Positron Emission Tomography-computed Tomography Scanner Research Articles

Reproducibility of quantitative myocardial perfusion and coronary flow capacity by positron emission tomography: 3D digital silicon photomultiplier solid state vs. legacy 2D analogue systems for clinical practice and trials.

Quantitative rest-stress myocardial perfusion in millilitres per minute per gram among multiple 2D and 3D positron emission tomography-computed tomography (PET-CT) scanners is essential for personalized cardiac management and clinical trials. Accordingly, this study reports the accuracy and precision of quantitative rest-stress millilitres per minute per gram and coronary flow capacity among 2D and two different digital 3D silicon photomultiplier (SiPM) PET-CT scanners for quantifying the severity of coronary pathophysiology for clinical trials or guiding interventions vs. medical treatment. One hundred seventy-one participants underwent 748 paired serial rest or stress PET perfusion imaging in the same person on 'same day' or 'different days' using rubidium-82 (Rb-82) pharmacologic stress on 2D and two different digital 3D SiPM PET-CT scanners for global myocardial perfusion in millilitres per minute per gram. For methodological variability of 66 'same-day' serial paired PETs in the same person by 2D and two different 3D SiPM PET-CT scanners, rest-stress global myocardial millilitres per minute per gram had no significant bias (P = 0.464, mean difference 0.014 ± 0.21 mL/min/g) with coefficient of variation (COV) of ±14%. For methodological plus biological variability of 154 'different-day' serial paired PETs, rest-stress global perfusion had no significant bias (P = 0.136), mean difference (0.028 ± 0.33), and COV of ±20%. Coronary flow reserve had a small bias of 0.095 ± 0.57 (P = 0.041) and COV of ±20%. Coronary flow capacity was not different by Kolmogorov-Smirnov test (P = 0.99). For quantifying myocardial perfusion in the same person on 'same day' or 'different days' using Rb-82, 3D SiPM PET-CT is comparably reproducible to analogue 2D PET-CT with the HeartSee perfusion model as the basis for quantifying physiologic severity of coronary heart disease to guide clinical decision-making or randomized clinical trials confirming these outcomes.

Multi-Tracer Studies of Brain Oxygen and Glucose Metabolism Using a Time-of-Flight Positron Emission Tomography - Computed Tomography Scanner.

The authors have developed a paradigm using positron emission tomography (PET) with multiple radiopharmaceutical tracers that combines measurements of cerebral metabolic rate of glucose (CMRGlc), cerebral metabolic rate of oxygen (CMRO2), cerebral blood flow (CBF), and cerebral blood volume (CBV), culminating in estimates of brain aerobic glycolysis (AG). These in vivo estimates of oxidative and non-oxidative glucose metabolism are pertinent to the study of the human brain in health and disease. The latest positron emission tomography-computed tomography (PET-CT) scanners provide time-of-flight (TOF) imaging and critical improvements in spatial resolution and reduction of artifacts. This has led to significantly improved imaging with lower radiotracer doses. Optimized methods for the latest PET-CT scanners involve administering a sequence of inhaled 15O-labeled carbon monoxide (CO) and oxygen (O2), intravenous 15O-labeled water (H2O), and 18F-deoxyglucose (FDG)-all within 2-h or 3-h scan sessions that yield high-resolution, quantitative measurements of CMRGlc, CMRO2, CBF, CBV, and AG. This methods paper describes practical aspects of scanning designed for quantifying brain metabolism with tracer kinetic models and arterial blood samples and provides examples of imaging measurements of human brain metabolism.

Technical NEMA NU2-2018 Performance Assessment of Time-of-Flight-Integrated Digital PET-CT System.

