Survival Outcome with Routine Clinical Use of 82Rb PET/CT Myocardial Blood Flow (MBF) Quantification

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): NIHR Biomedical Research Centre, University College London Hospitals

Background

The prognostic value of 82Rb PET/CT derived myocardial blood flow (MBF) is increasingly recognised in both general and specific cardiovascular populations.

Purpose

This study investigates the prognostic potential of MBF in a large cohort of patients undergoing routine 82Rb PET/CT examination.

Methods

1148 consecutive patients (687 males, mean age 64 +/- 12 years) whom had been referred for 82Rb PET/CT examination in a single centre were included in this study.  All patients completed a stress 82Rb PET/CT with adenosine infusion, paired with a rest study.  Dynamic PET acquisitions were performed in both. Cardiovascular risk factors were documented as per clinical routine. Images were checked for quality and analysed using a proprietary software by an experienced operator to derive MBF parameters.  Overall survival was recorded following the study.

Results

Median follow-up period was 71 +/- 28 months.  Mean survival was 121 (95% CI: 118-124) months. On univariate analysis, global myocardial flow reserve <1.77 was associated with a higher all-cause mortality (p < 0.001). Other parameters including higher age (> =76 years), lower BMI (<21), qualitative abnormality on the myocardial perfusion scan (MPS), low hyperaemic ejection fraction on the gated studies (stress < 37 and rest < 34). Patients being on cardiac glycosides and diuretics were also significant predictor of poor prognosis (p < 0.001) on univariate analysis, presumably reflecting underlying arrhythmia and heart failure. A multivariate Cox regression analysis (step-wise Forward Wald), comprising of the above significant univariate markers, highlighted global myocardial flow reserve (HR: 2.6, 95%CI: 1.8-3.6, p < 0.001), age (HR: 2.8, 95%CI: 2.0-3.9, p < 0.001),, BMI (HR: 2.7, 95%CI: 1.7-4.1, p < 0.001),, ejection fraction (stress - HR: 3.3, 95%CI: 2.3-4.8, p < 0.001), MPS (HR: 1.5, 95%CI: 1.1-2.1, p = 0.024), and patients on diuretics (HR: 1.8, 95%CI: 1.2-2.5, p = 0.003) were independent predictors of overall survival (overall model: p < 0.001)

Discussion

We show that high volume routinely derived MBF in patients undergoing 82Rb PET/CT is a strong predictor of mortality and independent of other risk factors. This has important clinical implication for measuring not only interventional treatment but also measuring the effect of lifestyle and medical strategies.

Can deep learning identify normal coronary flow reserve from rubidium myocardial PET perfusion?

Funding Acknowledgements

Type of funding sources: None.

Background

Impaired vasodilator function is an early manifestation of coronary artery disease (CAD) and may precede angiographic stenosis.  Rest and stress myocardial blood flow (MBF) are calculated from dynamic imaging during rest/stress Rubidium (Rb) myocardial PET perfusion.  Coronary flow reserve (CFR) equals stress divided by rest MBF.  CFR is an independent predictor of cardiac mortality in patients with known or suspected CAD.  We evaluated the prediction of CFR from analysis of stress/rest PET images by deep learning (DL) as compared with standard calculation of CFR using supervised learning applied methodology using within a commercial DL training platform.

Methods

1036 patients (625 male, 411 female, mean age: 64.3 years old) were studied. Patients underwent Stress/rest Rb PET perfusion, and CFR calculated using MBF software by an expert user. Abnormal CFR was defined as <2.0. The left ventricle myocardium was segmented using standard software.

DL was trained using polar distribution of normalized PET uptake at stress and rest, processed stress and rest images were cropped, the stress images were then subtracted from the rest images. DL was trained using 935 subtracted images and tested using the remaining 101 images. DL was trained with supervision to classify images. The image shows examples of subtracted  abnormal cases (1a & 1b).

