Comparison of radiation dose, contrast enhancement and image quality of prospective ECG-Gated CT coronary angiography: Single versus dual source CT

INTRODUCTION

The updated National Institute of Clinical Excellence (NICE) guidelines of 2017 state that new generation cardiac CT scanners (Aquilion ONE, Brilliance iCT, Discovery CT750 HD and Somatom Definition Flash) are recommended as an option for first-line imaging of the coronary arteries in people with suspected stable coronary artery disease (with an estimated likelihood of coronary artery disease of 10-29%) in whom imaging with earlier generation CT scanners is difficult. New generation cardiac CT scanners are also recommended as an option for first-line evaluation of disease progression, to establish need for revascularisation in people with known coronary artery disease in whom imaging with earlier generation CT scanners is difficult. CT scanning might not be necessary in situations in which immediate revascularisation is being considered. The European Society of Cardiology 2019 clinical practice guidelines recommend non-invasive functional imaging for myocardial ischaemia or coronary CT angiography (CTA) as the initial test to diagnose CAD in symptomatic patients in whom obstructive CAD cannot be excluded by clinical assessment alone. Given increased computed tomography coronary angiogram (CTCA) utilisation, radiation dose, contrast enhancement and image quality of prospective ECG-gated CTCA between 256-slice single-source and 192x2-slice dual-source CT scanners were retrospectively evaluated.

METHODS

Prospectively gated CTCA data from 63 patients on a 256-slice CT (group A) and 71 patients on a 192x2-slice dual source CT (group B) from January to December 2016 were retrospectively evaluated respectively. Scanner-reported dose length product values were used with a conversion factor (k = 0.014 mSv/mGy x cm) to estimate effective dose. Contrast enhancement was assessed with mean CT attenuation at selected regions of interest on axial coronary images. Image quality of the coronary arteries was assessed by a 4-point grading score (1 = non-diagnostic, 4 = excellent image quality).

RESULTS

The radiation doses in group B were significantly lower than group A (3.68 + 2.13 mSv versus 4.81 + 1.56 mSv, p < 0.001). There were no significant differences in contrast enhancement in the left coronary artery, proximal right coronary artery and left ventricular wall for both groups. Vessel image quality scores for group B were higher than group A (right coronary artery (RCA): 3.2 + 0.7 versus 2.4 + 0.7, p < 0.001; left anterior descending (LAD) artery: 3.0 + 0.8 vs 2.5 + 0.6, p < 0.001; left circumflex (LCx) artery: 3.3 + 0.7 vs 2.6 + 0.6, p < 0.001). Coronary artery contour scores for group B were significantly higher than group A (RCA: 3.2 + 0.8 versus 2.3 + 0.7, p < 0.001; LAD: 3.0 + 0.7 versus 2.4 + 0.6, p < 0.001; LCx: 3.3 + 0.6 versus 2.5 + 0.6, p < 0.001).

CONCLUSION

Prospective ECG-gated CTCA performed on 192x2-slice CT results in better image quality and lower radiation dose than 256-slice CT. There were no significant differences in contrast enhancement in left main coronary artery (LMCA), proximal RCA and left ventricular wall in both groups.

IMPLICATIONS FOR PRACTICE

In institutions with both 256-slice and 192x2-slice CT scanners, we recommend that CTCAs be preferentially performed using the 192x2-slice CT scanner.

MRI for transformation of preserved organs and their pathologies into digital formats for medical education and creation of a virtual pathology museum. A pilot study

AIM

To evaluate the feasibility of magnetic resonance imaging (MRI) for the transformation of preserved organs and their disease entities into digital formats for medical education and creation of a virtual museum.

MATERIALS AND METHODS

MRI of selected 114 pathology specimen jars representing different organs and their diseases was performed using a 3 T MRI machine with two or more MRI sequences including three-dimensional (3D) T1-weighted (T1W), 3D-T2W, 3D-FLAIR (fluid attenuated inversion recovery), fat-water separation (DIXON), and gradient-recalled echo (GRE) sequences. Qualitative assessment of MRI for depiction of disease and internal anatomy was performed. Volume rendering was performed on commercially available workstations. The digital images, 3D models, and photographs of specimens were archived into a workstation serving as a virtual pathology museum.

RESULTS

MRI was successfully performed on all specimens. The 3D-T1W and 3D-T2W sequences demonstrated the best contrast between normal and pathological tissues. The digital material is a useful aid for understanding disease by giving insights into internal structural changes not apparent on visual inspection alone. Volume rendering produced vivid 3D models with better contrast between normal tissue and diseased tissue compared to real specimens or their photographs in some cases. The digital library provides good illustration material for radiological-pathological correlation by enhancing pathological anatomy and information on nature and signal characteristics of tissues. In some specimens, the MRI appearance may be different from corresponding organ and disease in vivo due to dead tissue and changes induced by prolonged contact with preservative fluid.

