant therapy could achieve long-term recurrence-free survival (RFS). The patient's prognosis could not be confidently estimated based solely on the evaluation of thyroglobulin levels. We investigated the recurrence rate and RFS of patients who received adjuvant RAI therapy after surgery for DTC to clarify the relationship between changes in pre- and post-therapy serum thyroglobulin levels and RFS. MATERIALS AND METHODS: Patients who underwent adjuvant RAI therapy between May 2007 and March 2021 were included in this study, whereas those with positive anti-thyroglobulin antibodies, distant metastases, or gross residual tumors were excluded. The change in pre- and post-treatment serum thyroglobulin levels under thyroid-stimulating hormone stimulation was calculated and classified as follows: group A, thyroglobulin levels decreased by ˃10%; group B, thyroglobulin levels within a range of 10% or less; and group C, thyroglobulin levels increased by ˃10%. RFS outcomes were analyzed using the Kaplan-Meier method. Univariate analysis was performed using the log-rank test, and multivariate analysis was performed using the Cox proportional hazard model. RESULTS: A total of 74 patients were included. Relapse was seen in 13 of 46 patients in group A, 9 of 15 in group B, and 10 of 13 in group C. Median RFS was 129.00 (95% confidence interval CI 77.79-180.21), 113.00 (95% CI 86.83-139.17), and 33 months (95% CI 6.026-59.974) in groups A, B, and C, respectively. Patients in group C exhibited significantly shorter RFS than those in groups A and B (P = 0.001). CONCLUSIONS: Changes in thyroglobulin levels pre- and post-therapy were associated with RFS. Patients with decreased post-therapy thyroglobulin levels had a favorable prognosis, even if their thyroglobulin levels were positive after RAI therapy.

Booster administration of Tc-99m PMT for delayed static imaging in patients with biliary atresia.

OBJECTIVE: Tc-99m N-pyridoxyl-5-methyl-tryptophan (PMT) hepatobiliary scintigraphy has high diagnostic performance for biliary atresia. Our hospital implements standard Tc-99m PMT administration followed by a 6 h static imaging review; booster doses are given in cases requiring 24 h delayed scans. This study aimed to evaluate the diagnostic performance of this method. METHODS: A total of 37 pediatric patients who underwent Tc-99m PMT biliary scintigraphy were classified into the surgically-diagnosed biliary atresia or non-biliary atresia groups. The absence of tracer accumulation in the small bowel was considered a hepatobiliary scintigraphic diagnosis of biliary atresia. The Clopper-Pearson method was used to calculate the 95% confidence intervals (CIs) for determining the diagnostic accuracy, negative predictive value, positive predictive value, sensitivity, and specificity of Tc-99m PMT biliary scintigraphy. RESULTS: Among the 37 patients, 12 were classified into the diagnosis of biliary atresia group. Regarding biliary scintigraphy findings, 16 of 37 patients demonstrated tracer accumulation in the small bowel within 6 h of testing. These cases were diagnosed as non-biliary atresia, requiring no further testing or booster administration. In contrast, 21 patients underwent delayed testing requiring booster administration, which revealed 13 without tracer excretion and 11 who were diagnosed with biliary atresia. Among the eight patients with tracer accumulation, only one was diagnosed with biliary atresia. Furthermore, two cases without tracer excretion and seven cases with tracer excretion were clinically diagnosed as non-biliary atresia. The diagnostic performance of our examination was as follows: a diagnostic accuracy of 91.9% (34/37; 95% CIs 78.0-98.3%), sensitivity of 91.6% (11/12; 95% CIs 61.5-99.8%), specificity of 92.0% (23/25; 95% CIs 74.0-99.0%), a positive predictive value of 84.6% (11/13; 95% CIs 54.6-98.0%), and a negative predictive value of 95.8% (23/24; 95% CIs 78.9-99.9%). CONCLUSIONS: Our protocol for Tc-99m PMT biliary scintigraphy using tracer booster administration demonstrated reliable diagnostic performance for biliary atresia. Notably, 43% of cases did not require booster administration, indicating that lesser radiation exposure may still yield comparable diagnostic accuracy.

Carnival Mask Sign on Bone Scan of Craniofacial Metastasis of Neuroblastoma.

