Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen, Germany

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Utilizing 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) to define suspected nonenhancing tumor for radiation therapy planning of glioblastoma

AIM

The authors sought to evaluate the impact of 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) on radiation therapy planning for patients diagnosed with glioblastoma (GBM) and the presence of suspected nonenhancing tumors compared with standard magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Patients with GBM and contrast-enhanced MRI scans showing regions suspicious of nonenhancing tumor underwent postoperative FET-PET before commencing radiation therapy. Two clinical target volumes (CTVs) were created using pre- and postoperative MRI: MRI fluid-attenuated inversion recovery (FLAIR) sequences (CTV_FLAIR) and MRI contrast sequences with an expansion on the surgical cavity (CTV_Sx). FET-PET was used to create biological tumor volumes (BTVs) by encompassing FET-avid regions, forming BTV_FLAIR and BTV_Sx. Volumetric analyses were conducted between CTVs and respective BTVs using Wilcoxon signed-rank tests. The volume increase with addition of FET was analyzed with respect to BTV_FLAIR and BTV_Sx. Presence of focal gadolinium contrast enhancement within previously nonenhancing tumor or within the FET-avid region was noted on MRI scans at 1 and 3 months after radiation therapy.

RESULTS

Twenty-six patients were identified retrospectively from our database, of whom 24 had demonstrable FET uptake. The median CTV_FLAIR, CTV_Sx, BTV_FLAIR, and BTV_Sx were 57.1 mL (range, 1.1-217.4), 83.6 mL (range, 27.2-275.8), 62.8 mL (range, 1.1-307.3), and 94.7 mL (range, 27.2-285.5), respectively. When FET-PET was used, there was a mean increase in volume of 26.8% from CTV_FLAIR to BTV_FLAIR and 20.6% from CTV_Sx to BTV_Sx. A statistically significant difference was noted on Wilcoxon signed-rank test when assessing volumetric change between CTV_FLAIR and BTV_FLAIR (P < .0001) and CTV_Sx and BTV_Sx (P < .0001). Six of 24 patients (25%) with FET avidity before radiation therapy showed focal gadolinium enhancement within the radiation therapy portal.

CONCLUSIONS

FET-PET may help improve delineation of GBM in cases with a suspected nonenhancing component. This may result in improved radiation therapy target delineation and reduce the risk of potential geographical miss.

SUMMARY

We investigated the impact of 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) on radiation therapy planning for patients diagnosed with glioblastoma (GBM) and a suspected nonenhancing tumor compared with standard magnetic resonance imaging. We performed volumetric analyses between clinical target volumes and respective biological target volumes using Wilcoxon signed-rank tests. FET-PET may help improve delineation of GBM in cases with a suspected nonenhancing component and reduce the risk of potential geographical miss.

Peripheral ventilation heterogeneity determines the extent of bronchoconstriction in asthma

In asthma, bronchoconstriction causes topographically heterogeneous airway narrowing, as measured by three-dimensional ventilation imaging. Computation modeling suggests that peripheral airway dysfunction is a potential determinant of acute airway narrowing measured by imaging. We hypothesized that the development of low-ventilation regions measured topographically by three-dimensional imaging after bronchoconstriction is predicted by peripheral airway function. Fourteen asthmatic subjects underwent ventilation single-photon-emission computed tomography/computed tomography scan imaging before and after methacholine challenge. One-liter breaths of Technegas were inhaled from functional residual capacity in upright posture before supine scanning. The lung regions with the lowest ventilation (Vent_low) were calculated using a thresholding method and expressed as a percentage of total ventilation (Vent_total). Multiple-breath nitrogen washout was used to measure diffusion-dependent and convection-dependent ventilation heterogeneity (Sacin and Scond, respectively) and lung clearance index (LCI), before and after challenge. Forced expiratory volume in 1 s (FEV₁) was 87.6 ± 15.8% predicted, and seven subjects had airway hyperresponsiveness. Vent_low at baseline was unrelated to spirometry or multiple-breath nitrogen washout indices. Methacholine challenge decreased FEV₁ by 23 ± 5% of baseline while Vent_low increased from 21.5 ± 2.3%Vent_total to 26.3 ± 6.7%Vent_total (P = 0.03). The change in Vent_low was predicted by baseline Sacin (r_s  = 0.60, P = 0.03) and by LCI (r_s  = 0.70, P = 0.006) but not by Scond (r_s  = 0.30, P = 0.30). The development of low-ventilation lung units in three-dimensional ventilation imaging is predicted by ventilation heterogeneity in diffusion-dependent airways. This relationship suggests that acinar ventilation heterogeneity in asthma may be of mechanistic importance in terms of bronchoconstriction and airway narrowing.NEW & NOTEWORTHY Using ventilation SPECT/CT imaging in asthmatics, we show induced bronchoconstriction leads to the development of areas of low ventilation. Furthermore, the relative volume of the low-ventilation regions was predicted by ventilation heterogeneity in diffusion-dependent acinar airways. This suggests that the pattern of regional airway narrowing in asthma is determined by acinar airway function.

