RPS 1714 - Medical imaging challenges: nuclear medicine and radiography

Purpose:

Porphyrins, due to their chemical, photophysical, and biological properties, could conjugate in a single molecule; drug properties with multimodal and/or theranostics applications. Such properties can be an excellent answer to the challenging demand of novel contrast media acting as multimodal and theranostic agents (MTCA).

Those type of compounds were already studied in magnetic resonance (MRI) and near-infrared fluorescence imaging, but very few studies were developed in iodinated contrast media.

Our aim was to develop new iodinated-porphyrin contrast agents with suitable x-ray beam attenuation and low toxicity, which can potentially be used as MTCA.

Methods and materials:

Iodinated-porphyrin derivatives were prepared through 3 synthetic approaches.

X-ray beam attenuation was assessed measuring Hounsfield units (HU) after compound exposure to a standardised computed tomography scan.

Cytotoxicity was assessed in 3 cell lines exposed to the new iodinated-porphyrins derivatives using the MTT cellular viability assay.

Results were internally compared with iomeprol, a contrast agent already on the market.

Results:

12 stable iodinated-porphyrin derivatives were successfully obtained with moderate to good yields.

All compounds showed an x-­ray beam attenuation ability similar to iomeprol (iomeprol: 488.2±1.2 HU; compounds: min-Por7 with 461.2±2.5 HU; max-Por4 with 483.5±2.6 HU).

7 of the iodinated-porphyrin derivatives showed similar viability to iomeprol, although only Por1 and Por2 presented better IC₅₀ than iomeprol.

Conclusion:

All synthesised compounds showed a proper x-ray beam attenuation ability to been used as contrast media.

Por1 and Por2 (the last one with multimodal properties) showed decreased cytotoxicity when compared with iomeprol. Also, Por5, Por11, and Por12 showed promisor cytotoxicity evaluation results.

Limitations:

Only toxicity in the dark was evaluated.

Ethics committee approval

n/a

Funding:

Financial support for the QOPNA research Unit (FCT UID/QUI/00062/2019) by University of Aveiro and FCT/MCT.

Purpose:

In order to minimise adverse effects or injuries related to the effect of iodinated contrast media (ICM) on the thyroid, international guidelines recommend developing routines for the identification and management of patients at risk of developing thyroid dysfunction. This study aimed to investigate thyroid-related ICM administration routines among diagnostic imaging departments in Norway.

Methods and materials:

A cross-sectional survey including 24 hospitals and 75 respondents (37 radiographers and 15 radiologists) with a 69% response rate was conducted. The survey covered routines for assessment and the management of risk-patients and rationale for the routines.

Results:

The findings show a variation in routines among hospitals. The use of checklists as recommended by international guidelines was quite modest (15%), the respondents preferred other methods to identify risk and contraindications. Only 20% reported checking for scheduled thyroid scintigraphy or radioactive iodine therapy. 42% did not have thyroid-related ICM routines and the main reported reason was a lack of knowledge on the topic. Radiographers and radiologists expressed uncertainty about each other’s roles and routines.

Conclusion:

This study revealed the need for optimisation of routines regarding ICM administration to thyroid-related risk-patients. Training courses and activities that improve the interprofessional network might facilitate effective implementing of the guidelines.

Limitations:

The low number of participant radiologists, which might reduce the precision of estimate and mask potential significant differences between the occupational groups.

Ethics committee approval

The Regional Committee for Medical and Health Research Ethics waived the need for approval as the project was considered a quality assurance project which did not involve any health-related or personal information. Participants were informed about the purpose of the study and that submitting the survey was regarded as implied consent.

Funding:

No funding was received for this work.

Purpose:

To investigate whether the results of a pre-determined triage tool recorded a statistically significant relationship with MPS results. The triage tool had been designed to assist in identifying patients who might not achieve the necessary exercise level.

Methods and materials:

The triage tool was composed of 11 clinical questions and was used to collect data from 300 patients referred for MPS exercise stress testing in the state general hospital in Malta. Data was collected from March-June 2018. Scan data included the duration of exercise stress tests, results of the Duke treadmill score, summed stress score (SSS), and the total perfusion deficit (TPD).

