Physical and dosimetric characterisation of different Contrast-Enhanced digital mammographic systems: A multicentric study.

PURPOSE: Contrast-enhanced digital mammography (CEDM) is a relatively new imaging technique recombining low- and high-energy mammograms to emphasise iodine contrast. This work aims to perform a multicentric physical and dosimetric characterisation of four state-of-the-art CEDM systems. METHODS: We evaluated tube output, half-value-layer (HVL) for low- and high-energy and average glandular dose (AGD) in a wide range of equivalent breast thicknesses. CIRS phantom 022 was used to estimate the overall performance of a CEDM examination in the subtracted image in terms of the iodine difference signal (S). To calculate dosimetric impact of CEDM examination, we collected 4542 acquisitions on patients. RESULTS: Even if CEDM acquisition strategies differ, all the systems presented a linear behaviour between S and iodine concentration. The curve fit slopes expressed in PV/mg/cm2 were in the range [92-97] for Fujifilm, [31-32] for GE Healthcare, [35-36] for Hologic, and [114-130] for IMS. Dosimetric data from patients were matched with AGD values calculated using equivalent PMMA thicknesses. Fujifilm exhibited the lowest values, while GE Healthcare showed the highest. CONCLUSION: The subtracted image showed the ability of all the systems to give important information about the linearity of the signal with the iodine concentrations. All the patient-collected doses were under the AGD EUREF 2D Acceptable limit, except for patients with thicknesses ≤35 mm belonging to GE Healthcare and Hologic, which were slightly over. This work demonstrates the importance of testing each CEDM system to know how it performs regarding dose and the relationship between PV and iodine concentration.

Small Renal Masses: Developing a Robust Radiomic Signature.

(1) Background and (2) Methods: In this retrospective, observational, monocentric study, we selected a cohort of eighty-five patients (age range 38-87 years old, 51 men), enrolled between January 2014 and December 2020, with a newly diagnosed renal mass smaller than 4 cm (SRM) that later underwent nephrectomy surgery (partial or total) or tumorectomy with an associated histopatological study of the lesion. The radiomic features (RFs) of eighty-five SRMs were extracted from abdominal CTs bought in the portal venous phase using three different CT scanners. Lesions were manually segmented by an abdominal radiologist. Image analysis was performed with the Pyradiomic library of 3D-Slicer. A total of 108 RFs were included for each volume. A machine learning model based on radiomic features was developed to distinguish between benign and malignant small renal masses. The pipeline included redundant RFs elimination, RFs standardization, dataset balancing, exclusion of non-reproducible RFs, feature selection (FS), model training, model tuning and validation of unseen data. (3) Results: The study population was composed of fifty-one RCCs and thirty-four benign lesions (twenty-five oncocytomas, seven lipid-poor angiomyolipomas and two renal leiomyomas). The final radiomic signature included 10 RFs. The average performance of the model on unseen data was 0.79 ± 0.12 for ROC-AUC, 0.73 ± 0.12 for accuracy, 0.78 ± 0.19 for sensitivity and 0.63 ± 0.15 for specificity. (4) Conclusions: Using a robust pipeline, we found that the developed RFs signature is capable of distinguishing RCCs from benign renal tumors.

MR-based simplified extraprostatic extension evaluation: comparison of performances of different predictive models.

