Occupational radiation dose associated with Rb-82 myocardial perfusion positron emission tomography imaging

BACKGROUND: We determined staff radiation dose during rest and stress rubidium 82 myocardial perfusion positron emission tomography (PET) imaging. METHODS AND RESULTS: Patients received 1,587 +/- 163 MBq (42.9 +/- 4.4 mCi) Rb-82 during rest or pharmacologic stress. A pressurized ion chamber was used to monitor radiation exposure in 50 examinations. For comparison, staff exposure during pharmacologic stress in 20 other patients receiving 1,204 +/- 55.5 MBq (32.54 +/- 1.5 mCi) technetium 99m 2-methoxy isobutyl isonitrile (MIBI) was measured. For Rb-82 infusion and PET acquisition, the mean dose was 0.45 +/- 0.25 microSv (0.045 +/- 0.025 mrem). Exposure for routine stress testing at variable distances from the patient was equivalent to background. Similar exposure for pharmacologic stress testing through 7 minutes after injection of Tc-99m MIBI at variable distances was 1.075 +/- 0.32 microSv (0.108 +/- 0.03 mrem). However, exposure for stress tests starting 7 minutes after Rb-82 infusion at 0.5 m was estimated at 0.4 microSv (0.04 mrem). To determine the potential radiation dose for those responding to a medical emergency or otherwise in close proximity to a patient, we measured the mean cumulative dose at 0.5 m from 0 to 7 minutes of Rb-82 infusion, which resulted in 19.1 +/- 5.8 microSv (1.9 +/- 0.58 mrem). CONCLUSIONS: Radiation doses for all tasks during routine Rb-82 stress-rest PET are lower than measured Tc-99m MIBI values. However, the radiation dose in close proximity to the patient during or immediately after Rb-82 infusion can be considerably higher, underscoring the need for strict attention to source distance and contact times.     

Optimizing radiation dose and imaging time with conventional myocardial perfusion SPECT: Technical aspects

Journal of Nuclear Cardiology -     

双源CT双能量心肌灌注成像的图像质量及辐射剂量研究

目的：探讨运用双源CT双能量技术行冠状动脉血管成像的图像质量和辐射剂量。方法：204例患者分为两组行双源CT冠状动脉血管造影检查,A组采用双能量扫描方案,B组采用传统单能量扫描方案,比较两组的图像质量及辐射剂量。结果：A、B两组冠状动脉图像质量评分分别为（4.70±0.72）分、（4.70±0.71）分,两组间差异无统计学意义（t=-1.000,P=0.318）。A、B两组图像左、右冠状动脉信噪比（SNR）分别为A组20.0±3.4和19.0±3.0、B组20.1±3.2和19.9±3.2,且两组间差异均无统计学意义（t=1.967,P=0.051;t=-0.233,P=0.816）。A、B两组的容积CT剂量指数（CTDIvol）、剂量长度乘积（DLP）、有效辐射剂量（ED）分别为（48.27±8.70）mGy、（54.10±8.77）mGy;（565.63±115.48）mGy.cm、（702.75±144.04）mGy.cm;（9.62±1.96）mSv、（11.95±2.45）mSv,A组的CTDIvol、DLP及ED明显低于B组,差异均有统计学意义（t=-4.764,P=0.000;t=-7.501,P=0.000;t=-7.501,P=0.000）。结论：双能量心肌灌注成像技术在不降低图像质量的情况下,能够显著降低患者的有效辐射剂量,有很高的临床应用价值。     

Feasibility of myocardial perfusion imaging with half the radiation dose using ordered-subset expectation maximization with resolution recovery software

Objective

This study sought to assess the feasibility of performing myocardial perfusion imaging (MPI) with half the technetium activity using ordered-subset expectation maximization with resolution recovery (OSEM-RR), an iterative reconstruction software developed to improve count statistics and acquisition time.

Methods

Two hundred eighteen patients referred for MPI were randomly allocated to undergo stress-rest or rest-stress protocols with standard full-dose (FD) injections of technetium (Tc)-99m sestamibi or half-dose (HD) injections and OSEM-RR processing. Dose activities were adjusted individually by weight. The groups were compared for image quality and clinical results.