Results:

The tool demonstrated statistical significance in identifying patients who had a reduced functional ability, therefore being incapable of successfully completing their MPS treadmill exercise stress test. Gender (p<0.001), chest pain when walking uphill (p<0.001), and the presence of previous revascularisation procedures (p=0.015) were all found to be statistically related to the treadmill exercise test duration. Moreover, a statistical significance was found between the triage tool results and the results of the DTS (p<0.001), SSS (p=0.048), and the TPD (p<0.001) scores.

Conclusion:

The findings of the study identified that out of 82 participants who had a positive triage tool result, 93.9% had an inconclusive exercise stress test, confirming the value of this tool as a means of triaging patients prior to undergoing MPS exercise stress tests.

Limitations:

The sample of participants was taken over a specific period of time, therefore further research is recommended to collect data prospectively over a longer timeframe.

Ethics committee approval

This study was performed following ethical permission from the University of Malta Research Ethics Committee.

Funding:

No funding was received for this work.

Purpose:

To evaluate CT dose values used on PET-CT with ¹⁸F-FDG for oncology examinations and to optimise the institution practices in order to reduce patient exposure.

Methods and materials:

The study was carried out in two phases. A retrospective phase, phase 1, analysed the clinical practice based on CT dose descriptors, acquisition parameters, and the influence of arm position on whole-body PET-CT protocols with ¹⁸F-FDG on Philips Gemini GXL 16 and Siemens Biograph 6 equipment. Diagnostic reference levels (DRL’s) were established per CT scanner. During phase 2, several protocols were tested on a PBU-60 anthropomorphic phantom in order to analyse the dose reduction in comparison to the current protocol. Objective image quality analysis was performed based on regions of interest.

Results:

The obtained DRLs were in accordance with the literature. Significant differences were founded in examination dose values performed with different patient arm positioning. Significant differences were also founded in CT dose values per equipment PET-CT scanner using the same protocol.

Conclusion:

This study contributed to the harmonisation of the procedures of ¹⁸F-FDG PET-CT in oncological patients. Experimental tests revealed the potential for optimisation with a lower impact on image noise.

Limitations:

The experimental tests were similar, however, the PET-CT equipment technology differences didn't allow the testing of the exact the same protocols.

Ethics committee approval

Ethical approval was obtained from the institution.

Funding:

No funding was received for this work.

Purpose:

To assess mobile radiography services in nursing homes using the model for assessment of telemedicine applications (MAST).

Methods and materials:

As MAST is a multidisciplinary assessment, multiple methods were used. Six out of 7 domains in MAST was assessed. A systematic literature review and statistical analysis were used to assess the following domains: (1) health problem and description of the application, (2) safety, (3) clinical effectiveness, and (4) patient perspectives. Cost-analysis using a decision-model was used for assessment of (5) economic aspects. Individual semi-structured interviews were used to assess (6) organisational aspects.

Results:

Mobile radiography services were found to be safe with adequate image quality and the examinations affecting treatment and care (domains 1-3). The number of examinations was significantly higher in areas with mobile radiography; 0.5 per nursing home beds compared to 0.36 without this service; p=<0.001 (domain 1). The treatment given became more personalised when an examination was made in the nursing home. Patients and their relatives prefered mobile radiography (domain 4). In domain 5, mobile radiography was found to reduce costs by 30% compared to hospital-based services, a significant difference; p=<0.001. Managers experienced a need for organisational change when implementing mobile radiography (domain 6).

Conclusion:

A mobile radiography service is a safe, high-quality telemedicine service, which contributes to increasing the quality of care and reducing costs. However, to facilitate a full-scale implementation of these services, there seems to be a need for changing the way health services are funded and managed.

Limitations:

This PhD-project on mobile radiography services was mainly assessed in a Norwegian context, limiting its transferability.

Ethics committee approval

Approved by REC - project no. 2468. Approved by NSD - ref. 45739

Funding:

No funding was received for this work.

Purpose:

The advent of digital radiography facilitated the easy addition of digital anatomical side markers to medical images, however, this is not considered best practice. Reported here is a subset of a larger study investigating how qualified medical doctors, radiographers, and students review image quality in general, with a particular focus on the importance of anatomical side markers.

