Four-channel multidetector CT in facial fractures: do we need 2 x 0.5 mm collimation?

OBJECTIVE: Our aim was to optimize acquisition protocols and multiplanar reformation algorithms for the evaluation of facial fractures using multidetector CT (MDCT) and to determine whether 2 x 0.5 mm collimation is necessary. MATERIALS AND METHODS: A cadaveric head with artificial blunt facial trauma was examined using a four-channel MDCT scanner. The influence of acquisition parameters (collimation, 2 x 0.5 mm, 4 x 1 mm, 4 x 2.5 mm; tube current, 120 mAs, 90 mAs, 60 mAs), image reconstruction algorithms (standard vs ultra-high-resolution modes; reconstructed slice thicknesses, 0.5 mm, 1 mm, 3 mm; increment, 0.3 mm, 0.6 mm, 1.5 mm), and reformation algorithms (slice thicknesses, 0.5 mm, 1 mm, 3 mm; overlap, 0.5 mm, 1 mm, 3 mm) on detectability of facial fractures in multiplanar reformations with MDCT was analyzed. RESULTS: Fracture detection was significantly higher with thin multiplanar reformations (0.5 and 0.5 mm, 1 and 0.5 mm, and 1 and 1 mm) (p < or = 0.014) acquired with 2 x 0.5 mm collimation (p < or = 0.046) in ultra-high-resolution mode (p < 0.0005) with 120 mAs (p < or = 0.025). Interobserver variability showed very good agreement (kappa > or = 0.942). Non-ultra-high-resolution mode, lower milliampere-seconds, and thick multiplanar reformations (3 and 0.5 mm, 3 and 1 mm, and 3 and 0.5 mm) showed significantly decreased fracture detectability. CONCLUSION: Although thin multiplanar reformations obtained from thin collimation (2 x 0.5 mm) are statistically superior for the detection of subtle fractures, 4 x 1 mm collimation is sufficient for routine diagnostic evaluation. Ultra-high-resolution mode with 120 mAs is mandatory for detection of clinically relevant fractures.     

Computed tomographic angiography in acute pulmonary embolism: do we need multiplanar reconstructions to evaluate the right ventricular dysfunction?

PURPOSE: To compare the indices of right ventricular dysfunction (RVD) obtained from axial transverse images with those derived from the reconstructed 4-chamber and short-axis views in patients with acute pulmonary embolism (PE). MATERIALS AND METHODS: Eighty-eight patients with acute PE were retrospectively enrolled. For each patient, axial transverse images and reconstructed 4-chamber and short-axis views were reviewed. Measurements of the ratios of right ventricle to left ventricle (RV/LV) diameters and RV/LV areas were then obtained from all series. Values derived from each method were compared and correlated to arterial obstruction index. RESULTS: In the studied cohort, RV/LV diameters and RV/LV areas obtained from axial transverse images and the reconstructed 4-chamber views were not statistically different. In contrast, a statistically significant difference was observed between the values of RV/LV areas derived from both axial transverse and 4-chamber views and those obtained from short-axis views (P < 0.0001). There was a weak to moderate correlation between both RV/LV diameters and RV/LV areas and the computed tomographic obstruction index. However, when the study cohort was divided into 3 subgroups with an arterial obstruction index of less than 15% (n = 26), 15% to 30% (n = 21), and greater than 30% (n = 41), those who had values greater than 30% revealed the highest correlation with the indices of RVD. CONCLUSIONS: In patients with acute PE, the indices of RVD derived from axial transverse images and the reconstructed 4-chamber views yield comparative values. Given the simplicity of the former analysis, it should be taken into consideration for risk stratification in acute PE.     

Assessment of chest pain in the emergency room: What is the role of multidetector CT?

