Smart scanning for two: [18F]FDG dose optimization for pregnant patients using LAFOV PET/CT technology.

Radiotherapy may be suggested for pregnant cancer patients when treatment cannot be delayed, with careful targeting to minimize fetal dose. Considering that a successful case for a pregnant patient treated with proton beam craniospinal irradiation (CSI) was reported, carbon therapy can be also considered applicable for the CSI treatment to pregnant patients. We investigated fetal organ doses from carbon beam CSI during pregnancy by performing Monte Carlo dose calculations. We employed the high-quality pregnant female phantom series developed by University of Florida (UF) for eight gestational ages (8, 10, 15, 20, 25, 30, 35, and 38weeks). The phantoms were converted into DICOM-RT CT images and implemented in a treatment planning system (TPS) with the prescribed relative biological effectiveness (RBE)-weighted dose of 36Gy. A carbon CSI plan created from TPS was used to perform TOPAS MC dose calculations after commissioned to the carbon beam measurement data. Fetal organ absorbed doses for 28 organs considered radiosensitive were calculated and compared with those estimated for proton therapy in a previous study. The organ/tissue doses for 35weeks showed the largest variation, ranging from 13.2 mGy (esophagus) to 88.3 mGy (lens), whereas those for 8weeks showed the smallest variation, ranging from 21.0 mGy (gall bladder) to 30.3 mGy (brain). The fetal whole-body doses decreased from early to mid-gestational ages, but increased again during the later stage as the fetus grew predominantly in the superior direction, reducing the overall distance to the beam field. Considering the significant attention to carbon therapy, as a first dedicated effort, the result would be clinically informative to estimate the fetal dose from carbon therapy during pregnancy.

Objective: In situations where computed tomography (CT) scans are necessary for pregnant patients, such as in cases of trauma or other conditions that provide clinical benefit, accurately estimating the radiation dose to which the fetus is exposed is crucial. However, current methods are not sufficiently practical or feasible for routine clinical use. This study aims to assess and calculate the fetal dose and associated organ doses resulting from CT scans in pregnant patients using the Monte Carlo Simulation Method. Methods: Monte Carlo (MC) simulations and related calculations were conducted on pregnant patient phantoms for different gestational periods (8-15 weeks) using a 64-slice CT scanner (Discovery CT750 HD GE Healthcare) to estimate fetal doses. Organ dose calculations were also carried out. The MC code simulating dose distributions was validated with measurements from the CT Dose Index (CTDI) following AAPM protocols. Volumetric CTDI values from the MC simulations were normalized, enabling the development of a calculation algorithm for fetal dose assessments across different body regions and exposure settings. The algorithm, approved by the institutional review board, was validated through patient-specific MC simulations on CT data from pregnant patients (with gestational ages of 8-15 weeks) who had undergone CT scans. Results: Based on the data, it can be concluded that the fetus was exposed to low radiation doses, which do not present significant risk to fetal development. The doses observed in the study fell within acceptable clinical limits, indicating that fetal radiation exposure during CT scans can be managed safely with appropriate protocols. However, minimizing radiation exposure during pregnancy is essential. The use of low-dose protocols, as demonstrated in this study, is especially important for these patients. Moreover, the study’s findings highlight the importance of optimizing CT scan parameters and adopting radiation reduction strategies in routine clinical practice. Alternative imaging methods that utilize non-ionizing radiation, such as ultrasound or MRI, should also be considered when clinically appropriate. Conclusions: This study provides a clinically applicable approach to calculating fetal radiation doses during CT scans. The developed algorithm can help reduce fetal exposure and ensure patient safety. Future studies could expand on this research by validating the algorithm in larger patient cohorts and different gestational stages. The findings emphasize the need for radiology technologists to use the lowest possible dose protocols and explore non-ionizing imaging alternatives whenever feasible. .

