Partial volume correction strategies for quantitative FDG PET in oncology

Purpose  

Quantitative accuracy of positron emission tomography (PET) is affected by partial volume effects resulting in increased underestimation of the standardized uptake value (SUV) with decreasing tumour volume. The purpose of the present study was to assess accuracy and precision of different partial volume correction (PVC) methods.     

Automated quantitative Rb-82 3D PET/CT myocardial perfusion imaging: Normal limits and correlation with invasive coronary angiography

Background

We aimed to characterize normal limits and to determine the diagnostic accuracy for an automated quantification of 3D 82-Rubidium (Rb-82) PET/CT myocardial perfusion imaging (MPI).

Methods

We studied 125 consecutive patients undergoing Rb-82 PET/CT MPI, including patients with suspected coronary artery disease (CAD) and invasive coronary angiography, and 42 patients with a low likelihood (LLk) of CAD. Normal limits for perfusion and function were derived from LLk patients. QPET software was used to quantify perfusion abnormality at rest and stress expressed as total perfusion deficit (TPD).

Results

Relative perfusion databases did not differ in any of the 17 segments between males and females. The areas under the receiver operating characteristic curve for detection of CAD were 0.86 for identification of ??50% and ??70% stenosis. The sensitivity/specificity was 86%/86% for detecting ??50% stenosis and 93%/77% for ??70% stenosis, respectively. In regard to normal limits, mean rest and stress left ventricular ejection fraction (LVEF) were 67%?±?10% and 75%?±?9%, respectively. Mean transient ischemic dilation ratio was 1.06?±?0.14 and mean increase in LVEF with stress was 7.4%?±?6.1% (95th percentile of 0%).

Conclusion

Normal limits have been established for 3D Rb-82 PET/CT analysis with QPET software. Fully automated quantification of myocardial perfusion PET data shows high diagnostic accuracy for detecting obstructive CAD.     

Right and left ventricular uptake with Rb-82 PET myocardial perfusion imaging: Markers of left main or 3 vessel disease

Background

Relative myocardial perfusion imaging may underestimate severity of coronary disease (CAD), particularly in cases of balanced ischemia. Can quantification of peak left (LV) and right (RV) ventricular Rb-82 uptake measurements identify patients with left main or 3 vessel disease?

Methods

Patients (N = 169) who underwent Rb-82 PET MPI and coronary angiography were categorized as having no significant coronary stenosis (n = 60), 1 or 2 vessel disease (n = 81), or left main disease/3 vessel disease (n = 28), based on angiography. Maximal LV and RV ventricular myocardial Rb-82 uptake was measured during stress and rest.

Results

Failure to augment LV uptake by ≥ 8500 Bq/cc at stress, predicted left main or 3 vessel disease with a sensitivity of 93% and specificity of 61% (area under curve = 0.83). A ≥10% increase in RV: LV uptake ratios with stress over rest was 93% specific (area under curve = 0.74) for left main or 3 vessel disease. These indices incrementally predicted left main or 3 vessel disease compared to models including age, gender, cardiac risk factors, and summed stress and difference scores.

Conclusion

Quantifying maximal rest and stress LV and RV uptake with PET myocardial perfusion imaging may independently and incrementally identify patients with left main or 3 vessel disease.

     

静息/负荷82Rb PET门控心肌灌注显像定量分析的价值

目的 探讨门控和定量分析技术在82Rb PET心肌灌注显像中的应用价值.方法 对32例临床可疑冠心病患者进行静息/腺苷负荷82Rb PET门控心肌灌注显像.原始数据按常规处理成断层图像,再应用定量分析软件Emory Cardiac Toolbox(ECTb)进行定量分析.由3位有经验的核医学科医师分别对图像质量(优、良、一般、差、无法分析)、左心室射血分数(LVEF)的可信程度(同意、基本同意、不确定、基本不同意、不同意)、左心室功能的其他指标对诊断的价值(很有帮助、有帮助、不确定、基本无帮助、无帮助)进行评价.将观察指标分为肯定组和否定组,分别计算其百分率和90%可信区间.结果 192组分析结果中,图像质量优良者共计160组,占83.3%(160/192),其95%可信区间为78.1%～88.6%;图像质量为一般和差的共计32组,占16.7%(32/192),其95%可信区间为11.4%～21.9%.对LVEF的结果表示同意和基本同意者共计164组,占85.4%(164/192),其95%可信区间为80.4%～90.4%;认为不确定和基本不同意或不同意者共计28组,占14.6%(28/192),其95%可信区间为9.6%～19.6%.应用定量分析软件获得的除LVEF以外左心室功能的其他指标,认为很有帮助和有帮助者共计102组,占53.1%(102/192),其95%可信区间为46.1%～60.2%;不确定和基本无帮助或无帮助者90组,占46.9%(90/192),其95%可信区间为39.8%～53.9%.结论 门控和定量分析技术有助于PET图像阅片者作出更正确的诊断.     

