Agreement between left ventricular ejection fraction assessed in patients with gated IQ-SPECT and conventional imaging

BACKGROUND: The aim of the study was to assess the agreement between the left ventricular ejection fraction (LVEF) values obtained with IQ-SPECT and those obtained with a conventional gamma camera equipped with low-energy high-resolution (LEHR), considered as the method of reference. METHODS: Gated-stress MPI using 99mTc-tetrofosmin was performed in 55 consecutive patients. The patients underwent two sequential acquisitions (Method A and B) performed on Symbia-IQ SPECT with different acquisition times and one (Method C) on a Ecam SPECT equipped with LEHR collimators. The values of the different datasets were compared using the Bland-Altman analysis method: the bias and the limits of agreement (LA) were estimated in a head-to-head comparison of the three protocols. RESULTS: In the (Method A-Method C) comparison for LVEF, the bias was 3.8% and the LAs ranged from - 9.3% to 16.8%. The agreement was still lower between Method B and C, whilst only slightly improved when Methods A and B were compared. CONCLUSIONS: The wide amplitude in LA intervals of about 30% indicates that IQ and LEHR GSPECT are not interchangeable. The values obtained with IQ-SPECT should only be used with caution when evaluating the functional state of the heart

Evaluation of Single-Photon Emission Computed Tomography Myocardial Perfusion Detection Capability through Physical Descriptors

A comprehensive validation of data acquired by different myocardial perfusion imaging (MPI) systems was performed to evaluate contrast, self-attenuation properties, and perfusion detection capability. An anthropomorphic phantom with a myocardial insert and perfusion defect was used to simulate 99mTc-tetrofosmin distribution. Different MPI systems were evaluated: a SPECT system with iterative reconstruction algorithms and resolution recovery (IRR) with/without scatter correction (SPECT-IRR-SC and SPECT-IRR), and a cardio-centric IQ SPECT/CT system with IRR, with/without scatter and attenuation corrections (IQ-IRR-SC-AC and IQ-IRR). The image quality was assessed through physical descriptors: the contrast between the left ventricular (LV) wall and LV inner chamber (CLV/LVIC), intrinsic contrast (IC), and net contrast (NC). CLV/LVIC was found to be superior for IQ-IRR-SC-AC. The IC results showed non-uniformity of the signal intensity in the LV wall for the SPECT systems. The lowest IC values were obtained for IQ-IRR-SC-AC, except for septal position, where an underestimation of the signal intensity was revealed. The NC was found to be the highest for IQ-IRR-SC-AC and SPECT-IRR-SC. Additionally, for IQ-IRR-SC-AC, the NC increased in posterior and septal positions compared to IQ-IRR, enabling better perfusion detection capability over short-axis images. IQ-IRR showed performances comparable to SPECT-IRR. The characterization and evaluation perfusion detection capability of the MPI systems enabled the investigation of the systems’ performance and limitations

Patients undergoing multiphase CT scans and receiving a cumulative effective dose of 65\u2009100\ua0mSv in a single episode of care

OBJECTIVES: To estimate the number of patients who receive a cumulative effective dose (CED) of 65100mSv from computed tomography (CT) in a single day or episode of care.METHODS: We examined 28,870 patients who underwent 49,834 CT examinations in a tertiary care centre in Italy in 2.5years. Radiation exposures were retrieved from the hospital's automatic exposure monitoring system. Two cohorts were identified as those who received a CED of 65100mSv in a single day and within a month starting from the first examination. Organ doses were estimated for the first cohort.RESULTS: Among the 1765 (6.1%) patients who received CED 65100mSv in the observation period, 427 received a CED of 65100mSv within a month (and 70 patients in a single day). This group represented 1.5% of all patients who underwent CT exams and 24% of those who received CED 65100mSv in the observation period. The clinical indication for referral included cancer in 132 patients (31%) and non-oncological indications in 295 patients (69%). In 68/70 patients with CED>100mSv in a single day, at least one organ/tissue received a dose of 65100mGy.CONCLUSIONS: The finding of a sizeable percentage of patients undergoing CT exams and receiving CED 65100mSv in a single episode of care points toward the need of imaging appropriateness criteria, to revise the routine protocols, to replace older machines, and to provide to the radiologist the patient's prior radiation history to facilitate an appropriate decision-making process.KEY POINTS: Patients can receive effective doses greater than 100mSv in a single CT or in multiple CT examinations performed in a single episode of care in 1.5% of patients in a 2.5-year period. In this study, the clinical indication for CT referral was non-oncological in 69% of patients. The patient's prior radiation history should be provided to the referring physicians and the radiological medical practitioner to facilitate an appropriate decision-making process

Conversion factors for effective dose and organ doses with the air kerma area product in patients undergoing percutaneous transhepatic biliary drainage and trans arterial chemoembolization