PURPOSE In this work, an online system for the evaluation of fetal doses from both medical and occupational exposures of pregnant woman in diagnostic radiology was developed. This system, called “Dose Fetal Web”, also calculates the risks of in uterus exposure. METHODS AND MATERIAL The methodology used estimates the fetal dose from data related to radiologic diagnostic examinations of a pregnant patient, or from the routine individual monitoring dosimetry of a pregnant worker. The input data of this program are associated to the conversion‐coefficients tables of uterine‐to‐fetal dose, NUD, generated by means of Monte Carlo simulations. This system incorporates operational information of radiological equipment and hospitals facilities which are attended by a Quality Assurance (QA) program, as well as real maternal and fetal data collected during obstetricultrasound. RESULTS The fetal dose from both medical and occupational exposures of the pregnant woman, as well as the risks associated with these exposures, were evaluated by means of simulated case studies using the online system, which can be accessed through the address http://www.fma.if.usp.br/dosefetal. An example using real data from radiographic examination shows a fetal dose of 4.61 mGy, and other example considering a pregnant worker in a Cath Lab show a fetal equivalent dose estimated in 0.02 mSv/month. CONCLUSION This work is a contribution to fetal dose and radiological risks evaluations of medical and occupational exposures of the pregnant women. It also presents some hypothetical case studies related to situations of inadvertent exposure. This kind of study is especially important if the exposure has occurred during the first weeks of pregnancy that is the period where the pregnancy can be unknown. These evaluations can benefit in the taking of decisions and the counseling the pregnant with regard to the effect of the ionizing radiation to the unborn child.

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Evaluation of Compressed SENSE on Image Quality and Reduction of MRI Acquisition Time: A Clinical Validation Study

Fetal dose estimates for radiotherapy of brain tumors during pregnancy

Multi-band whole-body diffusion-weighted imaging with inversion recovery fat saturation: Effects of respiratory compensation

Identification of image quality degradation factors in abdominal free-breathing dynamic contrast-enhanced magnetic resonance imaging (MRI).

Purpose: According to AAPM Report 50, there are in excess of 4000 women per year that require radiotherapy. In the past ten years, the technology of radiation therapy has advanced considerably with the advent of IMRT and IGRT. The purpose of this work was to measure fetal doses on a helical tomotherapy delivery system. Method and Materials: A water-equivalent phantom was constructed for measuring the dose outside of a helical tomotherapy treatment field. The phantom was 60-cm in total length, and the thickness varied from 15 to 17-cm. The phantom was divided into four sections: (1) Head, (2) Shoulders, (3) Torso, and (4) Pelvis. Absolute measurements were taken inside the pelvis section following the TG-51 protocol with a farmer chamber at depths of 1.5, 5.0, and 10.0-cm. Measurements were taken with distance from the chamber to the bottom edge of the field set to 5, 10, 15, 20, and 25-cm. Results: The Tomotherapy fetal doses are substantially larger (4.3% verses 1.4%) at 5-cm from the field edge. However, the fetal doses from APPA and helical tomotherapy treatment delivery are within 1 percent beyond 10-cm from the field edge. This is particularly surprising given that the MUs are over a factor of 10 larger for the tomotherapy delivery. The reason is that the head leakage component in the tomotherapy delivery system is much less than a conventional linear accelerator due to the 20-cm of tungsten shielding in primary jaws, the multi-leaf collimator, and head shielding. Conclusion: The dose to the fetus on a helical tomotherapy system is within 1% of the fetal dose from conventional APPA delivery. Depending on the total dose and the distance to the fetus, pregnant patients could receive a highly modulated and conformal treatment delivery without exceeding fetal dose tolerance.

Monte Carlo (MC) simulations or measurements in anthropomorphic phantoms are recommended for estimating fetal dose in pregnant patients in radiotherapy. Among the many existing phantoms, there is no commercially available physical phantom representing the entire pregnant woman. In this study, the development of a low-cost, physical pregnant female phantom was demonstrated using commercially available materials. This phantom is based on the previously published computational phantom. Three tissue substitution materials (soft tissue, lung and bone tissue substitution) were developed. To verify Tena's substitution tissue materials, their radiation properties were assessed and compared to ICRP and ICRU materials using MC simulations in MV radiotherapy beams. Validation of the physical phantom was performed by comparing fetal doses obtained by measurements in the phantom with fetal doses obtained by MC simulations in computational phantom, during an MV photon breast radiotherapy treatment. Materials used for building Tena phantom are matched to ICRU materials using physical density, radiation absorption properties and effective atomic number. MC simulations showed that percentage depth doses of Tena and ICRU material comply within 5% for soft and lung tissue, up to 25cm depth. In the bone tissue, the discrepancy is higher, but again within 5% up to the depth of 5cm. When the phantom was used for fetal dose measurements in MV photon breast radiotherapy, measured fetal doses complied with fetal doses calculated using MC simulation within 15%. Physical anthropomorphic phantom of pregnant patient can be manufactured using commercial materials and with low expenses. The files needed for 3D printing are now freely available. This enables further studies and comparison of numerical and physical experiments in diagnostic radiology or radiotherapy.

