scholarly journals Optimization of SPECT/CT imaging protocols for quantitative and qualitative 99mTc SPECT

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Dennis Kupitz ◽  
Heiko Wissel ◽  
Jan Wuestemann ◽  
Stephanie Bluemel ◽  
Maciej Pech ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Quantitative Imaging ◽  
Scatter Correction ◽  
Reconstruction Algorithm ◽  
Weighting Factor ◽  
Quantitative Spect ◽  
Pet Ct ◽  
Spect Acquisition ◽  
The Mean ◽  
A Minor

Abstract Background The introduction of hybrid SPECT/CT devices enables quantitative imaging in SPECT, providing a methodological setup for quantitation using SPECT tracers comparable to PET/CT. We evaluated a specific quantitative reconstruction algorithm for SPECT data using a 99mTc-filled NEMA phantom. Quantitative and qualitative image parameters were evaluated for different parametrizations of the acquisition and reconstruction protocol to identify an optimized quantitative protocol. Results The reconstructed activity concentration (ACrec) and the signal-to-noise ratio (SNR) of all examined protocols (n = 16) were significantly affected by the parametrization of the weighting factor k used in scatter correction, the total number of iterations and the sphere volume (all, p < 0.0001). The two examined SPECT acquisition protocols (with 60 or 120 projections) had a minor impact on the ACrec and no significant impact on the SNR. In comparison to the known AC, the use of default scatter correction (k = 0.47) or object-specific scatter correction (k = 0.18) resulted in an underestimation of ACrec in the largest sphere volume (26.5 ml) by − 13.9 kBq/ml (− 16.3%) and − 7.1 kBq/ml (− 8.4%), respectively. An increase in total iterations leads to an increase in estimated AC and a decrease in SNR. The mean difference between ACrec and known AC decreased with an increasing number of total iterations (e.g., for 20 iterations (2 iterations/10 subsets) = − 14.6 kBq/ml (− 17.1%), 240 iterations (24i/10s) = − 8.0 kBq/ml (− 9.4%), p < 0.0001). In parallel, the mean SNR decreased significantly from 2i/10s to 24i/10s by 76% (p < 0.0001). Conclusion Quantitative SPECT imaging is feasible with the used reconstruction algorithm and hybrid SPECT/CT, and its consistent implementation in diagnostics may provide perspectives for quantification in routine clinical practice (e.g., assessment of bone metabolism). When combining quantitative analysis and diagnostic imaging, we recommend using two different reconstruction protocols with task-specific optimized setups (quantitative vs. qualitative reconstruction). Furthermore, individual scatter correction significantly improves both quantitative and qualitative results.

PET/CT BiographTM Sensation 16

2006 ◽  
Vol 45 (03) ◽  
pp. 126-133 ◽  
Author(s):  
Y. Bercier ◽  
M. Schwaiger ◽  
S. I. Ziegler ◽  
M.-J. Martínez
Keyword(s):  
Image Quality ◽  
Count Rate ◽  
Signal To Noise Ratio ◽  
Reconstruction Algorithm ◽  
Considerable Change ◽  
Acquisition Time ◽  
Average Increase ◽  
Scatter Fraction ◽  
Pet Ct ◽  
Before And After