Results

Using our supervised training methodology, the commercial MBF software platform reported 465 cases as abnormal, with 48 of these were included in the DL test set. The DL platform produced abnormal output classifiers for all the whole test set. DL accurately detected over 70% of abnormal cases.

The commercial MBF software reported 571 cases as normal; with 50 of these contributing to the DL test set. DL was accurate in 48.0% of normal cases. Statistical results are shown in the table.

Conclusion

We have shown the proof of concept that DL algorithms trained with supervision can detect abnormal CFR. Our work shows that further work is needed to develop supervised learning methodology in order to improve accuracy for clinical use.

Statistical Results Statistic Value Sensitivity 63.16% Specificity 56.67% + Predictive Value 48.00% - Predictive Value 70.83% Accuracy 59.18% Abstract Figure.

Simultaneous 68Ga DOTATATE Positron Emission Tomography/Magnetic Resonance Imaging in Meningioma Target Contouring: Feasibility and Impact Upon Interobserver Variability Versus Positron Emission Tomography/Computed Tomography and Computed Tomography/Magnetic Resonance Imaging

AIMS

The increasing use of highly conformal radiation techniques to treat meningioma confers a greater need for accurate targeting. Several groups have shown that positron emission tomography/computed tomography (PET/CT) information alters meningioma targets contoured by single observers, but whether this translates into improved accuracy has not been defined. As magnetic resonance imaging (MRI) is the cornerstone of meningioma target contouring, simultaneous PET/MRI may be superior to PET/CT. We assessed whether ⁶⁸Ga DOTATATE PET imaging (from PET/CT and PET/MRI) reduced interobserver variability (IOV) in meningioma target volume contouring.

MATERIALS AND METHODS

Ten patients with meningioma underwent simultaneous ⁶⁸Ga DOTATATE PET/MRI followed by PET/CT. They were selected as it was anticipated that target volume definition in their cases would be particularly challenging. Three radiation oncologists contoured target volumes according to an agreed protocol: gross tumour volume (GTV) and clinical target volume (CTV) on CT/MRI alone, CT/MRI+PET(CT) and CT/MRI+PET(MRI). GTV/CTV Kouwenhoven conformity levels (KCL), regions of contour variation and qualitative differences between PET(CT) and PET(MRI) were evaluated.

RESULTS

There was substantial IOV in contouring. GTV mean KCL: CT/MRI 0.34, CT/MRI+PET(CT) 0.38, CT/MRI+PET(MRI) 0.39 (P = 0.06). CTV mean KCL: CT/MRI 0.31, CT/MRI+PET(CT) 0.35, CT/MRI+PET(MRI) 0.35 (P = 0.04 for all groups; P > 0.05 for individual pairs). One observer consistently contoured largest and one smallest. Observers rarely decreased volumes in relation to PET. Most IOV occurred in bone followed by dural tail, postoperative bed and venous sinuses. Tumour edges were qualitatively clearer on PET(MRI) versus PET(CT), but this did not affect contouring.

CONCLUSION

IOV in contouring challenging meningioma cases was large and only slightly improved with the addition of ⁶⁸Ga DOTATATE PET. Simultaneous PET/MRI for meningioma contouring is feasible, but did not improve IOV versus PET/CT. Whether volumes can be safely reduced according to PET requires evaluation.

CT-based texture analysis potentially provides prognostic information complementary to interim fdg-pet for patients with hodgkin's and aggressive non-hodgkin's lymphomas

OBJECTIVES

The purpose of this study was to investigate the ability of computed tomography texture analysis (CTTA) to provide additional prognostic information in patients with Hodgkin's lymphoma (HL) and high-grade non-Hodgkin's lymphoma (NHL).

