Differential Diagnosis of a Solitary Bone Lesion Using SPECT/CT Method

Relevance: Radionuclide bone scan signs of lesions are not specific and require radiological identification. Hybrid tomographic technology is a combination of spatial distribution of radiopharmaceuticals and its anatomical binding. Thus, makes it possible to accurately identify the affected bone structure and also determine the nature of this changes (radiological anatomy). In cancer patients, SPECT/CT method allows to visualize tumor pathology in the bones, but also keeps to a minimum errors and other excessive examinations.Purpose: To demonstrate the most frequent diseases and conditions that simulate tumor lesions in bones on bone scan.Material and methods: We analyzed the results of examinations of 81 patients with various tumor diseases (2015–2020). Bone scan was performed in the whole body 3 hours later, after intravenous administration of 99mTc-phosphotech on a Symbia E, T2 (Siemens, Germany). SPECT/CT was performed after WB Bone Scan.Results: The most frequent reasons for the focal increased uptake of radiopharmaceutical were: reactive increase in metabolism and as a result additional mineral repair: deforming osteoarthritis, osteophytes; post‑traumatic and postoperative changes; fractures (osteoporosis and stress fractures); inflammatory processes; focal uptake due to the benign neoplasms of bones and dysplasia. Combination of highly sensitive but non-specific scintigraphy with highly specific computed tomography makes it especially useful in anatomically difficult areas.Conclusion: SPECT/CT reveals a direct pater of anatomical and structural abnormalities with changes in bone tissue metabolism in case of different injuries and minimizes a number of ambiguous conclusions. SPECT/CT in oncological practice greatly helps nuclear medicine physician in the differential diagnostic process and reduces time of examination for the patient.

An Incidental Pancreatic Finding at 18F-Choline PET/CT: Chronic Mass-Forming Pancreatitis

We present a case of a chronic mass-forming pancreatitis (CMFP) detected by 18F-choline (FCH) PET/CT in a male affected by prostate cancer. FCH PET/CT scan showed a focal uptake in the uncinate process of the pancreas, later diagnosed as a CMFP at biopsy. Although the physiological distribution of FCH in the pancreas, a careful interpretation of the images in this area is warranted.

Artificial intelligence could alert for focal skeleton/bone marrow uptake in Hodgkin’s lymphoma patients staged with FDG-PET/CT

To develop an artificial intelligence (AI)-based method for the detection of focal skeleton/bone marrow uptake (BMU) in patients with Hodgkin’s lymphoma (HL) undergoing staging with FDG-PET/CT. The results of the AI in a separate test group were compared to the interpretations of independent physicians. The skeleton and bone marrow were segmented using a convolutional neural network. The training of AI was based on 153 un-treated patients. Bone uptake significantly higher than the mean BMU was marked as abnormal, and an index, based on the total squared abnormal uptake, was computed to identify the focal uptake. Patients with an index above a predefined threshold were interpreted as having focal uptake. As the test group, 48 un-treated patients who had undergone a staging FDG-PET/CT between 2017–2018 with biopsy-proven HL were retrospectively included. Ten physicians classified the 48 cases regarding focal skeleton/BMU. The majority of the physicians agreed with the AI in 39/48 cases (81%) regarding focal skeleton/bone marrow involvement. Inter-observer agreement between the physicians was moderate, Kappa 0.51 (range 0.25–0.80). An AI-based method can be developed to highlight suspicious focal skeleton/BMU in HL patients staged with FDG-PET/CT. Inter-observer agreement regarding focal BMU is moderate among nuclear medicine physicians.