Clinical and imaging-based prognostic factors in radioembolisation of liver metastases from colorectal cancer: a retrospective exploratory analysis

Background

The aim of this study was to investigate the relationship between absorbed dose and response of colorectal cancer liver metastases treated with [⁹⁰Y]-resin microspheres and to explore possible clinical and imaging derived prognostic factors.

Methods

FDG PET/CT was used to measure response of individual lesions to a measured absorbed dose, derived from post-treatment ⁹⁰Y PET imaging. Predicted dose was also derived from planning [^99mTc]-MAA SPECT data. Peak standardised uptake value and total lesion glycolysis (TLG) were explored as response measures, and compared to dose metrics including average dose (D_avg), biologically effective dose, minimum dose to 70% of lesion volume and volume receiving at least 50 Gy. Prognostic factors examined included baseline TLG, RAS mutation status, FDG heterogeneity and dose heterogeneity. In an exploratory analysis, response and clinico-pathological variables were evaluated and compared to overall survival.

Results

Sixty-three lesions were analysed from 22 patients. Poor agreement was seen between predicted and measured dose values. TLG was a superior measure of response, and all dose metrics were significant prognostic factors, with a D_avg of ~50 Gy derived as the critical threshold for a significant response (>50% reduction in TLG). No significant correlation was found between baseline TLG or RAS mutation status and response. Measured dose heterogeneity was a significant prognostic factor and when combined with D_avg had a positive predictive value for response >80%. In the exploratory analysis for prognostic factors of survival, low hepatic tumour burden and mean reduction in TLG >65% were independently associated with improved overall survival.

Conclusions

Lesions receiving an average dose greater than 50 Gy are likely to have a significant response. For lesions receiving less than 50 Gy, dose heterogeneity is a significant prognostic factor. Lesions receiving an average dose less than 20 Gy are unlikely to respond. A reduction in TLG may be associated with improved overall survival.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-017-0292-1) contains supplementary material, which is available to authorized users.

(68)Ga PET Ventilation and Perfusion Lung Imaging-Current Status and Future Challenges

Gallium-68 ((68)Ga) is a positron-emitting radionuclide suitable for positron emission tomography (PET) imaging that has a number of convenient features-it has a physical half life of 68 minutes, it is generator produced at the PET facility and needs no local cyclotron, and being a radiometal is able to be chelated to a number of useful molecules for diagnostic imaging with PET. (68)Ga has recently been investigated as a radiotracer for ventilation and perfusion (V/Q) lung imaging. It is relatively easy to produce both V/Q radiopharmaceuticals labeled with (68)Ga for PET studies, it offers higher spatial resolution than equivalent SPECT studies, the short half life allows for multiple (repeated) scans on the same day, and low amounts of radiotracer can be used thus limiting the radiation dose to the subject. In the usual clinical setting requiring a V/Q scan, that of suspected pulmonary embolism, the role of (68)Ga V/Q PET may be limited from a logistical perspective, however, in nonacute applications such as lung function evaluation, radiotherapy treatment planning, and respiratory physiology investigations it would appear to be an ideal modality to employ.

Dual Somatostatin Receptor/FDG PET/CT Imaging in Metastatic Neuroendocrine Tumours: Proposal for a Novel Grading Scheme with Prognostic Significance

Background: PET scans using FDG and somatostatin receptor imaging agents have both been used to study neuroendocrine tumours. Most reports have documented the sensitivity and specificity of each radiopharmaceutical independently, and even suggested the superiority of one over the other for different grades of disease.