CONCLUSIONS

MRI of pathology specimens is feasible and provides excellent images for education and creating a virtual pathology museum that can serve as permanent record of digital material for self-directed learning, improving teaching aids, and radiological-pathological correlation.

Unusual case of unrepaired omphalocoele and uncorrected tetralogy of Fallot in a young adult

An omphalocoele is a congenital defect that affects the development of the abdominal wall in the umbilical region, resulting in a hernial-type sac of variable size. The condition is usually diagnosed prenatally and corrected in early infancy to prevent rupture of the covering membranes, which carries a high mortality and morbidity rate. Tetralogy of Fallot is the most common cyanotic congenital heart defect during infancy that is associated with this condition. Most patients experience cyanosis at birth and die in childhood if there is no surgical intervention. Overall, it is uncommon for untreated patients with both omphalocoele and tetralogy of Fallot to survive into adulthood. We report the rare case of a 17-year-old young adult with untreated omphalocoele and uncorrected tetralogy of Fallot.

Effort thrombosis in a young triathlete: an unusual presentation of painless neck swelling secondary to right brachiocephalic vein thrombosis

Effort thrombosis of the upper extremity is secondary to thrombosis of the axillary and/or subclavian veins that develop from heavy arm exertion. This case illustrates venous thrombosis of the right brachiocephalic vein in a 32-year-old man who presented with a cyst-like swelling in the right neck with no associated pain or trauma. Our patient, a trained athlete, was preparing for a triathlon at the time of presentation. He was treated by first-line therapy of subcutaneous and oral anti-coagulation medication. In this study, we highlight the importance of early investigation and treatment of symptomatic athletes so that long-term disability can be prevented. This study also shows the timely use of computed tomography imaging, which can help to identify the syndrome in previously undiagnosed patients.

Clinics in diagnostic imaging (128). Portal pyaemia

A 66-year-old man presented with epigastric pain. Computed tomography (CT) of the abdomen showed portal venous gas with partial thrombosis of the portal veins, consistent with portal pyaemia. CT also showed nonspecific peripancreatic fat stranding. The patient was treated conservatively but did not improve, necessitating a laparotomy that revealed ischaemic colitis and bowel necrosis. He underwent a right hemicolectomy and showed clinical improvement. Portal pyaemia is a combination of infection and thrombosis within the portal veins. The presence of gas in the portal vein is a known feature in portal pyaemia. We showed radiological examples of hepatic and portal venous gas in several patients who presented to our institution, with a brief discussion of their radiological findings, causes, management and outcome. The mortality rate of patients with portal venous gas depends on the underlying cause. The high mortality rate of patients with portal venous gas due to bowel necrosis or ischaemia may necessitate emergent surgical intervention.

Clinics in diagnostic imaging (117)

A 76-year-old woman presented with a five-day history of fever and abdominal pain. Her urine culture grew Candida albicans. She was treated with intravenous antibiotics, as having a urinary tract infection, but her fever persisted. Computed tomography of the abdomen showed a cystic mass at the pancreatic head and uncinate process with peripancreatic lymph nodes. Given the patientos high operative risk and her clinical picture favouring sepsis, endoscopic ultrasonographical fine-needle aspiration (EUS-FNA) which was performed, revealed pus with acid-fast bacilli seen in the cell block material. The patient was started on antituberculous medication with rapid improvement of symptoms. Pancreatic tuberculosis (TB) is rare and can mimic pancreatic carcinoma both clinically and radiologically. Histological diagnosis is crucial before administration of appropriate therapy. The usefulness of EUS-FNA and its pitfalls, as well as the other radiological modalities for the evaluation and assessment of pancreatic TB are discussed.

Clinics in diagnostic imaging (98). Heterotopic pregnancy with an intrauterine blighted ovum and a live tubal ectopic pregnancy

A 26-year-old woman who was six weeks amenorrhoeic presented with vaginal spotting and mild abdominal pain. She had been coming to the 24 hours women's clinic at two-day intervals for the past week with the same symptoms. Ultrasonography two days ago showed one intrauterine gestational sac (IUGS) with a yolk sac within. Her pregnancy was clomiphene-related. Repeat transvaginal ultrasonography during this admission showed an IUGS, together with a left live tubal ectopic pregnancy. Heterotopic pregnancies used to be a rare entity. Now, given the increasing rise in assisted reproduction techniques, there should be a high index of suspicion for heterotopic pregnancy as this would impact upon clinical management. The ultrasonographical features of heterotopic pregnancy and its differential diagnoses are discussed.