Retrospective study of Ct brain imaging findings indicated for infants at a tertiary care hospital

Computed tomography in the diagnosis of pathologies in children is becoming increasingly popular. The aim: to study findings of referrals for CT scans (Computerised Tomography) of the brain in children in the department of Radiology in a developing environment. Materials and methods: retrospective imaging observational study was done in a 1000 bedded tertiary care hospital in South India in the year 2022 from April to August for 5 months under 16 slice CT scan. Cases are referred from the department of Pediatrics to the department of Radiology as part of the routine clinical evaluation and treatment protocol. Results: Our sample includes 100 infants; after exclusion criteria total of 60 infants' brain CTs were taken into account, and analysed their imaging from radiology department records. Of 60 cases, 18 (30 %) showed HIE Pattern, and 42 (70 %) had normal plain CT Brain findings. However, due to clinical signs and symptoms, they are evaluated under сontrast CT imaging (after checking creatinine levels), showing 20 cases (33.3 %) are standard, 10 cases (16.6 %) show meningitis, and 2 cases (3.3 %) show SOL. Out of 18 cases of HIE, 10 cases (16.6 %) are under less than 6 months and they undergone neuro sonogram showing 4 cases (6.6 %) normal NSG, 2 cases (3.3 %) showing grade IV HIE, another 2 cases (3.3 %) showing grade II, III HIE Findings. Conclusions: Our study concluded that plain CT brain showed normal in the majority of the cases which came to the department of Radiology after admission to the hospital. Those cases with strong clinical history are evaluated with contrast CT and evaluated the findings. After contrast imaging, most cases showing their infective, obstructive, and other causes of illness are interpreted. However, its role is minimal for seizures in which CT/CECT shows normal study. Under 6 months, NSG is a suitable method for evaluating and screening the infant's brain.

Contrast Medium Use in Computed Tomography for Patients Presenting with Headache: 4-year Retrospective Two-Center Study in Central and Western Regions of Ghana

Background

Contrast medium (CM) administration during computed tomography (CT) enhances the accuracy in the detection and interpretation of abnormalities. Evidence from literature also validate the essence of CM in imaging studies. CT, by virtue of its ubiquity, ease of use, speed, and lower financial footprint, is usually the first investigation in cases of headache. Through a multicenter retrospective analysis, we compared findings of contrast-enhanced CT (CECT) to noncontrast-enhanced CT (NCECT) head examinations among patients presenting with headache.

Methods

A multicenter retrospective analysis of four years' CT head examination data at two radiology centers located in Central and Western Regions of Ghana were reviewed. Records of patients who presented with headache as principal complaint between January 2017 and December 2020 were reviewed. A total of 477 records of patients with headache were identified, retrieved and evaluated. A Chi-square test and Fisher exact test were used to compare the CECT and NCECT groups. Binary logistic regression analysis was computed to assess association between CECT and each CT findings. Statistical significance was considered at p < 0.05 with a 95% confidence interval.

Results

A significant proportion of the patients was females (51.8% in CECT and 60% in NCECT). The NCECT group (40.06 ± 14.76 years) was relatively older than the CECT group (38.43 ± 17.64 years). There was a significant difference between the CECT and NCECT in terms of age (p=0.002) and facility CT was performed (p < 0.0001). The rate of abnormalities was higher in CECT (43.5%, 166/382) compared NCECT (37.9%, 36/95). There was no significant association between CT head findings and contrast enhancement.

Conclusion

CECT examination accounted for 5.6% increase in the detection of head abnormalities. Efforts required to establish local standard operation procedures (SOPs) for contrast medium use especially in CT head examinations. Further studies to improve the knowledge of agents, mechanism of action, and safety of contrast media used among practitioners in Ghana is recommended.

The Effect of Contrast Material on Radiation Dose at CT: Part II. A Systematic Evaluation across 58 Patient Models