Aim: The aim of this work was to develop a grading scheme that describes the joint results of both the FDG and somatostatin receptor imaging PET scans in staging subjects with neuroendocrine tumours in a single combined parameter. The grading scheme that has been developed is referred to as the NETPET grade.

Methods: This is a retrospective study which assessed subjects who had both FDG and somatostatin receptor PET imaging at our institution within 31 days of each other. The NETPET grade was assigned by experienced nuclear medicine physicians and compared with other clinical data such as WHO grade and overall survival.

Results: In the period 2011-2015 we were able to recruit 62 subjects with histologically proven metastatic neuroendocrine tumour for review. The NETPET grade incorporating both the FDG and somatostatin receptor imaging results was significantly correlated with overall survival by univariate analysis (p=0.0018), whereas in this cohort the WHO grade at the time of diagnosis did not correlate with survival.

Conclusions: The NETPET grade has promise as a prognostic imaging biomarker in neuroendocrine tumours. It permits the capturing of the complexity of dual radiotracer imaging in a single parameter which describes the subjects' disease and is readily amenable to use in patient management and further research.

Changing Therapeutic Paradigms: Predicting mCRC Lesion Response to Selective Internal Radionuclide Therapy (SIRT) based on Critical Absorbed Dose Thresholds: A Case Study

A 65 year old male with metastatic colorectal cancer (mCRC) in the liver was referred for selective internal radionuclide therapy (SIRT) following a history of extensive systemic chemotherapy. ⁹⁰Y PET imaging was performed immediately after treatment and used to confirm lesion targeting and measure individual lesion absorbed doses. Lesion dosimetry was highly predictive of eventual response in the follow-up FDG PET performed 8 weeks after therapy. The derived radiation dose map was used to plan a second SIRT procedure aiming to protect healthy liver by keeping absorbed dose below the critical dose threshold, whilst targeting the remaining lesions that had received sub-critical dosing. Again, ⁹⁰Y PET was performed immediately post-treatment and used to derive absorbed dose measures to both lesions and healthy parenchyma. Additional follow-up FDG PET imaging again confirmed the role of the ⁹⁰Y PET dose map as an early predictor of response, and a tool for safe repeat treatment planning.

Combined PET/MRI: from Status Quo to Status Go. Summary Report of the Fifth International Workshop on PET/MR Imaging; February 15-19, 2016; Tübingen, Germany

This article provides a collaborative perspective of the discussions and conclusions from the fifth international workshop of combined positron emission tomorgraphy (PET)/magnetic resonance imaging (MRI) that was held in Tübingen, Germany, from February 15 to 19, 2016. Specifically, we summarise the second part of the workshop made up of invited presentations from active researchers in the field of PET/MRI and associated fields augmented by round table discussions and dialogue boards with specific topics. This year, this included practical advice as to possible approaches to moving PET/MRI into clinical routine, the use of PET/MRI in brain receptor imaging, in assessing cardiovascular diseases, cancer, infection, and inflammatory diseases. To address perceived challenges still remaining to innovatively integrate PET and MRI system technologies, a dedicated round table session brought together key representatives from industry and academia who were engaged with either the conceptualisation or early adoption of hybrid PET/MRI systems. Discussions during the workshop highlighted that emerging unique applications of PET/MRI such as the ability to provide multi-parametric quantitative and visual information which will enable not only overall disease detection but also disease characterisation would eventually be regarded as compelling arguments for the adoption of PET/MR. However, as indicated by previous workshops, evidence in favour of this observation is only growing slowly, mainly due to the ongoing inability to pool data cohorts from independent trials as well as different systems and sites. The participants emphasised that moving from status quo to status go entails the need to adopt standardised imaging procedures and the readiness to act together prospectively across multiple PET/MRI sites and vendors.