Aim The objective of this study includes the NEMA (National Electrical Manufacturer Association) NU2-2018 performance evaluation of the uMIvista PET-CT (positron emission tomography-computed tomography) system. Methods The latest NEMA NU2-2018 guidelines have been followed for the evaluation of performance parameters of this PET-CT scanner: axial, tangential, and radial spatial resolution, sensitivity, counting losses, scatter, randomness, random and counting loss correction, image quality, time and energy resolution, image uniformity, and image registration alignment post installation of country first uMIvista PET-CT. Results The measured NEMA sensitivity of the uMIvista PET scanner was 12.053 cps/kBq. The spatial resolutions of the PET were measured as tangential, radial, and transaxial spatial resolutions at 10 mm, with 3.01 mm, 2.95 mm, and 2.93 mm, respectively; at 100 mm, with 3.17 mm, 3.42 mm, and 3.05 mm, respectively; and at 200 mm, with 3.65 mm, 4.54 mm, and 3.17 mm, respectively, at full-width half-maximum (FWHM); while at full-width tenths-maximum (FWTM), the values at 10 mm were 5.79 mm, 5.57 mm, and 5.69 mm, respectively, and at 100 mm were 5.59 mm, 5.96 mm, and 5.91 mm, respectively. The measured time-of-flight (TOF) timing resolution was 302.294 ps and the measured energy resolution was 11.76% with FWHM and FWTM. Conclusion The NEMA NU2-2018 performances of this TOF-integrated digital PET-CT system are extremely good in all parameters.

Operational and Performance Experience with uMI550 Digital PET-CT during Routine Quality Control Procedures.

Introduction The quality control (QC) procedures for positron emission tomography (PET) scanners are covered by National Electrical Manufacturers Association and International Electrotechnical Commission. QC must be carried out at regular intervals according to the specifications of the scanner manufacturer. Daily and weekly QC plays a valuable role in monitoring positron emission tomography (PET) scanner performance changes. This study shares operational and performance experience of QC procedures that do not require a radioactive Ge-68 source to perform daily QC and experience with fluorodeoxyglucose F18 ( 18 F-FDG) as a substitute for germanium-68/sodium-22 (Ge-68/Na-22) source for weekly QC. Method This study was performed on an uMI550 digital positron emission tomography-computed tomography (PET-CT) scanner. In this scanner daily QC checks system temperature and humidity, system count rate, data link status, and voltage. QC was performed at the console control, the position of the scanner table was in the home position pulled out from the gantry, and the room was closed during the quick QC. Weekly full QC check items include look-up table drift, energy drift, time-of-flight status, C-map status, temperature and humidity, and voltage. Weekly full QC was performed with a 18 F-FDG source in a rod phantom source. Results Over 200 daily QC tests without a radioactive source Ge-68 phantom and 50 full weekly QC tests using a 18 F-FDG rod phantom were performed with this scanner according to the manufacturer's instructions and a test report was generated. No daily QC errors or warnings were observed during this period. Conclusion The new approach for the daily PET QC does not expose operators to radiation. This translates into commercial and operational merits with consistent performance and results. Implications for Practice Reduction in radiation exposure to operating staff during QC procedure in PET-CT scanner.

Technical and clinical assessment of latest technology SiPM integrated digital PETCT scanner

ObjectiveThe aim of this study was to conduct a technical and clinical evaluation of a Silicon Photomultiplier (SiPM) integrated digital Positron Emission Tomography – Computed Tomography (PETCT) Scanner using National Electrical Manufacturers Association (NEMA) NU 2- 2018 standards. MethodsSystem sensitivity was measured by using a NEMA sensitivity phantom. Scatter fraction, count-rate performance, accuracy of count loss, and timing resolution were all computed. Clinical images were acquired and image quality was assessed and compared with published studies. ResultsAt 1 cm, tangential, radial, and axial spatial resolutions were 3.02 mm, 3.02 mm, and 2.73 mm at full width half maximum (FWHM), respectively. Sensitivity at centre and 10 cm was 10.359 cps/kBq and 9.741 cps/kBq, respectively. The timing resolution was measured at 372 ps. ConclusionThe digital PETCT exhibits a high-spatial resolution and a superior timing resolution, which advances the diagnostic ability to detect small lesions and boosts the diagnostic confidence. Implications for practiceIncreases clinical relevance by improving the ability to detect and differentiate tiny or low-contrast lesions without compromising radiopharmaceutical dose or overall scan time.

