Incidence of residual perfusion defects by lung scintigraphy in patients treated with rivaroxaban compared with warfarin for acute pulmonary embolism.

Residual perfusion defects (RPD) as detected by lung scintigraphy occur in over 50% of patients with acute pulmonary embolism (PE) treated with vitamin K antagonists but there is lack of data in patients treated with direct oral anticoagulants. The aim of this retrospective study was to estimate the incidence of RPD detected by ventilation perfusion (VQ) scan at 3-6 months in patients with first acute symptomatic PE treated with rivaroxaban compared to warfarin. Consecutive eligible patients treated with rivaroxaban as part of a previous study were identified. The Monash Health Radiology database was used to identify a historical cohort of age matched (± 5 years) patients treated with warfarin. Follow-up VQ scans were classified as normal (no perfusion defect) or abnormal (matched or unmatched perfusion defects) by two independent nuclear medicine physicians blinded to treatment. Any disagreement was resolved by consensus. One hundred and ninety patients with PE (95 in each cohort) were included (mean age 56.8 years; 41.1% males; 54.2% unprovoked). In the overall cohort, 31.1% had RPD with a significantly lower incidence of RPD in rivaroxaban treated patients 23.2% (95% CI 15.8-32.6), compared to warfarin 38.9% (95% CI 29.8-49.0). Treatment with rivaroxaban was associated with a significantly lower incidence of RPD detected by VQ scan at 3-6 months compared to warfarin. This supports recent in-vitro data suggesting an indirect enhancement of fibrinolysis by direct oral Xa inhibitors but requires confirmation in larger studies.

Solid ectopic cervical thymus in neonates with thyroid agenesis.

We report a series of ectopic thymus glands as detected by sonography in infants with thyroid agenesis. The patients were children who underwent nuclear medicine and sonography for congenital hypothyroidism. Of the 12 patients with a diagnosis of thyroid agenesis over a 5-year period, 4 (33%) were shown to have ectopic thymic tissue. Although a cervical ectopic thymus has been previously reported, there is very little discussion of it occurring in conjunction with thyroid agenesis. This case series highlights the importance of recognition of ectopic thymic tissue when examining for thyroid tissue in the setting of congenital hypothyroidism.

Integrated clinical and genomic evaluation of guadecitabine (SGI-110) in peripheral T-cell lymphoma.

Peripheral T-cell lymphoma (PTCL) is a rare, heterogenous malignancy with dismal outcomes at relapse. Hypomethylating agents (HMA) have an emerging role in PTCL, supported by shared mutations with myelodysplasia (MDS). Response rates to azacitidine in PTCL of follicular helper cell origin are promising. Guadecitabine is a decitabine analogue with efficacy in MDS. In this phase II, single-arm trial, PTCL patients received guadecitabine on days 1-5 of 28-day cycles. Primary end points were overall response rate (ORR) and safety. Translational sub-studies included cell free plasma DNA sequencing and functional genomic screening using an epigenetically-targeted CRISPR/Cas9 library to identify response predictors. Among 20 predominantly relapsed/refractory patients, the ORR was 40% (10% complete responses). Most frequent grade 3-4 adverse events were neutropenia and thrombocytopenia. At 10 months median follow-up, median progression free survival (PFS) and overall survival (OS) were 2.9 and 10.4 months respectively. RHOAG17V mutations associated with improved PFS (median 5.47 vs. 1.35 months; Wilcoxon p = 0.02, Log-Rank p = 0.06). 4/7 patients with TP53 variants responded. Deletion of the histone methyltransferase SETD2 sensitised to HMA but TET2 deletion did not. Guadecitabine conveyed an acceptable ORR and toxicity profile; decitabine analogues may provide a backbone for future combinatorial regimens co-targeting histone methyltransferases.

PET/MRI in paediatric disease.

Nuclear medicine and molecular imaging have a small but growing role in the management of paediatric and neonatal diseases. During the past decade, combined PET/MRI has emerged as a clinically important hybrid imaging modality in paediatric medicine due to diagnostic advantages and reduced radiation exposure compared to alternative techniques. The applications for nuclear medicine, radiopharmaceuticals and combined PET/MRI in paediatric diagnosis is broadly similar to adults, however there are some key differences. There are a variety of clinical applications for PET/MRI imaging in children including, but not limited to, oncology, neurology, cardiovascular, infection and chronic inflammatory diseases, and in renal-urological disorders. In this article, we review the applications of PET/MRI in paediatric and neonatal imaging, its current role, advantages and disadvantages over other hybrid imaging techniques such as PET/CT, and its future applications. Overall, PET/MRI is a powerful imaging technology in diagnostic medicine and paediatric diseases. Higher soft tissue contrasts and lower radiation dose of the MRI makes it the superior technology compared to other conventional techniques such as PET/CT or scintigraphy. However, this relatively new hybrid imaging has also some limitations. MRI based attenuation correction remains a challenge and although methodologies have improved significantly in the last decades, most remain under development.