Methods and materials:

The research participants were 57 qualified radiographers and 65 student radiographers who volunteered at the EFRS Research Hub 2019 . They completed an image-viewing task whereby they reviewed 26 projection radiographs and decided if the images were ready to be sent to the PACS system for reporting. They could respond: a) optimal=send to PACS, b) acceptable=but could be improved, and c) unacceptable=action required before sending. They were not prompted to consider side markers or any other factors in particular. 8 images had no side marker, 7 had a digital marker, and 11 a lead marker.

Results:

Participants rated 21.71% (qualified)/23.27% (students) of images with no marker as optimal, with a further 38.6%/39.42% rated “acceptable”, implying that 60.31%/62.69% of images would be sent to PACS without a marker. 32.75% of images with a digital marker were rated “optimal=send to PACS”.

Conclusion:

Radiographers may underestimate the importance of anatomical side markers and further research is warranted.

Limitations:

Selection bias; participants were present at ECR and therefore may be more research/professionally active. Participants from some countries/institutions may be overrepresented. Language may have inhibited understanding of the task in participants without English as a first language.

Ethics committee approval

The home institution Human Research Ethics Committee declared the work exempt from full review.

Funding:

No funding was received for this work.

Purpose:

This presentation reports 4 separate but associated studies which shared the common aim of establishing whether the use of automatic exposure control in direct digital radiography could be better optimised in some Irish hospitals.

Methods and materials:

Various phantoms (PIXY without and with added layers of fat; ATOM paediatric phantoms age 1,5, 10, and 15) were x-rayed in 3 hospitals to simulate chest, pelvis, and lumbar spine radiography. AEC settings such as patient size and system speed were varied in order to change the dose constant controlling the AEC. The dose area product (DAP) and exposure index (EI) were recorded. Selected images were evaluated; noise levels were measured through the calculation of the signal-difference-to-noise ratio (SDNR) and the visual image quality was assessed through a visual grading analysis (VGA). At each site, all measurements were compared with those obtained at prevailing clinical exposures.

Results:

Radiographers can manipulate the AEC dose constant using the patient size and system speed selections. Such manipulations produced considerable (up to 54%) reduction in DAP. While DAP and SDNR values decreased with reduced AEC dose constant, the visual image quality as appraised by VGA was preserved to a point, demonstrating the maintenance of diagnostic image quality.

The dose and image quality data from these phantom experiments showed consistent findings across examinations representing adults, obese adults, and children.

Conclusion:

For the examinations tested, the dose constant programmed into the AEC in all sites results in an unnecessarily large dose.

Radiographers can and should manipulate the AEC settings to control automatic exposure and thus better optimise examinations.

Limitations:

A phantom study is appropriate to this experimental research. The findings justify further investigation of AEC manipulation during patient examinations with an evaluation of clinical images.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

To investigate how exposure parameters or, more precisely, the tube voltage affects radiation dose to the patient in lumbar spine imaging.

Methods and materials:

The data for patient weight, height, image field size, and DAP were collated for 100 patients that were referred for lumbar spine radiography on 2 different x-ray units. The first unit used the tube voltage in line with the European guidelines (79kV) while the other unit’s tube voltage was not in line with the EU guidelines (63 kV). The data was collected only for the AP projection. After the data collection, the calculations of BMI, effective dose, and dose to selected organs were calculated using a PCXMC2.0 Monte Carlo simulation program.

Results:

No statistically significant difference was found between the BMIs of the compared groups (p=0.671). When the optimal exposure parameters were used, the DAP value was lower by 79% (p<0.001), the effective dose by 62% (p<0.001), and the average dose to the organs by 73% (p<0.001). The image field was significantly larger when the optimal parameters were used. Therefore, the dose difference should be even higher when the optimal exposure parameters were used if the field size would be the same.

Conclusion:

Based on the results, we can conclude that the DAP, effective dose, and dose to organs are significantly higher when the exposure parameters used are not in line with the European guidelines.