A craniofacial mass may cause the first clinical symptoms of malignancy. In pediatric patients, neuroblastoma, Langerhans cell histiocytosis (LCH), and acute lymphoblastic leukemia (ALL) are the most common diseases initially manifesting with bone lesions, and bone scintigraphy is a useful modality to evaluate them. The purpose of this pictorial essay was to show the scintigraphy findings of the craniofacial bones in three patients, with neuroblastoma, ALL, and LCH, and to provide a useful scintigraphic sign to differentiate these diseases. In the bone scintigraphy of neuroblastoma with craniofacial bone metastases, strong tracer uptake was evident, resembling a carnival mask. In contrast, in the two cases with LCH and ALL involving the craniofacial bones, the tracer uptake was lower than in neuroblastoma and with different distributions. Bone metastases of neuroblastoma usually occur in the periorbital craniofacial bones, and these metastases may be locally aggressive, destroying the bones; which show stronger uptake than other cranial bones. LCH is associated with varying degrees of disease activity, and its bone imaging findings differ based on its activity. Therefore, these lesions present low uptake in bone scintigraphy, showing as "cold spots". Therefore, LCH scintigraphy of the craniofacial bones does not resemble a carnival mask. The bone marrow infiltration by leukemic cells usually shows as diffuse bone marrow. Therefore, in bone scintigraphy of leukemia, the tracer uptake in the periorbital craniofacial bones is similar to other cranial bones, not presenting as a carnival mask. In conclusion, bone scintigraphy to evaluate malignant craniofacial lesions could provide useful differential diagnostic information.

Complete Remission of Renal Scarring in Follow-Up DMSA Renal Scintigraphy After Urinary Tract Infection.

Our study aimed to investigate the association between the characteristics of patients/images and complete remission of renal scarring shown in the first chronic phase Technetium-99m dimercaptosuccinic acid (DMSA) renal scintigraphy images in children with urinary tract infection (UTI). Fifty children, who underwent the chronic phase of DMSA scintigraphy more than twice following UTI diagnosis and had renal scarring in the first chronic phase DMSA renal scintigraphy, were enrolled. They were classified into 2 groups: with and without complete remission of renal scarring on the second chronic phase DMSA renal scintigraphy. Renal scarring was classified into 3 grades based on severity per the image findings. Seven cases had complete remission from renal scarring. There were significant differences in age and severity. Renal scarring might be completely reversed in young children without severe findings on DMSA renal scintigraphy. Additional chronic phase examination may aid in follow-up completion and patients' peace of mind.

Incidence of renal scarring on technetium-99 m dimercaptosuccinic acid renal scintigraphy after acute pyelonephritis, acute focal bacterial nephritis, and renal abscess.

OBJECTIVE: To evaluate the association between the incidence of renal scarring on technetium-99 m dimercaptosuccinic acid (DMSA) renal scintigraphy and the severity of renal parenchymal infections, such as acute pyelonephritis (APN), acute focal bacterial nephritis (AFBN), and renal abscess, based on computed tomography (CT) diagnosis. METHODS: Sixty-one children with renal parenchymal infections were included and classified into two groups: those with (renal scarring group) and without renal scarring (non-renal scarring group) on chronic-phase DMSA renal scintigraphy. The severity of renal parenchymal infection was classified into three grades using CT: APN, AFBN, and renal abscess as grades 1, 2, and 3, respectively. The severity of renal parenchymal infection, vesicoureteral reflux (VUR) grade, and intrarenal reflux occurrence during voiding cystourethrography (VCUG) were evaluated between the renal and non-renal scarring groups. Fisher's exact test and Mann-Whitney U test were used for statistical analysis. RESULTS: Renal scars were detected in 28 (45.9%) of the 61 patients. We found that 2/9 (22.2%), 18/41 (43.9%), and 8/11 (72.7%) patients with APN (grade 1), AFBN (grade 2), and renal abscess (grade 3) had renal scarring, respectively. There was a significant difference in the grade of severity of renal parenchymal infection between the renal (median = 2 [interquartile range, 2-3]) and non-renal (median = 2 [interquartile range, 2-2]) scarring groups (p = 0.023). There was a significant difference in the grade of VUR between the renal (median = 3 [interquartile range, 0-4]) and non-renal (median = 0 [interquartile range, 0-2]) scarring groups (p = 0.004). No significant difference in intrarenal reflux occurrence was observed between the renal (present/absent: 3/25) and non-renal (present/absent: 0/29) scarring groups (p = 0.112). CONCLUSION: Our results showed that pediatric patients with renal scarring on chronic-phase DMSA renal scintigraphy tended to have a more severe renal infection.

