Patient effective radiation dose and associated risk from transmission scans using 153Gd line sources in cardiac spect studies

Liquid scintillation efficiencies, gamma-ray emission intensities, and half-life for Gd-153

Gadolinium-153 was standardized for activity by live-timed anticoincidence counting and an ampoule was submitted to the international reference system (SIR). Absolute emission intensities for the main γ rays were determined with calibrated high-purity germanium (HPGe) and lithium-drifted silicon (Si(Li)) detectors. A revised decay scheme is indicated, with no probability of direct electron capture to the 153Eu ground state. Triple-to-double coincidence ratio (TDCR) efficiency curves indicate that the revised decay scheme is consistent with experiment. Half-life measurements agree with a previous NIST determination and show no sensitivity to chemical environment.

Organ doses and normalized organ doses for various age groups in ultralow dose pediatric C-arm cone-beam CT

OBJECTIVES

To estimate organ dose to major radiosensitive organs during pediatric body C-arm CBCT and determine normalized organ doses using a state-of-the-art equipment.

METHODS

This is a study performed utilizing physical anthropomorphic phantoms. Four anthropomorphic phantoms that simulate the average individual as a neonate, 1-year-old, 5-year-old, and 10-year-old child were used. Personalized Monte Carlo (MC)-based dosimetry was performed to estimate organ doses in children referred to thorax and abdomen C-arm CBCT acquisitions on a recently released latest generation C-arm CBCT system. Age-specific normalized organ doses were generated and organ dose was estimated for skin, bone, breast, lungs, esophagus, thymus, and heart, in the thorax, and liver, adrenals, kidneys, pancreas, stomach, gall bladder, and spleen in the abdomen. Estimated doses were compared to corresponding values obtained with physical measurements performed using thermoluminescent dosimeters (TLD).

RESULTS

The results consist of organ doses for thorax and abdomen acquisition protocols. The majority of organs received a dose below 1 mSv. For all ages, the normalized organ doses decreased from neonate to 10-year-old. The difference between the organ doses obtained with MC and TLDs was less than 8%.

CONCLUSIONS

Normalized organ doses in pediatric C-arm CBCT varied with age. Pediatric C-arm CBCT with latest-generation systems may be performed with sub mGy dose for most organs.

KEY POINTS

• The dose to the majority of organs from pediatric C-arm CBCT is in the sub mSv level. • The normalized organ doses decreased from neonate to 10-year-old. • Reported normalized organ doses may be used to estimate organ dose in pediatric C-arm cone-beam CT on modern equipment.

Contemporary Cardiac SPECT Imaging-Innovations and Best Practices: An Information Statement from the American Society of Nuclear Cardiology

This information statement from the American Society of Nuclear Cardiology highlights advances in cardiac SPECT imaging and supports the incorporation of new technology and techniques in laboratories performing nuclear cardiology procedures. The document focuses on the application of the latest imaging protocols and the utilization of newer hardware and software options to perform high quality, state-of-the-art SPECT nuclear cardiology procedures. Recommendations for best practices of cardiac SPECT imaging are discussed, highlighting what imaging laboratories should be doing as the standard of care in 2018 to achieve optimal results (based on the ASNC 2018 SPECT guideline [Dorbala et al., J Nucl Cardiol. 2018. https://doi.org/10.1007/s12350-018-1283-y ]).

Pediatric radiation dose and risk from bone density measurements using a GE Lunar Prodigy scanner

Effective radiation doses associated with bone mineral density examinations performed on children using a GE Lunar Prodigy fan-beam dual-energy X-ray absorptiometry (DXA) scanner were found to be comparable to doses from pencil-beam DXA devices, i.e., lower than 1 μSv. Cancer risks associated with acquisitions obtained in this study are negligible.

INTRODUCTION

No data were found in the literature on radiation doses and potential risks following pediatric DXA performed on GE Lunar DXA scanners. This study aimed to estimate effective doses and associated cancer risks involved in pediatric examinations performed on a GE Lunar Prodigy scanner.

