Computed tomography overexposure as a consequence of extended scan length

Contribution of CT scan to patient's radiation exposure in parathyroid SPECT/CT scintigraphy

INTRODUCTION

Dual phase technetium-99mTc-methoxy isobutyl isonitrile (MIBI) single-photon emission computed tomography with computed tomography (SPECT/CT) may be the most accurate conventional imaging approach for localization of enlarged parathyroid gland (EPG). The imaging is based on the radiopharmaceutical (RP) retention in EPG compared to washout from normal thyroid and normal parathyroid glands. This study aimed to estimate and optimize the contribution of computed tomography (CT) scan and scan range to effective dose (ED) in dual-phase MIBI SPECT/CT parathyroid scintigraphy.

METHODS

The study included seventy-four patients; thirty-seven with reduced and thirty-seven with extended CT scan range. The ED caused by the CT scan was calculated using Dose Length Product (DLP) data and estimated using the Imaging Performance Assessment of CT scanners (ImPACT) calculator.

RESULTS

For all patients, the contribution of CT to the ED in a combined SPECT/CT examination was 2.62 ± 0.29 mSv (48%). The contribution of CT to the total ED was 1.8 ± 0.18 mSv (33%) when using reduced and 3.44 ± 0.23 mSv (64%) when using extended scan range. The DLP and ED were statistically significantly different between the reduced and extended CT scan range (p < 0.001) in the first and second phases. The individual organ dose was reduced from 8% to 94%.

CONCLUSION

The hybrid SPECT/CT improves the interpretation of nuclear medicine images and also increases the radiation dose to the patient. An adequately defined CT scan range on SPECT/CT imaging, can significantly reduce a patient's ED.

IMPLICATIONS FOR PRACTICE

The research findings showed that knowledge of anatomy, pathology and technology can provide optimising diagnostic procedures and reduce patient ED after SPECT/CT scans.

The feasibility of low dose chest CT acquisition protocol for the imaging of COVID-19 pneumonia

OBJECTIVE

To investigate the feasibility of low dose chest CT acquisition protocol for the imaging of either the confirmed case of COVID-19 disease or the suspected case of this disease in adults.

METHOD

In this retrospective case-control study, the study group consisted of 141 patients who were imaged with low dose chest CT acquisition protocol. The control group consisted of 92 patients who were imaged with the standard protocol. Anteroposterior and lateral diameters of chest, effective diameter and scan length, qualitative and quantitative noise levels, volumetric CT dose index (CTDIvol), dose length product (DLP), and size-specific dose estimations were compared between groups.

RESULTS

Radiation dose reduction by nearly 90% (CTDIvol and DLP values 1.06 mGy and 40.3 mGy.cm vs. 8.07 mGy and 330 mGy.cm, p < 0.001, respectively) was achieved with the use of low dose acquisition chest CT protocol. Despite higher image noise with low dose acquisition protocol, no significant effect on diagnostic confidence was encountered. Cardiac and diaphragm movement-related artifacts were similar in both groups (p = 0.275). Interobserver agreement was very good in terms of diagnostic confidence assessment.

CONCLUSION

For the imaging of either the confirmed case of COVID-19 related pneumonia or the suspected case of this disease in adults, low dose chest CT acquisition protocol provides remarkable radiation dose reduction without adversely affecting image quality and diagnostic confidence.

The proportion of computed tomography kidneys, ureters and bladder (CTKUB) scans that comply with scan extent protocol in an emergency department: a clinical audit and dose ramification study

INTRODUCTION

To assess computed tomography kidneys, ureters and bladder (CTKUB) scan extent protocol compliance and associated doses in the Emergency Department (ED) of an Australian tertiary hospital.

METHODS

A retrospective clinical audit of 150 consecutive ED CTKUB cases was completed. For each patient, scan extent compliance at the superior (kidneys) and inferior (pubic symphysis) borders, in reference to the protocol was recorded. Compliance and non-compliance (over-/under-scanning) was identified, described (superior/inferior), quantified (via IMPAX measurements) and recorded via a purpose-built audit tool. In addition, a PBU40 phantom was scanned to assess the percentage of dose (DLP) increase per centimetre of over-scanning to contextualise results.

RESULTS

A notable non-compliance with department protocol was noted. Eight cases (5.3%) demonstrated overall CT scan extent compliance. The remaining 142 cases (94.7%) demonstrated some form of non-compliance; superiorly, inferiorly or both. Analysing the 150 superior and 150 inferior data points independently, the most common non-compliance was over-scanning at the kidneys by 4 cm to5 cm (19 cases, ~10% extra DLP) beyond tolerance and over-scanning inferiorly at the pubic symphysis by 1 cm to 2 cm (29 cases, ~6.4% extra DLP). Estimated dose increases of up to 35% to 45% were found when clinical audit results were simulated using a PBU40.

CONCLUSIONS

Over-scanning is a predominant occurrence in CTKUB scans in this department. Reasons for over-scanning weren't investigated. It's anticipated this audit will lead to greater awareness of scan extent compliance and dose ramifications of non-compliance. The usage of more easily identified anatomical landmarks and a follow-up audit is suggested.

Radiation doses from head, neck, chest and abdominal CT examinations: an institutional dose report

PURPOSE

We aimed to obtain typical values for head, neck, chest, and abdominal computed tomography (CT) examinations from routine patients in 2018, and to review our data with national and international diagnostic reference levels (DRLs).