Computed tomography radiation dose optimization for the diagnosis of acute rib fractures in infants investigated for suspected physical abuse: An experimental animal study.

Time-of-flight technology (TOF) is at the leading edge of advancements in PET/CT imaging, and is made possible due to the availability of new scanner design, scintillating materials and fast computers. The location of annihilation is estimated according to the time difference between scintillation events produced by two 511KeV gamma photons travelling in opposite directions. The additional information is incorporated into image reconstruction to suppress noise propagation and increase signal-to-noise ratio. As shown in previous studies, these properties can be translated in to clinical usage to obtain improved image quality using the same acquisition time, while also enhancing image quality under shortened acquisition or reduce tracer dosage injected to patients.\n\nSemi-quantification units such as standardized uptake value (SUV) and standard deviation (SD) are measured on static PET images and are widely used clinically to quantify the rate of cell metabolism. Signal-to-noise ratio (SNR) and coefficient of variation (CV) can be calculated to assess image quality. However, these parameters depend on image reconstruction and are therefore expected to change with the use of TOF.\n\nBreath holding (BH) PET/CT imaging protocol has been suggested to help evaluation of lesions affected by respiratory motion. However, the PET image quality is significantly degraded since the acquisition time is shortened (e.g. 30 seconds). Noise on BH PET image may cause inaccuracy in semi-quantitation and difficulties in visual assessment. TOF can be applied to improve the image quality and enhance subtle lesions, thus helping the characterization of small lung nodules (SLN) with potential clinical impact.\n\nThis thesis aims to evaluate the impact of TOF on PET image quality and the quantification of SUV in clinical practice. Firstly, the performance of a TOF PET/CT scanner is tested using a phantom mimicking human body trunk with ‘lesions’. Using the same acquisition time (2 minutes/bed), TOF images outperformed conventional images in terms of lesion detectability and background uniformity, especially for small spheres and under low lesion-to-background ratio. Moreover, TOF images acquired using a shorter scan time (1.5 minutes/bed) also maintained acceptable image quality. In the second study, the influence on SUV measurement and image quality (in terms of CV) are evaluated in twelve normal organ structures on whole-body FDG PET/CT images. TOF significantly decreased SUVmax (9/12) and SUVmean (8/12) among the twelve normal organ structures investigated. It also improved the image quality, particularly in solid organs in the abdomen. The combined utility of TOF and BH PET/CT imaging protocol for the detection of SLN is demonstrated in the third study. Lesions showing PET activity, which were misaligned with anatomical location on CT, had higher SUVmax and comparable SNR on BH images. PET/CT fusion was also markedly improved. The additional use of TOF further enhanced lesion detection and improved SNR.\n\nThe results demonstrate the benefits of using TOF in clinical PET/CT, including its advantage with breath holding PET/CT imaging. This information not only offers a better understanding of this increasingly popular technology in modern PET/CT scanners, but also highlights its potential applications in clinical practice.