Conversion factors used to estimate effective (E) and organ doses (HT) from air Kerma area product (KAP) are required to estimate population doses in percutaneous transhepatic biliary drainage (PTBD) and trans arterial chemoembolization (TACE) interventional procedures. In this study, E and HT for ten critical organs/tissues, were derived in 64 PTBD and 48 TACE procedures and in 14,540 irradiation events from dosimetric, technical and geometrical information included in the radiation dose structured report using the PCXMC Monte Carlo model, and the ICRP 103 organ weighting factors. Conversion factors of: 0.13; 0.19; 0.26 and 0.32 mSv Gy−1 cm−2 were established for irradiation events characterized by a Cu filtration of 0.0; 0.1; 0.4 and 0.9 mm, respectively. While a single coefficient of conversion is not able to provide estimates of E with enough accuracy, a high agreement is obtained between E estimated through Monte Carlo methods and E estimated through E/KAP conversion factors accounting separately for the different modes of fluoroscopy and the fluorography component of the procedures. An algorithm for the estimation of effective and organ doses from KAP has been established in biliary procedures which considers the Cu filtration in the X-ray irradiation events. A similar algorithm could be easily extended to other interventional procedures and incorporated in radiation dose monitoring systems to provide dosimetric estimates automatically with enough accuracy to assess population doses

The role of activity, scan duration and patient's body mass index in the optimization of FDG imaging protocols on a TOF-PET/CT scanner

BACKGROUND: Time-of-flight (TOF) PET technology determines a reduction in the noise and improves the reconstructed image quality in low count acquisitions, such as in overweight patients, allowing a reduction of administered activity and/or imaging time. However, international guidelines and recommendations on the 18F-fluoro-2-deoxyglucose (FDG) activity administration scheme are old or only partially account for TOF technology and advanced reconstruction modalities. The aim of this study was to optimize FDG whole-body studies on a TOF-PET/CT scanner by using a multivariate approach to quantify how physical figures of merit related to image quality change with acquisition/reconstruction/patient-dependent parameters in a phantom experiment.METHODS: The NEMA-IQ phantom was used to evaluate contrast recovery coefficient (CRC), background variability (BV) and contrast-to-noise ratio (CNR) as a function of changing emission scan duration (ESD), activity concentration (AC), target internal diameter (ID), target-background activity ratio (TBR) and body mass index (BMI). The phantom was filled with an average concentration of 5.3kBq/ml of FDG solution and the spheres with TBR of 21.2, 8.8 and 5.0 in 3 different sessions. Images were acquired at varying background activity concentration from 5.1 to 1.3kBq/ml, and images were reconstructed for ESD of 30-151s per bed position with and without point spread function (PSF) correction. The parameters were all considered in a single analysis using multiple linear regression methods.RESULTS: As expected, CRC depended only on sphere ID and on PSF application, while BV depended on sphere ID, ESD, AC and BMI of the phantom, in order of decreasing relevance. Noteworthy, ESD and AC resulted as the most significant predictors of CNR variability with a similar relevance, followed by the BMI of the patient and TBR of the lesion.CONCLUSIONS: AC and ESD proved to be effective tools in modulating CNR. ESD could be increased rather than AC to improve image quality in overweight/obese patients to fulfil ALARA principles

Radiation exposure from medical imaging in dialyzed patients undergoing renal pre-transplant evaluation

BACKGROUND AND AIM: Ionizing radiation exposure from medical procedures is rising sharply-the per-capita annual effective dose in the US is 3.0 millisieverts (mSv). Hemodialyzed and kidney transplanted patients receive still higher doses of ionizing radiation due to the presence of multiple comorbidities. The aim of this study was to assess the cumulative effective dose (CED) among dialyzed patients undergoing renal pre-transplant evaluation. PATIENTS AND METHODS: We evaluated 70 hemodialysis patients between June 2009 and December 2014, aged 46.4 \ub1 12.0 years. The number and type of radiologic procedures were collected through the Radiology Information System. CED was expressed as total mSv/patient and annual CED (mSv/patient/year). RESULTS: A total of 744 radiologic procedures were performed, accounting for 3869 mSv of ionizing radiation: conventional radiology, computed tomography and nuclear medicine accounted for 78, 14 and 8 % of the procedures, but they represented, respectively, 8, 83 and 9 % of the total CED. The mean (median) annual CED was 35 (7) mSv/patient/year, while total CED was 72 (32) mSv/patient. Thirty-seven patients were active waitlisted and received 47 (10) mSv during the pre-transplant evaluation and 36 (5) mSv during the waiting phase to maintain active status. Concerning cancer risk, 4 (7 %) patients were classified at low risk (<3 mSv/year), 19 (35 %) at moderate risk (3 to <20 mSv/year), 8 (15 %) at high risk (20 to <50 mSv/year), and 23 (43 %) at very high risk ( 6550 mSv/year). CONCLUSIONS: Our study demonstrated that during renal pre-transplant evaluation, dialyzed patients receive a high dose of ionizing radiation. Considering that transplanted individuals have a high incidence of cancer due to multifactorial etiology, it is mandatory to reduce the ionizing radiation imaging

Reply: High Intraindividual Variability of Global Myocardial ¹⁸F-FDG Uptake over Time

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Quality control in PET/CT and PET/MRI: Results of a survey amongst European countries.

