Antero-posterior (AP) pelvis x-ray imaging on a trolley: Impact of trolley design, mattress design and radiographer practice on image quality and radiation dose

Effects of body part thickness on low-contrast detail detection and radiation dose during adult chest radiography

INTRODUCTION

Differences in patient size often provide challenges for radiographers, particularly when choosing the optimum acquisition parameters to obtain radiographs with acceptable image quality (IQ) for diagnosis. This study aimed to assess the effect of body part thickness on IQ in terms of low-contrast detail (LCD) detection and radiation dose when undertaking adult chest radiography (CXR).

METHODS

This investigation made use of a contrast detail (CD) phantom. Polymethyl methacrylate (PMMA) was utilised to approximate varied body part thicknesses (9, 11, 15 and 17 cm) simulating underweight, standard, overweight and obese patients, respectively. Different tube potentials were tested against a fixed 180 cm source to image distance (SID) and automatic exposure control (AEC). IQ was analysed using bespoke software thus providing an image quality figure inverse (IQFinv ) value which represents LCD detectability. Dose area product (DAP) was utilised to represent the radiation dose.

RESULTS

IQFinv values decreased statistically (P = 0.0001) with increasing phantom size across all tube potentials studied. The highest IQFinv values were obtained at 80 kVp for all phantom thicknesses (2.29, 2.02, 1.8 and 1.65, respectively). Radiation dose increased statistically (P = 0.0001) again with increasing phantom thicknesses.

CONCLUSION

Our findings demonstrate that lower tube potentials provide the highest IQFinv scores for various body part thicknesses. This is not consistent with professional practice because radiographers frequently raise the tube potential with increased part thickness. Higher tube potentials did result in radiation dose reductions. Establishing a balance between dose and IQ, which must be acceptable for diagnosis, can prevent the patient from receiving unnecessary additional radiation dose.

Evaluation of radiation dose to organs of neonatal patients during portable X-ray examination in incubators: A Monte Carlo simulation study

BACKGROUND

Infants admitted to neonate intensive care units (NICUs) are placed in incubators to maintain body temperature and condition, which undergo normal radiographs and are exposed to radiation. Furthermore, different incubator structures in different hospitals exhibit varying object to image receptor distance (OID), source to image receptor distance (SID), presence of canopy, which results in variations in X-ray radiation conditions and doses absorbed by the neonatal patients.

OBJECTIVE

To measure organ dose exposed to neonatal patient in different incubator settings.

METHODS

A portable X-ray was performed on a neonatal patient placed in an incubator to identify disease progress, the injection path of the drug, and various factors. To minimize direct contact between neonatal patients and image receptor, radiologic technologists place the image receptor on a tray underneath the incubator and place the portable X-ray tube on top of the acrylic canopy of the incubators. SID and OID settings and value of organ dose exposed to the patient varied based on the incubator structure, and the organ absorbed dose was determined using Monte Carlo N-Particle (MCNP) simulation, PC-based Monte Carlo program (PCXMC) 2.0 simulation, and neonate phantoms.

RESULTS

Evaluations of organ dose of neonatal patients in three hospitals with different incubator settings reveal that the average organ dose differs by 36% depending on change in OID and SID settings and reduces by 10% with an acrylic canopy. Therefore, owing to the presence of an acrylic canopy on the top of the incubator and the longer SID with the corresponding shorter OID, a lower dose was absorbed by organs of neonatal patient.

CONCLUSION

Our results provide proof that proper incubator standard decreases organ dose to neonatal patient during continuously diagnostic X-ray procedure.

The effect of different statistical approaches on image quality data obtained from radiological examinations

INTRODUCTION

Selection of optimal image acquisition protocols in medical imaging remains a grey area, the superimposed use of the Likert scale in radiological image quality evaluations creates an additional challenge for the statistical analysis of image quality data. Using a simulation study, we have trialled a novel approach to analysing radiological image quality Likert scale data.

METHODS

A simulation study was undertaken where simulated datasets were generated based on the distribution of Likert scale values according to varying image acquisition protocols from a real dataset. Simulated Likert scale values were pooled in four different ways; the mean, median, mode and the summation of patient Likert scale values of which the total was assigned a categorical Likert scale value. Estimates of bias, MAPE and RMSPE were then calculated for all four pooling approaches to determine which method most accurately represented an expert's opinion.