METHODS

Four physical anthropomorphic phantoms representing newborn, 1-, 5-, and 10-year-old patients were employed to simulate DXA exposures. All acquisitions were carried out using the Prodigy scanner. Dose measurements were performed for spine and dual femur using the phantoms simulating the 5- and 10-year-old child. Moreover, doses associated with whole-body examinations were measured for the four phantoms used in the current study.

RESULTS

The gender-average effective dose for spine and hip examinations were 0.65 and 0.36 μSv, respectively, for the phantom representing the 5-year-old child and 0.93 and 0.205 μSv, respectively, for the phantom representing the 10-year-old child. Effective doses for whole-body examinations were 0.25, 0.22, 0.19, and 0.15 μSv for the neonate, 1-, 5-, and 10-year old child, respectively. The estimated lifetime cancer risks were negligible, i.e., 0.02-0.25 per million, depending on the sex, age, and type of DXA examination. A formula is presented for the estimation of effective dose from examinations performed on GE Lunar Prodigy scanners installed in other institutions.

CONCLUSIONS

The effective doses and potential cancer risks associated with pediatric DXA examinations performed on a GE Lunar Prodigy fan-beam scanner were found to be comparable to doses and risks reported from pencil-beam DXA devices.

Comprehensive assessment of myocardial perfusion defects, regional wall motion, and left ventricular function by using 64-section multidetector CT

PURPOSE

To evaluate the accuracy of 64-section multidetector computed tomography (CT) for the assessment of perfusion defects (PDs), regional wall motion (RWM), and global left ventricular (LV) function.

MATERIALS AND METHODS

All myocardial infarction (MI) patients signed informed consent. The IRB approved the study and it was HIPAA-compliant. Cardiac multidetector CT was performed in 102 patients (34 with recent acute MI and 68 without). Multidetector CT images were analyzed for myocardial PD, RWM abnormalities, and LV function. Global LV function and RWM were compared with transthoracic echocardiography (TTE) by using multidetector CT. PD was detected by using multidetector CT and was correlated with cardiac biomarkers and single photon emission CT (SPECT) myocardial perfusion imaging. Multidetector CT diagnosis of acute MI was made on the basis of matching the presence of PD with RWM abnormalities compared with clinical evaluation.

RESULTS

Correlation between multidetector CT and TTE for global function (r = 0.68) and RWM (kappa = 0.79) was good. The size of PD on multidetector CT had a moderate correlation against SPECT (r = 0.48, -7% +/- 9). There was good to excellent correlation between cardiac biomarkers and the percentage infarct size by using multidetector CT (r = 0.82 for creatinine phosphokinase, r = 0.76 for creatinine phosphokinase of the muscle band, and r = 0.75 for troponin). For detection of acute MI in patients, multidetector CT sensitivity was 94% (32 of 34) and specificity was 97% (66 of 68). Multidetector CT had an excellent interobserver reliability for ejection fraction quantification (r = 0.83), as compared with TTE (r = 0.68).

CONCLUSION

Patients with acute MI can be identified by using multidetector CT on the basis of RWM abnormalities and PD.

Effective doses to patients from CT acquisitions on the GE Infinia Hawkeye: a comparison of calculation methods

BACKGROUND

Nuclear medicine scans may be accompanied by CT acquisitions to provide localization of radioisotope uptake through image fusion and for use in attenuation correction. The effective doses to patients resulting from radioisotope administrations and from diagnostic CT scans are well documented. However, the development of gamma cameras with low dose CT attachments introduces the requirement for calculation of effective doses arising from non-standard CT acquisitions. In this study, the CT function of the GE Infinia Hawkeye was investigated and effective doses were calculated using various methods in order to assess the suitability of standard CT dose calculation methods.

METHODS

Dose measurements were performed using Perspex head and body phantoms and the results were used in three calculation methods: (1) the ImPACT CT dosimetry calculator used Monte Carlo dose data to calculate effective doses; (2) organ fractions exposed by each scan were estimated and applied to dose measurements and ICRP tissue weighting factors; (3) standard conversion factors were used with measured and displayed dose indices to provide the simplest method of calculation.