A single-center experience of using milk scintigraphy in 251 pediatric patients: A retrospective study.

To report our experience with milk gastroesophageal scintigraphy and the management of gastroesophageal reflux (GER) in children. In 251 pediatric patients we recorded age, underlying disease, central nervous system (CNS) disorders, and GER management. GER management was classified based on treatment plans: grade 0, non-pharmacological treatment; grade 1, non-pharmacological but using a nasogastric tube; grade 2, pharmacological treatment; grade 3, transpyloric feeding; and grade 4, Nissen fundoplication surgery. Patients were included in classified groups with (grades 2, 3, and 4) and without (grades 0 and 1) GER treatment. We evaluated the GER height (classified based on the height of GER, grade 0; no GER, 1; GER in the lower esophagus, 2; GER in the upper esophagus), GER duration in the lower and upper esophagus, presence or absence of massive GER amounts in the lower and upper esophagus, and gastric emptying time. We compared milk scintigraphy results and patient characteristics between groups with (grades 2, 3, and 4) and without (grades 0 and 1) GER treatment. We treated 121 patients for GER. CNS disorders (presence/absence: 46/74 with vs 21/110 without treatment, P < .001). The GER height grade (1.7 ±â€…0.5 [range, 0-2] with vs 1.5 ±â€…0.7 [range, 0-2] without treatment, P = .002), massive GER amount (present/absent: 21/99 with vs 9/122 without treatment, P = .011), and duration of GER (seconds) (324.5 ±â€…508.3 [range, 0-1800] vs 125.0 ±â€…291.9 [range, 0-1750], P < .001) in the upper esophageal half differed significantly. Similarly massive GER amount (present/absent: 54/66 with vs 34/97 without treatment, P = .002) and GER duration (621.3 ±â€…601.0 [range, 0-1800] vs 349.8 ±â€…452.4 [range, 0-1800], P < .001) in the lower esophageal half differed significantly. Additionally, CNS disorders, age, and massive GER in the upper esophageal half differed significantly among grades 2 and 4 in treated patients (P < .05, P < .001, P < .05, respectively). Milk scintigraphy is useful for deciding whether GER treatment is indicated. However, the treatment plan needs to be decided based on each patient's condition.

[Development of a simple quantitative method for the strontium-89 concentration of radioactive liquid waste using the plastic scintillation survey meter for beta rays].

Strontium-89 (89Sr: pure beta, E; 1.495 MeV-100%, halflife: 50.5 days) chloride is used as pain relief from bone metastases. An assay of 89Sr is difficult because of a pure beta emitter. For management of 89Sr, we tried to evaluate a simple quantitative method for the 59Sr concentration of radioactive liquid waste using scintillation survey meter for beta rays. The counting efficiency of the survey meter with this method was 35.95%. A simple 30 minutes measurement of 2 ml of the sample made the quantitative measurement of 89Sr practical. Reducing self-absorption of the beta ray in the solution by counting on the polyethlene paper improved the counting efficiency. Our method made it easy to manage the radioactive liquid waste under the legal restrictions.

Clinical practice guidelines for high-resolution breast PET, 2019 edition.

Breast positron emission tomography (PET) has had insurance coverage when performed with conventional whole-body PET in Japan since 2013. Together with whole-body PET, accurate examination of breast cancer and diagnosis of metastatic disease are possible, and are expected to contribute significantly to its treatment planning. To facilitate a safer, smoother, and more appropriate examination, the Japanese Society of Nuclear Medicine published the first edition of practice guidelines for high-resolution breast PET in 2013. Subsequently, new types of breast PET have been developed and their clinical usefulness clarified. Therefore, the guidelines for breast PET were revised in 2019. This article updates readers as to what is new in the second edition. This edition supports two different types of breast PET depending on the placement of the detector: the opposite-type (positron emission mammography; PEM) and the ring-shaped type (dedicated breast PET; dbPET), providing an overview of these scanners and appropriate imaging methods, their clinical applications, and future prospects. The name "dedicated breast PET" from the first edition is widely used to refer to ring-shaped type breast PET. In this edition, "breast PET" has been defined as a term that refers to both opposite- and ring-shaped devices. Up-to-date breast PET practice guidelines would help provide useful information for evidence-based breast imaging.