Limitations:

The data was obtained for AP projection only and the image quality was not assessed in the study.

Ethics committee approval

The national medical ethics committee and patient consent form were obtained prior to the study.

Funding:

No funding was received for this work.

Purpose:

To investigate the feasibility of replacing an anti-scatter grid with an air-gap technique to achieve a dose reduction for lateral lumbar spine radiography while maintaining image quality on a direct digital radiography (DDR) system.

Methods and materials:

The study comprised of 2 phases. Phase 1 was an experimental study using an anthropomorphic phantom to identify the optimal air-gap technique. Phase 2 was performing lateral projections of the lumbar spine on patients (n=50). Patients were randomly assigned into a control group (n=25, imaged using the anti-scatter grid) and an experimental group (n=25, imaged using the air-gap technique). The dose area product (DAP) of all examinations was recorded, keeping all other variables constant. Image quality evaluation was performed by 5 radiologists performing absolute visual grading analysis (VGA) using an image quality score tool, with the resultant scores analysed using visual grading characteristics (VGC).

Results:

A 10 cm air-gap in conjunction with a source-to-image distance (SID) of 121 cm was found as the optimal air-gap technique. The clinical application of this technique resulted in a statistically significant (p<0.05) reduction in the radiation dose of 72% in terms of DAP. Image quality scores were higher for the anti-scatter grid but the variation between the image quality of the two techniques was not significant (p>0.05).

Conclusion:

The results imply that replacing the anti-scatter grid with an optimal air-gap technique in lateral lumbar spine digital radiography provides a significant dose reduction whilst still maintaining diagnostic image quality.

Limitations:

Differences in lateral thickness was a variable, limited by matching mean thickness for both groups. More air-gap/SID combinations were available, but particular distances were due to the physical room limitations.

Ethics committee approval

Approval obtained from the University of Malta Research and Ethics Committee.

Funding:

No funding was received for this work.

Purpose:

To determine the change of radiation dose to the patient and impact on image quality when the collimation referred to in the professional literature is used for thoracic spine radiography.

Methods and materials:

The study was performed on 84 patients who were referred for thoracic spine radiography in a Croatian hospital using a CR imaging system. Patients were randomly divided into 2 equal groups. The first group was imaged with the current collimation protocol and the second group with the collimation protocol mentioned in the professional literature. For each patient, weight and height, image-field size, exposure conditions, and DAP were measured while the effective dose and absorbed organ doses were calculated using the PCXMC Monte-Carlo simulation method. Image quality was assessed by 2 radiologists and 1 radiographer using the image software ViewDEX.

Results:

There was no statistically significant difference in BMIs between the groups. With the optimal usage of collimator, it was found that the size of the primary field in the AP projection was reduced by 45% (p<0.001) and in the LAT projection by 41% (p<0.001). The study also showed reduced values of DAP for AP projection by 34% (p=0.007) and for LAT projection by 23% (p=0.040). The effective dose was reduced by 54% (p<0.001) for AP projection and 29% (p<0.001) for LAT projection. The mean absorbed dose to selected organs decreased by 26% in the AP projection and 28% in the LAT projection. Image quality evaluation showed improvement in AP projection by 13% (p=0.001) and in LAT projection by 15% (p<0.001).

Conclusion:

Optimal collimation in thoracic spine imaging has a strong influence on the reduction of patient exposure to radiation and the improvement of image quality.

Limitations:

n/a

Ethics committee approval

Ethics committee approval obtained.

Funding:

No funding was received for this work.

Purpose:

To produce a transparent algorithm with the capacity to quickly and cheaply measure the relative performance of plain radiography imaging systems (IS).

Methods and materials:

We used an ETR-1 test plate in combination with several plain radiography IS based on both CR and DR detector technology. We collected 20 radiographs for each focal spot (FS) setting using every IS. The test plate was placed at 20 mm intervals along the z-axis in order to reveal the potential impact of the anode heel effect and focal effect on image quality. We used exposures of 0.5 mAs at 81 kVp in order to avoid noise elimination and saturation. We upgraded our pilot FIJI macro to include affine image transformation functionality and DICOM header interaction. The macro was used to carry out the consistent characterisation of ETR-1's line-pair segments. This data was exported to a series of spreadsheets which were subjected to percentile-based formatting as well as an absolute threshold. We also compared equivalent data points belonging to different FS sizes using subtraction.

