PyDAP: Automated dental OPG beam area measurement using python and raspberry Pi camera.

INTRODUCTION: This study investigates if inexpensive computer hardware, open-source computer vision and a phosphor screen from disused CR (computed radiography) Cassette can be used to quantitatively assess beam shape and area. MATERIALS AND METHODS: The phosphor screen was affixed to a Carestream CS 8100 dental OPG system and the camera was mounted above the X-ray tube. Videos were acquired of the green light emissions during the tomographic irradiation. Images of a chessboard pattern, attached to the detector were used to correct for camera angulation and provide image pixel size calibration. K-Means colour clustering was used to define beam area. The effect of light conditions on beam dimension measurement was also investigated. The beam width measurement from optimised methodology was compared with that determined from dose calibrated GAFChromicTM XR-SP2film. RESULTS: Videos in dark conditions provided the most reproducible results. FW20M gained from initial sampling matched that obtained using the GAFChromicTM film within the errors of the measurements,6.41 ± 0.09 mm FW20M from this methodology,compared with FW20M (full width at 20 % of maximum) 6.4 ± 0.1 mm from film. The height and area were 126 ± 0.22 mm and 807 ± 11 mm2 respectively. The chess pattern imaging provided a robust means of perspective correction and pixel calibration. There is potential for this methodology to be employed using any digital camera, provided the camera acquisition settings remain constant, the sensor pixels are square, and the camera position is fixed. CONCLUSION: The potential of this low-cost open-source method of beam area measurement using computer vision is thus proven.

Development of a scatter correction technique for planar 99mTc-MAA imaging to improve accuracy in lung shunt fraction estimation.

PURPOSE: Prior to 90Y selective internal radiation therapy (SIRT) treatment, 99mTc-MAA scintigraphy imaging is used in the estimation of the lung shunt fraction (LSF). Planar imaging is recommended for determining a LSF ratio. However, the estimate may be affected by scatter contributions, attenuation and respiratory motion. The objective of this study was to correct for the effects of scatter in the LSF, towards the determination of a more accurate estimation method of LSF derived from planar scintigraphy imaging, which is recommended by international guidelines. METHODS: The open access SIMIND Monte Carlo modelling software was used to estimate an optimum scatter window (SW) for scatter correction. The uncertainties associated with scatter and scatter contributions from the liver on the LSF were evaluated using an anthropomorphic thorax phantom and a virtual Vox-Man phantom. A brief retrospective examination of patient scans and tumour location investigated the impact that the inclusion of the simulated scatter corrections had on the LSF estimation. RESULTS: The percentage overestimation of the manufacturer recommended method of LSF estimation was 192%. SW corrections improved the uncertainty to within 19% for the range of known LSFs. Similar findings were observed for our patient and tumour location studies. CONCLUSION: The incorporated scatter corrections can significantly improve the accuracy of the LSF estimation, thereby providing a robust gamma camera, patient and tumour depth specific correction which is easily implementable. This is supported by Monte Carlo, phantom and preliminary patient studies.

Patient radiation dose during angiography and embolization for abdominal hemorrhage: the influence of CT angiography, fluoroscopy system, patient and procedural variables.