International audiencePurpose: An EFOMP Working Group (WG) was created in 2020 to establish recommendations for PET/CT/MRI Quality Control (QC). The WG's intention was to create a document containing a set of measurements suitable for routine practice. In order to map the current situation in PET facilities, the WG prepared a survey addressed to European Medical Physics Experts (MPE).Methods: The survey was conducted using an electronic questionnaire with 10 sections, for a total of 43 multiple choice or open questions. Data regarding general information, model of installed scanners, contract of maintenance and phantoms available were collected. The focal part of the questionnaire concerned the QC protocol adopted and accreditation programs.Results: 123 answers from 24 countries were collected. 90.2% of the respondents are affiliated as staff MPEs; 45% have non-digital TOF PET/CT scanners with a contract of maintenance (97.6%). In 98.4% and 86.8% of responding centres a sealed source for daily QC and the NEMA Image Quality Phantom were present. 94.3% of respondents perform daily QC according to manufacturer recommendations, while NEMA Tests are not performed routinely (51.2%). 56.1% of the respondents have scanners accredited by a national or international organization. 56% of the centres perform annual CT tests, while more than 90% do not perform any MRI QCs.Conclusions: The results of the survey show that there is a lack of harmonization in the PET QC procedures across Europe. The information obtained will guide the WG in proposing a guideline containing a set of measurements suitable for the clinical routine

Cumulative radiation exposure from radiological imaging in patients with Hodgkin and diffuse large b-cell lymphoma not submitted to radiotherapy

Objective: To assess the cumulated exposure to radiation due to imaging in Hodgkin (HL) and diffuse large B-cell (DLBCL) lymphoma patients who were not submitted to radiotherapy. Methods: The study population included 51 and 83 adult patients with HL and DLBCL, with a follow-up duration >1 year. The cumulated exposure was expressed using patient-specific data as cumulated effective dose (CED). Results: Fifty-one HL patients (median age 47 years) were followed for a median of 3.5 years. The median total CED per subject was 104 mSv. CT and PET/CT examinations accounted for 75 and 25% of the total CED, respectively. 26 patients (49%) had a total CED ≥ 100 mSv and the maximum CED was 302 mSv. Eighty-three DLBCL patients (median age 66 years) were followed for a median of 3.7 years. The median total CED per subject over the study period was 134 mSv. CT and PET/CT for 86% and 13% of the total CED, respectively. 56 patients (67%) had a total CED ≥100 mSv. The maximum CED was 557 mSv. Conclusion: Our study demonstrated the large number of imaging procedures performed for patients with lymphoma. Overall, 61% of the patients accrued a CED ≥ 100 mSv. Imaging policies were only in a partial agreement with current international guidelines. Advances in knowledge: The cumulated exposure radiation exposure may be of concern in HL patients and the contribution of CT procedures to the total CED is significant. The standardisation of clinical guidelines for managing patients with lymphoma is warranted

Application of a smart [18F] FDG-PET adaptive threshold segmentation algorithm for the biological target volume delineation in head and neck cancer

Background: The aim of the present study is to evaluate the reliability of a 18F-Fluorodeoxyglucose ([18F]FDG) PET adaptive threshold segmentation (ATS) algorithm, previously validated in a preclinical setting on several scanners, for the biological target volume (BTV) delineation of head and neck radiotherapy planning. Methods: [18F]FDG PET ATS algorithm was studied in treatment plans of head and neck squamous cell carcinoma on a dedicated workstation (iTaRT, Tecnologie Avanzate, Italy). BTVs segmented by the present ATS algorithm (BTVATS) were compared with those manually segmented for the original radiotherapy treatment planning (BTVVIS). We performed a qualitative and quantitative volumetric analysis with a comparison tool within the ImSimQA TM software package (Oncology Systems Limited, UK -OSL, www.imismqa.com-). We reported figures of merit (FOMs) to convey complementary information: Dice Similarity Coefficient, Sensitivity Index, and Inclusiveness Index. Results: The study was conducted on 32 treatment plans. Median BTVATS was 11 cm3 while median BTVVIS was 14 cm3. The median Dice Similarity Coefficient, Sensitivity Index, Inclusiveness Index were 0.72, 63%, 88%, respectively. Interestingly, the median volume and the median distance of the voxels that are over contoured by ATS were respectively 1 cm3 and 1 mm. Conclusions: ATS algorithm could be a smart and an independent operator tool when implemented for [18F] FDG-PET-based tumour volume delineation. Furthermore, it might be relevant in case of BTV-based dose painting