Errors in Chest Radiology

Errors in Chest Radiology

Errors in chest radiology are caused by improper technique, by failure to interpret

results correctly, or by inadequate knowledge of the patients's clinical history on

the part of the radiologist.

Errors in Technique

Errors in technique include (a) under- or overexposure, (b) poor inspiratory effort,

(c) off-centering (off-centering to a grid results in a severe unilateral grid cutoft),

(d) rotation of patient, (e) the use of only one projection, and, (t) the presence of

artifacts.

Proper indication for a chest study not only requires a correctly exposed radiograph

but also requires that a lateral view be included. Specific areas of the lung

are obscured by the diaphragm, the heart, and bony structures, and can only be visualized

in the lateral chest radiograph. The lateral view also clarifies abnormalities

noted in the frontal view, such as hilar versus juxtahilar disease.

We have observed pulmonary densities which were missed on overexposed

frontal chest radiographs. Likewise, extensive involvement of the mediastinum

with encasement of the trachea can be missed when dealing with underexposed

radiographs. If the heart appears very white and the spine is not apparent behind

the heart, the chest radiograph has been underexposed.

When the central X-ray beam is not centered and is aimed at one of the hemithoraces,

the resultant iatrogenic hyperlucency can simulate pulmonary emphysema,

massive embolism, or absence of soft tissues in the ipsilateral hemithorax.

Improper use of the film-screen combination and processing can also lead to

errors from the presence of artifacts or from lack of representation of a pulmonary

and/or mediastinal pathology. Improper positioning (rotation) of the patient can

obscure certain regions of the lung, such as the hila, and can produce a distorted

position of the trachea, which can be misinterpreted as a paratracheal mass. Poor

inspiratory effort not only will lead to poor definition of the lower lobes, but

also can simulate blunted costodiaphragmatic sulci, which are seen with pleural

effusions and pseudocardiac enlargement.

According to John E. Cullinan, "the number one error by radiographers is the

failure to use adequate contrast media (air) for the study. With automatic exposure

equipment, variations in inspiration are compensated for by longer exposure

times. With conventional timers, with less air in the lung, more exposure is re

quired; as much as 2 to 2 ~ times more MAs or an increase to 10 to 15 kVp.

Radiographers using conventional exposure times soon learn to try for maximum

inspiration. Radiographers using automatic exposure controls produce a variety of

chest appearances (all proper densities) due to various degrees of inspiration".

Errors in Interpretation

Failure to interpret results correctly are due to:

1. Errors of omission. Difficult areas to evaluate include the lung apices, juxtavertebral

regions, peri- and retrocardiac regions, juxtadiaphragmatic areas, the hila,

and cardiac calcification.

2. Errors of commission (overreading). Errors in evaluation include pseudoinfiltrates

(crowded markings from hypoventilation), emphysema (overexposure, hypovolemia

or off-centering of X-ray beam), and "chronic changes" (in the presence

of senile lung and of interstitial edema).

3. Inadequate clinical history.

Difficult Areas of Interpretation

Difficult areas to assess are:

1. Lung apices

2. Paravertebral regions, especially in upper thorax

3. Mediastinum

4. Juxtadiaphragmatic lung

Subtle pulmonary pathology may be obscured by small lung volume in the uppermost

portion of the lung, the crisscrossing of ribs and clavicle, and often the

presence of hypertrophic spurs at the medial sternoclavicular articulation. Whenever

in doubt, obtaining of a frontal radiograph, with the patient's arms vertically

stretched, or an apical lordotic view, is suggested. Pulmonary cancers have been

confused with hypertrophic spurs. Pulmonary nodules have been diagnosed in patients

with bone islands, an error which has then been subsequently detected by

computed tomography (Cn.

Centrally located masses may not be observed in the hilar or paratracheal regions,

but may be noted below the tracheal bifurcation on penetrated chest radiographs.

The only suggestion of a mediastinal mass may be displacement of the

pleuroazygoesophageal line. Likewise, mediastinal abnormalities may be detected

if displacement of normal air-soft tissue interfaces of the mediastinum, such as the

posterior junction line, is observed. Minimal thickening of the right paratracheal

stripe may not be appreciated unless a previous radiograph for comparative purposes

exists. Pulmonary densities in the paravertebral regions may be totally missed

on frontal radiographs, and on the lateral views of the chest they may not be seenor may be confused with hypertrophic spurs of the spine. Conversely, hypertrophic

changes of the thoracic spine can be misintetpreted as pulmonary nodules.