Image quality is a key issue in radiology, particularly in a clinical setting where it is important to achieve accurate diagnoses while minimizing radiation dose. Some computed tomography (CT) manufacturers have introduced algorithms that claim significant dose reduction. In this study, we assessed CT image quality produced by two reconstruction algorithms provided with GE Healthcare's Discovery 690 Elite positron emission tomography (PET) CT scanner. Image quality was measured for images obtained at various doses with both conventional filtered back‐projection (FBP) and adaptive statistical iterative reconstruction (ASIR) algorithms. A standard CT dose index (CTDI) phantom and a pencil ionization chamber were used to measure the CT dose at 120 kVp and an exposure of 260 mAs. Image quality was assessed using two phantoms. CT images of both phantoms were acquired at tube voltage (kV) of 120 with exposures ranging from 25 mAs to 400 mAs. Images were reconstructed using FBP and ASIR ranging from 10% to 100%, then analyzed for noise, low‐contrast detectability, contrast‐to‐noise ratio (CNR), and modulation transfer function (MTF). Noise was 4.6 HU in water phantom images acquired at 260 mAs/FBP 120 kV and 130 mAs/50% ASIR 120 kV. The large objects (frequency<7 lp/cm) retained fairly acceptable image quality at 130 mAs/50% ASIR, compared to 260 mAs/FBP. The application of ASIR for small objects (frequency>7 lp/cm) showed poor visibility compared to FBP at 260 mAs and even worse for images acquired at less than 130 mAs. ASIR blending more than 50% at low dose tends to reduce contrast of small objects (frequency>7 lp/cm). We concluded that dose reduction and ASIR should be applied with close attention if the objects to be detected or diagnosed are small (frequency>7 lp/cm). Further investigations are required to correlate the small objects (frequency>7 lp/cm) to patient anatomy and clinical diagnosis.PACS number(s): 87.57.‐s, 87.57.C, 87.57.cf, 87.57.cj, 87.57.cm, 87.57.cp, 87.57.N, 87.57.nf, 87.57.np, 87.57.nt, 87.57.Q, 87.59.‐e, 87.59.B

The treatment of brain tumors in pregnant patients poses challenges, as the out-of-field dose exposure to the fetus can potentially be harmful. A pregnant patient with prior radiation treatment was presented with a brain tumor at our clinic. This work reports on our pre-treatment study that compared fetal dose exposure between intensity-modulated proton therapy (IMPT) using pencil beam scanning (PBS) and conventional photon 3D conformal radiation therapy (3DCRT) and volumetric-modulated arc therapy (VMAT), and the subsequent pregnant patient's radiation treatment. Pre-treatment measurements of clinical plans, 3DCRT, VMAT, and IMPT, were conducted on a phantom. Measurements were performed using a device capable of neutron detections, closely following AAPM guidelines, TG158. For photon measurements, fetus shielding was utilized. On patient treatment days, which was determined to be proton treatment, shielding was used only during daily imaging for patient setup. Additionally, an in vivo measurement was conducted on the patient. Measurements showed that IMPT delivered the lowest fetal dose, considering both photon and neutron out-of-field doses to the fetus, even when shielding was implemented for photon measurements. Additionally, the proton plans demonstrated superior treatment for the mother, a reirradiation case. The patient was treated with proton therapy, and the baby was subsequently delivered at full term with no complications. This case study supports previous clinical findings and advocates for the expanded use of proton therapy in this patient population.

Introduction: Today film-based technologies are largely abandoned in dental radiology. New technologies based on digital detectors are being adopted. This change is part of the global digitalization of radiological procedures. A person operating the radiological device needs to be educated and well informed about radiological procedures and technologies, as well as to know how the system operates and to be sure about the dose required for the adequate image quality. The awareness of radiation doses received by patients is necessary for the estimation of risk from ionizing radiation.Material and methods: The aim of this study was to evaluate whether patient doses in intraoral dental radiology affect image quality. The study included subjective analysis of radiological image quality for an intraoral x-ray device with possibility to use both digital and film detector. Subjective assessment of image quality is performed according to criteria taken from the literature and is expressed using the Likert scale, grade 1–5. In order to improve the quality of inferential statistics related ratings to detector quality and image quality were collected, thus introducing two variables: the detector quality index and the technique quality index.Results: Z-test proportions column shows that the number of grades four given as a contrast score is significantly higher in the RVG detector (65%) compared to the film (40%). There is also a significant difference in the number of given grades five as a rating of the apex preview. The share of grades five in film is 19%, while in RVG it is 42%. It is similar in the evaluation of the preview of the dental canal, where there is also a significant difference in the number of given grades five, so that the share in the film is 11% and in RVG 35%.Conclusion: Analysis of the subjective quality of the radiological image in devices for intraoral radiography with the possibility of recording using digital and film detectors indicates that the digital detector is superior to film in low contrast resolution, apex and dental canal preview.