RESULTS

When compared to an expert's opinion, the method of summation and categorisation of Likert scale values was most accurate 49 times out of the 114 (43.0%) tests. The mean 28 times out of 114 (24.6%), the median 23 times out of 114 (20.2%) and the mode 17 times out of 114 (14.9%).

CONCLUSION

We conclude that our method of summation and categorisation of Likert scale values is most often the best representation of the simulated data compared to the expert's opinion.

IMPLICATIONS FOR PRACTICE

There is scope to reproduce this simulation study with multiple observers to reflect clinical reality more accurately with the dynamic nature of multiple observers. This also prompts future investigation into other anatomical areas, to see if the same methods produce similar results.

Pressure distribution analysis of X-Ray table mattresses

BACKGROUND

There is a risk of developing pressure ulcers from lying on an X-ray table mattress, if the mattress pressure redistribution properties are poor.

AIM

To assess the pressure redistribution properties of 'new' and 'in current clinical use' X-ray table mattresses.

METHODS AND MATERIALS

Twenty one X-ray table mattresses, each of 2.5 cm thickness, were evaluated. An anthropomorphic human phantom of adult stature with five different weights (minimum, first quartile, mean, third quartile and maximum) was used to simulate human head, pelvis and heels (pressure ulcer jeopardy areas). Using Xsensor technology, peak pressure was measured and Interface Pressure Ratio was calculated for the three pressure ulcer jeopardy areas 'with' and 'without' an X-ray table mattress.

RESULTS

For all mattresses, statistically significant differences (p < 0.05) were found between the peak pressure values with and without using an X-ray table mattress for the three pressure ulcer jeopardy areas; similarly, for all mattresses, statistically significant differences (p < 0.05) were found between the Interface Pressure Ratio values with and without using x-ray table mattress. The type and age of the mattress was observed to have an impact on peak pressure values and Interface Pressure Ratios, with older mattresses performing worse.

CONCLUSION

Peak pressure values and Interface Pressure Ratios are reduced significantly when using newer X-ray table mattresses. This could be because newer mattresses use more appropriate materials in their construction and/or older mattresses have lost their pressure redistribution properties. Radiology departments should consider assessing mattresses pressure redistribution properties, perhaps on an annual basis.

Optimising image quality and radiation dose for neonatal incubator imaging

INTRODUCTION

Neonates often require imaging within incubators however limited evidence exists as to the optimal method and acquisition parameters to achieve these examinations. This study aims to standardise and optimise neonatal chest radiography within incubators.

METHODS

A neonatal anthropomorphic phantom was imaged on two different incubators under controlled conditions using a DR system. Exposure factors, SID and placement of image receptor (direct v tray) were explored whilst keeping all other parameters consistent. Image quality was evaluated using absolute visual grading analysis (VGA) with contrast-to-noise ratio (CNR) also calculated for comparison. Effective dose was established using Monte Carlo simulation using entrance surface dose within its calculations.

RESULTS

VGA and CNR reduced significantly (p < 0.05) whilst effective dose increased significantly (p < 0.05) for images acquired using the incubator tray. The optimal combinations of parameters for incubator imaging were: image receptor directly behind neonate, 0.5 mAs, 60 kV at 100 cm SID, however, if tray needs to be used then these need to be adapted to: 1 mAs at maximum achievable SID. Effective dose was highest for images acquired using both incubator tray and 100 cm SID owing to a decrease in focus to skin distance. There is significant increase (p < 0.01) in VGA between using 0.5 mAs and 1 mAs but an apparent lack of increase between 1 and 1.5 mAs.

CONCLUSION

Using the incubator tray has an adverse effect on both image quality and radiation dose for incubator imaging. Direct exposure is optimal for this type of examination but if tray needs to be used, both mAs and SID need to be increased slightly to compensate.

IMPLICATIONS FOR PRACTICE

This study can help inform practice in order to both standardise and optimise chest imaging for neonates in incubators.