Combined PET/MR: The Real Work Has Just Started. Summary Report of the Third International Workshop on PET/MR Imaging; February 17-21, 2014, Tübingen, Germany

This paper summarises the proceedings and discussions at the third annual workshop held in Tübingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited presentations from active researchers in this and associated fields augmented by round-table discussions and dialogue boards with specific themes. These included the use of PET/MRI in paediatric oncology and in adult neurology, oncology and cardiology, the development of multi-parametric analyses, and efforts to standardise PET/MRI examinations to allow pooling of data for evaluating the technology. A poll taken on the final day demonstrated that over 50 % of those present felt that while PET/MRI technology underwent an inevitable slump after its much-anticipated initial launch, it was now entering a period of slow, progressive development, with new key applications emerging. In particular, researchers are focusing on exploiting the complementary nature of the physiological (PET) and biochemical (MRI/MRS) data within the morphological framework (MRI) that these devices can provide. Much of the discussion was summed up on the final day when one speaker commented on the state of PET/MRI: "the real work has just started".

Combined PET/MRI: Multi-modality Multi-parametric Imaging Is Here: Summary Report of the 4th International Workshop on PET/MR Imaging; February 23-27, 2015, Tübingen, Germany

This paper summarises key themes and discussions from the 4th international workshop dedicated to the advancement of the technical, scientific and clinical applications of combined positron emission tomography (PET)/magnetic resonance imaging (MRI) systems that was held in Tübingen, Germany, from February 23 to 27, 2015. Specifically, we summarise the three days of invited presentations from active researchers in this and associated fields augmented by round table discussions and dialogue boards with specific topics. These include the use of PET/MRI in cardiovascular disease, paediatrics, oncology, neurology and multi-parametric imaging, the latter of which was suggested as a key promoting factor for the wider adoption of integrated PET/MRI. Discussions throughout the workshop and a poll taken on the final day demonstrated that attendees felt more strongly that PET/MRI has further advanced in both technical versatility and acceptance by clinical and research-driven users from the status quo of last year. Still, with only minimal evidence of progress made in exploiting the true complementary nature of the PET and MRI-based information, PET/MRI is still yet to achieve its potential. In that regard, the conclusion of last year's meeting "the real work has just started" still holds true.

In vivo quantification of (177)Lu with planar whole-body and SPECT/CT gamma camera imaging

Background

Advances in gamma camera technology and the emergence of a number of new theranostic radiopharmaceutical pairings have re-awakened interest in in vivo quantification with single-photon-emitting radionuclides. We have implemented and validated methodology to provide quantitative imaging of ¹⁷⁷Lu for 2D whole-body planar studies and for 3D tomographic imaging with single-photon emission computed tomography (SPECT)/CT.

Methods

Whole-body planar scans were performed on subjects to whom a known amount of [¹⁷⁷Lu]-DOTA-octreotate had been administered for therapy. The total radioactivity estimated from the images was compared with the known amount of the radionuclide therapy administered. In separate studies, venous blood samples were withdrawn from subjects after administration of [¹⁷⁷Lu]-DOTA-octreotate while a SPECT acquisition was in progress and the concentration of the radionuclide in the venous blood sample compared with that estimated from large blood pool structures in the SPECT reconstruction. The total radioactivity contained within an internal SPECT calibration standard was also assessed.

Results

In the whole-body planar scans (n = 28), the estimated total body radioactivity was accurate to within +4.6 ± 5.9 % (range −17.1 to +11.2 %) of the correct value. In the SPECT reconstructions (n = 12), the radioactivity concentration in the cardiac blood pool was accurate to within −4.0 ± 7.8 % (range −16.1 to +7.5 %) of the true value and the internal standard measurements (n = 89) were within 2.0 ± 8.5 % (range −16.3 to +24.2 %) of the known amount of radioactivity contained.

Conclusions

In our hands, state-of-the-art hybrid SPECT/CT gamma cameras were able to provide accurate estimates of in vivo radioactivity to better than, on average, ±10 % for use in biodistribution and radionuclide dosimetry calculations.

Periodontal diagnosis in private dental practice: a case-based survey

BACKGROUND

Despite the prevalence of periodontitis in Australia, there are few reports regarding periodontal diagnosis and therapies in the general dental practice setting. This study aimed to assess the degree of diagnostic accuracy in periodontal cases of Victorian general dental practitioners.