Results

The groups were similar for mean patient age, weight, and body mass index, sex distribution, pre-test probability of CAD and CAD prevalence. Mean Tc-99m activities for the low-dose and high-dose stages were as follows: FD group: 429?±?85?MBq and 1132?±?200?MBq; HD group: 263?±?129?MBq and 629?±?85?MBq (P?<?.0001 for both). Mean effective dose per study was 13.6?±?1.4?mSv in the FD group and 7.7?±?1.0?mSv in the HD group (P?<?.001). Over all image quality was good-to-excellent in 98% and 95% of the groups, respectively. However, when we analyzed the low-dose stage separately, image quality was slightly worse in the HD than the FD, though still within the good-to excellent range.

Conclusions

MPI with nearly half the radiation dose is feasible with good image quality.     

Use of myocardial perfusion imaging and estimation of associated radiation doses in Germany from 2005 to 2012

Purpose

For several years the Working Group Cardiovascular Nuclear Medicine of the German Society of Nuclear Medicine has been performing a regular survey to obtain information on technique, utilization and development of myocardial perfusion scintigraphy (MPS). Currently, data of six surveys from 2005 to 2012 are available. The aim of this paper is to deliver a general and comprehensive overview of all surveys documenting the course of patient doses over time and the development of the method.

Methods

A one-page questionnaire with number of MPS patients, number of stress and rest MPS, referral structure and several technical issues was sent to all centres performing MPS in Germany and evaluated. With the data on protocol utilization, effective MPS patient doses were estimated.

Results

MPS per million population (pmp) varied between 2,380 and 2,770. In 2012, MPS pmp showed a slight increase for the first time. From 2005 to 2009 the angiography to MPS ratio increased from 3.4 to 4.4, and the revascularization to MPS ratio decreased from 0.66 to 0.53. In 2012, both indices demonstrated an opposite trend for the first time (4.1 and 0.55). A total of 108 centres participated in all surveys. They showed an increase in MPS patients of 4.0 % over the reporting period. In 2012, more than 50 % of the centres experienced no change or an increase in MPS numbers. The leading single competitor was MRI, followed by angiography and stress echocardiography. ²⁰¹Tl studies have decreased since 2005 from 20 to 5 %. ^99mTc MPS studies showed a mild increase in 2-day protocols. In 2012, the average effective dose per patient was estimated at 7.4 mSv. Due to the decreasing use of ²⁰¹Tl, a mild decline over the observation period can be documented. Dynamic exercise stress was the most common stress test and adenosine the leading pharmacological stress agent, with a growing percentage. In 2012, the regadenoson percentage was 9 %. Gated single photon emission computed tomography (SPECT) noted an increasing acceptance with >70 % in 2012. The segmental scoring of perfusion studies had a low acceptance. Ambulatory care cardiologists represented the major referral group.

Conclusion

Germany has a moderate to moderate-high MPS utilization rate. Nevertheless, coronary artery disease (CAD) diagnosis and disease management are dominated by angiography. The survey data reveal a positive trend in MPS and a decrease in average patient dose reflecting good practice with guideline adherence, the implementation of technical improvements and success in training.     

Optimization of image sampling rate to lower the radiation dose of dynamic myocardial CT perfusion

BackgroundDynamic myocardial CT perfusion (CTP) has emerged as a potential strategy to combine anatomical and functional evaluation in a single modality. However, this method results in a high radiation dose.MethodsDynamic CTP was performed in 56 patients with suspected or known ischemic heart disease of whom 48 had complete CT-data. Datasets with reduced sampling rate of 2- and 3 RR-intervals (2RR and 3RR) were constructed post hoc. Myocardial blood flow (MBF) estimates from the 2RR and 3RR datasets were compared with estimates based on the full dataset (1RR) using the two one-sided test of equivalence for paired samples.ResultsSignificant equivalence was found for rest MBF_LV (p ​< ​0.001), stress MBF_LV (p ​< ​0.001) and for the CFR_LV (p ​= ​0.005) when comparing 2RR blood flow estimates with the results based on the 1RR dataset. The 2RR reconstruction protocol led to an estimated reduction in radiation dose of 35.4 ​± ​3.8%.ConclusionMBF can be quantitated with dynamic CTP using a sampling strategy of one volume for every second heartbeat. This strategy could lead to a significant reduction in radiation dose.     

