Short summary

The aim of this study is to evaluate the feasibility, time-use by staff, examination time and diagnostic accuracy of ultra low dose CT of the chest in a population of acute admitted patients in which a supine chest x-ray is performed.

Rationale

Typically, CXR is the first line imaging modality in the assessment of the patient admitted with respiratory symptoms or signs of respiratory failure. CXR can diagnose the most common diseases seen in these patients (e.g. decompensated HF, pneumonia) as well as common complications and important differential diagnoses (e.g. pleural effusion, pneumothorax, tumour). The conventional CXR also has its drawbacks and pitfalls. CXR misses a significant proportion of patients admitted to an ED with either decompensated HF or pneumonia. Furthermore, in the most critically ill patients the CXR can only be performed with the patient in the supine position. For many diseases the diagnostic accuracy of a supine CXR is considerably lower than a CXR in 2 views with the patient standing up.

Computed tomography (CT) and high resolution (HR-CT) of the chest has a better diagnostic accuracy than conventional chest x-ray for the above mentioned conditions.  CT however also has its drawbacks when compared to chest x-ray. Many of the drawbacks are related to department logistics (e.g. costs, availability, and increased examination time) but also patient safety issues (increased examination time, increased radiation exposure).

Ideally the initial imaging modality in patients with respiratory symptoms should have a high diagnostic accuracy and as few patient safety issues as possibly. One possible approach would be a combination of the high diagnostic accuracy of CT of the chest, with the low radiation exposure of the conventional chest x-ray. In theory this could possibly be achieved by using an ultra low-dose CT (ULD-CT) of the chest in which the radiation exposure had been limited to a minimum, while maintaining an acceptably high diagnostic accuracy of the most common acute diseases in these patients.

The aim of this study is to evaluate the feasibility, time-use by staff, examination time and diagnostic accuracy of ULD-CT of the chest in a population of acute admitted patients in which a supine chest x-ray is performed. HR-CT is used as gold standard for the analysis of diagnostic accuracy.

Description of the cohort

Study design:

Descriptive cross-sectional study of acute admitted patients in which a supine chest x-ray is performed.

Setting:

The study is performed in the emergency department at Odense University Hospital, Denmark

Inclusion criteria:

• Both of the following criteria:
• Patient admitted to the ED
• Supine chest x-ray performed

Exclusion criteria:

• One or more of the following:
• Permanent mental disability
• Informed consent not obtained
• Patient age < 40 years
• Severely critically ill patient where treating physician deems that ULD-CT and HR-CT cannot be performed as it will cause delay in life-saving treatment or transport.
• Patients admitted due to trauma

Data and biological material

If the patient meets the inclusion criteria and none of the exclusion criteria, the patient is included in the project by the radiographer performing the supine chest x-ray. Subsequently a ULD-CT and a HR-CT is performed.

The attending radiologist in ED according to usual department guidelines assesses the supine chest x-ray. A radiologist especially trained in chest radiology performs blinded assessment of the HR-CT. Blinded assessment of the ULD-CT is performed by a group of radiologist and a group of clinicians normally attending the ED.

Supine chest x-ray:

Supine chest x-ray is performed according to the department's guidelines. The supine chest x--ray can be performed in the radiology department's section of the ED or in the ED itself using portable x-ray machines.

LR-CT:

A special designed ULD-CT protocol was created using a chest phantom (N1 "Lungmann", KYOTO Kagaku, Japan) corresponding to an 80 kg male in corporation with a radiographer, a medical physicist, a radiologist and a pulmonologist to evaluate diagnostic usefulness.  We used a 64-multidetector CT scanner (Discovery CT750 HD; GE Healthcare, Milwaukee, US). ULD-CT is performed after the supine chest x-ray. Estimated radiation from one ULD -CT is 0.1 mSv compared to 6.5 mSv from a standard chest CT.

HR-CT:

HR-CT of the chest is performed after the ULD-CT. The HR-CT is performed according to the radiology department's normal guidelines; imaging is however only performed during inspiration in order to minimize patient radiation exposure. Estimated radiation from one HR-CT is 2.2 mSv compared to 6.5 mSv from a standard chest CT.

Registration after procedures:

Following the supine chest x-ray and ULD-CT, the following data are registered:

• Time used by the staff for the examination (defined as the time spent by the radiology staff in order to prepare, perform and complete the imaging modality)
• Number of staff members needed for the examination
• Examination time (defined as the time from the patient enters the room in which the imaging modality is performed to the patient the leaves the room)
• Whether the examination had to be cancelled due to lack of patient cooperation or patient safety issues
• Occurrence of adverse events while the examination was performed (e.g. clinical deterioration, acute treatment needed, cardiac arrest)

Additional data collection:

Apart from the separate data registration performed as part of the project it is planed to collect data from:

• Patient baseline information from the EMR (electronic patient record system)(e.g. patient symptoms, objective findings, vital signs, medication comorbidities, length of hospital stay, results of diagnostics tests performed)
• Information from the radiology departments electronic archiving system (e.g. types of imaging performed and results)

Collaborating researchers and departments

Department of Respiratory Medicine, Odense University Hospital

• Clinical associate professor Christian Borbjerg Laursen, MD, PhD

Department of Radiology, Odense University Hospital

• Associate professor Ole Graumann, MD, PhD
• Mie Kiszka Nielsen, MD
• Radiographer Kristian Fog Farsø Blessing
• Radiographer Kim Pelle Christensen
• Medical Physicist Benedikte Klærke

Department of Emergency Medicine, Odense University Hospital

• Clinical associate professor Stefan Posth, MD, PhD