METHODS

Following ethics approval, dentists were invited to complete a scenario-based questionnaire on the Australian Dental Association Victorian Branch (ADAVB) website. Five text-based clinical scenarios (from a total of 10) were randomly presented, representing patients with a range of disease levels from periodontal health/gingivitis to severe periodontitis, and respondents were asked what examinations they would usually perform. Based upon the presented results of periodontal and radiographic examinations, a periodontal diagnosis was requested.

RESULTS

One hundred and thirty-five dentists attempted the survey. Most were in group practice and based in Melbourne; 22.5% of respondents worked in a practice employing a hygienist. The clinical parameters most commonly measured to diagnose periodontal disease were pocket depth and mobility. The majority of respondents diagnosed health, gingivitis and mild periodontitis correctly compared to American Academy of Periodontology guidelines. However, moderate periodontitis tended to be diagnosed as severe.

CONCLUSIONS

Dentists in Victoria used appropriate clinical parameters when assessing periodontal disease and were generally accurate in their diagnoses. There is a need for consensus regarding diagnostic definitions.

Measurement of preoperative lobar lung function with computed tomography ventilation imaging: progress towards rapid stratification of lung cancer lobectomy patients with abnormal lung function

OBJECTIVES

In lung cancer preoperative evaluation, functional lung imaging is commonly used to assess lobar function. Computed tomography ventilation (CT-V) imaging is an emerging lung function imaging modality. We compared CT-V imaging assessment of lobar function and its prediction of postoperative lung function to that achieved by (i) positron emission tomography ventilation (PET-V) imaging and (ii) the standard anatomical segment counting (ASC) method. We hypothesized (i) that CT-V and PET-V have similar relative lobar function and (ii) that functional imaging and anatomic assessment (ASC) yield different predicted postoperative (ppo) lung function and therefore could change clinical management.

METHODS

In this proof-of-concept study, 11 patients were subjected to pulmonary function tests, CT-V and PET-V imaging. The Bland-Altman plot, Pearson's correlation and linear regression analysis were used to assess the agreement between the CT-V-, PET-V- and ASC-based quantification of lobar function and in the ppo lung function.

RESULTS

CT-V and PET-V imaging demonstrated strong correlations in quantifying relative lobar function (r = 0.96; P < 0.001). A Wilcoxon-signed rank test showed no significant difference in the lobar function estimates between the two imaging modalities (P = 0.83). The Bland-Altman plot also showed no significant differences. The correlation between ASC-based lobar function estimates with ventilation imaging was low, r < 0.45; however, the predictions of postoperative lung function correlated strongly between all three methods.

CONCLUSIONS

The assessment of lobar function from CT-V imaging correlated strongly with PET-V imaging, but had low correlations with ASC. CT-V imaging may be a useful alternative method in preoperative evaluation for lung cancer patients.

Dramatic response to selective internal radiation therapy for unresectable hepatocellular carcinoma

A 54-year-old woman with a known history of multifocal hepatocellular carcinoma was treated with selective internal radiation therapy (SIRT) using yttrium-90 (⁹⁰Y) microspheres, despite disease relapses after surgical resection and transarterial chemoembolization. She developed a dramatic clinical, radiological and metabolic response after 9 weeks. This case provides visual illustration of the potential roles of SIRT in the treatment of hepatocellular carcinoma.

A multicentre comparison of quantitative (90)Y PET/CT for dosimetric purposes after radioembolization with resin microspheres : The QUEST Phantom Study

Purpose

To investigate and compare the quantitative accuracy of ⁹⁰Y imaging across different generation PET/CT scanners, for the purpose of dosimetry after radioembolization with resin microspheres.

Methods

A strict experimental and imaging protocol was followed by 47 international sites using the NEMA 2007/IEC 2008 PET body phantom with an 8-to-1 sphere-to-background ratio of ⁹⁰Y solution. The phantom was imaged over a 7-day period (activity ranging from 0.5 to 3.0 GBq) and all reconstructed data were analysed at a core laboratory for consistent processing. Quantitative accuracy was assessed through measures of total phantom activity, activity concentration in background and hot spheres, misplaced counts in a nonradioactive insert, and background variability.