Results:

Our results take the form of 1 spreadsheet for each combination of IS and FS setting, containing contrast maintenance values for 20 different spatial frequencies belonging to each exposure. Percentile-based formatting revealed a deterioration of image quality at the margin of every FOV. This effect was more pronounced on the anode side. Threshold implementation revealed minimum levels of contrast at spatial frequencies consistent with each datasets’ respective IS limiting spatial resolution. Subtraction revealed that larger FS produce lower quality radiographs.

Conclusion:

Our upgraded FIJI macro appears to possess the capacity to produce useful and accurate assessments of image quality in plain radiography.

Limitations:

Only one set of exposure conditions was used.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Contemporary approaches to optimisation often involve physical phantoms which represent human anatomy. Images are analysed using mathematical techniques. Inferences are then made to predict whether abnormalities would be visible in human images. Such approaches have limitations, such as that some abnormalities are not included and phantoms are simple representations of anatomy. We report our initial work to determine whether artificial intelligence (AI) can be used in dose optimisation with anthropomorphic phantoms containing abnormalities.

Methods and materials:

A deep convolutional neural network (DCNN) was trained on human chest x-ray images. PBU-60 anthropomorphic chest phantom images with synthetic nodules at 5 different locations and a ‘no nodule condition’ were acquired using 65kVp-125kVp in 10kVp steps; mAs was set to automatic exposure control (AEC) level, quarter, half, double, and four times AEC. SID was 200 cm. For each nodule condition, 4 phantom thicknesses were used: 0 cm, 2.5 cm, 5 cm, and 7.5 cm of PMMA. ROC area under the curve (AUC), sensitivity, and specificity were calculated from the output probabilities of DCNN for each kVp-mAs combination. Adequate image quality was considered at AUC >0.9, sensitivity>0.9, and specificity>0.6.

Results:

For all exposures, >AEC the AUC was ≥0.9. Image quality was adequate for tube load half AEC at 85kVp suggesting possible dose reduction, for AEC at 85-95kVp suggesting mid-range tube potential settings as optimal, and for double AEC at 75-95kVp and four times AEC at 65-105kVp supporting the dose creep phenomenon.

Conclusion:

These preliminary results suggest AI has the potential to be used in dose optimisation with anthropomorphic chest phantoms.

Limitations:

n/a

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

To identify if fluoroscopy is used to guide the patients’ positioning during conventional radiography procedures in clinical practice and the main reasons to do it.

Methods and materials:

A questionnaire was developed, tested, and distributed to radiographers working in radiological departments that collaborated with an educational institution in French-speaking Switzerland. The questionnaire was composed of 32 questions exploring socio-demographic aspects, professional experience, context, and radiographic practice. Descriptive statistics and thematic analysis were performed according to the nature of the questions.

Results:

The participation rate was 33% (87/264). From those participants, 39% were using fluoroscopy to guide the positioning of patients that needed radiographs of the spine, knee, and shoulder. They were working mainly in private practice (67%). The main reasons presented to use fluoroscopy were radioprotection, patient size, patient collaboration, previous surgeries, and to achieve a higher level of image quality. The radiographers that were not using fluoroscopy presented reasons as reducing radiation exposure time and dose and that the competence, professional experience, and practice were solid enough to achieve the adequate results to respond to the clinical demands.

Conclusion:

In general, radiographers are not using fluoroscopy to guide patient positioning except in contexts that are more challenging, such as non-collaborative patients or after surgeries. It seems that experience and expertise are important aspects to reduce the use of fluoroscopy during radiography examinations. Further work is necessary to identify the limitations and benefits of using fluoroscopy. Radiographers’ training to harmonise practice is also important to increase competences and confidence.

Limitations:

Only French-speaking Switzerland was included and no evidence was provided to verify which practice (use or non-use of fluoroscopy) is the most appropriated.

Ethics committee approval

n/a

Funding:

No funding was received for this work.