Comment

Health effects of ionising radiation from diagnostic CT

To calculate the lifetime risk of malignancy in young adult patients with hip pain using 5 different imaging and radiation dose protocols with or without pre- and postoperative computed tomography (CT).

Radiographic and CT patient radiation doses were retrospectively reviewed. Imaging protocols for hip pain composed of radiographs with or without pre- and postoperative CT scans were modeled and radiation doses were estimated using the PCXMC computer code. Based on these radiation doses, lifetime attributable risks of cancer and mortality for a 10- through 60-year-old male and female were calculated as published by the committee on the Biological Effects of Ionizing Radiation (BEIR) in the BEIR VII report. Relative risks and number needed to harm (NNH) were calculated for each protocol.

Based on a review of our institutional database, 2 CT scan doses were used for this study: a high 5.06 mSv and a low 2.86 mSv. Effective doses of radiation ranged from 0.59 to 0.66 mSv for radiographs alone to 10.71 to 10.78 mSv for radiographs and CT both pre- and postoperatively at the higher dose. Lifetime attributable risk of cancer for radiographs alone was 0.006% and 0.011% for a 20-year-old male and female, respectively. Lifetime attributable risk of cancer for radiographs along with pre- and postoperative CT scans at higher dose was 0.105% and 0.177% for a 20-year-old male and female, respectively. Radiographs alone lead to an NNH of 16,667 for males and 9,090 for females, whereas the protocol with pre- and postoperative CT scans at the higher dose led to an NNH of 952 for males and 564 for females. The relative risk of this protocol compared to radiographs alone was 17.5 for males and 16.1 for females.

Protocols with CT scans of the hip/pelvis pose a small lifetime attributable risk (0.034%-0.177% for a 20-year-old) but a large relative risk (5-17 times) of cancer compared with radiographs alone in the imaging evaluation for hip pain that decreases with increasing age.

This study illustrates the need for clinicians to understand the imaging protocols used at their institution to understand the risks and benefits of using those protocols in their practice.

Objectives: To construct an artificial neural network (ANN) model that can predict the presence of acute CT findings with both high sensitivity and high specificity when applied to the population of patients ≥ age 65 years who have incurred minor head injury after a fall.

Methods: An ANN was created in the Python programming language using a population of 514 patients ≥ age 65 years presenting to the ED with minor head injury after a fall. The patient dataset was divided into three parts: 60% for “training”, 20% for “cross validation”, and 20% for “testing”. Sensitivity, specificity, positive and negative predictive values, and accuracy were determined by comparing the model's predictions to the actual correct answers for each patient.

Results: On the “cross validation” data, the model attained a sensitivity (“recall”) of 100.00%, specificity of 78.95%, PPV (“precision”) of 78.95%, NPV of 100.00%, and accuracy of 88.24% in detecting the presence of positive head CTs. On the “test” data, the model attained a sensitivity of 97.78%, specificity of 89.47%, PPV of 88.00%, NPV of 98.08%, and accuracy of 93.14% in detecting the presence of positive head CTs.

Conclusions: ANNs show great potential for predicting CT findings in the population of patients ≥ 65 years of age presenting with minor head injury after a fall. As a good first step, the ANN showed comparable sensitivity, predictive values, and accuracy, with a much higher specificity than the existing decision rules in clinical usage for predicting head CTs with acute intracranial findings.

To compare dose, reader assessments, and noise between ultra-low-dose (ULD) and low-dose (LD) renal stone computed tomography (CT) using multiple reconstruction methods.

Prospective study of 19 patients having noncontrast LD and ULD renal stone CT reconstructed using filtered back projection, adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR). Dose, noise measurements, and subjective image assessments were recorded.

ULD volume CT dose index was 61% less. Noise was 50% less with ULD MBIR than with LD ASIR (P < .001); no other significant differences existed.

ULD MBIR is comparable to our standard of care, LD ASIR, with 61% lower dose and 50% less noise.

Intravenous urography (IVU) and CT urography (CTU) are efficient radiological examinations for the evaluation of the urinary system disorders. However patients are exposed to a significant radiation dose. The objectives of this study are to: (i) measure and compare patient radiation dose by computed tomography urography (CTU) and conventional intravenous urography (IVU) and (ii) evaluate organ equivalent dose and cancer risks from CTU and IVU imaging procedures. A total of 141 patients were investigated. A calibrated CT machine (Siemens-Somatom Emotion duo) was used for CTU, while a Shimadzu X ray machine was used for IVU. Thermoluminescence dosimeters (TLD-GR200A) were used to measure patients' entrance surface doses (ESD). TLDs were calibrated under reproducible reference conditions. Patients radiation dose values (DLP) for CTU were 172±61 mGy cm, CTDI_vol 4.75±2 mGy and effective dose 2.58±1 mSv. Patient cancer probabilities were estimated to be 1.4 per million per CTU examination. Patients ESDs values for IVU were 21.62±5 mGy, effective dose 1.79±1 mSv. CT involves a higher effective dose than IVU. In this study the radiation dose is considered low compared to previous studies. The effective dose from CTU procedures was 30% higher compared to IVU procedures. Wide dose variation between patient doses suggests that optimization is not fulfilled yet.

Radiation exposure from medical imaging has received increasing attention in recent years. Ongoing calls to report radiation doses received during radiology studies as a means of recording cumulative exposure and identifying rare over-exposures have culminated in the State of California passing a mandatory reporting requirement effective July 1, 2012. Herein we describe a radiology housestaff-led quality improvement project to track radiation dose reporting a full year prior to state reporting mandates using a template-driven reporting system and our results over the first 12 months of its implementation.

Effective July 2011, all radiology trainees were instructed to use a standard computed tomography (CT) report template that included a CT dose measurement derived from dose information routinely displayed on our picture archiving and communication system. Consecutive reports from July 1, 2011, to June 30, 2012, of patients who underwent CT examinations at our institution were then retrospectively reviewed. Compliance of each study with the reporting requirement was assessed based on the presence or absence of a radiation dose statement within the finalized report.

A total of 36,217 eligible consecutive CT reports were identified within the review period. Of these, 91.9% reported the radiation dose for the examination, greatly exceeding the initial goal of 80% compliance with the dose reporting requirement.

Successful reporting of CT radiation doses resulted from template-driven reporting, readily accessible calculation tools to facilitate dose calculation, and minimization of reporting burden on the radiologist a full year prior to state regulatory mandates.