There are definite limitations in the ability to recognize small pulmonary nodules.

Standard tomography generally shows more nodules than standard chest radiography,

and CT of the chest may even show nodules not detected by either chest

radiography or standard tomography. In patients with soft tissue or bony sarcomas

in which there is a high probability of pulmonary metastasis, chest CT is

recommended prior to radical surgery.

The detection of hilar or juxtahilar pathology may be quite difficult. Occasionally,

an increase in the density of hilar shadow may be the only indication of the presence

of a hilar or juxtahilar mass. Lateral and/or 55° oblique tomography may then reveal

the pathological process that would account for the increase in the density of the

hilum.

It is imperative to compare results obtained at different dates. A sudden increase

in the cardiomediastinal shadow may be the only sign of an extensive infiltrating

tumor of the mediastinum. This abnormality may not become apparent unless a previous

study exists showing the cardiomediastinal shadow to be smaller. Esophageal

and juxtaesophageal pathology may remain undetected on improperly exposed radiographs.

Properly interpreted studies may reveal deviation of the trachea in the

frontal and/or lateral projection, air in a dilated esophagus, a displaced pleuroazygoesophageal

line, and a small or absent gastric bubble.

The nature of pleural effusion or of a pulmonary infiltrate may be suspected

by observing associated mediastinal and/or subdiaphragmatic pathology, such as

adenopathies and hepatic and/or splenic enlargement.

A chest radiographic examination may be absolutely negative for pathology, yet

the patient may die a few minutes later from a massive myocardial infarction, or

may have extensive meadiastinal tumor at autopsy. Areas of akinesis or hypokinesis

can only be detected by fluoroscopy, with gated chest radiography, or by

nOrrlnvasive and invasive imaging techniques. Considerable difficulty in breathing

can be the result of diaphragmatic dysfunction. The latter may be observed by

careful fluoroscopic examination of the diaphragm.

A systematic approach for the interpretation of the chest radiograph must include

careful examination of the following:

- Lungs

-Hila

- Mediastinum

- Diaphragm and

juxtadiaphragmatic regions

Compare the right and left pulmonary zones.

Assess carefully the lung parenchyma at the site

of crisscrossing of ribs and clavicles.

Evaluate the density and morphology of the hila.

Assess the retrocardiac region.

Evaluate the cardiomediastinal shadow.

Study the trachea and major bronchi.

Assess the air-soft tissue interfaces.

Decide if basilar densities represent pulmonary,

pleural, diaphragmatic, or subdiaphragmatic

pathology.

-Neck

- Upper abdomen

Skeletal structures

Study the ribs, clavicles, scapulae, and spine.

Evaluate the soft tissue.

Compare the two sides and study the larynx

and trachea.

Analyze the liver, stomach, spleen, and gas

pattern of the upper abdomen.

Pertinent clinical findings may be essential for a correct interpretation of the radiological

examination and should always be available.

The following techniques are to be recommended in addition to the chest radiographs:

The esophagogram is a useful examination when posterior mediastinal pathology

are to be ruled out.

Computed tomography (CT) may reveal pulmonary nodules not seen on chest

radiographs. This technique occasionally allows the nature of pulmonary nodules

to be determined, and makes possible the early diagnosis of fibrosing alveoli tis,

emphysema, and bronchiectasis. CT is specific for the diagnosis of fatty masses and

some cysts, and is the best imaging modality for evaluating the stages of bronchial

carcinoma.

Scintigraphy, ultrafast CT and magnetic resonance imaging (MRl) are particularly

suitable for evaluating diseases of the heart.

Sonography is the best modality for studying pathology of the heart and pericardium

as well as for studying juxtacardiac, paravertebral, and pleural fluid collections.

Angiography is the only suitable method for assessing the coronary arteries and

is of great value for examining the pulmonary circulation, the heart, the aorta, and

the systemic and pulmonary veins.

Ventilation/perfusion scans are more sensitive than chest radiography in patients

with pulmonary thromboembolism (PTE). The chest radiograph is negative in 30%

of patients with PTE.

Endoscopic biopsy is most suitable for inner-third lung lesions. Lesions in other

locations should be biopsied under fluoroscopic control. Anterior and middle mediastinal

masses can be sampled using the suprasternal or the paraxyphoid _a pproaches.

Don't procrastinate! Do not observe the growth of a cancer. The second best

approach to prevention is to diagnose and treat a small lesion.