Purpose To estimate the radiation dose as a result of contrast medium administration in a typical abdominal computed tomographic (CT) examination across a library of contrast material-enhanced computational patient models. Materials and Methods In part II of this study, first, the technique described in part I of this study was applied to enhance the extended cardiac-torso models with patient-specific iodine-time profiles reflecting the administration of contrast material. Second, the patient models were deployed to assess the patient-specific organ dose as a function of time in a typical abdominal CT examination using Monte Carlo simulation. In this hypothesis-generating study, organ dose refers to the total energy deposited in the unit mass of the tissue inclusive of iodine. Third, a study was performed as a strategy to anticipate the biologically relevant dose (absorbed dose to tissue) in highly perfused organs such as the liver and kidney. The time-varying organ-dose increment values relative to those for unenhanced CT examinations were reported. Results The results from the patient models subjected to the injection protocol indicated up to a total 53%, 30%, 35%, 54%, 27%, 18%, 17%, and 24% increase in radiation dose delivered to the heart, spleen, liver, kidneys, stomach, colon, small intestine, and pancreas, respectively. The biologically relevant dose increase with respect to the dose at an unenhanced CT examination was in the range of 0%-18% increase for the liver and 27% for the kidney across 58 patient models. Conclusion The administration of contrast medium increases the total radiation dose. However, radiation dose, while relevant to be included in estimating the risk associated with contrast-enhanced CT, may still not fully characterize the total biologic effects. Therefore, given the fact that many CT diagnostic decisions would be impossible without the use of iodine, this study suggests the need to consider the effect of iodinated contrast material on the organ doses to patients undergoing CT studies when designing CT protocols. ^© RSNA, 2017 Online supplemental material is available for this article.

Comparison of dose calculations between pencil-beam and Monte Carlo algorithms of the iPlan RT in arc therapy using a homogenous phantom with 3DVH software

BACKGROUND

To create an arc therapy plan, certain current general calculation algorithms such as pencil-beam calculation (PBC) are based on discretizing the continuous arc into multiple fields to simulate an arc. The iPlan RT™ treatment planning system incorporates not only a PBC algorithm, but also a more recent Monte Carlo calculation (MCC) algorithm that does not need beam discretization. The objective of this study is to evaluate the dose differences in a homogenous phantom between PBC and MCC by using a three-dimensional (3D) diode array detector (ArcCHECK™) and 3DVH software.

METHODS

A cylindrically shaped 'target' region of interest (ROI) and a 'periphery ROI' surrounding the target were designed. An arc therapy plan was created to deliver 600 cGy to the target within a 350° rotation angle, calculated using the PBC and MCC algorithms. The radiation doses were measured by the ArcCHECK, and reproduced by the 3DVH software. Through this process, we could compare the accuracy of both algorithms with regard to the 3D gamma passing rate (for the entire area and for each ROI).

RESULTS

Comparing the PBC and MCC planned dose distributions directly, the 3D gamma passing rates for the entire area were 97.7% with the gamma 3%/3 mm criterion. Comparing the planned dose to the measured dose, the 3D gamma passing rates were 98.8% under the PBC algorithm and 100% under the MCC algorithm. The difference was statistically significant (p = 0.034). Furthermore the gamma passing rate decreases 7.5% in the PBC when using the 2%/2 mm criterion compared to only a 0.4% decrease under the MCC. Each ROI as well as the entire area showed statistically significant higher gamma passing rates under the MCC algorithm. The failure points that did not satisfy the gamma criteria showed a regular pattern repeated every 10°.

CONCLUSIONS

MCC showed better accuracy than the PBC of the iPlan RT in calculating the dose distribution in arc therapy, which was validated with the ArcCHECK and the 3DVH software. This may suggest that the arc step of 10° is too large in the PBC algorithm in the iPlan RT.

Feasibility of kilovoltage x-ray energy modulation by gaseous media and its application in contrast-enhanced radiotherapy

PURPOSE

To present a method to modulate the energy contents of a kilovoltage x-ray beam that makes use of a gas as the modulating medium. The method is capable of producing arbitrary x-ray spectra by varying the pressure of the modulating gas and the peak kilovoltage (kVp) of the x-ray beams whose energy is being modulated.

METHODS

An aluminum chamber was machined with a 0.5 cm wall thickness, designed to withstand pressures of more than 80 atm. A pressure sensor and electrovalves were used to monitor and regulate the gas pressure. Argon was used as the modulating gas. A CdTe spectrometer was used to measure x-ray spectra for different combinations of kVp and gas pressure, thus obtaining a set of basis x-ray functions. An arbitrary x-ray spectrum can then be formed by the linear combination of such basis functions. In order to show one possible application of the modulation method, a contrast-enhanced radiotherapy prostate treatment was optimized with respect to the x-ray beam energy, without restrictions on the possible shape of the resultant x-ray spectra.

RESULTS

The x-ray spectra basis functions obtained display a smooth and gradual variation of their average energy as a function of the gas pressure for a given kVp, sometimes in the order of 1 or 2 keV. This gradual variation would be difficult to obtain with a conventional aluminum or copper filters, as the change in thickness necessary to reproduce the data presented would be in the order of micrometers, making necessary the use of a large number of such filters. Using the modulation method presented here, the authors were able to reconstruct the optimized x-ray spectra from the measured basis functions, for different optimization objectives.