Relapse-free survival after adjuvant radioactive iodine therapy in patients with differentiated thyroid carcinoma with a microscopically positive tumor margin.

OBJECTIVE: In patients with differentiated thyroid carcinoma (DTC) with a microscopically positive tumor margin, the optimal first dose of I-131 during adjuvant radioactive iodine (RAI) therapy to improve relapse-free survival (RFS) is unclear. Due to the limited number of hospital beds, 1110 MBq of I-131 is administered to such patients in Japan. This study primarily aimed to retrospectively determine the difference in RFS between high-dose (3700 MBq) and low-dose (1110 MBq) adjuvant RAI therapies in DTC patients with a microscopically positive tumor margin. The secondary aim was to investigate the background factors affecting RFS. METHODS: Forty-eight consecutive patients (15 men and 33 women) who underwent total thyroidectomy between April 2007 and December 2017 for DTC without gross residual tumors and distant metastasis, and who were diagnosed with a positive margin histopathologically, followed by RAI therapy, were enrolled. We retrospectively investigated initial I-131 dose, classifying it into high-dose and low-dose groups. The primary endpoint was RFS. Relapse was considered in the following cases: patients with visible recurrent tumor and/or metastasis on neck ultrasound and/or computed tomography, and patients without visible tumor, but with clearly increasing thyroglobulin levels on follow-up every 3-6 months. RFS outcomes were analyzed using the Kaplan-Meier method. Univariate analysis was performed using the log-rank test, and multivariate analysis was undertaken using the Cox proportional hazard model. RESULTS: There were nine cases of recurrence (52.9%) in the low-dose group and seven in the high-dose group (22.5%) during follow-up. The estimated median RFS was 69.4 months in the low-dose group and 120.7 months in the high-dose group. High-dose administration was associated with improved RFS, as demonstrated by Kaplan-Meier survival curves (log-rank test [P = 0.009]). Patient factors associated with worse RFS included low-dose administration (hazard ratio [HR] = 91.9; 95% confidence interval [CI] = 7.66-1102.79); P < 0.001), T4 stage (HR = 1.88; 95% CI = 0.44-8.10; P = 0.015), and presence of central lymph node metastases (HR = 190; 95% CI = 3.80-9496; P = 0.009). The most common type of recurrence was lymph node metastasis. CONCLUSION: Patients with microscopically positive tumor margins could benefit from RAI with high activities.

Investigation of the new non-invasive semi-quantitative method of 123I-IMP pediatric cerebral perfusion SPECT.

In pediatric cases requiring quantification of cerebral blood flow (CBF) using 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) single-photon emission computed tomography (SPECT), arterial blood sampling is sometimes impossible due to issues such as movement, crying, or body motion. If arterial blood sampling fails, quantitative diagnostic assessment becomes impossible despite radiation exposure. We devised a new easy non-invasive microsphere (e-NIMS) method using whole-body scan data. This method can be used in conjunction with autoradiography (ARG) and can provide supportive data for invasive CBF quantification. In this study, we examined the usefulness of e-NIMS for pediatric cerebral perfusion semi-quantitative SPECT and compared it with the invasive ARG. The e-NIMS estimates cardiac output (CO) using whole-body acquisition data after 123I-IMP injection and the body surface area from calculation formula. A whole-body scan was performed 5 minutes after the 123I-IMP injection and CO was estimated by region of interest (ROI) counts measured for the whole body, lungs, and brain using the whole-body anterior image. The mean CBF (mCBF) was compared with that acquired via ARG in 115 pediatric patients with suspected cerebrovascular disorders (age 0-15 years). Although the mCBF estimated by the e-NIMS indicated a slight deviation in the extremely low- or high-mCBF cases when compared with the values acquired using the invasive ARG, there was a good correlation between the two methods (r = 0.799; p < 0.001). There were no significant differences in the mCBF values based on physical features, such as patients' height, weight, and age. Our findings suggest that 123I-IMP brain perfusion SPECT with e-NIMS is the simplest semi-quantitative method that can provide supportive data for invasive CBF quantification. This method may be useful, especially in pediatric brain perfusion SPECT, when blood sampling or identifying pulmonary arteries for CO estimation using the graph plot method is difficult.

[The Nationwide Survey on Avoidance of Targeted Radionuclide Therapy in Patients with Limited Activities of Daily Living and Those Undergoing Hemodialysis].