Angiographic correlation of myocardial perfusion imaging with half the radiation dose using ordered-subset expectation maximization with resolution recovery software

Background

We previously described the feasibility of performing myocardial perfusion imaging (MPI) with half the technetium (Tc-99m) activity using ordered-subset expectation maximization with resolution recovery (OSEM-RR) processing. This study sought to assess the accuracy of this technique by correlating the findings with coronary angiography.

Methods

Of 290 patients who underwent MPI-gated SPECT using a half dose of Tc-99m sestamibi and OSEM-RR software in 2010-2012 at a tertiary medical center, 62 were referred for invasive coronary angiography within 90 days and formed the study group. Ischemia was defined as a summed difference score (SDS) of >3 on the MPI scan. Luminal stenosis of ≥70% on invasive coronary angiography served as the reference.

Results

Mean Tc-99m activity per study was 23.9 ± 11.5 mCi and mean effective radiation dose was 7.2 ± 3.4 mSv. MPI revealed no abnormalities in 10 patients (16.2%), myocardial infarction only in 8 patients (12.9%), and ischemia in 44 patients (71.1%). Overall sensitivity, specificity, and positive and negative predictive values for MPI compared to invasive angiography were 89.1%, 75.0%, 91.1%, and 70.5%, respectively.

Conclusions

MPI SPECT performed with a half dose of Tc-99m and OSEM-RR image processing correlates well with invasive angiography. (J Nucl Cardiol 2013)     

Impact of a new ultrafast CZT SPECT camera for myocardial perfusion imaging: fewer equivocal results and lower radiation dose

Purpose  

The new ultrafast cardiac single photon emission computed tomography (SPECT) cameras with cadmium-zinc-telluride (CZT)-based detectors are faster and produce higher quality images as compared to conventional SPECT cameras. We assessed the need for additional imaging, total imaging time, tracer dose and 1-year outcome between patients scanned with the CZT camera and a conventional SPECT camera.     

心肌灌注显像常见伪影分析

伪影是造成心肌灌注显像出现假阳性的主要原因之一,有必要对造成伪影的因素、伪影的表现形式和校正方法进行系统、全面的认识。心肌灌注显像中的伪影主要可归结为与检测仪器有关的伪影,与病人因素有关的伪影,与图像处理有关的伪影,以及与非冠状动脉疾病有关的伪影等。     

Radiopharmaceuticals for imaging myocardial perfusion

A replacement for 201Tl used in myocardial perfusion imaging with a 99mTc-labeled complex is a long-sought goal. Now, at least three varieties of 99mTc-complexes are being made available for clinical studies. This review summarizes the development of these agents and presents basic research data accumulated in this area. Also, relevant clinical radiopharmaceutical protocols and relative merits of competing 99mTc-agents are discussed.     

Molecular imaging will replace myocardial perfusion imaging

Conclusion   “The order is rapidly fadin’. And the first one now will later be last ...” In 2008 myocardial perfusion imaging is the main-stay of nuclear cardiology. However, the lyrics of Dylan from the 1960s are applicable today, as we are in rapidly changing times in medicine. We are seeing a paradigm shift in disease detection and treatment from a focus on cardiovascular morphology, function, and pathophysiology to genetic and molecular events. Cardiovascular molecular imaging will be the vanguard of noninvasive imaging in this era. Nuclear cardiology is uniquely positioned to play a central role in both the clinical and research applications of cardiovascular molecular imaging. The question should not be whether myocardial perfusion imaging will remain the dominant clinical application but how does nuclear cardiology transition to embrace and foster cardiovascular molecular imaging. If we do not do this, there are several other imaging specialties that will be more than willing to fill this void.     

Dynamic CT myocardial perfusion imaging

Cardiac CT offers several approaches to establish the hemodynamic severity of coronary artery obstructions. Dynamic myocardial perfusion CT (MPI_CT) is based on serial CT imaging to measure the inflow of contrast medium into the myocardium and calculate absolute measures of myocardial perfusion. This review describes the MPI_CT acquisition protocol, post-image acquisition processing and calculation of quantitative parameters, the diagnostic performance of MPI_CT and the potential incremental value of this technique in comparison to alternative approaches. Further technical innovation using different scanner platforms and establishment of reproducible diagnostic thresholds to differentiate significant coronary artery disease will be crucial in the path to broader clinical implementation.