Delineation and agreement of FET PET biological volumes in glioblastoma: results of the nuclear medicine credentialing program from the prospective, multi-centre trial evaluating FET PET In Glioblastoma (FIG) study-TROG 18.06.

PURPOSE: The O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) PET in Glioblastoma (FIG) trial is an Australian prospective, multi-centre study evaluating FET PET for glioblastoma patient management. FET PET imaging timepoints are pre-chemoradiotherapy (FET1), 1-month post-chemoradiotherapy (FET2), and at suspected progression (FET3). Before participant recruitment, site nuclear medicine physicians (NMPs) underwent credentialing of FET PET delineation and image interpretation. METHODS: Sites were required to complete contouring and dynamic analysis by ≥ 2 NMPs on benchmarking cases (n = 6) assessing biological tumour volume (BTV) delineation (3 × FET1) and image interpretation (3 × FET3). Data was reviewed by experts and violations noted. BTV definition includes tumour-to-background ratio (TBR) threshold of 1.6 with crescent-shaped background contour in the contralateral normal brain. Recurrence/pseudoprogression interpretation (FET3) required assessment of maximum TBR (TBRmax), dynamic analysis (time activity curve [TAC] type, time to peak), and qualitative assessment. Intraclass correlation coefficient (ICC) assessed volume agreement, coefficient of variation (CoV) compared maximum/mean TBR (TBRmax/TBRmean) across cases, and pairwise analysis assessed spatial (Dice similarity coefficient [DSC]) and boundary agreement (Hausdorff distance [HD], mean absolute surface distance [MASD]). RESULTS: Data was accrued from 21 NMPs (10 centres, n ≥ 2 each) and 20 underwent review. The initial pass rate was 93/119 (78.2%) and 27/30 requested resubmissions were completed. Violations were found in 25/72 (34.7%; 13/12 minor/major) of FET1 and 22/74 (29.7%; 14/8 minor/major) of FET3 reports. The primary reasons for resubmission were as follows: BTV over-contour (15/30, 50.0%), background placement (8/30, 26.7%), TAC classification (9/30, 30.0%), and image interpretation (7/30, 23.3%). CoV median and range for BTV, TBRmax, and TBRmean were 21.53% (12.00-30.10%), 5.89% (5.01-6.68%), and 5.01% (3.37-6.34%), respectively. BTV agreement was moderate to excellent (ICC = 0.82; 95% CI, 0.63-0.97) with good spatial (DSC = 0.84 ± 0.09) and boundary (HD = 15.78 ± 8.30 mm; MASD = 1.47 ± 1.36 mm) agreement. CONCLUSION: The FIG study credentialing program has increased expertise across study sites. TBRmax and TBRmean were robust, with considerable variability in BTV delineation and image interpretation observed.

Factors associated with delay to carotid endarterectomy for acute ischaemic stroke in South Australia: A multicentre retrospective cohort study.

BACKGROUND: The greatest benefits of carotid endarterectomy (CEA) accrue when performed within two weeks of acute ischaemic stroke (AIS) due to symptomatic carotid stenosis. Previous studies have identified multiple factors contributing to CEA delay. AIMS: To determine factors associated with delayed CEA in patients admitted to tertiary stroke centres within a major metropolitan region with AIS METHODS: In a retrospective cohort study, consecutive patients admitted to the tertiary hospitals with stroke units within South Australia (Lyell McEwin Hospital, Royal Adelaide Hospital and Flinders Medical Centre) between 2016 to 2020 were included. Univariable and multivariable logistic regression were used to identify individual factors associated with time from symptom onset to CEA of over two weeks. RESULTS: A total of 174 patients were included. The median time to CEA was 5 days (IQR 3-9.75). Delayed CEA beyond 14 days occurred in 28/174 (16%). Factors most associated with delayed CEA included presentation to a tertiary hospital without onsite Vascular Surgical Unit (OR 3.71, 95%CI 1.31-10.58), history of previous stroke (OR 3.38, 95% CI 1.11-9.84) and presenting NIHSS above 6 (OR 5.16, 95% CI 1.60-16.39). CONCLUSION: This study identified that presentation to a tertiary hospital without a Vascular Surgery Unit, history of previous stroke and presenting NIHSS above 6 were associated with delay to CEA in AIS patients in South Australia. Interventional studies aiming to improve the proportion of patients that receive CEA within 14 days are required.

Primary leptomeningeal low-grade Schwann cell neoplasm.

We discuss an extremely rare case of low-grade Schwann cell leptomeningeal neoplasm with no evident intradural primary, presenting with rapid neurological decline leading to death reflecting the aggressive biological behaviour of this entity despite its low-grade morphology. Notwithstanding extensive investigations, the diagnosis was only established on autopsy as clinical presentation is non-specific making diagnosis challenging. This condition could be considered in patients presenting with leptomeningeal disease if initial workup of more common causes is non-revealing.

Cerebral microbleed distribution following cardiac surgery can mimic cerebral amyloid angiopathy.

BACKGROUND AND AIMS: Having anecdotally noted a high frequency of lobar-restricted cerebral microbleeds (CMBs) mimicking cerebral amyloid angiopathy (CAA) in patients with previous cardiac surgery (especially valve replacement) presenting to our transient ischaemic attack (TIA) clinic, we set out to objectively determine the frequency and distribution of microbleeds in this population. METHODS: We performed a retrospective comparative cohort study in consecutive patients presenting to two TIA clinics with either: (1) previous coronary artery bypass grafting (CABG) (n=41); (2) previous valve replacement (n=41) or (3) probable CAA (n=41), as per the Modified Boston Criteria, without prior cardiac surgery. Microbleed number and distribution was determined and compared. RESULTS: At least one lobar-restricted microbleed was found in the majority of cardiac surgery patients (65%) and 32/82 (39%) met diagnostic criteria for CAA. Valve replacement patients had a higher microbleed prevalence (90 vs 51%, p<0.01) and lobar-restricted microbleed count (2.6±2.7 vs 1.0±1.4, p<0.01) than post-CABG patients; lobar-restricted microbleed count in both groups was substantially less than in CAA patients (15.5±20.4, p<0.01). In postcardiac surgery patients, subcortical white matter (SWM) microbleeds were proportionally more frequent compared with CAA patients. Receiver operator curve analysis of a 'location-based' ratio (calculated as SWM/SWM+strictly-cortical CMBs), revealed an optimal ratio of 0.45 in distinguishing cardiac surgery-associated microbleeds from CAA (sensitivity 0.56, specificity 0.93, area under the curve 0.71). CONCLUSION: Lobar-restricted microbleeds are common in patients with past cardiac surgery, however a higher proportion of these CMBs involve the SWM than in patients with CAA.

Influenza B-related meningoencephalitis in adults.

We present a case involving an 85-year-old man with acute confusion and new onset seizure following a 1-week history of respiratory prodrome. This case report describes a case of influenza B-related meningoencephalitis supported by evidence of an influenza B infection and temporal relation of the neurological event and respiratory illness in the absence of other identifiable cause. Diagnosis is guided by cerebrospinal fluid profile and nasopharyngeal PCR. Treatment is largely supportive and the effect of vaccination on prevention of this neurological complication remains unclear.

Autoimmune limbic encephalitis with anti-contactin-associated protein-like 2 antibody secondary to pembrolizumab therapy.

Immune checkpoint inhibitors such as Pembrolizumab are used to restore antitumour immune response. It is important to be vigilant of immune mediated adverse events related to such therapy. We report a case of autoimmune limbic encephalitis with Contactin-Associated Protein-like 2 (CASPR2) antibody secondary to Pembrolizumab therapy for metastatic melanoma.