OBJECTIVES: To test reproducibility and predictive value of a simplified score for assessment of extraprostatic tumor extension (sEPE grade). METHODS: Sixty-five patients (mean age ± SD, 67 years ± 6.3) treated with radical prostatectomy for prostate cancer who underwent 1.5-Tesla multiparametric magnetic resonance imaging (mpMRI) 6 months before surgery were enrolled. sEPE grade was derived from mpMRI metrics: curvilinear contact length > 15 mm (CCL) and capsular bulging/irregularity. The diameter of the index lesion (dIL) was also measured. Evaluations were independently performed by seven radiologists, and inter-reader agreement was tested by weighted Cohen K coefficient. A nested (two levels) Monte Carlo cross-validation was used. The best cut-off value for dIL was selected by means of the Youden J index to classify values into a binary variable termed dIL*. Logistic regression models based on sEPE grade, dIL, and clinical scores were developed to predict pathologic EPE. Results on validation set were assessed by the main metrics of the receiver operating characteristics curve (ROC) and by decision curve analysis (DCA). Based on our findings, we defined and tested an alternative sEPE grade formulation. RESULTS: Pathologic EPE was found in 31/65 (48%) patients. Average κw was 0.65 (95% CI 0.51-0.79), 0.66 (95% CI 0.48-0.84), 0.67 (95% CI 0.50-0.84), and 0.43 (95% CI 0.22-0.63) for sEPE grading, CLL ≥ 15 mm, dIL*, and capsular bulging/irregularity, respectively. The highest diagnostic yield in predicting EPE was obtained by combining both sEPE grade and dIL*(ROC-AUC 0.81). CONCLUSIONS: sEPE grade is reproducible and when combined with the dIL* accurately predicts extraprostatic tumor extension. KEY POINTS: • Simple and reproducible mpMRI semi-quantitative scoring system for extraprostatic tumor extension. • sEPE grade accurately predicts extraprostatic tumor extension regardless of reader expertise. • Accurate pre-operative staging and risk stratification for optimized patient management.

Integrated prognostication of intrahepatic cholangiocarcinoma by contrast-enhanced computed tomography: the adjunct yield of radiomics.

PURPOSE: To test radiomics for prognostication of intrahepatic mass-forming cholangiocarcinoma (IMCC) and to develop a comprehensive risk model. METHODS: Histologically proven IMCC (representing the full range of stages) were retrospectively analyzed by volume segmentation on baseline hepatic venous phase computed tomography (CT), by two readers with different experience (R1 and R2). Morphological CT features included: tumor size, hepatic satellite lesions, lymph node and distant metastases. Radiomic features (RF) were compared across CT protocols and readers. Univariate analysis against overall survival (OS) warranted ranking and selection of RF into radiomic signature (RSign), which was dichotomized into high and low-risk strata (RSign*). Models without and with RSign* (Model 1 and 2, respectively) were compared. RESULTS: Among 78 patients (median follow-up 262 days, IQR 73-957), 62/78 (79%) died during the study period, 46/78 (59%) died within 1 year. Up to 10% RF showed variability across CT protocols; 37/108 (34%) RF showed variability due to manual segmentation. RSign stratified OS (univariate: HR 1.37 for R1, HR 1.28 for R2), RSign* was different between readers (R1 0.39; R2 0.57). Model 1 showed AUC 0.71, which increased in Model 2: AUC 0.81 (p < 0.001) and AIC 89 for R1, AUC 0.81 (p = 0.001) and AIC 90.2 for R2. CONCLUSION: The use of RF into a unified RSign score stratified OS in patients with IMCC. Dichotomized RSign* classified survival strata, its inclusion in risk models showed adjunct yield. The cut-off value of RSign* was different between readers, suggesting that the use of reference values is hampered by interobserver variability.

Automatic feathering algorithm for VMAT craniospinal irradiation: A comprehensive comparison with other VMAT planning strategies.