SummaryAim: The new PET/CT Biograph Sensation 16 (BS16) tomographs have faster detector electronics which allow a reduced timing coincidence window and an increased lower energy threshold (from 350 to 400 keV). This paper evaluates the performance of the BS16 PET scanner before and after the Pico-3D electronics upgrade. Methods: Four NEMA NU 2–2001 protocols, (i) spatial resolution, (ii) scatter fraction, count losses and random measurement, (iii) sensitivity, and (iv) image quality, have been performed. Results: A considerable change in both PET count-rate performance and image quality is observed after electronics upgrade. The new scatter fraction obtained using Pico-3D electronics showed a 14% decrease compared to that obtained with the previous electronics. At the typical patient background activity (5.3 kBq/ml), the new scatter fraction was approximately 0.42. The noise equivalent count-rate (RNEC) performance was also improved. The value at which the RNEC curve peaked, increased from 3.7·104s-1 at 14 kBq/ml to 6.4·104s-1 at 21 kBq/ml (2R-NEC rate). Likewise, the peak true count-rate value increased from 1.9·105s-1 at 22 kBq/ml to 3.4·105s-1 at 33 kBq/ml. An average increase of 45% in contrast was observed for hot spheres when using AW-OSEM (4ix8s) as the reconstruction algorithm. For cold spheres, the average increase was 12%. Conclusion: The performance of the PET scanners in the BS16 tomographs is improved by the optimization of the signal processing. The narrower energy and timing coincidence windows lead to a considerable increase of signal- to-noise ratio. The existing combination of fast detectors and adapted electronics in the BS16 tomographs allow imaging protocols with reduced acquisition time, providing higher patient throughput.

scholarly journals Performance evaluation of the Q.Clear reconstruction framework versus conventional reconstruction algorithms for quantitative brain PET-MR studies

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Daniela Ribeiro ◽  
William Hallett ◽  
Adriana A. S. Tavares
Keyword(s):  
Kinetic Modelling ◽  
Signal To Noise Ratio ◽  
Reconstruction Algorithm ◽  
Reconstruction Algorithms ◽  
Brain Pet ◽  
Good Spatial Resolution ◽  
Positron Emission ◽  
Pet Ct ◽  
Modelling Studies ◽  
Pet Scans

Abstract Background Q.Clear is a Bayesian penalized likelihood (BPL) reconstruction algorithm that presents improvements in signal-to-noise ratio (SNR) in clinical positron emission tomography (PET) scans. Brain studies in research require a reconstruction that provides a good spatial resolution and accentuates contrast features however, filtered back-projection (FBP) reconstruction is not available on GE SIGNA PET-Magnetic Resonance (PET-MR) and studies have been reconstructed with an ordered subset expectation maximization (OSEM) algorithm. This study aims to propose a strategy to approximate brain PET quantitative outcomes obtained from images reconstructed with Q.Clear versus traditional FBP and OSEM. Methods Contrast recovery and background variability were investigated with the National Electrical Manufacturers Association (NEMA) Image Quality (IQ) phantom. Resolution, axial uniformity and SNR were investigated using the Hoffman phantom. Both phantoms were scanned on a Siemens Biograph 6 TruePoint PET-Computed Tomography (CT) and a General Electric SIGNA PET-MR, for FBP, OSEM and Q.Clear. Differences between the metrics obtained with Q.Clear with different β values and FBP obtained on the PET-CT were determined. Results For in plane and axial resolution, Q.Clear with low β values presented the best results, whereas for SNR Q.Clear with higher β gave the best results. The uniformity results are greatly impacted by the β value, where β < 600 can yield worse uniformity results compared with the FBP reconstruction. Conclusion This study shows that Q.Clear improves contrast recovery and provides better resolution and SNR, in comparison to OSEM, on the PET-MR. When using low β values, Q.Clear can provide similar results to the ones obtained with traditional FBP reconstruction, suggesting it can be used for quantitative brain PET kinetic modelling studies.

Comparison of Fluorine(18)-fluorodeoxyglucose and Gallium(68)-citrate PET/CT in patients with tuberculosis

2019 ◽  
Vol 58 (05) ◽  
pp. 371-378
Author(s):  
Alfred O. Ankrah ◽  
Ismaheel O. Lawal ◽  
Tebatso M.G. Boshomane ◽  
Hans C. Klein ◽  
Thomas Ebenhan ◽  
...  
Keyword(s):  
Tracer Uptake ◽  
Pet Ct ◽  
The Mean ◽  
18F Fdg ◽  
Definition Of ◽  
Gallium 68 ◽  
Attending Physician ◽  
Pet Scans ◽  
The Brain