CONCLUSIONS

A method has been developed that allows for the controlled modulation of the energy contents of kilovoltage x-ray spectra. The method has been shown to be able to reproduce spectra of arbitrary shape, such as those obtained from the optimization of contrast-enhanced radiotherapy. The method may have other applications as well, such as in the precise matching of diagnostic x-ray catalog spectra.

Effect of anode angle on photon beam spectra and depth dose characteristics for X-RAD320 orthovoltage unit

BACKGROUND

In radiation therapy with orthovoltage units, the tube design has a crucial effect on its dosimetric features.

AIM

In this study, the effect of anode angle on photon beam spectra, depth dose and photon fluence per initial electron was studied for a commercial orthovoltage unit of X-RAD320 biological irradiator.

MATERIALS AND METHODS

The MCNPX MC code was used for modeling in the current study. We used the Monte Carlo method to model the X-RAD320 X-ray unit based on the manufacturer provided information. The MC model was validated by comparing the MC calculated photon beam spectra with the results of SpekCalc software. The photon beam spectra were calculated for anode angles from 15 to 35 degrees. We also calculated the percentage depth doses for some angles to verify the impact of anode angle on depth dose. Additionally, the heel effect and its relation with anode angle were studied for X-RAD320 irradiator.

RESULTS

Our results showed that the photon beam spectra and their mean energy are changed significantly with anode angle and the optimum anode angle of 30 degrees was selected based on less heel effect and appropriate depth dose and photon fluence per initial electron.

CONCLUSION

It can be concluded that the anode angle of 30 degrees for X-RAD320 unit used by manufacturer has been selected properly considering the heel effect and dosimetric properties.

Monte Carlo modeling of converging small-field contrast-enhanced radiotherapy of prostate

Radiation therapy using a kilovoltage X-ray source to irradiate a target previously loaded with a radiological contrast agent, contrast-enhanced radiotherapy (CERT), has been shown both theoretically and in a preliminary experimental study to represent a potential alternative to high-energy treatments. It has also been shown, however, to produce an integral dose that can be up to twice that resulting from a conventional megavoltage treatment. In this work, using a realistic patient model and Monte Carlo simulation, a CERT prostate treatment plan is designed that makes use of a plurality of small circular beams aimed at the target in such a way as to minimize the radiological trajectory to the target volume. Gold nanoparticles are assumed to be the contrast agent. Two cases are examined, one with a concentration level in the target of 10 mg-Au per gram of tissue and the second with a concentration of 3 mg-Au per gram of tissue in the target. A background concentration of 1 mg of contrast agent per gram of tissue was assumed everywhere else in both cases. The Cimmino feasibility algorithm was then used to find each beam weight in order to obtain the prescribed target dose, set at 72 Gy to 100% of the tumor volume. It is shown that the approach using the small circular fields, a radiosurgery treatment, produces treatment plans with excellent absorbed dose distributions while at the same time it reduces by up to 60% the non-tumor integral dose imparted to the irradiated subject. A brief discussion on the technology necessary to clinically implement this treatment modality is also presented.

A Monte Carlo study on tissue dose enhancement in brachytherapy: a comparison between gadolinium and gold nanoparticles

The aim of this study was to quantify the dose enhancement by gadolinium and gold nanoparticles in brachytherapy. MCNPX Monte Carlo code was used to simulate four brachytherapy sources: (60)Co, (198)Au, (192)Ir, (169)Yb. To verify the accuracy of our simulations, the obtained values of dose rate constants and radial dose functions were compared with corresponding published values for these sources. To study dose enhancements, a spherical soft tissue phantom with 15 cm in radius was simulated. Gadolinium and gold nanoparticles at 10, 20 and 30 mg/ml concentrations were separately assumed in a 1 × 1 × 1 cm(3) volume simulating tumour. The simulated dose to the tumour with the impurity was compared to the dose without impurity, as a function of radial distance and concentration of the impurity, to determine the enhancement of dose due to the presence of the impurity. Dose enhancements in the tumour obtained in the presence of gadolinium and gold nanoparticles with concentration of 30 mg/ml, were found to be in the range of -0.5-106.1 and 0.4-153.1 % respectively. In addition, at higher radial distances from the source center, higher dose enhancements were observed. GdNPs can be used as a high atomic number material to enhance dose in tumour volume with dose enhancements up to 106.1 % when used in brachytherapy. Regardless considering the clinical limitations of the here-in presented model, for a similar source and concentration of nanoparticles, gold nanoparticles show higher dose enhancement than gadolinium nanoparticles and can have more clinical usefulness as dose enhancer material.