A Unique Presentation of a Paraganglioma and Its Consequences

Introduction: Paragangliomas (PGL) are extremely rare tumors arising from extra-adrenal neural crest cells with an incidence of 0.8 per 100,000 person-years. Sympathetic chain PGLs usually arise in the abdomen, with about 75% of them arising intra-abdominally [2]. On CT or MRI, PGLs are usually have homogenous enhancement or central areas of low attenuation. The consequences of PGLs are many, and one complication that is rarely noted is glycemic disturbances with catecholamine excess. Here, we present a case of a radiographically unique appearing PGL that resulted in dramatic improvement of diabetes after resection. Case: 41 year old male with a past medical history of diabetes, CKD and developmental delay presented with hyperglycemia. Patient’s home regimen of Glargine 15 units qHS and Humalog 5 units TID AC had run out a few days prior. Patient had Hemoglobin A1c of 11.8% mg/dL and a C-peptide of 0.4 ng/ml. Endocrine was initially consulted for glucose management. Hospital course was complicated by abdominal pain and CT imaging showed low attenuation splenic masses, retroperitoneal lymphadenopathy and a large, necrotic appearing mesenteric mass consistent with lymphoma. MRI reaffirmed mass with peripheral enhancement and central necrosis consistent with neoplasm. Patient underwent biopsy of lymphadenopathy, which came back benign and then went for biopsy of mass. As the needle entered the mass, the patient became acutely hypertensive and tachycardic. He received phentolamine with good response and labs were drawn for catecholamine producing tumor. Plasma norepinephrine level was 6048 pg/ml and a chromogranin level of 4788 ng/ml. An MIBG scan revealed focal uptake at the lesion without evidence of metastasis. In the subsequent weeks, he was alpha- and then beta-blocked and underwent resection of mass that was complicated by transient hypotension and hypoglycemia. Eventually, patient’s blood pressure was controlled and insulin requirements dropped precipitously to just requiring 4 units of glargine by discharge. Discussion: This patient had a mass on CT scan that appeared to be consistent with lymphoma as opposed to PGL that led to biopsy and subsequent catecholamine crisis. Fortunately, this was controlled and subsequent resection led to improvement in the patient’s glycemic control. It has been thought that glucose intolerance in PGL patients is due to impaired insulin release through desensitization of the beta-adrenergic receptor. Furthermore, Catecholamines, as counter-regulatory hormones, have been well documented to raise blood sugar on this basis as well. Fortunately for our patient, he survived an initial biopsy and post-operatively, was able to actually have an improvement in his glycemic control. It also is a reminder to always do a screen for PGL before doing a needle biopsy of a compatible abdominal mass.

In Vivo Imaging of Thyroid Cancer with 99mTc-TR1401 and 99mTc-TR1402: A Comparison Study in Dogs

Differentiated thyroid cancer (DTC) cells may lose NIS expression and iodine uptake, but usually express TSH receptors (TSHR). Therefore, the aim of our study was to compare two radiolabeled superagonist TSH analogues for DTC imaging. These analogues (namely TR1401 and TR1402) have a higher TSHR binding affinity than recombinant human TSH (Thyrogen®). Radiolabeling was performed with technetium-99m using an indirect method via HYNIC conjugation and was followed by in vitro quality controls and binding assay on TSHR-positive cell lines (ML-1). An in vitro binding assay was also performed and compared with radiolabeled human recombinant TSH. In vivo imaging was performed in four dogs with spontaneous follicular thyroid carcinoma with solid poorly differentiated areas with 99mTc-TR1401 SPECT/CT, 99mTc-TR1402 SPECT/CT, and [18F]FDG PET/CT on different days within 2 weeks. TR1401 and TR1402 were labeled with high specific activity (8.3 ± 1.2 MBq/µg) and retention of their biological activity and structural integrity. Both agonists were able to efficiently bind TSHR receptors expressed by cell lines with dissociation constants (Kd) of 2.7 nM for 99mTc-TR1401 and 0.5 nM for 99mTc-TR1402 compared with 99mTc-Thyrogen (Kd = 8.4 nM). In tumor-targeting experiments, a focal uptake was observed in dogs with spontaneous intraglandular thyroid carcinoma, in which TSHR expression was confirmed by immunohistochemistry. 99mTc-TR1402 provided higher T/B than 99mTc-TR1401 and [18F]FDG (12.9 ± 1.3, 10.2 ± 0.7, and 3.8 ± 0.6, respectively; all p < 0.001). Given these results, 99mTc-TR1402 appears to be a useful tool for in vivo imaging of thyroid cancer.