Results

Of the 69 scanners assessed, 37 had both time-of-flight (ToF) and resolution recovery (RR) capability. These current generation scanners from GE, Philips and Siemens could reconstruct background concentration measures to within 10 % of true values over the evaluated range, with greater deviations on the Philips systems at low count rates, and demonstrated typical partial volume effects on hot sphere recovery, which dominated spheres of diameter <20 mm. For spheres >20 mm in diameter, activity concentrations were consistently underestimated by about 20 %. Non-ToF scanners from GE Healthcare and Siemens were capable of producing accurate measures, but with inferior quantitative recovery compared with ToF systems.

Conclusion

Current generation ToF scanners can consistently reconstruct ⁹⁰Y activity concentrations, but they underestimate activity concentrations in small structures (≤37 mm diameter) within a warm background due to partial volume effects and constraints of the reconstruction algorithm. At the highest count rates investigated, measures of background concentration (about 300 kBq/ml) could be estimated on average to within 1 %, 5 % and 2 % for GE Healthcare (all-pass filter, RR + ToF), Philips (4i8s ToF) and Siemens (2i21s all-pass filter, RR + ToF) ToF systems, respectively. Over the range of activities investigated, comparable performance between GE Healthcare and Siemens ToF systems suggests suitability for quantitative analysis in a scenario analogous to that of postradioembolization imaging for treatment of liver cancer.

Abstract P1-09-09: Determination of the first evidence-based diagnosis of secondary upper limb lymphedema

Background: The incidence of secondary upper limb lymphedema after treatment for breast cancer is unclear due to the wide variety of measurement tools and diagnostic thresholds that are used in both the literature and clinical practice. Furthermore, this lack of clarity in what constitutes lymphedema or not has prevented the progression of the field of lymphedema. Many of the thresholds have been chosen for ease of use only and have no evidence base to support them. The aim of this study, therefore, was to determine which clinical diagnostic threshold for unilateral upper limb lymphedema has the best sensitivity and specificity when compared to diagnosis by lymphoscintigraphy.

Methods: Women with and without a history of secondary upper limb lymphedema were assessed using lymphoscintigraphy, bioimpedance spectroscopy (BIS) as well as volume and circumference measurements using the perometer. Dermal backflow score was determined as the diagnostic criteria for the lymphoscintigraphy and was assessed by an experienced nuclear medicine physician. Determination of the presence of lymphedema by lymphoscintigraphy was compared with diagnosis by both commonly-used and normatively-determined diagnostic thresholds for circumference, volume and bioimpedance.

Normatively-and commonly-used diagnostic thresholds examinedWhole arm volumeCircumferenceWhole arm BISNormatively-determined thresholds examined3SD perometry threshold*Single elevated circ (3SD threshold)*3SD Cornish, 20012SD perometry threshold*Adjacent raised circ (3SD threshold)*2SD Cornish, 20013SD frustrum threshold*Single raised threshold (2 SD)*3SD, Ward 20112SD frustum threshold*Adjacent raised circ (2SD threshold)*2SD, Ward 2011 3SD SOAC*  2SD SOAC* Commonly-used thresholds examined200 ml interlimb difference2 cm single interlimb difference 10% differenceAdjacent 2 cm interlimb difference  5 cm SOAC * Dylke et al, 2012; Sum of arm circumferences (SOAC); Circumference measure (Circ)

Results: For those with widespread dermal backflow, any clinical diagnostic criteria could differentiate between those with and without lymphedema. In contrast, for those with mild to moderate dermal backflow, only the normatively-determined threshold, set at 2 standard deviations above the norm, for arm circumference and full arm bioimpedance (Cornish et al 2001) had adequate sensitivity and specificity. Both of these thresholds had clinically relevant positive (23 and 10 respectively) and negative (0.2 and 0.3) likelihood ratios.

Conclusion: Evidence-based diagnostic thresholds have been established for the diagnosis of secondary upper limb lymphedema. In determining if lymphoedema is present in those with mild lymphedema, normatively-determined circumference and bioimpedance thresholds that account for limb dominance should be used. Adoption of these evidence-based criteria will allow, for the first time, comparison between studies, clarifying the incidence and risk factors for lymphedema, allowing the field to make meaningful progress forward in determining who is at-risk for lymphedema and how to prevent it from developing.

Acknowledgements: Cancer Australia and National Breast Cancer Foundation.