Bronchiectasis simulating pulmonary metastases on iodine-131 scintigraphy in well-differentiated thyroid carcinoma.

Differentiated thyroid cancer is an uncommon disease that carries a good prognosis when treated adequately. Radioiodine treatment is often used as an adjunct to surgery because this has been associated with increased survival, particularly in the presence of iodine-avid soft tissue metastases. Multiple different false-positive scans can occur in the absence of residual thyroid tissue or metastases. Recognition of these potential false-positive iodine-131 (I-131) scans is critical to avoid the unnecessary exposure to further radiation from repeated therapeutic doses of radioactive iodine. We report a case of physiological uptake of radioactive iodine in the bronchiectatic bronchial tree bilaterally, potentially masquerading as pulmonary metastases.

Intravascular small cell neuroendocrine tumor in the neck.

A 40-year-old man presented with a painless enlarging right neck mass over several weeks without a history of trauma or infection. Ultrasound, contrast-enhanced CT, and MRI showed a mass in an expanded vein extending into the parotid gland. Blood-stained fine-needle aspiration biopsy demonstrated atypical lymphoid cells, but there was insufficient material for a diagnosis. The mass was intensely avid on 18F-FDG PET/CT and was suggestive of a neoplasm. Excision confirmed a mass within the external jugular vein with areas of invasion through the vessel wall. A diagnosis of small cell neuroendocrine carcinoma was made on histology.

The role of scintigraphy and ultrasound in the imaging of neonatal hypothyroidism: 5-year retrospective review of single-centre experience.

INTRODUCTION: Congenital hypothyroidism (CH), as indicated by an elevation of capillary thyroid-stimulating hormone (TSH) at newborn screening, is a preventable cause of mental retardation with varying aetiology; it can be transient or permanent. Radionuclide assessment is currently the gold standard for imaging CH. This study aimed to (i) review the different scintigraphic patterns and correlate them with TSH levels/patient outcomes, (ii) assess the role of sonography in neonates with apparent agenesis as indicated by scintigraphy and (iii) develop a diagnostic investigative algorithm. METHODS: The technetium thyroid scans of 83 consecutive patients (49 females, average age 32 days) with CH scanned between 2005 and 2009 were retrospectively reviewed. Two nuclear medicine physicians blinded to the clinical details interpreted the scans in consensus. Scintigram appearances were categorised into five groups. Patients scintigraphically diagnosed with thyroid agenesis were evaluated with ultrasound. TSH values and scintigraphic and sonographic findings were correlated with patients' final diagnosis. RESULTS: Based on scintigraphy, 14, 13 and 19 patients out of 83 were assessed as having normal thyroid sites with normal, increased and decreased uptake, respectively. Twenty-two of 83 patients had no uptake, and 15 of 83 patients had ectopic uptake. Higher median TSH levels were seen in no-uptake and ectopic uptake subgroups. Eighteen of 22 patients with no uptake were evaluated with ultrasound. Three of the 18 patients had a normal thyroid gland, and three of 18 patients had a hypoplastic thyroid. CONCLUSION: Scintigram findings in patients with congenital hypothyroidism fall into five major categories, which have therapeutic implications (lifelong thyroxine in agenesis versus trial of stopping thyroxine in other subgroups). Sonographic demonstration of thyroid tissue in patients scintigraphically diagnosed with thyroid agenesis has major management implications.

(11)C-acetate PET/CT in a case of recurrent hemangiopericytoma.

Intracranial hemangiopericytoma (IHPC) is a rare tumor representing less than 1% of all CNS tumors and is often indistinguishable from meningioma on structural imaging alone. Unlike meningioma, IHPC is an aggressive tumor with the propensity for early locoregional recurrence and distant metastases. Hence, its management strategies differ greatly from that of meningioma. Some investigators have reported the potential role of multitracers (F-FDG, C-methionine, and O-H2O) PET imaging in distinguishing IHPC from meningioma. We described the findings of dual-tracer (C-acetate and F-FDG) PET/CT imaging in a histopathologically proven case of IHPC with extensive extracranial osseous metastases that showed significantly greater C-acetate avidity.

Malignant pheochromocytoma metastasis to the breast shown on I-123 MIBG scan.

A 36-year-old woman was referred to our department for I-123 metaiodobenzylguanidine (MIBG)-SPECT/CT scan 3 years after surgical excision of pheochromocytoma. She was referred due to recurrence of her symptoms as well as raised urinary catecholamines. Review of I-123 MIBG scan revealed multiple MIBG-avid metastatic lesions. Most of these were bony lesions, however, there were also 2 soft tissue lesions in the left breast. She subsequently underwent ultrasound-guided fine-needle aspiration of the left breast lesions. Fine-needle aspiration revealed cytologic changes consistent with pheochromocytoma. There has only been 1 previous reported case of pheochromocytoma metastasizing to the breast. This is the first case in which the metastasis was detected by I-123 MIBG scan.