Penile secondary lesions: a rare entity detected by PET/CT

While penile metastases are rare, PET/CT has facilitated their detection. We aimed to describe penile secondary lesions (PSL) identified by PET/CT. We reviewed 18F-FDG and Ga68-PSMA PET/CT records performed in a single center during May 2012-March 2020, for PSL. Of 16,774 18F-FDG and 1,963 Ga68-PSMA-PET scans, PSL were found in 24(0.13%) men with a mean age of 74. PSMA detected PSL in 12 with prostate cancer; FDG identified PSL in 4 with lymphoma, 3 with colorectal cancer, 2 with lung cancer, and one each with bladder cancer, pelvic sarcoma, and leukemia. Mean SUVmax of PSL was 7.9 ± 4.2 with focal uptake in 13(54%). Mean lesion size was 16.5 ± 6.8 mm; 8 at the penile root, 4 along the shaft, and 1 at the glans. CT detected loss of the penile texture in 15(63%). PSL were observed only during relapse or follow-up of disseminated disease. Among those with prostate cancer, PSA varied widely. Fifteen (62.5%) died, at a mean 13.3 ± 15.9 months following PSL demonstration, nine had non-prostate malignancies. PET/CT identified and characterized PSL in a fraction of cancer patients, most commonly those with prostate cancer. PSL universally surfaced in advanced disease, and signaled high mortality, especially in non-prostate cancers.

Hyperparathyroidism-Jaw Tumor Syndrome

Primary hyperparathyroidism is a relatively common endocrine disorder, affecting 7 out of 1,000 adults. The median age at onset is the 6th decade of life. Our objective was to present a young patient with primary hyperparathyroidism who has a positive CDC73 mutation. A 23-year-old woman was evaluated for hypercalcemia that was found after surgery for bilateral ovarian cyst removal. Her family history included multiple family members with nephrolithiasis. The physical examination revealed a well-appearing Caucasian woman with no palpable neck mass. The laboratory results showed serum calcium at 11.7 mg/dL (ref. 8.4–10.2), ionized calcium at 1.44 mmol/L (ref. 1.12–1.32), and serum PTH at 192 pg/mL (ref. 11–65). A technetium-99 sestamibi scan revealed focal uptake inferior to the left thyroid lobe. Thyroid ultrasound showed a left parathyroid adenoma. The patient subsequently underwent left inferior parathyroidectomy, which confirmed parathyroid adenoma, with resultant normalization of serum calcium and PTH levels. Due to her young age at diagnosis, genetic testing was performed, which revealed a mutation of CDC73. Although penetrance and expression are variable, the CDC73 mutation is associated primarily with hyperparathyroidism-jaw tumor syndrome, familial isolated hyperparathyroidism, and sporadic parathyroid carcinoma. This patient currently has no evidence of jaw, uterine or renal tumors on screening imaging. Given the potential impact of inheritable neoplasia, all young patients with unexplained hyperparathyroidism should be considered for genetic screening.

Clinical validation of time reduction strategy in continuous step-and-shoot mode during SPECT acquisition