Citation Format: Sharon L Kilbreath, Elizabeth S Dylke, Geoff P Schembri, Leigh C Ward, Dale L Bailey, Deborah Black, Elizabeth A Bailey, Jane M Beith, Kathryn M Refshauge. Determination of the first evidence-based diagnosis of secondary upper limb lymphedema [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-09-09.

Lutetium-177 DOTATATE Production with an Automated Radiopharmaceutical Synthesis System

OBJECTIVES

Peptide Receptor Radionuclide Therapy (PRRT) with yttrium-90 ((90)Y) and lutetium-177 ((177)Lu)-labelled SST analogues are now therapy option for patients who have failed to respond to conventional medical therapy. In-house production with automated PRRT synthesis systems have clear advantages over manual methods resulting in increasing use in hospital-based radiopharmacies. We report on our one year experience with an automated radiopharmaceutical synthesis system.

METHODS

All syntheses were carried out using the Eckert & Ziegler Eurotope's Modular-Lab Pharm Tracer® automated synthesis system. All materials and methods used were followed as instructed by the manufacturer of the system (Eckert & Ziegler Eurotope, Berlin, Germany). Sterile, GMP-certified, no-carrier added (NCA) (177)Lu was used with GMP-certified peptide. An audit trail was also produced and saved by the system. The quality of the final product was assessed after each synthesis by ITLC-SG and HPLC methods.

RESULTS

A total of 17 [(177)Lu]-DOTATATE syntheses were performed between August 2013 and December 2014. The amount of radioactive [(177)Lu]-DOTATATE produced by each synthesis varied between 10-40 GBq and was dependant on the number of patients being treated on a given day. Thirteen individuals received a total of 37 individual treatment administrations in this period. There were no issues and failures with the system or the synthesis cassettes. The average radiochemical purity as determined by ITLC was above 99% (99.8 ± 0.05%) and the average radiochemical purity as determined by HPLC technique was above 97% (97.3 ± 1.5%) for this period.

CONCLUSIONS

The automated synthesis of [(177)Lu]-DOTATATE using Eckert & Ziegler Eurotope's Modular-Lab Pharm Tracer® system is a robust, convenient and high yield approach to the radiolabelling of DOTATATE peptide benefiting from the use of NCA (177)Lu and almost negligible radiation exposure of the operators.

Quantitative and qualitative assessment of Yttrium-90 PET/CT imaging

Yttrium-90 is known to have a low positron emission decay of 32 ppm that may allow for personalized dosimetry of liver cancer therapy with ⁹⁰Y labeled microspheres. The aim of this work was to image and quantify ⁹⁰Y so that accurate predictions of the absorbed dose can be made. The measurements were performed within the QUEST study (University of Sydney, and Sirtex Medical, Australia). A NEMA IEC body phantom containing 6 fillable spheres (10–37 mm ∅) was used to measure the ⁹⁰Y distribution with a Biograph mCT PET/CT (Siemens, Erlangen, Germany) with time-of-flight (TOF) acquisition. A sphere to background ratio of 8∶1, with a total ⁹⁰Y activity of 3 GBq was used. Measurements were performed for one week (0, 3, 5 and 7 d). he acquisition protocol consisted of 30 min-2 bed positions and 120 min-single bed position. mages were reconstructed with 3D ordered subset expectation maximization (OSEM) and point spread function (PSF) for iteration numbers of 1–12 with 21 (TOF) and 24 (non-TOF) subsets and CT based attenuation and scatter correction. Convergence of algorithms and activity recovery was assessed based on regions-of-interest (ROI) analysis of the background (100 voxels), spheres (4 voxels) and the central low density insert (25 voxels). For the largest sphere, the recovery coefficient (RC) values for the 30 min –2-bed position, 30 min-single bed and 120 min-single bed were 1.12±0.20, 1.14±0.13, 0.97±0.07 respectively. For the smaller diameter spheres, the PSF algorithm with TOF and single bed acquisition provided a comparatively better activity recovery. Quantification of Y-90 using Biograph mCT PET/CT is possible with a reasonable accuracy, the limitations being the size of the lesion and the activity concentration present. At this stage, based on our study, it seems advantageous to use different protocols depending on the size of the lesion.