BACKGROUND: Angiography and embolization (AE) is a lifesaving, high radiation dose procedure for treatment of abdominal arterial hemorrhage (AAH). Interventional radiologists have utilized pre-procedure CT angiography (CTA) and newer fluoroscopic systems in an attempt to reduce radiation dose and procedure time. PURPOSE: To study the factors contributing to the radiation dose of AE for AAH and to compare to the reference standard. MATERIALS AND METHODS: This retrospective single-centre observational cohort study identified 154 consecutive AE procedures in 138 patients (median age 65 years; interquartile range 54-77; 103 men) performed with a C-arm fluoroscopic system (Axiom Artis DTA or Axiom Artis Q (Siemens Healthineers)), between January 2010 and December 2017. Parameters analysed included: demographics, fluoroscopy system, bleeding location, body mass index (BMI), preprocedural CT, air kerma-area product (PKA), reference air kerma (Ka,r), fluoroscopy time (FT) and the number of digital subtraction angiography (DSA) runs. Factors affecting dose were assessed using Mann-Whitney U, Kruskal-Wallis one-way ANOVA and linear regression. RESULTS: Patients treated with the new angiographic system (NS) had a median PKA, median Ka,r, Q3 PKA and Q3 Ka,r that were 74% (p < 0.0005), 66%(p < 0.0005), 55% and 52% lower respectively than those treated with the old system (OS). This dose reduction was consistent for each bleeding location (upper GI, Lower GI and extraluminal). There was no difference in PKA (p = 0.452), Ka,r (p = 0.974) or FT (p = 0.179), between those who did (n = 137) or did not (n = 17) undergo pre-procedure CTA. Other factors significantly influencing radiation dose were: patient BMI and number of DSA runs. A multivariate model containing these variables accounts for 15.2% of the variance in Ka,r (p < 0.005) and 45.9% of the variance of PKA (p < 0.005). CONCLUSION: Radiation dose for AE in AAH is significantly reduced by new fluoroscopic technology. Higher patient body mass index is an independent key parameter affecting patient dose. Radiation dose was not influenced by haemorrhage site or performance of pre-procedure CTA.

MODELLING AUTOMATIC EXPOSURE CONTROL RESPONSE TO THE PRESENCE OF THE PATIENT SCANNING BED IN A HYBRID PET/CT SCANNER.

Automatic Exposure Control (AEC) systems optimise radiation dose to the patient while providing adequate image quality. This study examined the effect that the increased localiser region of interest of a hybrid PET/CT has on the CTDIvol, focussing on the role of extraneous objects and patient attenuation profiles. A Siemens Biograph™ 16 Horizon PET/CT system and a Siemens Somatom Sensation 64, both employing the Siemens CAREDose 4D AEC system, were used for acquisition of a range of phantoms. The effect of patient miscentring and effect of the patient bed impinging on the localiser was established and modelled. For PA localiser scans, a non-linear relationship between miscentring and CTDIvol was observed, attributable to the presence of the patient bed being misinterpreted as the patient width. The model identified how the presence of the patient bed led to an increase in the CTDIvol significantly larger than expected (~12%, or 1 mSv), particularly prevalent for smaller patients.

Relative response of dosimeters to variations in scattered X-ray energy spectra encountered in interventional radiology.

PURPOSE: The new lower eye lens dose limit is of relevance in interventional radiology, where higher dose procedures result in increased scattered radiation to staff. The eye lens dose may be monitored using the directional dose equivalent at 3 mm depth, Hp(3), or through Hp(10) or Hp(0.07) measurements and using conversion factors. However, there are a considerable range of factors which contribute to measurement uncertainties, one of which is the incident photon energy. This study investigated the energy spectra of scattered radiation in interventional radiology, and the dosimetry accuracy of dosimeter types, evaluating their energy dependence. METHODS: Scatter X-ray energy spectra were recorded under varied conditions in a fluoroscopy imaging suite. Dosimetry accuracy of eye dosimeters, including TLDs (100 s, 100Hs), Landauer Hp(3), John Caunt ED3 and Electronic Personal dosimeters (EPDs) were compared to air kerma measurements across a range of tube voltages. RESULTS: The variation of energy spectra with changing phantom thickness, spectrometer angulation and filtration are presented. The 100 and 100H TLDs, and EPDs showed a consistent air kerma response (within 10%) with changes in energy. The real-time silicon diode detectors showed a variable over response of between 10 and 25% across the energies investigated while Landauers dedicated Hp(3) eye dosimeters showed considerable variation between dosimeters for similar conditions, a 17% variation at 50 kVp. CONCLUSION: The work aimed to validate the scattered energy spectra typically encountered in interventional radiology and to further determine the accuracy of eye dosimeters in relation to energy response variations.

Yttrium-90 selective internal radiation therapy, examining dose rates and radiation protection precautions.

