Iranian Journal of Nuclear Medicine
Volume:30 Issue: 2, Summer-Autumn 2022

The initial post-surgical radioactive iodine (RAI) therapy for patients with papillary thyroid cancer (PTC) is postponed due to increased demand as well as the limited number of centers to provide RAI therapy. Hence, our aim was to investigate the role of first RAI administration time following thyroidectomy on the number of incomplete response (IR) during the initial follow up, while considering other prognostic factors. Two hundred and thirty-five PTC patients who were admitted to our department for RAI therapy were included in this study. They were allocated into two groups with <3 months (early group) and ≥ 3 months (delayed group) time interval after the first RAI therapy, and the total thyroidectomy. Then, based on the response to RAI therapy, patients were categorized as excellent, biochemical incomplete, structural incomplete, or indeterminate responses (ER, BIR, SIR or IDR, respectively). With respect to age, gender, pathologic variables, RAI dose rate and IR (BIR+SIR) rate, significant differences were found between the two groups. The findings identified that early RAI failed to affect the rate of IR (univariate analysis: HR=1.09, 95%CI: 0.69-1.74, P=0.71; Cox model: HR=0.81, 95%CI: 0.46-1.44, P=0.47). However, Cox multivariate analysis found lymph node status and thyroglobulin level (Lymph node status: HR=2.88, 95%CI: 1.07-7.78, P=0 .04) as independent risk factors for IR during the initial follow up. Therefore, timing of the first post-surgery RAI therapy is not a significant prognosticator of the initial response of patients to therapy.

2-[18F]fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (2-[18F]FDG-PET/CT) is implemented in papillary thyroid cancer (PTC) patients with elevated Thyroglobulin (Tg) and negative Iodine-131 whole-body scan (131I-WBS). Here, we evaluated the impact of TSH stimulation after levothyroxine withdrawal on the detection rate of 2-[18F]FDG-PET/CT. A prospective study was performed on 60 PTC patients, presented with negative 131I-WBS and elevated or unjustifiably high Tg. 2-[18F]FDG-PET/CT was performed in 30 patients while they were on levothyroxine therapy (unstimulated-TSH [uns-TSH]) and after Levothyroxine withdrawal in the other 30 patients (stimulated-TSH [s-TSH]). Results of the two groups were compared using nonparametric tests. Receiver operating characteristic curve was used to find Tg cutoff values for predicting positive scan results. Overall, 2-[18F]FDG-PET/CT was positive in 63.3% of the patients, 80% (24/30) in s-TSH and 46.7% (14/30) in uns-TSH group. The detection rate was higher in s-TSH group (p=0.007). It was still significant in multiple regression analysis (p=0.041). In uns-TSH group, 2-[18F]FDG-PET/CT was more often positive in patients with higher uns-Tg level (p=0.002). An uns-Tg level of ≥19.00 ng/mL predicted positive results with the sensitivity of 0.786 and specificity of 0.750 (area under curve=0.819). Although statistically insignificant (p=0.055), s-Tg was higher in patients with positive 2-[18F]FDG-PET/CT studies in the s-TSH group. No relation was demonstrated between TSH and anti-Tg-antibody levels and 2-[18F]FDG-PET/CT positivity. TSH-stimulation after levothyroxine withdrawal might enhance the detection rate of 2-[18F]FDG-PET/CT in PTC patients. Additionally, 2-[18F]FDG-PET/CT is more often positive in patients with higher Tg levels.

Radiation monitoring of professionally exposed workers is obligatory in nuclear medicine departments. The purpose of our study was to evaluate the radiation exposure dose received by medical workers during radioguided sentinel lymph node biopsy in breast cancer and endometrial cancer patients. Radiation exposure dose of medical staff was prospectively recorded during 35 radioguided sentinel lymph node biopsy procedures in a 6-month period. All patients received 4 mCi [99mTc]Tc-SENTI-SCINT on the day of surgery. Thermoluminescent dosimeters in the shape of a bracelet, ring and badge were used for recordings and data was compared to dose limits imposed by the regulations. Mean time interval between activity administration and surgery was 223.63 min and mean duration of surgery was 142.5 min. The recorded 6-month cumulative dose was 0.33 mSv for the senior surgeon, 0.25 mSv for the surgeon's first assistant, 0.24 mSv for the anesthesiologist and 0.54 for both nuclear medicine physician and resident. The approximately equivalent dose for the surgical staff in each procedure was 9.7 µSv, 7.3 µSv and 7.05 µSv respectively, which means that the senior surgeon could perform 106 and 2127 sentinel lymph node biopsy procedures per year in order to reach the annual dose limit for a public member and a radiation worker. Occupational radiation exposure dose of medical staff during radioguided sentinel lymph node biopsy is low and under annual dose limits, requiring no routinely personal dosimetry for surgical staff performing the procedure.