Brain Activity after Intermittent Hypoxic Brain Condition in Rats.

Hypoxic brain injury is accompanied by a decrease in various functions. It is also known that obstructive sleep apnea (OSA) can cause hypoxic brain injury. This study aimed to produce a model of an intermittent hypoxic brain condition in rats and determine the activity of the brain according to the duration of hypoxic exposure. Forty male Sprague–Dawley rats were divided into four groups: the control group (n = 10), the 2 h per day hypoxia exposure group (n = 10), the 4 h per day hypoxia exposure group (n = 10), and the 8 h per day hypoxia exposure group (n = 10). All rats were exposed to a hypoxic chamber containing 10% oxygen for five days. Positron emission tomography–computed tomography (PET-CT) brain images were acquired using a preclinical PET-CT scanner to evaluate the activity of brain metabolism. All the rats were subjected to normal conditions. After five days, PET-CT was performed to evaluate the recovery of brain metabolism. Western blot analysis and immunohistochemistry were performed with vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF). The mean SUV was elevated in the 2 h per day and 4 h per day groups, and all brain regions showed increased metabolism except the amygdala on the left side, the auditory cortex on the right side, the frontal association cortex on the right side, the parietal association cortex on the right side, and the somatosensory cortex on the right side immediately after hypoxic exposure. However, there was no difference between 5 days rest after hypoxic exposure and control group. Western blot analysis revealed the most significant immunoreactivity for VEGF in the 2, 4, and 8 h per day groups compared with the control group and quantification of VEGF immunohistochemistry showed more expression in 2 and 4 h per day groups compared with the control group. However, there was no significant difference in immunoreactivity for BDNF among the groups. The duration of exposure to hypoxia may affect the activity of the brain due to angiogenesis after intermittent hypoxic brain conditions in rats.

Improved PET/MRI accuracy by use of static transmission source in empirically derived hardware attenuation correction

BackgroundAccurate quantification of radioactivity, measured by an integrated positron emission tomography (PET) and magnetic resonance imaging (MRI) system, is still a challenge. One aspect of such a challenge is to correct for the hardware attenuation, such as the patient table and radio frequency (RF) resonators. For PET/MRI systems, computed tomography (CT) is commonly used to produce hardware attenuation correction (AC) maps, by converting Hounsfield units (HU) to a linear attenuation coefficients (LAC) map at the PET energy level 511 keV, using a bilinear model. The model does not address beam hardening, nor higher density materials, which can lead to inaccurate corrections.PurposeIn this study, we introduce a transmission-based (TX-based) AC technique with a static Germanium-68 (Ge-68) transmission source to generate hardware AC maps using the PET/MRI system itself, without the need for PET or medical CT scanners. The AC TX-based maps were generated for a homogeneous cylinder, made of acrylic as a validator. The technique thereafter was applied to the patient table and posterior part of an RF-phased array used in cardiovascular PET/MRI imaging. The proposed TX-based, and the CT-based, hardware maps were used in reconstructing PET images of one cardiac patient, and the results were analysed and compared.ResultsThe LAC derived by the TX-based method for the acrylic cylinder is estimated to be 0.10851 ± 0.00380 cm−1 compared to the 0.10698 ± 0.00321 cm−1 theoretical value reported in the literature. The PET photon counts were reduced by 8.7 ± 1.1% with the patient table, at the region used in cardiac scans, while the CT-based map, used for correction, over-estimated counts by 4.3 ± 1.3%. Reconstructed in vivo images using TX-based AC hardware maps have shown 4.1 ± 0.9% mean difference compared to those reconstructed images using CT-based AC.ConclusionsThe LAC of the acrylic cylinder measurements using the TX-based technique was in agreement with those in the literature confirming the validity of the technique. The over-estimation of photon counts caused by the CT-based model used for the patient table was improved by the TX-based technique. Therefore, TX-based AC of hardware using the PET/MRI system itself is possible and can produce more accurate images when compared to the CT-based hardware AC in cardiac PET images.