Abstract 18F-FDG and 68Ga-citrate PET/CT have both been shown to be useful in the management of tuberculosis (TB). We compared the abnormal PET findings of 18F-FDG- and 68Ga-citrate-PET/CT in patients with TB. Methods Patients with TB on anti-TB therapy were included. Patients had a set of PET scans consisting of both 18F-FDG and 68Ga-citrate. Abnormal lesions were identified, and the two sets of scans were compared. The scan findings were correlated to the clinical data as provided by the attending physician. Results 46 PET/CT scans were performed in 18 patients, 11 (61 %) were female, and the mean age was 35.7 ± 13.5 years. Five patients also had both studies for follow-up reasons during the use of anti-TB therapy. Thirteen patients were co-infected with HIV. 18F-FDG detected more lesions than 68Ga-citrate (261 vs. 166, p < 0.0001). 68Ga-citrate showed a better definition of intracerebral lesions due to the absence of tracer uptake in the brain. The mean SUVmax was higher for 18F-FDG compared to 68Ga-citrate (5.73 vs. 3.01, p < 0.0001). We found a significant correlation between the SUVmax of lesions that were determined by both tracers (r = 0.4968, p < 0.0001). Conclusion Preliminary data shows 18F-FDG-PET detects more abnormal lesions in TB compared to 68Ga-citrate. However, 68Ga-citrate has better lesion definition in the brain and is therefore especially useful when intracranial TB is suspected.

Nondestructive Inspection of Thin, Low-Z Samples using Multiplexed Compton Scatter Tomography

1997 ◽  
Vol 503 ◽  
Author(s):  
B. L. Evans ◽  
J. B. Martin ◽  
L. W. Burggraf
Keyword(s):  
Signal To Noise Ratio ◽  
Reconstruction Algorithm ◽  
Filtered Backprojection ◽  
Line Broadening ◽  
Compton Scatter ◽  
X Ray ◽  
Tomography System ◽  
Transmission Computed Tomography ◽  
High Purity Germanium ◽  
Scattered Energy

ABSTRACTThe viability of a Compton scattering tomography system for nondestructively inspecting thin, low Z samples for corrosion is examined. This technique differs from conventional x-ray backscatter NDI because it does not rely on narrow collimation of source and detectors to examine small volumes in the sample. Instead, photons of a single energy are backscattered from the sample and their scattered energy spectra are measured at multiple detector locations, and these spectra are then used to reconstruct an image of the object. This multiplexed Compton scatter tomography technique interrogates multiple volume elements simultaneously. Thin samples less than 1 cm thick and made of low Z materials are best imaged with gamma rays at or below 100 keV energy. At this energy, Compton line broadening becomes an important resolution limitation. An analytical model has been developed to simulate the signals collected in a demonstration system consisting of an array of planar high-purity germanium detectors. A technique for deconvolving the effects of Compton broadening and detector energy resolution from signals with additive noise is also presented. A filtered backprojection image reconstruction algorithm with similarities to that used in conventional transmission computed tomography is developed. A simulation of a 360–degree inspection gives distortion-free results. In a simulation of a single-sided inspection, a 5 mm × 5 mm corrosion flaw with 50% density is readily identified in 1-cm thick aluminum phantom when the signal to noise ratio in the data exceeds 28.

scholarly journals OP0063 SINGLE CENTRE EXPERIENCE OF THE CLINICAL SPECTRUM, AETIOLOGIES AND MANAGEMENT OF NON-INFECTIOUS AORTITIS

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 34.1-34
Author(s):  
R. S. Andev ◽  
N. Ahmad ◽  
A. Verdiyeva ◽  
R. Luqmani ◽  
S. Dubey
Keyword(s):  
Systemic Inflammatory Response Syndrome ◽  
Inflammatory Response ◽  
Giant Cell Arteritis ◽  
Giant Cell ◽  
Systemic Inflammatory Response ◽  
Aortic Aneurysms ◽  
Large Vessel ◽  
Complication Rates ◽  
Pet Ct ◽  
The Mean