METHODS

Single-phase head, neck, chest, and abdominal CT scans of adults performed in 64-slice CT in 2018 were included in this study. Radiation dose parameters of CT scans were obtained from the picture archiving and communication system of our hospital. Volumetric CT dose index (CTDIvol) and dose length product (DLP) values were recorded. Effective dose (ED) and scan length was calculated. A 16 cm diameter phantom is referenced for head CT, and 32 cm diameter phantom is referenced for neck, chest, and abdominal CT. Descriptive statistics of the variables were given according to the normality testing.

RESULTS

Median CTDIvol value was 53 mGy for the head, 13.1 mGy for the neck, 8.3 mGy for the chest, and 8.6 mGy for the abdomen. Median DLP value was 988 mGy.cm for the head, 299 mGy.cm for the neck, 314 mGy.cm for the chest, and 457 mGy.cm for the abdomen. Median ED value was 2.07 mSv for the head, 1.76 mSv for the neck, 4.4 mSv for the chest, and 6.8 mSv for the abdomen. Considering national DRLs, median CTDIvol values of head, chest, and abdomen were lower, whereas median DLP and ED values of head and chest were higher. For the abdomen, the median DLP and ED values were lower.

CONCLUSION

Overall radiation dose parameters obtained in this study points out the need for optimization of head CT examinations in our institution.

EVALUATION OF THE RADIATION EXPOSURE IN SEQUENTIAL HEAD TOMOGRAPHIC EXAMS OF PATIENTS WITH TRAUMATIC BRAIN INJURY AND DECOMPRESSIVE CRANIECTOMY

Brain trauma patients who underwent decompressive craniectomy make several computed tomography (CT) scans until cranioplasty. Despite several recommendations to avoid unnecessary radiological exposure, few studies systematically analyzed the technical parameters employed. CT exams of 14 patients were retrospectively analyzed to find display field of view (DFOV), dose length product (DLP), volume computed tomography dose index (CTDIvol) and effective dose (ED). The values obtained were: 120 kVp [95% confidence interval (CI) of 0.5], 297 mA (95% CI of 5.6), scan range 20.8 cm (95% CI of 1.3), DFOV 24.5 cm (95% CI of 1.6), CTDIvol 67.5 mGy (95% CI of 10.17), DLP 1404.8 mGy.cm (95% CI of 235.0) and ED 2.9 mSv (95% CI of 0.5). In conclusion, these values were above the recommendations of several guidelines and raise concern for excessive radiological exposure in trauma patients despite being previously reported in the literature.

Radiation Dose Associated With Over Scanning in Neck CT

The increasing utilization of computed tomography scans exposes patients to significant amounts of radiation. One of the factors that can result in unnecessary radiation dose is scanning beyond the clinically indicated anatomical region. This study aims to assess the optimization in overscan frequency, scan length, and radiation dose following targeted educational talks aimed to address a routinely over scanned protocol; the computed tomography Neck. A targeted radiation awareness talk regarding scan adherence as a method of radiation dose optimization was delivered to all medical imaging technologists employed at a large teaching hospital. An audit of the radiation dose associated with computed tomography Neck protocols was conducted in the month before, a month after and 1 year after the awareness talk. Results show that following the radiation awareness talks there was a 15% reduction in overscan frequency, an average over scan length reduction of 33% and a 20% reduction in overall radiation dose. The targeted nature of the talk, explicitly addressing scan range in the neck region, significantly reduced radiation dose to the patients. The results of this study are effective in illustrating the potential clinical radiation dose saving from strict adherence to scan range.

Review article: sarcopenia in cirrhosis--aetiology, implications and potential therapeutic interventions

BACKGROUND

Sarcopenia (loss of muscle mass) is common in cirrhosis and is associated with poor outcomes. Current teaching recommends the use of protein supplementation and exercise, however, this fails to address many other factors which contribute to muscle loss in this setting.

AIMS

To summarise existing knowledge regarding the aetiology of sarcopenia in cirrhosis, diagnostic modalities and the clinical significance of this condition. In addition to discuss recent research findings that may allow the development of more effective treatments.

METHODS

We conducted a Medline and PubMed search using the search terms 'sarcopenia', 'muscle', 'body composition', 'cirrhosis', 'liver' and 'malnutrition' from inception to October 2015.

RESULTS

Cirrhotic patients with sarcopenia have reduced survival, experience increased rates of infection and have worse outcomes following liver transplantation. The aetiology of this condition is more complex than simple protein and calorie malnutrition. Cirrhosis also results in depleted glycogen stores and metabolic alterations that cause excessive protein catabolism, increased activation of the ubiquitin-proteasome pathway and inappropriate muscle autophagy. Satellite cell differentiation and proliferation is also reduced due to a combination of elevated myostatin levels, reduced IGF-1 and hypogonadism. Although there is some evidence supporting the use of late evening snacks, branched chain amino acid supplementation and high protein/high calorie diets, well designed clinical trials addressing the effects of treatment on body composition in cirrhosis are lacking.

CONCLUSION

Sarcopenia in cirrhosis has a complex pathogenesis and simple dietary interventions are insufficient. Improved understanding of the multiple mechanisms involved should allow the development of more effective therapies, which target the specific underlying metabolic derangements.