Addressing Global Inequities in Positron Emission Tomography-Computed Tomography (PET-CT) for Cancer Management: A Statistical Model to Guide Strategic Planning.

BackgroundAccording to the World Health Organization (WHO), non-communicable diseases are responsible for 71% of annual global mortality. National governments and international organizations are increasingly considering medical imaging and nuclear medicine access data in strategies to address epidemiologic priorities. Our objective here was to develop a statistical model to assist countries in estimating their needs for PET-CT systems for the management of specific cancer types.Material/MethodsWe introduce a patient-centered statistical model based on country-specific epidemiological data, PET-CT performance, and evidence-based clinical guidelines for PET-CT use for cancer. The output of the model was integrated into a Bayesian model to rank countries or world regions that would benefit the most from upscaling PET-CT scanners.ResultsWe applied our model to the IMAGINE database, recently developed by the International Atomic Energy Agency (IAEA). Our model indicates that at least 96 countries should upscale their PET-CT services and more than 200 additional PET-CT scanners would be required to fulfill their needs. The model also provides quantitative evidence indicating that low-income countries would benefit the most from increasing PET-CT provision. Finally, we discuss several cases in which the standard unit [number of scanners]/[million inhabitants] to guide strategic planning or address inequities is misleading.ConclusionsOur model may help in the accurate delineation and further reduction of global inequities in access to PET-CT scanners. As a template, the model also has the potential to estimate the costs and socioeconomic impact of implementing any medical imaging modality for any clinical application.

Repeatable and reproducible measurements of myocardial oxidative metabolism, blood flow and external efficiency using 11C-acetate PET

BackgroundNon-invasive approaches to investigate myocardial efficiency can help track the progression of heart failure (HF). This study evaluates the repeatability and reproducibility of 11C-acetate positron emission tomography (PET) imaging of oxidative metabolism. Methods and resultsDynamic 11C-acetate PET scans were performed at baseline and followup (47 ± 22 days apart) in 20 patients with stable HF with reduced ejection fraction. Two observers blinded to patients’ clinical data used FlowQuant® to evaluate test–retest repeatability, as well as intra- and inter-observer reproducibility of 11C-acetate tracer uptake and clearance rates, for the measurement of myocardial oxygen consumption (MVO2), myocardial external efficiency (MEE), work metabolic index (WMI), and myocardial blood flow. Reproducibility and repeatability were evaluated using intra-class-correlation (ICC) and Bland–Altman coefficient-of-repeatability (CR). Test–retest correlations and repeatability were better for MEE and WMI compared to MVO2. All intra- and inter-observer correlations were excellent (ICC = 0.95-0.99) and the reproducibility values (CR = 3%-6%) were significantly lower than the test–retest repeatability values (22%-54%, P < 0.001). Repeatability was improved for all parameters using a newer PET–computed tomography (CT) scanner compared to older PET-only instrumentation. Conclusion11C-acetate PET measurements of WMI and MEE exhibited excellent test–retest repeatability and operator reproducibility. Newer PET–CT scanners may be preferred for longitudinal tracking of cardiac efficiency.

Effect of Positron Emission Tomography Imaging in Women With Locally Advanced Cervical Cancer