Background:Aortitis, a rare form of large vessel vasculitis, may occur in the context of a primary systemic vasculitis, as a part of systemic autoimmune disease or in isolation. The evidence and guidelines to diagnose, manage and monitor aortitis remain limited. However, PET CT and vascular MRI scans have facilitated our ability to make the diagnosis more readily. The optimal management strategy and complication rates remain uncertain.Objectives:Our aim was to explore the clinical, laboratory and radiological features of aortitis. We sought to review the management and complications of this illness by collecting detailed information on the outcomes and treatments used, including disease modifying agents (DMARDs) and biologics.Methods:Patients diagnosed with aortitis since 2006 that had been managed in a single tertiary centre were identified using the Rheumatology Assessment Database Innovation in Oxford (RHADIO). Their medical notes were retrospectively reviewed using a local electronic patient record system and the following information was obtained: demographics, underlying risk factors, imaging and laboratory results (including biopsy reports if available), management and outcome.Results:We identified 155 patients who met the inclusion criteria. There was a female preponderance of 57.4% (n=89). At the time of diagnosis, the average age was 69 (range 30-92) and the mean symptomatology length prior to diagnosis was 12 months (range 0-120). The majority of patients (60.4%, n=94) had aortitis secondary to giant cell arteritis (GCA), isolated aortitis was identified in 29.7% (n=46) and IgG4-related disease aortitis was uncommon (2.6%, n=4). Those with cranial GCA-like symptoms were diagnosed on average 3.9 months before those who presented differently (10.1 months versus 14.0 months).Common presentations comprised: systemic inflammatory response syndrome (49.0%, n=76), cranial GCA-like symptoms (26.5%, n=41) and unexplained weight loss (24.5%, n=38). Importantly, 18.7% (n=29) of patients presented with ischaemic symptoms that included angina, TIAs/strokes and claudication. Aortic dissection was the primary presentation for 6.5% (n=10) of patients.At presentation, the mean CRP was 84 mg/L (range 1-249) and the ESR was 72 mm/hr (range 2-164). Most (73.5%, n=114) had diagnostic PET CT changes. For those patients with GCA, diagnostic ultrasound changes were seen in 27.7% (n=26).Nearly all were treated with prednisolone (92.3%, n=143) and all but 8 (5.1%) received a DMARD at some point. Methotrexate was the most commonly used DMARD (93.9%, n=138), followed by leflunomide (22.3%, n=35) and azathioprine (19.1%, n=28). Cyclophosphamide was used in 23.8% of patients (n=38) and 15 patients (9.7%) received tocilizumab.Around a third (34.1% n=53/155) had received at least two DMARDs during their treatment course. On average, patients required 3.46 drugs to manage their aortitis. Those who relapsed (43.2%, n=67) were more likely to have GCA (65.7%, n=44).Vascular sequelae were present in 37.4% (n=58). The most common complications were ischaemic in nature with stroke/TIA and claudication reported in 16.8% (n=26). Aortic aneurysms were recorded in 11.6% (n=18) of cases and 5.1% (n=8) developed dissections despite being on treatment for their aortitis. One patient developed renal infarcts and ischaemic bowel leading to intestinal failure because of florid vasculitis.Conclusion:Aortitis has a varied presentation with systemic inflammatory response syndrome being the most common. Delayed diagnosis remains a problem and especially for those with non-GCA related aortitis, which is likely to contribute to the risk of subsequent vascular complications. Vascular events including dissection are common, many of which could be preventable, emphasising the importance of early diagnosis and good disease control.References:[1]Koster M et al. Large-vessel giant cell arteritis: diagnosis, monitoring and management. Rheumatology [Internet]. 2018 Feb 1;57(suppl_2):ii32–42. Available from: https://doi.org/10.1093/rheumatology/kex424Disclosure of Interests:None declared

scholarly journals Comparison between silicon photomultiplier-based and conventional PET/CT in patients with suspected lung cancer—a pilot study