RESULTS

The maximum variation in effective dose using each calculation method was within 10% of the mean. Average effective doses from CT scans acquired using the Hawkeye were 0.9 mSv for a chest scan, 1.5 mSv for an abdomen-pelvis scan, and 0.1 mSv for a head scan, all significantly lower than doses resulting from diagnostic CT scans.

CONCLUSION

These doses may be used for justification of radiation exposures in accordance with IR(ME)R 2000, in association with the accompanying radioisotope dose.

The case in favor of screening for coronary artery disease with coronary CT angiography

Coronary computed tomographic angiography is leading a technologic revolution in the field of cardiac imaging. For the first time, it is possible to image the wall of the coronary artery noninvasively to assess plaque burden, characterize plaque, and assess the degree of stenosis. This paper explores the possibility of using coronary computed tomographic angiography as a screening tool. Key screening examination elements, the pros and cons of screening, the limitations of current technology, and potential pitfalls are discussed.

Radiation dose and risk from fluoroscopically guided percutaneous transluminal angioplasty and stenting in the abdominal region

The objective of this study was to estimate the radiation dose and associated risks resulting from fluoroscopically guided percutaneous transluminal angioplasty with or without stent placement in the abdominal region. Average examination parameters for renal and aortoiliac procedures were derived using data from 80 consecutive procedures performed in our institute. Organ and effective doses were estimated for endovascular procedures with the use of a Monte Carlo (MC) transport code and an adult mathematical phantom. Thermoluminescent dosimeters were used in an anthropomorphic phantom to verify MC calculations. Radiation-induced risks were estimated. Results are presented as doses normalized to dose area product, so that the patient dose from any technique and X-ray unit can be easily calculated for iliac and renal PTA/stenting sessions. The average effective dose varied from 75 to 371 microSv per Gycm(2) depending on the beam quality, procedure scheme and sex of the patient. Differences up to 17% were observed between MC-calculated data and data derived from thermoluminescent dosimetry. The radiation-induced cancer risk may be considerable for younger individuals undergoing transluminal angioplasty with stent placement.

How to Create a Cardiac CT Clinic

Coronary computed tomography (CT) angiography is taking an exponentially increasing role in the diagnostic algorithm of suspected coronary artery disease. It has the immediate potential of replacing stress tests as the first study a patient receives if suspected of having coronary artery disease. In the near future, it will likely precede all elective, diagnostic cardiac catheterizations secondary to its extraordinary negative predictive value. This paper discusses the 3 building blocks of a successful cardiac CT clinic, image quality, service, and marketing. It then discusses the significant differences in establishing a cardiac CT clinic depending on if the radiologist is hospital based or private office based.

Radiation dose and risk from fluoroscopically guided percutaneous transhepatic biliary procedures

PURPOSE

To estimate radiation dose and associated risks after fluoroscopically guided percutaneous transhepatic biliary (PTB) drainage and stent implantation procedures.

MATERIALS AND METHODS

Organ and effective doses, normalized to dose-area product (DAP), were estimated for PTB procedures with use of a Monte Carlo transport code and an adult mathematical phantom. Exposure parameters from 51 consecutive patients were used to determine average examination parameters for biliary drainage and stent implantation procedures. Thermoluminescent dosimeters were used in an anthropomorphic phantom to verify Monte Carlo calculations. Radiation-induced cancer and genetic risks were estimated.

RESULTS

The results consist of doses normalized to DAP so patient dose from any technique and x-ray unit can be easily calculated for left and right biliary access and for separate or combined biliary and metallic stent implantation sessions. A good agreement was found between Monte Carlo-calculated data and data derived from thermoluminescent dosimetry. The average effective dose varied from 1.8 to 5.4 mSv depending on procedure approach (left vs right access) and procedure scheme. A maximum effective dose of 13 mSv was estimated for 30 minutes of fluoroscopy.

CONCLUSIONS

Doses delivered to patients undergoing PTB procedures are comparable to those that arise from computed tomography protocols. Radiation-induced cancer risk may be considerable for young patients undergoing PTB drainage and stent implantation procedures.

Fluoroscopically guided implantation of modern cardiac resynchronization devices: radiation burden to the patient and associated risks

OBJECTIVES

To establish radiation risks for patients undergoing fluoroscopically guided cardiac resynchronization device implantation.