METHODS: Dose rates from 30 patients, treated over a 3-year period (2016-2018) were measured post therapy in contact with the patients' upper abdomen and at distances of 0.3 m and 1 m. Dose rates were compared with theoretical predictions and used as model inputs for calculating radiation doses received by family members and carers based on interaction patterns previously described in the literature. RESULTS: The average dose rate per activity from SIRT patients were:- In contact: 29 ±â€¯23 µSv.h-1.GBq-1; 0.3 m: 4.1 ±â€¯2.34 µSv.h-1.GBq-1 and 1 m: 0.59 ±â€¯0.42 µSv.h-1.GBq-1. Dose rates measured at 0.3 and 1 m followed a predictable distribution. Estimated doses based on proximity models demonstrated restrictions to be advisable, depending on the administered activity, considering the dose constraint and limit of 0.3 and 1 mSv, respectively, employed within the EU. CONCLUSIONS: In accordance with local dose constraints, and depending on administered activities, radiation protection precautions may be necessary for those individuals in regular contact with patients who have receive 90Y SIRT. A radiation protection precautions calculator has been devised to offer personalised instructions taking into account the administered activity and proximity models.

Artificial White Light vs Daylight Photodynamic Therapy for Actinic Keratoses: A Randomized Clinical Trial.

IMPORTANCE: Daylight photodynamic therapy using topical methyl 5-aminolevulinic acid (MAL) for actinic keratoses (AKs) is as effective as conventional photodynamic therapy but has the advantage of being almost pain free. Daylight photodynamic therapy, however, requires dry and warm weather conditions. OBJECTIVE: To establish if topical MAL photodynamic therapy using a white light light-emitting diode (LED) lamp is as effective and well-tolerated as daylight photodynamic therapy for the treatment of AKs. DESIGN, SETTING, AND PARTICIPANTS: Overall, 22 men with significant photodamage and a high number of AKs were enrolled in this prospective, randomized, single-blind study, employing a split-scalp design, comparing the effectiveness and adverse effects of daylight photodynamic therapy and artificial white light (AWL) LED photodynamic therapy for the treatment of AKs on the forehead and scalp. Organ transplant recipients were excluded. Patients were treated and evaluated at an academic tertiary referral dermatology center. Treatment lasted from April 2014 to July 2014 and follow-up visits occurred for 9 months posttreatment. INTERVENTIONS: Two symmetrical treatment fields were defined and AKs counted, mapped, and photographed at baseline, 1, 3, 6, and 9 months. Patients had half of their scalp treated with daylight photodynamic therapy and the other half treated with AWL photodynamic therapy 1 week apart and randomly allocated. MAL was applied, and treatment commenced 30 minutes later and lasted 2 hours. Irradiance, illuminance, and light spectra measurements were performed. The integrated dose in J/cm2 was measured. The effective light dose, weighted to the absorption spectrum for protoporphyrin IX, was calculated. MAIN OUTCOMES AND MEASURES: The primary end point was the reduction in total AK count per treatment field. Secondary end points included adverse effects and patient satisfaction. RESULTS: We enrolled 22 men with a median age of 72 years (range, 47-85 years) at baseline, the total (median of AKs per field) were 469 (20.5) for the DPDT group and 496 (20.5) for the AWLPDT group (P = .34). The median number and percentage of reduction in AKs per field were 12 and 62.3% for DPDT and 14 and 67.7% for AWLPDT at 1 month (P = .21 and P = .13, respectively). There was no significant difference in the reduction percentage of AKs for either treatment at 1, 3, and 6 months. At 9 months, the median number and percentage of reduction in AKs per field was 9.0 and 48.4% for DPDT and 12.0 and 64.4% for AWLPDT (P = .13 and P = .05, respectively). Pain was reported by 14 patients with DPDT and 16 patients with AWLPDT (median maximum score [out of 100], 4 vs 6; P = .51). Moderate erythema was reported by 9 patients after DPDT and 14 patients after AWLPDT. On a scale of 0 (intolerable) to 10 (very tolerable) patients rated DPDT as 9.5 and AWLPDT as 9 (P = .37). CONCLUSIONS AND RELEVANCE: Photodynamic therapy using an AWL source was as effective and well-tolerated as daylight photodynamic therapy. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT02520700.