Chest pain is one of the most frequent complaints for patients seen in the emergency department. The current article describes the clinical stratification of patients who present to the emergency department with chest pain and discusses imaging options and analysis for these patients. It reviews conventional imaging approaches to assessing chest pain including chest radiography and stress testing. The main discussion focuses on the potential utility use of cross-sectional imaging, particularly multidetector CT, in the evaluation of chest pain in the emergency department.     

Cancelled stereotactic biopsy of calcifications not seen using the stereotactic technique: do we still need to biopsy?

Objective

To determine the frequency of cancelled stereotactic biopsy due to non-visualisation of calcifications, and assess associated features and outcome data.

Methods

A retrospective review was performed on 1,874 patients scheduled for stereotactic-guided breast biopsy from 2009 to 2011. Medical records and imaging studies were reviewed.

Results

Of 1,874 stereotactic biopsies, 76 (4 %) were cancelled because of non-visualisation of calcifications. Prompt histological confirmation was obtained in 42/76 (55 %). In 28/76 (37 %) follow-up mammography was performed, and 7/28 subsequently underwent biopsy. Of 27 without biopsy, 21 (78 %) had follow-up. Nine cancers (9/49, 18 %) were found: 6 ductal carcinoma in situ (DCIS), 3 infiltrating ductal carcinoma (IDC). Of 54 patients with either biopsy or at least 2 years’ follow-up, 9 (17 %) had cancer (95 % CI 8–29). Cancer was present in 7/42 (17 %, 95 % CI 7–31 %) lesions that had prompt histological confirmation (DCIS?=?5, IDC?=?2) and in 2/28 (7 %, 95 % CI 0.8–24 %) lesions referred for follow-up (DCIS?=?1, IDC?=?1). Neither calcification morphology (P?=?0.2), patient age (P?=?0.7), breast density (P?=?1.0), personal history (P?=?1.0) nor family history of breast cancer (P?=?0.5) had a significant association with cancer.

Conclusion

Calcifications not visualised on the stereotactic unit are not definitely benign and require surgical biopsy or follow-up. No patient or morphological features were predictive of cancer.

Key points

? Half of cancelled stereotactic biopsies were due to non-visualisation of calcified foci. ? This reflects the improved detection of calcifications by digital mammography. ? Calcifications too faint for the stereotactic technique require alternative biopsy or follow-up ? 17?% of patients with biopsy or at least 2 years’ follow-up had cancer. ? No patient/morphological features were found to aid selection for re-biopsy vs. follow-up.     

Bone densitometry in the management of Colles' fractures: which site to measure?

This study assessed whether patients with Colles' fractures can be evaluated by measurement of peripheral bone mineral density (BMD) instead of the more established axial BMD technique. 205 consecutive patients who had sustained a recent Colles' fracture were invited to attend for BMD measurement at the lumbar spine, hip and forearm by dual energy X-ray absorptiometry (DXA) using a Hologic QDR4500C instrument. Hologic normal reference ranges were used for spine and ultradistal radius BMD, and the NHANES 111 reference range was used for the femoral neck. 158 patients attended, of whom only 61 had a T-score below -2.5 at one of the three measured sites (84 T<-2.0, 112 T<-1.5). 36 patients had bilateral forearm fractures and did not undergo a forearm measurement. After excluding these patients and using a T-score of -2.5 as a diagnostic threshold, a spine and hip measurement strategy missed 26% of osteoporotic patients and a forearm only strategy missed 33%. If a forearm strategy is adopted, with axial BMD performed only on those patients with an ultradistal radial T-score of <-1.5 and >-2.5, 27 further scans would be required and only four patients with T<-2.5 at the spine or hip would be undetected. Where axial BMD measurement is performed, this should be accompanied by forearm BMD measurement in some patients with Colles' fractures. A peripheral bone mineral densitometry strategy using forearm BMD alone will miss many individuals with osteoporosis. Therefore where forearm, and probably any peripheral scanning method, only is used for patient assessment there should be close liaison with an axial BMD centre with agreed joint protocols, as some patients should be advised to have an additional axial BMD measurement following their peripheral BMD measurement.     