Coronary calcium score scans for attenuation correction of quantitative PET/CT 13N-ammonia myocardial perfusion imaging

Purpose  

The aim of this study was to evaluate whether ECG-triggered coronary calcium scoring (CCS) scans can be used for attenuation correction (AC) to quantify myocardial blood flow (MBF) and coronary flow reserve (CFR) assessed by PET/CT with ¹³N-ammonia.     

Motion detection and correction for dynamic 15O-water myocardial perfusion PET studies

Purpose Patient motion during dynamic PET studies is a well-documented source of errors. The purpose of this study was to investigate the incidence of frame-to-frame motion in dynamic ¹⁵O-water myocardial perfusion PET studies, to test the efficacy of motion correction methods and to study whether implementation of motion correction would have an impact on the perfusion results.Methods We developed a motion detection procedure using external radioactive skin markers and frame-to-frame alignment. To evaluate motion, marker coordinates inside the field of view were determined in each frame for each study. The highest number of frames with identical spatial coordinates during the study were defined as non-moved. Movement was considered present if even one marker changed position, by one pixel/frame compared with reference, in one axis, and such frames were defined as moved. We tested manual, in-house-developed motion correction software and an automatic motion correction using a rigid body point model implemented in MIPAV (Medical Image Processing, Analysis and Visualisation) software. After motion correction, remaining motion was re-analysed. Myocardial blood flow (MBF) values were calculated for both non-corrected and motion-corrected datasets.Results At rest, patient motion was found in 18% of the frames, but during pharmacological stress the fraction increased to 45% and during physical exercise it rose to 80%. Both motion correction algorithms significantly decreased (p<0.006) the number of moved frames and the amplitude of motion (p<0.04). Motion correction significantly increased MBF results during bicycle exercise (p<0.02). At rest or during adenosine infusion, the motion correction had no significant effects on MBF values.Conclusion Significant motion is a common phenomenon in dynamic cardiac studies during adenosine infusion but especially during exercise. Applying motion correction for the data acquired during exercise clearly changed the MBF results, indicating that motion correction is required for these studies.     

SPECT attenuation artifacts in normal and overweight persons: insights from a retrospective comparison of Rb-82 positron emission tomography and TI-201 SPECT myocardial perfusion imaging

PURPOSE: Myocardial perfusion imaging can be performed using SPECT or positron emission tomography (PET). SPECT has lower specificity than PET, largely as a result of attenuation artifacts; however, it is more widely available. The authors describe a study of the effect of sex and body weight on the incidence of SPECT attenuation artifacts using a retrospective comparison of TI-201 SPECT and Rb PET. METHODS: One hundred sixty-one persons (101 men, 60 women; 81 normal weight, 80 overweight) underwent TI-201 SPECT and Rb PET. The incidence of observed perfusion defects was studied in territories of the three major coronary arteries. SPECT and PET results were also compared with those of angiography in a subset of 75 patients. RESULTS: One hundred fourteen defects were reported on Rb PET compared with 176 defects with TI-201 SPECT. Excess TI-201 SPECT defects occurred in male and female, normal-weight and overweight persons. The average specificity was 64% for TI-201 SPECT and 84% for Rb PET, reflecting this difference. CONCLUSIONS: Attenuation artifacts in TI-201 SPECT occur frequently and are not confined to easily identifiable subgroups of patients. Therefore, measures to improve specificity of SPECT (e.g., prone or gated imaging) or alternative imaging techniques such as PET have potential advantages for everyone, not simply for obese patients and women with large breasts. In addition, awareness of the prevalence of SPECT attenuation artifacts, in both sexes and all weight categories, may contribute to improved accuracy of interpretation.     

Myocardial perfusion quantification with Rb-82 PET: good interobserver agreement of Carimas software on global,regional, and segmental levels

Annals of Nuclear Medicine - To estimate the interobserver agreement of the Carimas software package (SP) on global, regional, and segmental levels for the most widely used myocardial perfusion PET...     

Manufacture of strontium-82/rubidium-82 generators and quality control of rubidium-82 chloride for myocardial perfusion imaging in patients using positron emission tomography

We describe a protocol to manufacture ⁸²Sr/⁸²Rb generators and ⁸²RbCl for myocardial imaging with PET. The generators are manufactured in 3 stages: (1) preparation of a tin oxide column, (2) leak test of the generator column and (3) loading of the generator with ⁸²Sr. The generators produced sterile and non-pyrogenic ⁸²RbCl for i.v. injection. No significant ⁸²Sr/⁸⁵Sr breakthroughs were observed after elution with 20 l of saline. The automated system delivered human doses of ⁸²RbCl accurately.     