Background The SwiftScan solution (General Electric Healthcare) combines a new low-energy high-resolution sensitivity collimator and a tomographic step-and-shoot continuous (SSC) mode acquisition. The purpose of this study is to determine whether SSC mode can be used in clinical practice with shorter examination times, while preserving image quality and ensuring accurate semi-quantification. Twenty bone scan and 10 lung scan studies were randomly selected over a period of 2 months. Three sets of image datasets were produced: step-and-shoot (SS) acquisition, simulated 25% count reduction using the Poisson resampling method (SimSS), and SimSS continuous acquisition (SimSSC), where SimSS was summed with counts acquired during detector head rotation. Visual assessment (5-point Likert scale, 2 readers) and semi-quantitative evaluation (50 focal uptake from 10 bone studies), assessed by SUVmean, coefficient of variation (COV), and contrast-to-noise ratio (CNR), were performed using t test and Bland-Altman analysis. Results Intra-reader agreement was substantial for reader 1 (k = 0.71) and for reader 2 (k = 0.61). Inter-reader agreement was substantial for SS set (k = 0.93) and moderate for SimSSC (k = 0.52). Bland-Altman analysis showed a good interchangeability of SS and SimSSC SUV values. The mean CNR between SS and SimSSC was not significantly different: 42.9 ± 43.7 [23.7–62.1] vs. 43.1 ± 46 [22.9–63.3] (p = 0.46), respectively. COV values, assessing noise level, did not deviate significantly between SS and SimSSC: 0.20 ± 0.08 [0.18–0.23] vs. 0.21 ± 0.08, [0.18–0.23] (p = 0.15), respectively, whereas a significant difference was demonstrated between SS and SimSS: 0.20 ± 0.08 [0.18–0.23] vs. 0.23 ± 0.09 [0.20–0.25] (p < 0.0001), respectively. Conclusions SSC mode acquisition decreases examination time by approximately 25% in bone and lung SPECT/CT studies compared to SS mode (~ 2 min per single-bed SPECT), without compromising image quality and signal quantification. This SPECT sensitivity improvement also offers the prospect of more comfortable exams, with less motion artifacts, especially in painful or dyspneic patients.

Dosimetry of 177Lu-DOTATOC First Circle Treatment in Patients With Advanced Metastatic Neuroendocrine Tumors: a Pilot Study in China

Objective: The aim of this study was to calculate the dosimetry of 177Lu-DOTATOC in the first circle of peptide receptor radionuclide treatment (PRRT) in patients with advanced neuroendocrine tumors (NETs). Patients and Methods: Eight patients (4 female, 4 male) with NETs were enrolled in this study. All these patients with unresectable primary lesion and multiple metastasis received 177Lu-DOTATOC treatment with a single activity of 1.59-3.49 GBq (43.1-94.2 mCi) and underwent a series of whole-body planar scan at 0.5 h, 24 h, 48 h and 72 h and SPECT/CT scan at 24 h after injection. The region of interest (ROI) was drawn on the primary and metastatic lesion, the mediastinum served as control area. Therefore, the ratio of tumor-to-mediastinum (T/NT) was also calculated. The Hermes hybrid viewer dosimetry module together with OLINDA/EXM 2.0 was used to determine absorbed doses of organs and tumors. Results: No significant changes in both laboratory test was found after 177Lu-DOTATOC treatment, including renal function and blood cell analysis ( F= 0.047-1.062, P =0.364-0.959). Physiological uptake of 177Lu-DOTATOC was seen in the liver, the spleen and the kidneys. Focal uptake of 177Lu-DOTATOC was found in the tumors including primary tumors and metastatic lesions, the ratio of T/NT was 39.45 ± 28.83. The residence time of 177Lu-DOTATOC was 0.82 ± 0.12 h for left kidney, 0.80 ± 0.15 h for right kidney, 1.35 ± 0.89 h for spleen, 1.80± 2.70 h for tumors, and 30.21 ± 11.29 h for total body. Organs with the highest absorbed doses per injected activity were tumors (1.2936 ± 0.8625 mGy/MBq), spleen (0.4608 ± 0.4084 mGy/MBq), and kidneys (0.3843 ± 0.1120 mGy/MBq). The mean effective dose was 0.0392 ± 0.0158 mSv/MBq with the range of 0.0158-0.0674 mSv/MBq. In addition, Photon cross-irradiation was found to reach 19.46 % in adrenals, whereas photon can contribute less than 3% of the kidneys’ total dose. Conclusion: This study demonstrates that absorbed dose in the kidneys and spleen are relatively lower, whereas the tumor shows longer retention time and higher internal radiation absorbed dose in PRRT. PRRT is a well-tolerated treatment strategy. 177Lu-DOTATOC SPECT /CT serves as independent predictor for the evaluation of response to PRRT, which contributes to predict the response to PRRT and the related adversity.