Physiological noise in MR images: An indicator of the tissue response to ischemia?

PURPOSE: To determine whether measuring signal intensity (SI) fluctuations in MRI time series data from acute stroke patients would identify ischemic tissue. MATERIALS AND METHODS: Prebolus perfusion-weighted MRI data from 32 acute ischemic stroke patients (N = 32) was analyzed as a time series. Ischemic and normal tissue regions were outlined and compared. RESULTS: The magnitude of the measured SI fluctuations was significantly lower in ischemic regions relative to normal tissue. Spatial differences in these fluctuations occurred in a manner that was different than other perfusion-based metrics. CONCLUSION: Prior studies have shown that SI fluctuations in MRI time series data correspond to the presence of physiological "noise," which includes vasomotion, an autoregulatory phenomenon that affects the tissue response to ischemia. In this study, SI fluctuations were found to decrease in ischemia, consistent with the notion that small vessels will remain open (fluctuations in vessel diameter will decrease) when there is a challenge to flow. Spatial variation in SI fluctuations appeared to be different from spatial variation seen on other perfusion-based metrics, suggesting that a separate contrast mechanism is responsible, one that might be of diagnostic and prognostic value in acute stroke in which the ability of tissue to withstand ischemia is currently not well visualized.     

Does CT have an additional diagnostic value over ultrasound in the evaluation of acute inflammatory neck masses in children?

Objectives  

We assessed the additional value of contrast-enhanced CT versus US for evaluation of acute cervical inflammatory masses and choosing treatment strategy.     

Arterial vs pancreatic phase: which is the best choice in the evaluation of pancreatic endocrine tumours with multidetector computed tomography (MDCT)?

PURPOSE: The aim of this study was to assess whether the pancreatic phase may replace the arterial phase in the evaluation of endocrine pancreatic tumours. MATERIALS AND METHODS: Twenty-nine endocrine pancreatic lesions with definitive morphological and immunohistochemical characterisation after surgical treatment (n=24) or fine-needle-aspiration cytology under endoscopic ultrasonography guidance (n=5) were retrospectively evaluated. All lesions were studied with triple-phase 16-row multidetector computed tomography (MDCT). Images obtained during each phase were separately interpreted by two senior radiologists experienced in pancreatic pathology and who were blinded to surgical results. Endocrine tumour and normal pancreas attenuation and the mean absolute tumour-to-gland attenuation difference were measured in each phase, and data were analysed with Student's t test. Visualisation of arterial vascular abnormalities and hypervascular liver metastases in the arterial and pancreatic phases and the diagnostic contribution of the two phases were compared. RESULTS: For both radiologists, the mean absolute tumour-to-gland attenuation difference was significantly higher (p<0.05) in the pancreatic phase (40+/-53 HU and 34+/-56 HU) than in the arterial phase (31+/-38 HU and 26+/-43 HU). There were no differences in the detection of arterial vascular abnormalities or hypervascular liver metastases in the two phases. The diagnostic contribution was higher in the pancreatic phase. CONCLUSIONS: In our experience, the pancreatic phase can replace the arterial phase in the evaluation of pancreatic endocrine tumours.     

A historical perspective on the specific activity of radiopharmaceuticals: what have we learned in the 35 years of the ISRC?

Specific activity (SA), defined as the amount of radioactivity per unit mass of a compound, is arguably one of the most important parameters in radiopharmaceutical development, particularly in quality control of carbon-11- and fluorine-18-labeled compounds. This review article will outline the progression of improvements in SA over the last few decades. The International Symposium of Radiopharmaceutical Chemistry abstracts were an excellent source of materials for this review and will be referenced throughout.     

Correction to: Does plain radiography still have a role in cases of fish bone ingestion in emergency rooms? A retrospective analysis

Emergency Radiology - A Correction to this paper has been published: https://doi.org/10.1007/s10140-021-01913-6