The incremental value of computed tomography of COVID-19 pneumonia in predicting ICU admission.

Triage is crucial for patient's management and estimation of the required intensive care unit (ICU) beds is fundamental for health systems during the COVID-19 pandemic. We assessed whether chest computed tomography (CT) of COVID-19 pneumonia has an incremental role in predicting patient's admission to ICU. We performed volumetric and texture analysis of the areas of the affected lung in CT of 115 outpatients with COVID-19 infection presenting to the emergency room with dyspnea and unresponsive hypoxyemia. Admission blood laboratory including lymphocyte count, serum lactate dehydrogenase, D-dimer and C-reactive protein and the ratio between the arterial partial pressure of oxygen and inspired oxygen were collected. By calculating the areas under the receiver-operating characteristic curves (AUC), we compared the performance of blood laboratory-arterial gas analyses features alone and combined with the CT features in two hybrid models (Hybrid radiological and Hybrid radiomics)for predicting ICU admission. Following a machine learning approach, 63 patients were allocated to the training and 52 to the validation set. Twenty-nine (25%) of patients were admitted to ICU. The Hybrid radiological model comprising the lung %consolidation performed significantly (p = 0.04) better in predicting ICU admission in the validation (AUC = 0.82; 95% confidence interval 0.73-0.97) set than the blood laboratory-arterial gas analyses features alone (AUC = 0.71; 95% confidence interval 0.56-0.86). A risk calculator for ICU admission was derived and is available at: https://github.com/cgplab/covidapp . The volume of the consolidated lung in CT of patients with COVID-19 pneumonia has a mild but significant incremental value in predicting ICU admission.

On the dependence of quantitative diffusion-weighted imaging on scanner system characteristics and acquisition parameters: A large multicenter and multiparametric phantom study with unsupervised clustering analysis.

PURPOSE: The purpose of this multicenter phantom study was to exploit an innovative approach, based on an extensive acquisition protocol and unsupervised clustering analysis, in order to assess any potential bias in apparent diffusion coefficient (ADC) estimation due to different scanner characteristics. Moreover, we aimed at assessing, for the first time, any effect of acquisition plan/phase encoding direction on ADC estimation. METHODS: Water phantom acquisitions were carried out on 39 scanners. DWI acquisitions (b-value = 0-200-400-600-800-1000 s/mm2) with different acquisition plans (axial, coronal, sagittal) and phase encoding directions (anterior/posterior and right/left, for the axial acquisition plan), for 3 orthogonal diffusion weighting gradient directions, were performed. For each acquisition setup, ADC values were measured in-center and off-center (6 different positions), resulting in an entire dataset of 84 × 39 = 3276 ADC values. Spatial uniformity of ADC maps was assessed by means of the percentage difference between off-center and in-center ADC values (Δ). RESULTS: No significant dependence of in-center ADC values on acquisition plan/phase encoding direction was found. Ward unsupervised clustering analysis showed 3 distinct clusters of scanners and an association between Δ-values and manufacturer/model, whereas no association between Δ-values and maximum gradient strength, slew rate or static magnetic field strength was revealed. Several acquisition setups showed significant differences among groups, indicating the introduction of different biases in ADC estimation. CONCLUSIONS: Unsupervised clustering analysis of DWI data, obtained from several scanners using an extensive acquisition protocol, allows to reveal an association between measured ADC values and manufacturer/model of scanner, as well as to identify suboptimal DWI acquisition setups for accurate ADC estimation.

Surgeon eye lens dose monitoring in catheterization lab: A multi-center survey: Invited for ECMP 2018 Focus Issue.