BACKGROUND

Cardiac resynchonization therapy (CRT) may be associated with extended fluoroscopic exposure.

METHODS

The fluoroscopy time, dose-area product (DAP), exposure parameters, and percentage contribution of the fluoroscopic projections commonly used were recorded in a series of 14 consecutive patients referred for cardiac resynchronization device implantation and compared to corresponding data obtained from a control group of 20 patients who underwent a conventional rhythm device implantation operation. The DAP to peak skin dose, DAP to effective dose, and DAP to gonadal dose conversion factors were determined for biventricular pacing and conventional rhythm device implantation using a humanoid phantom and thermoluminescence dosimetry.

RESULTS

The mean total fluoroscopy time and DAP values were 35.2 min and 4,765 cGy cm2, respectively, for biventricular pacing and 8.2 min and 1,106 cGy cm2, respectively, for conventional rhythm device implantation. Patient skin dose from biventricular pacing procedures requiring extended fluoroscopic exposure may exceed threshold dose for the induction of skin effects only if X-ray source-to-skin distance is kept low. The risk values for fatal cancer and severe hereditary disorders, respectively, associated with a typical CRT procedure were 273 per million and 0.2 per million treated patients.

CONCLUSIONS

Radiation risks associated with fluoroscopically guided CRT procedures may be considerable. Present data may be used for the estimation of patient radiation risks from CRT procedures performed in other institutions.

Fluoroscopically assisted surgical treatments of spinal disorders: conceptus radiation doses and risks

STUDY DESIGN

A series of anterior-posterior and lateral fluoroscopic exposures at 5 spinal levels were performed on anthropomorphic phantoms simulating the 3 trimesters of gestation.

OBJECTIVES

To provide normalized data for the determination of conceptus dose specific to gestational stage and treated spinal level. To estimate the conceptus radiation dose and risk associated with typical fluoroscopically guided spinal treatments performed on the pregnant patient.

SUMMARY OF BACKGROUND DATA

To our knowledge, there are no available data on conceptus doses and radiogenic risks resulting from fluoroscopically guided spinal surgery of the expectant mother.

METHODS

Direct measurement of conceptus doses from simulated fluoroscopic projections involved in orthopedic surgery at different spinal levels for the 3 trimesters of gestation with use of anthropomorphic phantoms and thermoluminescent dosimetry. Estimation of conceptus radiation risks from a typical pedicle screw fixation and kyphoplasty procedure using the experimentally derived data.

RESULTS

Conceptus doses from fluoroscopically guided spinal treatments are smaller than 4 mGy during all gestational stages, provided that the conceptus lies outside the primarily irradiated region. The associated risks of fatal cancer during childhood and congenital malformation on its progeny are at least 2 and 1500 times, respectively, lower than the spontaneous incidence rates. When the embryo is primarily irradiated, mean conceptus dose can be as high as 105 mGy from a nonoptimized exposure. At least 35 minutes of fluoroscopy are required for the induction of deterministic effects.

CONCLUSIONS

Individual dose assessment is paramount in every pregnancy. Variations in fluoroscopy practices and gestational stage significantly affect fetal doses.

Determination of dose-area product from panoramic radiography using a pencil ionization chamber: Normalized data for the estimation of patient effective and organ doses