In craniospinal irradiation, field matching is very sensitive to intrafraction positional uncertainties in cranio-caudal direction, which could lead to severe overdoses/underdoses inside the planning target volume. During the last decade, significant efforts were made to develop volumetric-modulated arc therapy strategies, which were less sensitive to setup uncertainties. In this study, a treatment planning system-integrated method, named automatic feathering (AF) algorithm, was compared against other volumetric-modulated arc therapy strategies. Three patients were retrospectively included. Five different planning techniques were compared, including overlap (O), staggered overlap (SO), gradient optimization (GO), overlap with AF algorithm turned on (O-AF), and staggered overlap with AF algorithm turned on (SO-AF). Three overlapping lengths were considered (5 cm, 7.5 cm, and 10 cm). The middle isocenter was shifted of ±1 mm, ±3 mm, and ±5 mm to simulate setup uncertainties. Plan robustness against simulated uncertainties was evaluated by calculating near maximum and near minimum dose differences between shifted and nonshifted plans (ΔD2%, ΔD98%). Dose differences among combinations of techniques and junction lengths were tested using Wilcoxon signed-rank test. Higher ΔD2% and ΔD98% were obtained using the overlap technique (ΔD2% = 15.4%, ΔD98% = 15.0%). O-AF and SO-AF provided comparable plan robustness to GO technique. Their performance improved significantly for grater overlapping length. For 10-cm overlap and 5-mm shift, GO, O-AF, and SO-AF yielded to the better plan robustness (5.7% < ΔD2% < 6.0%, 6.1% < ΔD98% < 7.6%). SO provided an intermediate plan robustness (9.8% < ΔD2% < 10.8%, 8.9% < ΔD98% < 10.3%). The addition of AF to the overlap technique significantly improves plan robustness especially if larger overlapping lengths are used. Using the AF algorithm, plans become as robust as plans optimized with more sophisticated and time-consuming approaches (like GO).

Patient dose in angiographic interventional procedures: A multicentre study in Italy.

PURPOSE: The Council Directive 2013/59/EURATOM considers interventional radiology to be a special practice involving high doses of radiation and requiring strict monitoring to ensure the best quality assurance programs. This work reports the early experience of managing dose data from patients undergoing angiography in a multicentre study. MATERIALS AND METHODS: The study was based on a survey of about 15,200 sample procedures performed in 21 Italian hospitals centres involved on a voluntary basis. The survey concerned the collection of data related to different interventional radiology procedures: interventional cardiology, radiology, neuroradiology, vascular surgery, urology, endoscopy and pain therapy from a C-Arm and fixed units. The analysis included 11 types of procedures and for each procedure, air-kerma, kerma-area product and fluoroscopy time were collected. RESULTS: The duration and dose values of fluoroscopic exposure for each procedure is strongly dependent on individual clinical circumstances including the complexity of the procedure; the observed distribution of patient doses was very wide, even for a specified protocol. The median values of the parameters were compared with the diagnostic reference levels (DRL) proposed for some procedures in Italy (ISTISAN) or internationally. This work proposes local DRL values for three procedures. CONCLUSION: This first data collection serves to take stock of the situation on patient's dosimetry in several sectors and is the starting point for obtaining and updating DRL recalling that these levels are dependent on experience and technology available.

Radiation dose reduction in myocardial perfusion imaging single-photon emission computed tomography/computed tomography using a dose-tracking software.

OBJECTIVE: We describe our experience with a dose-tracking software (Radimetrics) that was used to optimize, from a dosimetric point of view, the single-photon emission computed tomography/computed tomography protocols used in myocardial perfusion imaging. PATIENTS AND METHODS: We extracted and assessed the major dosimetric indices as the administered activity, the computed tomography dose index, the dose length product and the size-specific dose estimates for a large sample of patients before and after an optimization process. We also evaluated both the effective and the equivalent dose to organs for all the procedures. RESULTS: We achieved a reduction in administered activity by 17.8 and 4.5% for 2- and 1-day protocols, respectively; moreover size-specific dose estimates related to a single computed tomography acquisition was reduced by 50%. The organs that received the highest equivalent dose were the heart and the breast, and with the new protocols, these values were almost halved.The average single-photon emission computed tomography/computed tomography myocardial perfusion imaging effective dose decreased from 21.9±2.5 to 15.6±1.4 mSv for the 2-day protocol and from 17.8±1.7 to 13.6±1.5 mSv for the 1-day protocol. This meant that with a simple but targeted action on acquisition protocols, it was possible to achieve considerable dosimetric reduction.The adoption of a dose-tracking software represented an easy approach to optimization. Furthermore, we could easily calculate the main dosimetric indices and check their trends day by day to perform the necessary corrective actions in real timeVideo abstract: http://links.lww.com/NMC/A135.