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Johan Economou Lundeberg ◽  
Jenny Oddstig ◽  
Ulrika Bitzén ◽  
Elin Trägårdh
Keyword(s):  
Lung Cancer ◽  
Expectation Maximization ◽  
Image Interpretation ◽  
Imaging Study ◽  
Reconstruction Algorithm ◽  
Tnm Staging ◽  
Reconstruction Algorithms ◽  
Silicon Photomultiplier ◽  
Standardized Uptake Values ◽  
Pet Ct

Abstract Background Lung cancer is one of the most common cancers in the world. Early detection and correct staging are fundamental for treatment and prognosis. Positron emission tomography with computed tomography (PET/CT) is recommended clinically. Silicon (Si) photomultiplier (PM)-based PET technology and new reconstruction algorithms are hoped to increase the detection of small lesions and enable earlier detection of pathologies including metastatic spread. The aim of this study was to compare the diagnostic performance of a SiPM-based PET/CT (including a new block-sequential regularization expectation maximization (BSREM) reconstruction algorithm) with a conventional PM-based PET/CT including a conventional ordered subset expectation maximization (OSEM) reconstruction algorithm. The focus was patients admitted for 18F-fluorodeoxyglucose (FDG) PET/CT for initial diagnosis and staging of suspected lung cancer. Patients were scanned on both a SiPM-based PET/CT (Discovery MI; GE Healthcare, Milwaukee, MI, USA) and a PM-based PET/CT (Discovery 690; GE Healthcare, Milwaukee, MI, USA). Standardized uptake values (SUV) and image interpretation were compared between the two systems. Image interpretations were further compared with histopathology when available. Results Seventeen patients referred for suspected lung cancer were included in our single injection, dual imaging study. No statically significant differences in SUVmax of suspected malignant primary tumours were found between the two PET/CT systems. SUVmax in suspected malignant intrathoracic lymph nodes was 10% higher on the SiPM-based system (p = 0.026). Good consistency (14/17 cases) between the PET/CT systems were found when comparing simplified TNM staging. The available histology results did not find any obvious differences between the systems. Conclusion In a clinical setting, the new SiPM-based PET/CT system with a new BSREM reconstruction algorithm provided a higher SUVmax for suspected lymph node metastases compared to the PM-based system. However, no improvement in lung cancer detection was seen.

Model-based reconstruction algorithm in the detection of acute trauma-related lesions in brain CT examinations

2021 ◽  
pp. 197140092110087
Author(s):  
Andrea De Vito ◽  
Cesare Maino ◽  
Sophie Lombardi ◽  
Maria Ragusi ◽  
Cammillo Talei Franzesi ◽  
...  
Keyword(s):  
Image Quality ◽  
Iterative Reconstruction ◽  
Signal To Noise Ratio ◽  
Reconstruction Algorithm ◽  
Signal To Noise ◽  
Subjective Image Quality ◽  
Model Based ◽  
Hybrid Iterative Reconstruction ◽  
Noise Ratio ◽  
Enhanced Computed Tomography

Background and purpose To evaluate the added value of a model-based reconstruction algorithm in the assessment of acute traumatic brain lesions in emergency non-enhanced computed tomography, in comparison with a standard hybrid iterative reconstruction approach. Materials and methods We retrospectively evaluated a total of 350 patients who underwent a 256-row non-enhanced computed tomography scan at the emergency department for brain trauma. Images were reconstructed both with hybrid and model-based iterative algorithm. Two radiologists, blinded to clinical data, recorded the presence, nature, number, and location of acute findings. Subjective image quality was performed using a 4-point scale. Objective image quality was determined by computing the signal-to-noise ratio and contrast-to-noise ratio. The agreement between the two readers was evaluated using k-statistics. Results A subjective image quality analysis using model-based iterative reconstruction gave a higher detection rate of acute trauma-related lesions in comparison to hybrid iterative reconstruction (extradural haematomas 116 vs. 68, subdural haemorrhages 162 vs. 98, subarachnoid haemorrhages 118 vs. 78, parenchymal haemorrhages 94 vs. 64, contusive lesions 36 vs. 28, diffuse axonal injuries 75 vs. 31; all P<0.001). Inter-observer agreement was moderate to excellent in evaluating all injuries (extradural haematomas k=0.79, subdural haemorrhages k=0.82, subarachnoid haemorrhages k=0.91, parenchymal haemorrhages k=0.98, contusive lesions k=0.88, diffuse axonal injuries k=0.70). Quantitatively, the mean standard deviation of the thalamus on model-based iterative reconstruction images was lower in comparison to hybrid iterative one (2.12 ± 0.92 vsa 3.52 ± 1.10; P=0.030) while the contrast-to-noise ratio and signal-to-noise ratio were significantly higher (contrast-to-noise ratio 3.06 ± 0.55 vs. 1.55 ± 0.68, signal-to-noise ratio 14.51 ± 1.78 vs. 8.62 ± 1.88; P<0.0001). Median subjective image quality values for model-based iterative reconstruction were significantly higher ( P=0.003). Conclusion Model-based iterative reconstruction, offering a higher image quality at a thinner slice, allowed the identification of a higher number of acute traumatic lesions than hybrid iterative reconstruction, with a significant reduction of noise.