PURPOSE: To perform a multi-centre survey on the eye lens equivalent dose absorbed by primary interventionalist during catheterization procedures, using a personal dosimeter placed close to the eye lens. METHODS: 15 different cardiologists working in 3 different centers, for a total of 5 operating rooms were enrolled. All of them were provided with a single thermoluminescent dosimeter positioned on the inner side of the temples of eyeglasses. The dose monitoring, performed on a two-months basis, started in 2016 and is still running. All dose measurements were performed by a ISO 17025 standard accredited dosimetry service thus providing certified uncertainties as well. Correlation of eye lens and wrist dose with KAP was also investigated. RESULTS: A total number of 101 eye lens measurements were performed. Annual eye lens dose estimation was obtained for all 15 surgeons (mean, mode, range, standard deviation: 10.8, 8, 4.9-27.3, 5.6  mSv, respectively). Uncertainties on annual eye lens dose estimations ranged between 10% and 20%. No significant correlation was found between eye lens dose and KAP. CONCLUSIONS: Cardiologists involved in catheterization procedures may receive annual eye lens doses close to the ICRP 118 dose limit and thus individual monitoring with a dedicated dosimeter should be carried out. Uncertainty assessment play a relevant role in eye lens equivalent dose estimation to ensure not to exceed dose limit.

Dependence of apparent diffusion coefficient measurement on diffusion gradient direction and spatial position - A quality assurance intercomparison study of forty-four scanners for quantitative diffusion-weighted imaging.

PURPOSE: To propose an MRI quality assurance procedure that can be used for routine controls and multi-centre comparison of different MR-scanners for quantitative diffusion-weighted imaging (DWI). MATERIALS AND METHODS: 44 MR-scanners with different field strengths (1 T, 1.5 T and 3 T) were included in the study. DWI acquisitions (b-value range 0-1000 s/mm2), with three different orthogonal diffusion gradient directions, were performed for each MR-scanner. All DWI acquisitions were performed by using a standard spherical plastic doped water phantom. Phantom solution ADC value and its dependence with temperature was measured using a DOSY sequence on a 600 MHz NMR spectrometer. Apparent diffusion coefficient (ADC) along each diffusion gradient direction and mean ADC were estimated, both at magnet isocentre and in six different position 50 mm away from isocentre, along positive and negative AP, RL and HF directions. RESULTS: A good agreement was found between the nominal and measured mean ADC at isocentre: more than 90% of mean ADC measurements were within 5% from the nominal value, and the highest deviation was 11.3%. Away from isocentre, the effect of the diffusion gradient direction on ADC estimation was larger than 5% in 47% of included scanners and a spatial non uniformity larger than 5% was reported in 13% of centres. CONCLUSION: ADC accuracy and spatial uniformity can vary appreciably depending on MR scanner model, sequence implementation (i.e. gradient diffusion direction) and hardware characteristics. The DWI quality assurance protocol proposed in this study can be employed in order to assess the accuracy and spatial uniformity of estimated ADC values, in single- as well as multi-centre studies.

Design, preparation and characterization of ulvan based thermosensitive hydrogels.

The present study is focused on the exploitation and conversion of sulphated polysaccharides obtained from waste algal biomass into high value added material for biomedical applications. ulvan, a sulphated polysaccharide extracted from green seaweeds belonging to Ulva sp. was selected as a suitable material due to its chemical versatility and widely ascertained bioactivity. To date the present work represents the first successful attempt of preparation of ulvan-based hydrogels displaying thermogelling behaviour. ulvan was provided with thermogelling properties by grafting poly(N-isopropylacrylamide) chains onto its backbone as thermosensitive component. To this aim ulvan was properly modified with acryloyl groups to act as macroinitiator in the radical polymerization of N-isopropylacrylamide, induced by UV irradiation through a "grafting from" method. The thermogelling properties of the copolymer were investigated by thermal and rheological analyses. Sol-gel transition of the copolymer was found to occur at 30-31 °C thus indicating the feasibility of ulvan for being used as in-situ hydrogel forming systems for biomedical applications.

Quality assurance multicenter comparison of different MR scanners for quantitative diffusion-weighted imaging.