Considering that quantitative methods are usually more reproducible with lower inter-observer variability, the purpose of this research was to compare the prognostic value of the two quantitative method with quantitative perfusion SPECT (QPS) software. This study was performed prospectively and included 200 participants who were referred for myocardial perfusion imaging. These participants were selected by the convenience sampling method. All patients were followed up after one year. Patients were classified as those with and without major cardiac events, including cardiac death, non-fatal myocardial infarction, open-heart surgery, abnormal angiographic findings, and unstable angina. There were 62 male (31.0%) and 138 female (69.0%) patients, ranging in age from 30 to 86 years. The results indicated that the major cardiac events were significantly higher in moderate and severe categories based on summed stress score (SSS) (P=0.024) and total perfusion deficit (TPDs) (P=0.002) scores. SSS score with TPDs score (P = 0.764), summed rest score (SRS) with TPDr score (P = 0.583) and SDS with ΔTPD (P = 0.118) were compatible for predicting major heart events within a year. Total perfusion deficits obtained from QPS software is a useful method for predicting major cardiac events in patients with suspected cardiovascular disease (CVD). Predictive ability of TPD was similar to that of the semi-quantitative method with an expert interpreter's help. Moreover, this method can be helpful for CAD diagnosis and therapeutic evaluation of patients.

When ultrasensitive thyroglobulin (uTg) is measured serially in the first 12 months of treatment, it can probably predict recurrence of thyroid cancer without discontinuation of T4 or administration of rhTSH. Measurement of TSH, Tg, Anti-Tg Ab, and uTg was performed in all consecutive patients with low-intermediate risk DTC 2, 6, and 12 months after initial therapy. One year after surgery, response to therapy was evaluated. Tg and uTg levels in different time points and the trend of changes were used to predict response to therapy. Overall, 37 patients with a mean age of 40.3 years were studied. The mean initial uTg was significantly lower than fTg (P=0.01). Overall, the correlation coefficient was 0.45 and increased to 0.71 in ftg<10 ng/ml (P=0.005). The majority of patients (91.9%) received a mean dose of 3.3± 2.2GBq of I-131.  One year later, there was no significant difference in mean Tg and mean uTg between the two techniques (P=0.62). The mean offT4uTg is not significantly different between patients with incomplete response compared to other groups at the end of the follow-up (P=0.1). The slope of onT4uTg was 0.04±0.18 versus 0.24±0.82 in patients with and without incomplete response respectively (P=0.45). Using ROC analysis, onT4uTg slope of 0.0005 was the best cutoff to differentiate incomplete response from other responses, however, the sensitivity was only 54.5% and specificity was 75%. The trend of thyroglobulin level during suppressive therapy measured by the ultrasensitive technique cannot accurately predict excellent response in DTC patients.

Targeted radionuclide therapy with [177Lu]Lu-prostate-specific membrane antigen (PSMA) has shown promising results for the treatment of castration-resistant prostate cancer (mCRPC). Nevertheless, a proportion of patients do not respond to this therapy. Here, we aimed to evaluate the prognostic significance of the pretreatment pathologic and laboratory factors for the prediction of biochemical response to the first cycle of [177Lu]Lu-PSMA therapy. In this retrospective study, mCRPC patients, referred for [177Lu]Lu-PSMA therapy, were included. We retrieved the data of patients, undergone [177Lu]Lu-PSMA, from March 2019 to March 2021. Multiple baseline pathologic and laboratory parameters were extracted and correlated with the response to the first cycle. The prostate-specific antigen (PSA) level was evaluated six weeks after [177Lu]Lu-PSMA therapy for the biochemical response. Forty-three patients with a mean age of 69.8±10.2 were included. Bone and visceral metastases were present in 81.4% and 14.0% of the patients, respectively. Except for two, all patients had received hormone- and chemotherapy. The mean PSA level was 189.9±259.0 at baseline. Following one cycle of [177Lu]Lu-PSMA, “≥ 10% PSA response” and “≥ 50% PSA response” were seen in 81.4% and 44.2% of the patients, respectively. Patients with higher baseline PSA more frequently had ≥ 10% PSA response (p= 0.004). Also, the reduction in the PSA level correlated with baseline PSA (p=0.013, r=0.375). [177Lu]Lu-PSMA therapy results in the biochemical response in a considerable number of patients after one cycle. In nearly half of patients, PSA declines more than 50%. Higher baseline PSA is correlated with the level of PSA response.