scholarly journals Impact of the Q.Clear reconstruction algorithm on the interpretation of PET/CT images in patients with lymphoma

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Michał Wyrzykowski ◽  
Natalia Siminiak ◽  
Maciej Kaźmierczak ◽  
Marek Ruchała ◽  
Rafał Czepczyński
Keyword(s):  
Reconstruction Algorithm ◽  
Ct Images ◽  
Pet Ct

scholarly journals Impact of PET data driven respiratory motion correction and BSREM reconstruction of 68Ga-DOTATATE PET/CT for differentiating neuroendocrine tumors (NET) and intrapancreatic accessory spleens (IPAS)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Virginia Liberini ◽  
Fotis Kotasidis ◽  
Valerie Treyer ◽  
Michael Messerli ◽  
Erika Orita ◽  
...  
Keyword(s):  
Neuroendocrine Tumors ◽  
Motion Correction ◽  
Accessory Spleen ◽  
Pancreatic Neuroendocrine Tumor ◽  
Reconstruction Algorithm ◽  
Data Driven ◽  
Operating Characteristics ◽  
Quantitative Pet ◽  
Pet Ct ◽  
Accessory Spleens

AbstractTo evaluate whether quantitative PET parameters of motion-corrected 68Ga-DOTATATE PET/CT can differentiate between intrapancreatic accessory spleens (IPAS) and pancreatic neuroendocrine tumor (pNET). A total of 498 consecutive patients with neuroendocrine tumors (NET) who underwent 68Ga-DOTATATE PET/CT between March 2017 and July 2019 were retrospectively analyzed. Subjects with accessory spleens (n = 43, thereof 7 IPAS) and pNET (n = 9) were included, resulting in a total of 45 scans. PET images were reconstructed using ordered-subsets expectation maximization (OSEM) and a fully convergent iterative image reconstruction algorithm with β-values of 1000 (BSREM1000). A data-driven gating (DDG) technique (MOTIONFREE, GE Healthcare) was applied to extract respiratory triggers and use them for PET motion correction within both reconstructions. PET parameters among different samples were compared using non-parametric tests. Receiver operating characteristics (ROC) analyzed the ability of PET parameters to differentiate IPAS and pNETs. SUVmax was able to distinguish pNET from accessory spleens and IPAs in BSREM1000 reconstructions (p < 0.05). This result was more reliable using DDG-based motion correction (p < 0.003) and was achieved in both OSEM and BSREM1000 reconstructions. For differentiating accessory spleens and pNETs with specificity 100%, the ROC analysis yielded an AUC of 0.742 (sensitivity 56%)/0.765 (sensitivity 56%)/0.846 (sensitivity 62%)/0.840 (sensitivity 63%) for SUVmax 36.7/41.9/36.9/41.7 in OSEM/BSREM1000/OSEM + DDG/BSREM1000 + DDG, respectively. BSREM1000 + DDG can accurately differentiate pNET from accessory spleen. Both BSREM1000 and DDG lead to a significant SUV increase compared to OSEM and non-motion-corrected data.