Intensity-modulated radiation therapy and volumetric modulated arc therapy versus conventional conformal techniques at high energy: Dose assessment and impact on second primary cancer in the out-of-field region.

The aim of this work was to estimate peripheral neutron and photon doses associated with the conventional 3D conformal radiotherapy techniques in comparison to modern ones such as Intensity modulated radiation therapy and volumetric modulated arc therapy. Assessment in terms of second cancer incidence ought to peripheral doses was also considered. For that, a dosimetric methodology proposed by the authors has been applied beyond the region where there is no CT information and, thus, treatment planning systems do not calculate and where, nonetheless, about one third of second primary cancers occurs.

Development and Validation of a High-Pressure Liquid Chromatography Method for the Determination of Chemical Purity and Radiochemical Purity of a [68Ga]-Labeled Glu-Urea-Lys(Ahx)-HBED-CC (Positron Emission Tomography) Tracer.

Background: Prostate-specific membrane antigen (PSMA) has gained high attention as a useful biomarker in the imaging evaluation of prostate cancer with positron emission tomography (PET) during recent years. [68Ga]-labeled Glu-urea-Lys(Ahx)-HBED-CC ([68Ga]-PSMA-HBED-CC) is a novel PSMA inhibitor radiotracer which has demonstrated its suitability in detecting prostate cancer. Preparation conditions may influence the quality and in vivo behavior of this tracer, and no standard procedure for the quality control (QC) is available. The aim of this study was to develop a new rapid and simple high-pressure liquid chromatography method of analysis for the routine QCs of [68Ga]-PSMA-HBED-CC to guarantee the high quality of the radiopharmaceutical product before release. Methods: A stepwise approach was used based on the quality by design concept of the International Conference of Harmonisation Q2 (R1) and Q8 (Pharmaceutical Development) guidelines in accordance with the regulations and requirements of European Association of Nuclear Medicine, Society of Nuclear Medicine, International Atomic Energy Agency, World Health Organization, and Italian Association of Nuclear Medicine and Molecular Imaging. The developed analytical test method was validated because a specific monograph in the pharmacopoeia is not available for [68Ga]-PSMA-HBED-CC. Results: The purity and quality of the radiopharmaceutical obtained according to the proposed method resulted high enough to safely administrate it to patients. An excellent linearity was found between 0.8 and 5 µg/mL, with a detection limit of 0.2 µg/mL. Assay imprecision (% CV) was <2%. Conclusions: The developed method to assess the radiochemical and chemical purity of [68Ga]-PSMA-HBED-CC is rapid, accurate, and reproducible, allowing routinely the use of this PET tracer as a diagnostic tool for imaging prostate cancer and also assuring patient safety.

Effect of iterative reconstruction on image quality of low-dose chest computed tomography.

AIM: To assess quality and radiologists' preference of low-dose computed tomography (LDCT) reconstructed with filtered back projection (FBP) or Iterative Reconstruction. METHODS: Thin-section LDCTs (1-mm thick contiguous images; 120 kVp; 30 mAs) of 38 consecutive unselected patients, evaluated for various clinical indications, were reconstructed by four different reconstruction algorithms: FBP and Sinogram-AFfirmed Iterative Reconstruction (SAFIRE) with three different strengths, from 2 to 4 (i.e. S2, S3, S4). The image noise was recorded. Two thoracic radiologists visually compared both anatomic structures (interlobular septa, lung fissures, centrilobular artery, bronchial wall, and small vessels) and lung abnormalities (intralobular reticular opacities, nodules, emphysema, cystic lung disease, decreased-attenuation areas related to constrictive obliterans bronchiolitis, patchy ground-glass opacity, consolidation, and bronchiectasis) using a qualitative four-point scale grading system of the image quality. RESULTS: A lower amount of noise was recorded for LDCTs reformatted with any SAFIRE algorithm, as compared to FBP (P < 0.0001). The noise levels decreased as the SAFIRE strength increased from S2 to S4. The visual score of the subsegmental/segmental bronchial wall was greater for the FBP datasets compared to any SAFIRE dataset (P < 0.0001 for reviewer 1; P < 0.02 for reviewer 2). The decreased lung attenuation pattern score was lower on the S4 images for one reviewer, as compared to the other LDCT datasets (P = 0.003). No other differences in terms of radiologists' preference were recorded among FBP, S2, S3, and S4. Interobserver agreement was moderate only for fissures and bronchial wall, and good to excellent for the remainders. CONCLUSION: Iterative reconstructions showed lower image noise but did not provide any real improvement for the radiologists' evaluation of thin-section LDCT of the lung.