In women with locally advanced cancer of the cervix (LACC), staging defines disease extent and guides therapy. Currently, undetected disease outside the radiation field can result in undertreatment or, if disease is disseminated, overtreatment. To determine whether adding fludeoxyglucose F 18 positron emission tomography-computed tomography (PET-CT) to conventional staging with CT of the abdomen and pelvis affects therapy received in women with LACC. A randomized clinical trial was conducted. Women with newly diagnosed histologically confirmed International Federation of Gynecology and Obstetrics stage IB to IVA carcinoma of the cervix who were candidates for chemotherapy and radiation therapy (CRT) were allocated 2:1 to PET-CT plus CT of the abdomen and pelvis or CT alone. Enrollment occurred between April 2010 and June 2014 at 6 regional cancer centers in Ontario, Canada. The PET-CT scanners were at 6 associated academic institutions. The median follow-up at the time of the analysis was 3 years. The analysis was conducted on March 30, 2017. Patients received either PET-CT plus CT of the abdomen and pelvis or CT of the abdomen and pelvis. Treatment delivered, defined as standard pelvic CRT vs more extensive CRT, ie, extended field radiotherapy or therapy with palliative intent. One hundred seventy-one patients were allocated to PET-CT (n = 113) or CT (n = 58). The trial stopped early before the planned target of 288 was reached because of low recruitment. Mean (SD) age was 48.1 (11.2) years in the PET-CT group vs 48.9 (12.7) years in the CT group. In the 112 patients who received PET-CT, 68 (60.7%) received standard pelvic CRT, 38 (33.9%) more extensive CRT, and 6 (5.4%) palliative treatment. The corresponding data for the 56 patients who received CT alone were 42 (75.0%), 11 (19.6%), and 3 (5.4%). Overall, 44 patients (39.3%) in the PET-CT group received more extensive CRT or palliative treatment compared with 14 patients (25.0%) in the CT group (odds ratio, 2.05; 95% CI, 0.96-4.37; P = .06). Twenty-four patients in the PET-CT group (21.4%) received extended field radiotherapy to para-aortic nodes and 14 (12.5%) to common iliac nodes compared with 8 (14.3%) and 3 (5.4%), respectively, in the CT group (odds ratio, 1.64; 95% CI, 0.68-3.92; P = .27). There was a trend for more extensive CRT with PET-CT, but the difference was not significant because the trial was underpowered. This trial provides information on the utility of PET-CT for staging in LACC. ClinicalTrials.gov Identifier: NCT00895349.

PET-CT in the sub-arctic region of Norway 2010–2013. At the edge of what is possible?

BackgroundIt is challenging to obtain a similar access to positron emission tomography/computed tomography (PET-CT) within the whole region served. In the subarctic and arctic region of Norway, significant distances, weather conditions and seasonable darkness have been challenging when the health care provider has aimed for a high quality PET-CT service with similar availability to all inhabitants.MethodsThe PET-CT service at the University Hospital of North Norway (UNN) was established in May 2010. The glucose analogue tracer fluorine-18 fluorodeoxyglucose (FDG) was delivered from Helsinki, Finland. An ambulatory PET-CT scanner was initially employed and a permanent local one was introduced in October 2011. In March 2014, we analysed retrospectively all data on the PET-CT exams performed at the Section of Nuclear Medicine, Department of Radiology during a 32 months time period 2010–13. The following patient data were recorded: gender, age, diagnosis, residence and distance of travelling. There were in total 796 exams in 706 patients.ResultsFour hundred sixty-one PET-CT exams per million inhabitants were, on average, performed per year. Lung cancer (32.7 %), malignant melanoma (11.3 %), colorectal cancer (10.9 %) and lymphoma (9.7 %) constituted two-thirds of all exams. Three-fourths were males and the median age was 63.5 years (range 15.2–91.4 years). The access to PET-CT exam varied within the region. The southern county (Nordland) experienced a significantly less access (p < 0.0001) to the regional service. Except for malignant melanoma, this finding was observed in all major cancer subgroups. In colorectal cancer and lymphoma a lower consumption of PET-CT was also observed in the northeastern county (Finnmark). Patients’ mean distance of travelling by car (one way) was 373 km (median 313 km, range 5–936 km).ConclusionPET-CT was not similarly available within the region. Especially, inhabitants in the southern county experienced less access to the regional service. National and regional standards of care, new scanners and improved collaboration between hospital trusts may alter this situation.

A method for in vitro regional aerosol deposition measurement in a model of the human tracheobronchial tree by the positron emission tomography.