Targeted radionuclide therapy with high-dose radioisotopes should be performed in isolation rooms. Patients can be released only after radioactivity remaining in their bodies becomes less than the limits determined by the release criteria in order to secure public protection. Patients are asked to stay in isolation rooms for a few days. Physicians often face difficulties to carry out therapy in patients with limited activities of daily living and those undergoing hemodialysis, and have to avoid therapy in such cases. The Japanese Society of Nuclear Medicine conducted a nationwide survey in order to find out the actual situation. The survey results should reflect future improvement of therapeutic environment in collaborating with related societies and administrative bodies.

Diagnostic value of ultrasonography and TI-201/Tc-99m dual scintigraphy in differentiating between benign and malignant thyroid nodules.

PURPOSE: To evaluate the performance of ultrasonography (US) and TI-201/Tc-99m dual (Tl/Tc) scintigraphy in differentiating between benign and malignant thyroid nodules. METHODS: Eighty-six patients diagnosed to have a thyroid tumor on postoperative histopathologic examination between June 2009 and February 2017 were included in this retrospective study. A radiologist reviewed the US and Tl/Tc scintigraphy reports along with all available clinical and histopathologic information. On Tl/Tc scintigraphy, a nodule in which uptake was higher in the delayed phase than in the surrounding parenchyma was defined as a delayed accumulation pattern and a nodule in which uptake was higher in the delayed phase than in the early phase was defined as a persistent pattern. The Tl/Tc scintigraphy images were evaluated in a blinded manner to assess reproducibility. A statistical analysis was performed to identify features associated with malignancy. Interobserver variability was calculated using the κ statistic. RESULTS: US had higher sensitivity (81.2%), specificity (88.2%), and positive (96.6%) and negative (53.6%) predictive values than Tl/Tc scintigraphy. An ill-defined margin and microcalcification were independent predictors of a malignant thyroid nodule on multivariate logistic regression (P = 0.003 and P = 0.014, respectively). The persistent pattern had high specificity (85.7%) equivalent to that of US but had lower sensitivity (34.7%). The κ values for the delayed accumulation and persistent patterns were 0.66-0.78 and 0.32-0.50, respectively. CONCLUSIONS: An ill-defined margin and microcalcification on US were independent predictors of a malignant thyroid nodule. A persistent pattern seen on Tl/Tc scintigraphy could contribute to the differential diagnosis.

[Report in 2017 April ～ 2018 March].

Women physicians, scientists and nurses are addressing many problems encountered in the practice of their chosen fields. We carried out a survey of the women working in the nuclear medicine field. Two hundred and six professionals answered this questionnaire. The findings of our survey were that we have many female bosses (experts), a low number of sexual harassment issues and enough parental leave. Many members work very hard to practice in this field, but they do not have enough support from their hospitals or research centers, to join medical conferences. And almost a quarter of those surveyed thought it is hard to improve their careers after taking parental leave. A change of perception in how their male colleagues and counterparts regard women in the field of nuclear medicine is required. This change, along with women having a clear and realistic career plan are fundamental answers to the issues faced by women in nuclear medicine.

The outcome of I-131 ablation therapy for intermediate and high-risk differentiated thyroid cancer using a strict definition of successful ablation.

PURPOSE: This article examines the outcome of radioactive iodine ablation therapy for thyroid cancer in high-risk patients and investigates background factors influencing ablation failure. MATERIALS AND METHODS: We included 91 patients in this retrospective analysis and evaluated the ablation success rate. Successful ablation was defined as the absence of visible iodine-131 (I-131) accumulation in the thyroid bed after whole-body scans and thyroglobulin levels <2 ng/ml in a TSH-stimulated state after ablation. We extracted data on patients' age, sex, I-131 dose, pathology, resection stump findings, tumor T category and thyroglobulin levels, which could affect ablation outcome. RESULTS: Successful ablation was achieved in only 14 patients (15.4%). Pre-ablation serum thyroglobulin levels were significantly higher in the ablation failure group than in the success group (P < 0.001), while no significant differences were found for other factors between the groups. Furthermore, thyroglobulin levels >10 ng/ml were significantly related to ablation failure after multivariate analysis (odds ratio 27.2; 95% confidence interval 2.469-299.7; P = 0.007). CONCLUSION: The ablation success rate was very low because of high thyroglobulin levels, even with high-dose I-131. High-risk patients, especially those with high thyroglobulin levels (>10 ng/ml), are unlikely to reach levels low enough to meet successful ablation criteria.