Negative radioiodine (131I) whole-body scan with elevated serum thyroglobulin (Tg) level are found in 20% of patients with differentiated thyroid cancer (DTC), which can be a diagnostic challenge. We evaluated the efficacy of Technetium-99m-Hydrazinonicotinyl-Tyr3-Octreotide ([99mTc]Tc-HYNIC-TOC) somatostatin receptor scintigraphy (SRS) for detection of non-iodine-avid metastases and its impact on staging and management of these patients. The study population consisted of 35 DTC patients (25 females; PTC = 88.2%, FTC = 11.8%) who had elevated serum Tg levels despite negative post-ablation radioiodine whole-body scan. All patients underwent whole body SRS 3-4 hours after intravenous injection of 20mCi (740 MBq) of [99mTc]Tc-HYNIC-TOC. Sites of suspected radiotracer accumulation were confirmed with anatomic imaging. Ultimately, corresponding changes in the staging and management were recorded. SRS was positive in 27 (77.1%) cases. Patients with positive scan had significantly higher Tg levels at the time of scan, compared to those with negative scans (154.5±188.6 vs. 28.2±32.7 ng/mL, p-value = 0.005). Interestingly, previous history of neck external beam radiation therapy (EBRT) was significantly correlated with [99mTc]Tc-HYNIC-TOC avidity (Likelihood ratio = 11.2, p = 0.005). Addition of SSTR scintigraphy changed overall staging and management in 11% and 32.4% of the patients, respectively. SRS can be a useful diagnostic adjunct in DTC patients with highly elevated Tg and negative radioiodine whole-body scan. The likelihood of positive findings on [99mTc]Tc‑HYNIC‑TOC was higher in cases with previous history of EBRT or high Tg levels (i.e. suppressed-Tg >80 ng/mL) at the time of scan.

Auto-immune hypothyroidism being the common cause of hypothyroidism with usual clinical features like constipation, fatigue, cold intolerance and weight gain can rarely present with neurologic problems like reversible cerebellar ataxia, dementia, peripheral neuropathy, psychosis and coma.  In this manuscript we present a case that was evaluated with a suspicion of paraneoplastic syndrome for cerebellar ataxia. 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) PET-CT scan showed diffuse hypometabolism in both cerebellar lobes and diffusely increased metabolic activity in thyroid gland. Further investigations revealed the hypothyroidism with positive Anti-TPO antibody. Thyroid replacement therapy was started and patient showed significant clinical as well as biochemical improvement after 3 weeks. The main aim of this case report is to highlight the fact that hypothyroidism has to be considered in all patients who present with acute onset of cerebellar ataxia and [18F]FDG PET-CT scan was helpful as imaging modality in this case.

An eighty-year-old lady a with history of treated tuberculosis decades ago and polymerase chain reaction (PCR) proven COVID-19 pneumonia about four months ago was referred to our department for ventilation/perfusion scan due to deteriorating dyspnea to rule out P.E. Planar perfusion scan showed bilateral accentuated apical perfusion gradient and multiple segmental and non-segmental perfusion defects in both lungs, which were mismatched with relatively normal planar ventilation images. Perfusion SPECT images also showed multiple segmental, sub-segmental and semi-segmental perfusion defects, which proved to be concordant with consolidations, bilateral pleural effusion, right lung pneumothorax, and atelectasis which were consultant with CT findings. The ventilation SPECT/CT images also demonstrated uniform tracer activity throughout both lungs, with almost complete improvement in consolidations, lung pneumothorax, pleural effusion, and atelectasis. Our case highlights the importance of SPECT/CT imaging in avoiding false-positive interpretation of pulmonary embolism as well as the possibility for rapid resolution of the lung parenchymal abnormalities.

Occurrence of small-vessel occlusions (thrombotic microangiopathy, TMA) in association with antiphospholipid antibodies (aPL ab) has been documented. But isolated involvement of gall bladder due to TMA in secondary aPLS (antiphospholipid syndrome) in post-partum status has been unreported. aPL and systemic lupus erythematosus (SLE) are two closely related diseases that not only share lupus susceptibility genes but can also produce thrombosis. Here we present a young lady, recently delivered with SLE experiencing moderate to severe right abdominal pain and occasional vomiting. A hepatobiliary iminodiacetic acid (HIDA) scan revealed non visualization of gall bladder (GB) confirming the diagnosis of acute acalculous cholecystitis (AAC). Investigations revealed high titre of anti-β2 glycoprotein I (β2GPI) IgG and anti-Cardiolipin (aCL) IgG antibodies confirming aPL syndrome. Antinuclear antibody, double-strand dsDNA was found to be positive confirming SLE. Open cholecystectomy was performed and histology revealed AAC, vasculitis with small vessel ischemia of gallbladder. GB non visualization on HIDA scan (ACC) due to solitary thrombotic microangiopathy of GB is being highlighted in this case of active SLE and secondary aPLS. Early diagnosis is mandatory to avoid repetitive thrombotic occlusions in active cases of SLE with aPLS.

A 73 y/o male with first presentation of urinary retention from two months ago referred to our department by an urologist for prostate cancer staging. The patient had gleason score of 5+4 and total PSA of 79. He underwent [99mTc]Tc-MDP and [99mTc]Tc-HYNIC-PSMA scans on two different days. The bone study revealed diffuse uptake in sacrum and a focus of abnormal [99mTc]Tc-MDP activity in the right SI joint. Another focus was also noted in right pubic region best seen on anterior projection which later on SPECT/CT was confined to a bladder diverticulum with tracer accumulation protruding into the right inguinal canal forming a hernial sac. Following a few days, [99mTc]Tc-HYNIC-PSMA scan was carried out and depicted high uptake in sacrum and right pubic region as well. The uptake was again localized to the bladder hernia on dedicated SPECT/CT acquisition. The findings denotes an important differential diagnosis of the pubic metastases as well as added value of SPECT/CT imaging in aforementioned scans.