Researchers have been studying aerosol transport in human lungs for some decades. The overall lung deposition can be predicted with sufficient precision nowadays. However, the prediction of local deposition remains an unsolved problem. Numerical modeling of aerosol transport can provide detailed data with such precision and spatial resolution which were unavailable in the past. Yet, the necessary validation of numerical results represents a difficult task, as the experimental data in a sufficient spatial resolution are hardly available. This article introduces a method based on positron emission tomography, which allows acquisition of detailed experimental data on local aerosol deposition in a realistic model of human lungs. The method utilizes the Condensation Monodisperse Aerosol Generator modified for a safe production of radioactive aerosol particles and a special measuring rig. The scanning of the model is performed on a positron emission tomography-computed tomography scanner. The evaluation of aerosol deposition is based on a volume radioactivity analysis in a specialized, yet publicly available software. The reliability of the method was tested and its first results are discussed in the article. The measurements performed using the presented method can serve for validation of numerical simulations, since the presented lung model digital geometry is available.

PET-CT for assessing mediastinal lymph node involvement in patients with suspected resectable non-small cell lung cancer.

PET-CT for assessing mediastinal lymph node involvement in patients with suspected resectable non-small cell lung cancer.

Long-term results confirmed that 18F-FDG-PET/CT was an excellent diagnostic modality for early detection of vascular grafts infection.

We sought to evaluate the potential role of positron emission tomography-computed tomography (PET-CT) for the detection and diagnosis of potential infections of vascular grafts using combining metabolic (i.e., radioactive fluorine-fluoro-D-deoxyglucose [18F-FDG]) PET with morphological (CT) information and investigate long-term capability. Seventeen patients with suspected vascular-graft infection underwent thoracic-abdominal-pelvic FDG PET combined with contrast-enhanced CT using a hybrid PET-CT scanner providing co-registered PET and CT images. In this retrospect study, we suspected graft infection in 14 of 17 patients detected using PET-CT and increased the maximal uptake of 18F-FDG around the grafts. Other vascular localizations were not observed. All patients with positive PET-CT results underwent redo-surgery, and the infection was ultimately confirmed using microbiological testing in 12 of 14 patients. Follow-up time was median of 58 months (range 36-73 months) for all 17 patients. In these patients, there was no further evidence of graft infection found on clinical and imaging follow-up. This is first investigation presenting long-term follow-up, which confirmed that 18F-FDG-PET/CT is an excellent diagnostic modality for suspected vascular graft infection. 18F-FDG PET-CT exhibited a sensitivity of 100% and specificity of 71.4% for the detection of vascular-graft infection.

Specific recommendations for accurate and direct use of PET‐CT in PET guided radiotherapy for head and neck sites

To provide specific experience-based guidance and recommendations for centers wishing to develop, validate, and implement an accurate and efficient process for directly using positron emission tomography-computed tomography (PET-CT) for the radiotherapy planning of head and neck cancer patients. A PET-CT system was modified with hard-top couch, external lasers and radiotherapy immobilization and indexing devices and was subject to a commissioning and quality assurance program. PET-CT imaging protocols were developed specifically for radiotherapy planning and the image quality and pathway tested using phantoms and five patients recruited into an in-house study. Security and accuracy of data transfer was tested throughout the whole data pathway. The patient pathway was fully established and tested ready for implementation in a PET-guided dose-escalation trial for head and neck cancer patients. Couch deflection was greater than for departmental CT simulator machines. An area of high attenuation in the couch generated image artifacts and adjustments were made accordingly. Using newly developed protocols CT image quality was suitable to maintain delineation and treatment accuracy. Upon transfer of data to the treatment planning system a half pixel offset between PET and CT was observed and corrected. By taking this into account, PET to CT alignment accuracy was maintained below 1 mm in all systems in the data pathway. Transfer of structures delineated in the PET fusion software to the radiotherapy treatment planning system was validated. A method to perform direct PET-guided radiotherapy planning was successfully validated and specific recommendations were developed to assist other centers. Of major concern is ensuring that the quality of PET and CT data is appropriate for radiotherapy treatment planning and on-treatment verification. Couch movements can be compromised, bore-size can be a limitation for certain immobilization techniques, laser positioning may affect setup accuracy and couch deflection may be greater than scanners dedicated to radiotherapy. The full set of departmental commissioning and routine quality assurance tests applied to radiotherapy CT simulators must be carried out on the PET-CT scanner. CT image quality must be optimized for radiotherapy planning whilst understanding that the appearance will differ between scanners and may affect delineation. PET-CT quality assurance schedules will need to be added to and modified to incorporate radiotherapy quality assurance. Methods of working for radiotherapy and PET staff will change to take into account considerations of both parties. PET to CT alignment must be subject to quality control on a loaded and unloaded couch preferably using a suitable emission phantom, and tested throughout the whole data pathway. Data integrity must be tested throughout the whole pathway and a system included to verify that delineated structures are transferred correctly. Excellent multidisciplinary team communication and working is vital, and key staff members on both sides should be specifically dedicated to the project. Patient pathway should be clearly devised to optimize patient care and the resources of all departments. Recruitment of a cohort of patients into a methodology study is valuable to test the quality assurance methods and pathway.