METHODS

This retrospective, pilot-study approved by the IRB comprised 45 lymphoma patients undergoing routine 18F-FDG-PET-CT. Progression-free survival (PFS) was determined from clinical follow-up (mean-duration: 40 months; range: 10-62 months). Non-contrast-enhanced low-dose CT images were submitted to CTTA comprising image filtration to highlight features of different sizes followed by histogram-analysis using kurtosis. Prognostic value of CTTA was compared to PET FDG-uptake value, tumour-stage, tumour-bulk, lymphoma-type, treatment-regime, and interim FDG-PET (iPET) status using Kaplan-Meier analysis. Cox regression analysis determined the independence of significantly prognostic imaging and clinical features.

RESULTS

A total of 27 patients had aggressive NHL and 18 had HL. Mean PFS was 48.5 months. There was no significant difference in pre-treatment CTTA between the lymphoma sub-types. Kaplan-Meier analysis found pre-treatment CTTA (medium feature scale, p=0.010) and iPET status (p<0.001) to be significant predictors of PFS. Cox analysis revealed that an interaction between pre-treatment CTTA and iPET status was the only independent predictor of PFS (HR: 25.5, 95% CI: 5.4-120, p<0.001). Specifically, pre-treatment CTTA risk stratified patients with negative iPET.

CONCLUSION

CTTA can potentially provide prognostic information complementary to iPET for patients with HL and aggressive NHL.

KEY POINTS

• CT texture-analysis (CTTA) provides prognostic information complementary to interim FDG-PET in Lymphoma. • Pre-treatment CTTA and interim PET status were significant predictors of progression-free survival. • Patients with negative interim PET could be further stratified by pre-treatment CTTA. • Provide precision surveillance where additional imaging reserved for patients at greatest recurrence-risk. • Assists in risk-adapted treatment strategy based on interim PET and CTTA.

USING FLORBETAPIR PET TO INCREASE DIAGNOSTIC CERTAINTY IN ATYPICAL DEMENTIAS

Amyloid PET or CSF can be used to determine Alzheimer pathology in vivo. Few studies have assessed the additional value of amyloid imaging where CSF results are equivocal. We recruited 20 cognitive patients (65.5+/–7.6 y) with MRI, neuropsychology, and CSF Aβ1–42 and tau measured during their diagnostic assessment. Individuals were selected to have a range of CSF results; ten had amnestic and ten non-amnestic presentations. Following the investigations, the treating neurologist gave a diagnosis (AD or non-AD). Four controls (63+/–7.0y) also had CSF examination. All subjects had Florbetapir PET imaging, reported as positive/negative. The clinicians were given the PET results and asked to review their diagnoses. Eighteen patients had positive Florbetapir scans; two patients and all controls were Florbetapir negative. Following initial investigations, thirteen patients were diagnosed with AD, and seven with non-AD pathology. Providing the Florbetapir result led to a change in diagnosis in seven patients, five of whom had atypical phenotypes. For all seven the CSF results were close to or in a “grey” area, where results overlapped for positive and negative PET scans. Even in individuals with CSF measures of Aβ1–42, and tau, Florbetapir PET imaging may have diagnostic utility, particularly in atypical cases and/or equivocal CSF results.

Can upright myocardial perfusion imaging be used alone with a solid-state dedicated cardiac camera?

AIM

The novel solid state dedicated cardiac cameras provide fast high resolution cardiac imaging. The D-SPECT camera enables semi-reclining (upright) positioning, increasing comfort and potentially reducing movement during myocardial perfusion imaging. Physicians are generally familiar with supine imaging and the different positioning in upright imaging could potentially cause diagnostic challenges. The aim of this study was to compare the upright and supine imaging for diagnostic ability to assess Physician confidence and determine any artefacts in upright imaging.

METHODS

Fifty-five patients underwent myocardial perfusion imaging on the D-SPECT camera in both upright and supine positions. Where both images showed the same defects the 2 techniques were regarded as equally diagnostic. Where only one set showed a defect this was regarded as artefact and was defined as non-diagnostic. The location and cause of the artefact was recorded.

RESULTS

In 13 /55 patients either form of imaging was regarded as equally diagnostic. In 24/55 the supine images revealed artefact affecting interpretation. The reasons for this were most frequently large BMI, motion and gut uptake. In 18/55 upright images were considered non-diagnostic. In 16/18 this was due to an infero-apical defect seen in female patients (14/16) with raised BMI and/or large breasts.