Optimization of the acquisition geometry in digital tomosynthesis of the breast.

Digital tomosynthesis of the breast continues to be intensively studied as an adjunct or replacement of conventional mammography. Although many of the acquisition parameters found in tomosynthesis imaging are also found in conventional mammography and therefore most of the traditional values from mammography have been used in the former, two acquisition geometry parameters, the angular range covered during acquisition and the number of projections per projection set, are applicable only to tomosynthesis. Therefore, in the preclinical and clinical studies reported on tomosynthesis of the breast, a wide variety of values have been used for these two parameters. In this study, 63 different combinations of angular range and number of projections were evaluated using computer simulation methods to characterize how these two parameters affect reconstruction quality and to find which of these combinations maximize it. For this, a computer simulation of a digital tomosynthesis system that included empirically determined system response characteristics was developed and used to generate 9450 different breast tissue volume reconstructions. These reconstructions were analyzed objectively using metrics for in-plane lesion visibility and vertical resolution in the form of the contrast-to-noise ratio and artifact spread function (ASF). It was found that although maximizing the angular range covered does always increase the vertical resolution in tomosynthesis, increasing the number of projections in the acquisition set beyond a relatively low threshold does not further improve the vertical resolution. This threshold value for the minimal number of projections needed to minimize the ASF was found to vary proportionally with angular range. For example, for a 60 degrees angular range, the threshold number of projections was found to be 13. Given the clear inverse relationship between the number of projections and in-plane reconstruction quality under a limited total glandular dose condition, the optimum acquisition geometry in tomosynthesis imaging of the breast is that which maximizes the angular range while maintaining the number of projections close to the threshold values found. Finally, of the 63 acquisition geometries studied, the one that resulted in the highest quality reconstruction, considering both in-plane quality and vertical resolution, consisted of the acquisition of 13 projections over a 60 degrees angular range.

Physical characteristics of GE Senographe Essential and DS digital mammography detectors.

The purpose of this study was to investigate physical characteristics of two full field digital mammography (FFDM) systems (GE Senographe Essential and DS). Both are indirect conversion (x ray to light) alpha-Si flat panels coupled with a CsI(Tl) scintillator. The examined systems have the same pixel size (100 microm) but a different field of view: a conventional size 23 x 19.2 cm2 and a large field 24 X 30.7 cm2, specifically designed to image large breasts. In the GE Senographe Essential model relevant improvements in flat panel design were implemented and new deposition tools for metal, alpha-Si, and CsI(Tl) were introduced by GE. These changes in detector design are expected to be beneficial for advanced applications such as breast tomosynthesis. The presampling modulation transfer function (MTF), normalized noise power spectrum (NNPS), and detective quantum efficiency (DQE) were measured for a wide range of exposure (25-240 microGy) with a RQA-M2 technique (28 kVp with a Mo/Mo target/filter combination and 2 mm of additional aluminum filtration). At 1, 2, and at 4 lp/mm MTF is equal to 0.9, 0.76, and 0.46 for the conventional field detector and to 0.85, 0.59, and 0.24 for the large field detector. The latter detector exhibits an improved NNPS due to a lower electronic noise and a better DQE that reaches 60%. In addition a contrast-detail analysis was performed with CDMAM 3.4 phantom and CDCOM software: GE Senographe DS showed statistically significant poorer detection ability in comparison with the GE Senographe Essential. These results could have been expected, at least qualitatively, considering the relative DQE of the two systems.