PURPOSE: To propose a magnetic resonance imaging (MRI) quality assurance procedure that can be used for multicenter comparison of different MR scanners for quantitative diffusion-weighted imaging (DWI). MATERIALS AND METHODS: Twenty-six centers (35 MR scanners with field strengths: 1T, 1.5T, and 3T) were enrolled in the study. Two different DWI acquisition series (b-value ranges 0-1000 and 0-3000 s/mm(2) , respectively) were performed for each MR scanner. All DWI acquisitions were performed by using a cylindrical doped water phantom. Mean apparent diffusion coefficient (ADC) values as well as ADC values along each of the three main orthogonal directions of the diffusion gradients (x, y, and z) were calculated. Short-term repeatability of ADC measurement was evaluated for 26 MR scanners. RESULTS: A good agreement was found between the nominal and measured mean ADC over all the centers. More than 80% of mean ADC measurements were within 5% from the nominal value, and the highest deviation and overall standard deviation were 9.3% and 3.5%, respectively. Short-term repeatability of ADC measurement was found <2.5% for all MR scanners. CONCLUSION: A specific and widely accepted protocol for quality controls in DWI is still lacking. The DWI quality assurance protocol proposed in this study can be applied in order to assess the reliability of DWI-derived indices before tackling single- as well as multicenter studies.

Dosimetric impact of different multileaf collimators on prostate intensity modulated treatment planning.

AIM: The main purpose of this study is to perform a dosimetric comparison on target volumes and organs at risks (OARs) between prostate intensity modulated treatment plans (IMRT) optimized with different multileaf collimators (MLCs). BACKGROUND: The use of MLCs with a small leaf width in the IMRT optimization may improve conformity around the tumor target whilst reducing the dose to normal tissues. MATERIALS AND METHODS: Two linacs mounting MLCs with 5 and 10 mm leaf-width, respectively, implemented in Pinnacle(3) treatment planning system were used for this work. Nineteen patients with prostate carcinoma undergoing a radiotherapy treatment were enrolled. Treatment planning with different setup arrangements (7 and 5 beams) were performed for each patient and each machine. Dose volume histograms (DVHs) cut-off points were used in the treatment planning comparison. RESULTS: Comparable planning target volume (PTV) coverage was obtained with 7- and 5-beam configuration (both with 5 and 10 mm MLC leaf-width). The comparison of bladder and rectum DVH cut-off points for the 5-beam arrangement shows that 52.6% of the plans optimized with a larger leaf-width did not satisfy at least one of the OARs' constraints. This percentage is reduced to 10.5% for the smaller leaf-width. If a 7-beam arrangement is used the value of 52.6% decreases to 21.1% while the value of 10.5% remains unchanged. CONCLUSION: MLCs collimators with different widths and number of leaves lead to a comparable prostate treatment planning if a proper adjustment is made of the number of gantry angles.

A theoretical dose-escalation study based on biological effective dose in radioimmunotherapy with (90)Y-ibritumomab tiuxetan (Zevalin).

AIM: To investigate the variation in biological effective dose (BED) produced by the uncertainty in absorbed dose and radiobiological parameters in Zevalin radioimmunotherapy. METHODS: Eight patients scheduled for treatment with standard administration of (90)Y-ibritumomab tiuxetan (Zevalin) were studied. Patient-specific pretherapy dosimetry was performed by injection of (111)In-ibritumomab tiuxetan. Absorbed doses and BEDs were calculated for critical organs (COs) and tumours, assuming a 30% dose uncertainty and varying the radiobiological parameters in a reasonable range. In an activity-escalation study, BEDs for the COs were compared with the BED limits of external beam radiotherapy (EBRT) and BEDs for the tumour with the EBRT dose prescriptions. RESULTS: At standard activities, the absorbed doses per unit activity for the COs were in agreement with those in the literature. Absorbed doses to lesions were rather variable, ranging from 1.47 to 16.7 Gy/GBq. Median tumour absorbed dose to lesions in the range 80-110 g was 9.6 Gy/GBq (range 9.2-16.7 Gy/GBq), yielding a mean BED of about 12 Gy for administration of 15 MBq/kg. For the administration of the myeloablative activity of 45 MBq/kg, risk of liver toxicity in one patient would have been foreseen by the model. Considering also the dose uncertainty, the potential risk of liver toxicity in one more patient, lung toxicity in one patient, and kidney toxicity in one patient would have been suggested. The absorbed dose uncertainty was found to be the main source of uncertainty in the BED. As for radiobiological parameters, at myeloablative activities, the increase in the repair half-time for sublethally damaged tissue (T(mu)) from 0.5 h to 5 h induced more consistent increases in mean BED/BED(limit) than alpha/beta variation from 2 Gy to 5 Gy: at 53 MBq/kg, 38% for the liver, and 34% for the lungs and kidneys (about threefold higher than that obtained for the increase alpha/beta). CONCLUSION: At standard activities, absorbed doses to lesions appear to be effective, even though lower than prescribed by EBRT. At myeloablative dosages, the uncertainty associated with the absorbed doses and radiobiological parameters considerably affect BED evaluation and may account for possible "second-organ" toxicities.