CONCLUSION

Upright myocardial perfusion imaging on D-SPECT shows a common artefact (in up to 1/3 of cases) in the infero-apical region mainly in overweight female patients. Getting acquainted with this artefact this may increase Physician confidence in reporting, similarly as to conventional supine imaging. Indeed, some of the artefacts seen on supine imaging appear less commonly with upright imaging. Thus, upright imaging can potentially be used alone for diagnosis with D-SPECT. Performance of both supine and upright imaging can be reserved for overweight patients thereby minimizing impact on scanning time and clinical throughput in busy departments.

Sequential FDG-PET/CT as a surrogate marker of response to sunitinib in metastatic clear cell renal cancer

301

Background: The purpose of this study was to investigate sequential FDG PET-CT as a correlative marker in metastatic clear cell renal cancer (mRCC) patients treated with first line sunitinib. Three sequential scans were performed to determine the importance of the timing of scans.

Methods: Forty-four untreated mRCC patients with MSKCC intermediate risk and poor risk disease were enrolled into a prospective study. FDG PET-CT scans were performed before (n=44), after 4 weeks (n=43) and 16 weeks (n=40) of sunitinib given at standard doses as the translational aspect of this trial ( NCT01024205 ). The primary endpoint was to determine whether 18F-FDG PET-CT response (defined as a 20% reduction in SUVmax) correlated with survival.

Results: Forty-three (98%) patients had FDG PET-CT avid lesions at diagnosis (median SUVmax 6.8 range: <2.5–18.4). In multivariate analysis a high SUVmax and increased number of PET positive lesions correlated with worse overall survival (OS) (HR: 3.30 (95%CI: 1.36–8.45) and 3.67 (95%CI: 1.43–9.39) respectively[p<0.05]). After 4 weeks of sunitinib, metabolic responses occurred in 24 (57%) patients at 4 weeks, but this did not correlate with progression-free survival [PFS] (HR for responders= 0.87 [95%CI: 0.40–1.99]) or OS (HR for responders= 0.80 [95%CI: 0.34–1.85]) (p>0.05 for both). After 16 weeks of treatment, FDG PET-CT demonstrated disease progression in 28% (n=12) patients. At this time point, the FDG PET-CT correlated with both OS and PFS (HR 5.96 [95%CI: 2.43–19.02] and HR 12.13 [95%CI: 3.72–46.45] respectively).

Conclusions: Baseline FDG PET prior to sunitinib yields prognostically significant data. FDG PET response at 16 weeks predicts outcome, which is not the case at 4 weeks. This subsets of patients with a poor prognosis at 16 weeks could be investigated within the context of a randomized clinical trial.

[Table: see text]

The safety and efficacy of sunitinib before planned nephrectomy in metastatic clear cell renal cancer

Background: The safety and efficacy of upfront sunitinib, before nephrectomy in metastatic clear cell renal cancer (mCRC), has not been prospectively evaluated.

Methods: Two prospective single-arm phase II studies investigated either two cycles (study A: n = 19) or three cycles (study B: n = 33) of sunitinib before nephrectomy in mCRC.

Results: Overall, 38 of 52 (73%) of patients obtained clinical benefit (by RECIST) before surgery. The partial response rate of the primary tumour was 6% [median reduction in longest diameter of 12% (range 8%−35%)]. No patients became ineligible due to local progression of disease. A nephrectomy was carried out in 37 (71%) of patients. Necrosis (>50%) was a prominent feature at nephrectomy in 49%. Surgical complications (Clavien–Dindo classification) occurred in 10 (27%) patients, including one death (3%). The median blood loss and surgical time were 725 (90–4200) ml and 189 (70–420) min, respectively. The median progression-free survival was 8 months (95% confidence interval 6–15 months). A comparison of two versus three pre-surgery cycles showed no significant difference in terms of surgical complications or efficacy.