scholarly journals P205 The contemporary presentation and management of giant cell arteritis with large vessel vasculitis

Rheumatology ◽  
2021 ◽  
Vol 60 (Supplement_1) ◽  
Author(s):  
Owen Cronin ◽  
Neil D McKay ◽  
Hannah Preston ◽  
Helen Harris ◽  
Barbara Hauser
Keyword(s):  
Giant Cell Arteritis ◽  
Giant Cell ◽  
Polymyalgia Rheumatica ◽  
Large Vessel Vasculitis ◽  
Large Vessel ◽  
Ct Angiogram ◽  
Pet Ct ◽  
The Mean ◽  
Vessel Involvement

Abstract Background/Aims  Giant cell arteritis with large vessel vasculitis (LV-GCA) represents a distinct, less researched sub-category of giant cell arteritis (GCA). In comparison to cranial GCA, the patient’s diagnostic pathway is less well described and it is thought that LV-GCA is underdiagnosed, including in patients with polymyalgia rheumatica and cranial-GCA. Advances in imaging (e.g. PET-CT) and treatment (tocilizumab), have provided additional options in the diagnosis and management of LV-GCA. The aim was to describe the contemporary clinical journey for patients diagnosed with LV-GCA. Methods  The electronic patient health record system in NHS Lothian (TrakCare) was used to collect relevant data. Patients with imaging-confirmed large vessel vasculitis, diagnosed with GCA after 1 January 2017 were included. Follow-up was until August 2020. Results  Eighteen patients with LV-GCA were included. The mean age was 65 years and 66.7% were female. Two patients had known cranial-GCA but 89% of patients were diagnosed exclusively with large vessel involvement. The most common symptoms were malaise (55%), weight loss (55%), polymyalgia rheumatica (55%) and limb claudication (44%). Pyrexia of unknown origin was a feature in only 17% of patients. Two patients were asymptomatic and were investigated on the basis of raised inflammatory markers. Mean CRP at baseline was 99mg/L and ESR 85mm/hour. The mean time from symptom-onset to diagnosis was 6.8 months (range 1 to 15 months). Sixteen patients (89%) were reviewed by at least one other secondary care specialist. One third of patients were referred from General Medicine followed by Vascular Surgery (16%) and General Practice (16%). 7/18 patients were inpatients at the time of referral. 56% of patients required two modalities of imaging to confirm large vessel involvement. The most commonly used imaging techniques (in descending order) were CT-Chest/Abdomen/Pelvis, CT-angiogram, PET-CT and Vascular Ultrasound. 50% of patients underwent follow-up imaging, most commonly MR- or CT-angiography. Mean follow-up was for 1.6 years. The mean prednisolone dose at 3 months (n = 18) was 24mg daily and 8mg at 12 months (n = 12). 28% of patients relapsed during the follow-up period at 4, 5, 8, 9 and 24 months post-diagnosis. 7/18 patients were commenced on methotrexate for steroid-side effects or for relapse. 8/18 received subcutaneous tocilizumab in combination with methotrexate in two cases. Three patients were started on azathioprine but only one continued. Conclusion  In modern-day clinical practice, patients with LV-GCA experience a longer time to diagnosis than those with cranial symptoms. Patients with LV-GCA can experience an array of constitutional symptoms. Frequently, more than one imaging modality is required to confirm LV-GCA and the majority of patients will have seen other hospital specialists or have been admitted to hospital before diagnosis. Methotrexate and tocilizumab are the most frequently-used and effective steroid-adjunct in this single-centre cohort. Disclosure  O. Cronin: None. N.D. McKay: Consultancies; Gilead. Other; Has received support for conference attendance from Pfizer and Gilead, Has received educational support from UCB, Gilead, Celgene, Biogen, Sanofi, Abbvie, Novartis, Pfizer. H. Preston: None. H. Harris: None. B. Hauser: None.

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