Rectal adenocarcinoma metastatic to the tonsil; PET-CT observations with pathological confirmation: A case report

Metastasis of rectal adenocarcinoma develops by lymphatic or hematogenous spread. The usual sites of metastasis from rectal adenocarcinoma include local and distant lymph nodes, the liver and the lungs. The current case report presents a unique case of a mass that was identified in the tonsil by positron emission tomography-computed tomography (PET-CT), indicating a metastasis from rectal adenocarcinoma. Metastatic tumor to the tonsil is extremely rare and to the best of our knowledge, no previous studies have reported a case of tonsil metastasis from rectal adenocarcinoma. PET-CT scanners represent an important evolution in technology that is helping to bring anatomical imaging togeother with functional imaging in cancer diagnosis and therapy. Written informed consent was obtained from the patient.

Use of High-definition Computed Tomography to Assess Endotracheal Tube Luminal Narrowing after Mechanical Ventilation

202 July 2013 P and clearance of mucus are key mechanisms in the physiology of the respiratory system. Their regulation is often impaired in intubated patients who show superabundant production and inefficient clearance. As a result, a variably thick layer of mucus ultimately adheres to the inner surface of the endotracheal tube (ETT), reducing its original cross-sectional area. This luminal narrowing significantly impacts airflow resistance that varies inversely to the fourth power of the conduit’s radius according to the Poiseuille’s equation (ΔP = 8 μLQ(πr4)−1). Patient’s work of breathing may consequently increase.1 However, the importance of ETT progressive luminal narrowing during mechanical ventilation is still widely unrecognized, and currently used suctioning systems are unable to maintain the ETT function.2 To study the magnitude of this adverse event, we developed an innovative approach to visualize the accretion of mucus in extubated ETTs with high-definition computed tomography. The ETT is collected on extubation and sealed. Scanning is performed on a positron emission tomography-computed tomography scanner (Siemens, Malvern, PA), with resolution down to 15 μm. Multiplanar images of the ETT, particularly its lung end (terminal 10 cm), show the reduced inner diameter on coronal (fig. A) and transverse (fig. B) sections. 3D-volume rendering reconstructions of the lumen can also be obtained (fig. C). This technique precisely visualizes the morphology of the lumen and quantifies the existing amount of mucus. Measurements such as volume of secretions/air or minimum cross-sectional area can be collected, all of which may have exerted significant effects in vivo. High-definition computed tomography may also be useful to study the efficacy of devices for the maintenance of the ETT function.3

Imaging Copper Metabolism Imbalance in Atp7b −/− Knockout Mouse Model of Wilson’s Disease with PET-CT and Orally Administered 64CuCl2