High resolution scintimammography helps in differentiating benign from malignant findings in scintigraphic hot spots.

Several efforts have been focusing on the development of detectors devoted to high solution (99m)Tc sestamibi scintimammography to improve sensitivity for non palpable lesions. To this aim new high resolution scintillation gamma camera was developed under the "Integiated Mammographic Imaging" project. The gamma camera, made by CAEN and Pol.Hi.Tech, has an overall dimension of 112x120x75mm3. It consists of an array of 1 in. PSPMTs Hamamatsu H8520-C12 closely packed, a NaI(T1) scintillation array (1.8x1.8x6mm(3) pixel) and a general purpose collimator. By this gamma camera a clinical experience on a few patients with breast cancer suspicion was performed. In this paper we show how high resolution approach allows to better categorize the lesions on the basis of the morphology of the spatial distribution of the radiotracer in the breast tissue. By comparing conventional and high resolution images of a young patient (29 y.o.) with breast cancer suspicion, it appears clear how the Anger, camera images showed a defined hot spot, highly suggestive of malignant lesion; on the contrary, the high resolution scan shown a large and inhomogeneous uptake area with the absence of clear and focal character of the uptake, to be considered as a probably non malignant lesions. This resuh was confirmed by byoptical findings that diagnosed the echographic findings as a benign inflammatory lesion.

Principal component analysis of scintimammographic images.

The recent development of new gamma imagers based on scintillation array with high spatial resolution, has strongly improved the possibility of detecting sub-centimeter cancer in Scintimammography. However, Compton scattering contamination remains the main drawback since it limits the sensitivity of tumor detection. Principal component image analysis (PCA), recently introduced in scintimam nographic imaging, is a data reduction technique able to represent the radiation emitted from chest, breast healthy and damaged tissues as separated images. From these images a Scintimammography can be obtained where the Compton contamination is "removed". In the present paper we compared the PCA reconstructed images with the conventional scintimammographic images resulting from the photopeak (Ph) energy window. Data coming from a clinical trial were used. For both kinds of images the tumor presence was quantified by evaluating the t-student statistics for independent sample as a measure of the signal-to-noise ratio (SNR). Since the absence of Compton scattering, the PCA reconstructed images shows a better noise suppression and allows a more reliable diagnostics in comparison with the images obtained by the photopeak energy window, reducing the trend in producing false positive.

New devices for imaging in nuclear medicine.

Pinhole gamma camera imaging offers the ability to obtain high resolution images from single gamma ray emitting radiotracers playing a reasonable tradeoff between very small field of view (FoV) and sensitivity. On the other hand the total spatial resolution of a pinhole imaging device is predominantly affected by the detector intrinsic spatial resolution for reduced magnification factors. To design very compact pinhole SPET scanners with very high intrinsic spatial resolution, authors investigated a miniature gamma camera based on the newly developed Hamamatsu H8500 flat panel photomultiplier. The PSPMT was coupled to the following scintillation arrays: CsI(Tl) array with 0.2-mm, 1-mm, 1.4-mm pixel size and NaI (Tl) with 1-mm pixel size. The imaging performances were evaluated by 57Co spot and flood irradiations. NaI(Tl) array shows a better pixel identification for 1 mm pixel size, proving to be a good candidate to make a large area photodetector based on multi PSPMTs closely packed. Although CsI(Tl) array had the smallest pixel size, the low light output limited the best intrinsic spatial resolution to about 0.5 mm.