The aims of the present study were (a) to investigate the potential of pencil ionization chamber to be used for the determination of dose-width product (DWP) and dose-area product (DAP) from panoramic radiographic exposures and (b) to provide data normalized to DAP for the determination of patient effective and gonadal dose from panoramic radiography performed in any laboratory. A pencil ionization chamber commonly used to measure CT dose index (CTDI) in CT scanners was employed to determine DWP for various combinations of panoramic exposure settings at the beam exit slit of a Cranex Tome panoramic x-ray unit (Soredex, Helsinki, Finland). DWP values were also measured using an array of thermoluminescence dosimeters. Reproducibility of the DWP measurement was tested. The effect of milliamperage and kilovoltage of panoramic exposures on DWP was investigated. DAP was estimated using the value of DWP measured using the pencil ionization chamber and the beam exit slit length measured using dosimetric film attached on the beam exit slit. A Rando anthropomorphic phantom appropriately loaded with thermoluminescent dosimeters (TLDs) was used to obtain organ dose and effective dose values from panoramic radiography. Reproducibility of DWP determination using the proposed method was better than 1.5%. DWP was found to be linearly related to milliamperage (r>0.999, p<0.001) and to kilovoltage raised in a power ranging from 2.18 to 2.55. DWP measured using the pencil chamber was found to be up to 11% higher than the corresponding values determined using TLD array. The panoramic exposure obtained with settings appropriate for the typical adult patient was found to result in 0.008 mSv patient effective dose, 0.0002 mGy gonadal dose, and 11.3 cGy cm2 DAP. The use of a pencil ionization chamber is proposed for the determination of DWP and DAP from panoramic radiographic exposures. Normalized data over DAP were provided for the determination of patient effective and gonadal dose from panoramic radiography.

Radiogenic risks from hysterosalpingography

The aim of this study was to determine ovarian dose, effective dose and associated radiogenic risks from hysterosalpingography (HSG), and to provide data for the estimation of radiogenic risks related to HSG studies performed in any laboratory. The fluoroscopy time, number of radiographs taken and entrance surface dose were measured in a series of 78 consecutive patients undergoing HSG as part of their infertility work-up. Organ-dose values per radiograph and per minute of fluoroscopy were separately determined using an anthropomorphic phantom and thermoluminescence dosimetry. The radiogenic risk for deleterious effects on a possible future embryo and the radiogenic risk for cancer induction on the patient undergoing HSG were estimated. The average HSG procedure in our laboratory involves a mean fluoroscopic time of 0.3 min and a mean number of radiographs of 3.2. The dose to female gonads from an average HSG procedure was 2.7 mGy and the patient effective dose was 1.2 mSv. The risk for radiogenic anomalies in a future embryo of the woman undergoing an average HSG procedure and the risk for radiogenic fatal cancer induction in the exposed woman were estimated to be less than 10(-3) of the correspondent nominal risks. Radiation risks from a typical HSG are low, but they may be elevated if fluoroscopic and/or radiographic exposures are prolonged for any reason. Present data allow the estimation of radiogenic risks associated with HSG procedures performed in other laboratories with use of different equipment, screening time and number of radiographs taken.

Comparison of four methods for assessing patient effective dose from radiological examinations

Three methods of indirect effective dose estimation were reviewed and compared to a direct effective dose determination method. An anthropomorphic phantom and thermoluminescence dosimetry were used to obtain dosimetric data associated with anterior-posterior (AP) abdominal radiography, posterior-anterior (PA) chest radiography, PA head radiography, and AP heart fluoroscopy. Effective dose was determined using: (i) organ specific dose values directly determined by thermoluminescence dosimeters, (ii) data published by National Radiological Protection Board (NRPB) and entrance surface dose (ESD), (iii) NRPB data and dose area product (DAP), (iv) energy imparted derived from DAP. The effective dose values estimated from the Rando phantom measurements were 161, 32.3, and 8.4 microSv/projection for the abdomen, chest, and head radiographs, respectively. Cardiac fluoroscopy yielded an effective dose value of 111 microSv/min. The effective dose values obtained indirectly using NRPB data and DAP were in good agreement with directly assessed values in all simulated exposures (difference <8%). The effective doses using NRPB data and ESD values differed from directly assessed values by less than 15% for the radiographic exposures and 60% for heart fluoroscopy. The energy imparted method yielded 136, 31, and 6.6 microSv/projection for the abdomen, chest, and head radiographs, respectively, and 111 microSv/min for heart fluoroscopy. Indirect patient effective dose determination using the NRPB dosimetric data and the measured value of incident radiation allows for reliable patient effective dose estimates. The use of DAP rather than ESD is recommended because it yields accurate results even for complex radiologic exposures involving fluoroscopy. The value of energy imparted may be used for the accurate determination of patient effective dose, especially when specific organ dose values are not of interest. The calculation of energy imparted with the use of EAP provides a reliable starting point for estimation of effective dose from radiologic examinations for which dosimetric data are not provided by NRPB.