Impact of point spread function modeling and time-of-flight on myocardial blood flow and myocardial flow reserve measurements for rubidium-82 cardiac PET

Background

Myocardial flow reserve (MFR) obtained from dynamic cardiac positron emission tomography (PET) with rubidium-82 (Rb-82) has been shown to be a useful measurement in assessing coronary artery disease. Advanced PET reconstructions with point spread function modeling and time-of-flight have been shown to improve image quality but also have an impact on kinetic analysis of dynamic data. This study aims to determine the impact of these algorithms on MFR data.

Methods

Dynamic Rb-82 cardiac PET images from 37 patients were reconstructed with standard and advanced reconstructions. Area under curve (AUC) of the blood input function (BIF), myocardial blood flow (MBF) and MFR were compared with each reconstruction.

Results

No significant differences were seen in MFR for the two reconstructions. A relatively small mean difference in MBF data of +11.9% was observed with advanced reconstruction compared with the standard reconstruction but there was considerable variability in the degree of change (95% confidence intervals of ?16.2% to +40.0%). Small systematic relative differences were seen for AUC BIF (mean difference of ?6.3%; 95% CI ?17.5% to +5.4%).

Conclusion:

MFR results from Rb-82 dynamic PET appear to be robust when generated by standard or advanced PET reconstructions. Considerable increases in MBF values may occur with advanced reconstructions, and further work is required to fully understand this.     

Comparison of attenuation, dual-energy-window, and model-based scatter correction of low-count SPECT to 82Rb PET/CT quantified myocardial perfusion scores

Background

New reconstruction algorithms allow reduction in acquisition times or the amount of injected radioactivity. We examined the impact of different corrections on low-count clinical SPECT myocardial perfusion images (MPI) and compared to ⁸²Rb PET/CT. We compared no corrections (NC) to attenuation correction (AC) with and without scatter correction by either a dual-energy-window (AC-DEW) or model-based (AC-ESSE) approach. All reconstructions included resolution recovery.

Methods

56 Patients were imaged using a standard rest/stress Tc-99m-tetrofosmin MPI SPECT/CT protocol with an additional half-time acquisition. A ⁸²Rb-rest/stress PET/CT MPI was acquired within 4 weeks. Reconstruction methods were compared using summed rest/stress/difference scores from an objective algorithm (SRS/SSS/SDS).

Results

The SRS and SSS for NC were significantly (P < .01) higher than for AC, but well correlated (r ≥ 0.87). The correlation in SRS/SSS among AC, AC-DEW, and AC-ESSE was excellent (r ≥ 0.98). AC-ESSE and AC-DEW had higher SRS (P ≤ .05) than AC, but the SDS values were not significantly different. Concordance with PET normal/abnormal classification was 76% for NC and ≥85% for the AC methods.

Conclusion

AC significantly improves the accuracy of low-count myocardial perfusion SPECT half-time imaging for the detection of disease compared to NC. Compared to PET, there was no significant difference among AC, AC-DEW, and AC-ESSE.     

Comparison of the myocardial blood flow response to regadenoson and dipyridamole: a quantitative analysis in patients referred for clinical <Superscript>82</Superscript>Rb myocardial perfusion PET

Background  

Regadenoson is a novel selective A_2A adenosine receptor agonist, which is administered as an intravenous bolus at a fixed dose. It is currently not clear if the absolute flow increase in response to this fixed dose is a function of distribution volume in individual patients or if it is generally comparable to the previous standard agents dipyridamole or adenosine, which are dosed based on weight. We used quantitative analysis of clinical ⁸²Rb PET/CT studies to obtain further insights.     

Accuracy of low-dose rubidium-82 myocardial perfusion imaging for detection of coronary artery disease using 3D PET and normal database interpretation

Background

Our aim was to develop a normal database to be used for quantification of myocardial perfusion and diagnosis of ??obstructive coronary artery disease?? (CAD) using low-dose rubidium-82 three-dimensional (3D) positron emission tomography (PET)-CT.

Methods

From a record of 1,501 patients, 77 were identified as having low-likelihood (LLK) of CAD. Forty LLK patients were used to construct a normal database using 4DM-PET, the remainder used for validation of normalcy. A group of 70 patients with CAD who had invasive coronary angiography and PET-CT were used to evaluate the accuracy of the database for detecting CAD using the sum-stress-score. The effect of clinical exclusion criteria and the inclusion of LLK patients were evaluated.

Results

The normal database for CAD detection had a normalcy rate of 95%. Sensitivity was 100% for detecting patients with either 50% or 70% stenosis. Optimal specificity was 87% for either 50% or 70% stenosis. For localizing disease at 50% stenosis in the left anterior descending, left circumflex, and right coronary artery, sensitivity ranged from 59% to 68%, while specificity was maintained at 87-89%. Similarly, at 70% stenosis, sensitivity ranged from 64% to 79%, and specificity from 87% to 91%.

Conclusions

A normal database containing the relative perfusion scores of patients with LLK of CAD can be used to accurately diagnose obstructive coronary disease using low-dose Rb-82 with 3D PET-CT imaging.