Conclusions: Nephrectomy after upfront sunitinib can be carried out safely. It obtains control of disease. Randomised studies are required to address if this approach is beneficial.

Impact of combined (18)F-FDG PET/CT in head and neck tumours

To compare the interobserver agreement and degree of confidence in anatomical localisation of lesions using 2-[fluorine-18]fluoro-2-deoxy-D-glucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) and ¹⁸F-FDG PET alone in patients with head and neck tumours. A prospective study of 24 patients (16 male, eight female, median age 59 years) with head and neck tumours was undertaken. ¹⁸F-FDG PET/CT was performed for staging purposes. 2D images were acquired over the head and neck area using a GE Discovery LS™ PET/CT scanner. ¹⁸F-FDG PET images were interpreted by three independent observers. The observers were asked to localise abnormal ¹⁸F-FDG activity to an anatomical territory and score the degree of confidence in localisation on a scale from 1 to 3 (1=exact region unknown; 2=probable; 3=definite). For all ¹⁸F-FDG-avid lesions, standardised uptake values (SUVs) were also calculated. After 3 weeks, the same exercise was carried out using ¹⁸F-FDG PET/CT images, where CT and fused volume data were made available to observers. The degree of interobserver agreement was measured in both instances. A total of six primary lesions with abnormal ¹⁸F-FDG uptake (SUV range 7.2–22) were identified on ¹⁸F-FDG PET alone and on ¹⁸F-FDG PET/CT. In all, 15 nonprimary tumour sites were identified with ¹⁸F-FDG PET only (SUV range 4.5–11.7), while 17 were identified on ¹⁸F-FDG PET/CT. Using ¹⁸F-FDG PET only, correct localisation was documented in three of six primary lesions, while ¹⁸F-FDG PET/CT correctly identified all primary sites. In nonprimary tumour sites, ¹⁸F-FDG PET/CT improved the degree of confidence in anatomical localisation by 51%. Interobserver agreement in assigning primary and nonprimary lesions to anatomical territories was moderate using ¹⁸F-FDG PET alone (kappa coefficients of 0.45 and 0.54, respectively), but almost perfect with ¹⁸F-FDG PET/CT (kappa coefficients of 0.90 and 0.93, respectively). We conclude that ¹⁸F-FDG PET/CT significantly increases interobserver agreement and confidence in disease localisation of ¹⁸F-FDG-avid lesions in patients with head and neck cancers.

The absent kidney in99Tcm-MAG3 renogram: a dramatic reversible consequence of contrast nephrotoxicity superimposed on renal obstruction

99Tcm-mercaptoacetyltriglycine (MAG3) renogram is a robust imaging technique used to delineate upper urinary tract obstruction. The changes observed on the renogram are often reversible on relief of obstruction. We present two cases illustrating the extreme consequence of contrast nephrotoxicity on pre-existing obstructed kidneys. In one case, this led to severe impairment of perfusion and uptake observed on 99Tcm-MAG3 renogram and in the second case virtual non-visualization of the obstructed kidney. Subsequent treatment of obstruction, led to dramatic improvement in renal function. It is important for clinicians, nuclear medicine physicians and radiologists to be aware of the potential of contrast nephrotoxicity in obstructed kidneys.

Vertebral osteomyelitis without disc involvement

Vertebral osteomyelitis is most commonly due to pyogenic or granulomatous infection and typically results in the combined involvement of the intervertebral disc and adjacent vertebral bodies. Non-infective causes include the related conditions of chronic recurrent multifocal osteomyelitis (CRMO) and SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome. Occasionally, these conditions may present purely within the vertebral body, resulting in various combinations of vertebral marrow oedema and sclerosis, destructive lesions of the vertebral body and pathological vertebral collapse, thus mimicking neoplastic disease. This review illustrates the imaging features of vertebral osteomyelitis without disc involvement, with emphasis on magnetic resonance imaging (MRI) findings.