This study aims to determine the feasibility and utility of functional imaging of copper metabolism imbalance in Atp7b (-/-) knockout mouse model of Wilson's disease (WD) with positron emission tomography-computed tomography (PET-CT) using orally administered copper-64 chloride ((64)CuCl(2)) as a tracer. Atp7b (-/-) KO mice (N = 5) were subjected to PET scanning using a hybrid PET-CT scanner, after oral administration of (64)CuCl(2) as a tracer. Time-dependent PET quantitative analysis was performed to assess gastrointestinal absorption and biodistribution of (64)Cu radioactivity in the Atp7b (-/-) KO mice, using C57BL wild-type (WT) mice (N = 5) as a normal control. Estimates of human radiation dosimetry were calculated based on biodistribution of (64)Cu radioactivity in live animals. PET-CT analysis demonstrated higher (64)Cu radioactivity in the liver of Atp7b (-/-) knockout mice compared with that in the control C57BL WT mice (p < 0.001), following oral administration of (64)CuCl(2) as a tracer. In addition, (64)Cu radioactivity in the lungs of the Atp7b (-/-) knockout mice was slightly higher than those in the control C57BL WT mice (p = 0.01). Despite initially higher renal clearance of (64)Cu, there was no significant difference of (64)Cu radioactivity in the kidneys of the Atp7b (-/-) KO mice and the control C57BL WT mice at 24h post-oral administration of (64)CuCl(2) (p = 0.16). There was no significant difference in low (64)Cu radioactivity in the blood, brain, heart, and muscles between the Atp7b (-/-) knockout mice and control C57BL WT mice (p > 0.05). Based on the biodistribution of (64)Cu radioactivity in C57BL WT mice, radiation dosimetry estimates of (64)Cu in normal human subjects were obtained. An effective dose (ED) of 42.4μSv/MBq (weighted dose over 22 organs) was calculated and the lower large intestines were identified as the critical organ for radiation exposure (120μGy/MBq for males and 135μGy/MBq for females). Radiation dosimetry estimates for patients with WD, derived from the biodistribution of (64)Cu in Atp7b (-/-) KO mice, showed a slightly lower ED of 37.5μSv/MBq, with the lower large intestines as the critical organ for radiation exposure (83μSv/MBq for male and 95μSv/MBq for female). PET-CT quantitative analysis demonstrated an increased level of (64)Cu radioactivity in the liver of Atp7b (-/-) KO mice compared with that in the control C57BL WT mice, following oral administration of (64)CuCl(2) as a tracer. The results of this study suggest the feasibility and utility of PET-CT using orally administered (64)CuCl(2) as a tracer ((64)CuCl(2)-PET/CT) for functional imaging of copper metabolism imbalance in WD.

Patient Positioning, Immobilization Devices, and Fiducial Markers in Positron Emission Tomography-Computed Tomgraphy Scanner-Based Radiation Therapy Simulation

Positron emission tomography-computed tomography (PET-CT)-based radiation therapy (RT) treatment planning has become widely available in many RT practices. This broad acceptance has been facilitated by the RT specific features which are now commonly available on practically all modern PET-CT scanners. The quality and usability of PET-CT studies for RT treatment planning purposes strongly depends on patient positioning and immobilization during image acquisition. A well-developed clinical process and understanding of special needs for this type of imaging is crucial for successful use of PET-CT in radiation therapy planning and treatment. This article describes some of the important considerations in this process and provides several observations based on clinical experience with use of PET-CT imaging in radiation therapy planning and treatment. The use of fiducial markers in this process is also discussed.

Best Practices in PET/CT: Consensus on Performance of Positron Emission Tomography–Computed Tomography

Positron emission tomography-computed tomography (PET-CT) using the glucose metabolism tracer 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) has become a widespread and preferred imaging modality for evaluating most cancers. Since commercial PET-CT scanners became available in 2001, there has been rapid dissemination of this hybrid imaging modality and PET-CT scanners have largely replaced stand-alone PET scanners. How PET-CT scans are performed and applied to cancer management has varied considerably, in part reflecting the varied background of the practice settings and training experience of the physicians performing and interpreting the PET-CT studies. Combined PET/CT with FDG has become the gold standard in oncologic imaging by accurately defining anatomy and function of many tumors. From April 2-4, 2008, a focus group composed of physicians and technologists from different practice settings and training backgrounds entitled "Best Practices in PET/CT Symposium" was held in Sonoma, California. The symposium focused on optimization of PET-CT protocols but also included other pertinent topics related to PET-CT imaging in oncology. This article summarizes areas of consensus reached by the group regarding many of the discussion topics. The summary consensus covered in this article is meant to provide direction for future discussions on how to improve the application of this hybrid modality to patient care.