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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4534_Библиотеки_им_академика_М_И_Перельмана.pdf
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S. Taşar and R. Savaş
Fig. 12.13 In a mature newborn, there is an opaque appearance in a wide area in the right hemithorax on chest X-ray (a), and this area was found to belong to a mass consisting of multiple cysts
larger than 2cm in diameter on US examination (b). In the next stage, ndings correlated with the
contrast-enhanced CT examination (c, d). The pathology result of the operated patient was CPAM
(congenital pulmonary airway malformation)
Fig. 12.14 A newborn with a history of mechanical ventilation has pulmonary interstitial emphysema, especially in the right lung, and a pneumothorax that cannot be clearly distinguished on
plain radiographs (a). On US examination, comet tail artifacts originating from the pleura consistent with pneumothorax disappeared. We also see that the sliding of the lung has disappeared in the
dynamic examination. Since it is a real-time dynamic method, it is also used to evaluate diaphragmatic movements in phrenic nerve injuries (b)
12 Radiologic Evaluation ofLower Respiratory System
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The increase in radiation exposure from CT, especially in children, is an
important problem. An effective anteroposterior chest X-ray dose is 0.05 milliSievert (mSv), while the thorax conventional CT dose is 7.0mSv (10mm interval), HRCT dose is 0.7mSv, and thin section low-dose CT is 0.2mSv [7]. In the
respiratory system, the most common radiological method is CT in cases that
cannot be diagnosed by chest radiography and US.Good interpretation of chest
radiography ndings can prevent many unnecessary CT examinations. The
higher radiosensitivity and longer life expectancy of children, combined with the
increased use of CT, make it necessary to reduce the CT radiation dose while
maintaining diagnostic image quality. There are chest CT protocols that use variable tube voltages and tube currents, often determined by body size [8]. Lowering
the kV (kilovolt) from 120 to 100 reduces the dose by 30–70%. When the dose is
reduced, there is an increase in image noise [9]. Automatic exposure control
(AEC) is a method of dose reduction and common application in MDCT. The
lowest dose for which diagnostic data is provided and noise can be tolerated is
achieved with automatic exposure systems [10]. Electrocardiogram-triggered
sequential scanning may be used in CT to achieve fewer motion artifacts and a
lower radiation dose [11].
CT scan can be performed with or without contrast material, depending on the
clinical problem. In routine the use of precontrast and postcontrast (dual-phase)
chest CT should be avoided in pediatric patients as much as possible to minimize
radiation exposure.
CT is valuable in evaluating not only lungs, but also vascular abnormalities
(Fig.12.15), mediastinal, hilar, and chest wall abnormalities also can be assessed.
However, the soft tissue contrast resolution of CT is not as good as MRI.
Postprocessed and reconstructed CT images such as multiplanar reformatted
(MPR) and volüme rendering techniques considerably increase the diagnostic accuracy of pediatric chest CT [12].
Modern MDCT scanners, with an increasing number of detector rows, have further enhanced performance, with faster scan times (improved temporal resolution)
and a wider scan range. When this is combined with the use of smaller detector elements, it enables reduced partial volume artifacts. Thoracic CT in a spiral mode in
children, without the need for breath-holding and with minimal respiratory, cardiac,
and patient motion artifacts, reduces reliance on sedation and general anesthesia.
Using postprocessing software to restructure the overlapping thin sections due to
isotropic imaging, they are presented as two-dimensional or three-dimensional displays with a resolution close to the original.
Thoracic CT is frequently used to evaluate metastasis when scanning or when a
solitary pulmonary nodule is suspected, and in symptomatic patients with a normal
chest X-ray. It is also the most useful method in the characterization of diffuse lung
diseases.
Maximum intensity projection (MIP), a multiplanar reconstruction method is
used to extract contrast-enhanced anatomic structures than adjacent structures, as in
CT angiography. These thicker slabs are useful in detecting and localizing micronodular (Fig.12.16) or microtubular patterns [13].
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Fig. 12.15 It is observed that a convex-shaped linear density in the hypoplasic right lung lower
zone on the PA chest X-ray (a), belongs to an abnormal pulmonary venous return anomaly in coronal MIP CT images consistent with scimitar syndrome (arrows: Turkish sword) (b)
Fig. 12.16 A 10-year-old
girl with nodules that were
difcult or impossible to
select in the CT
examination taken to
determine the etiology of
fever could be detected
more easily with MIP
images
S. Taşar and R. Savaş
With volumetric imaging, the bronchial tree and cardiovascular system are better
evaluated (Fig.12.17). MDCT is now widely used as a replacement for conventional angiography in the evaluation of cardiovascular diseases (Fig.12.18). MDCT
is now widely used as a replacement for traditional angiography because it does not
require invasive intervention and sedation. The total radiation dose in MDCT is
signicantly lower than in conventional angiography. Although MDCT plays an
important role in the diagnosis of pulmonary embolism, arteriovenous malformation, aneurysm, and dissection, conventional angiography has the advantage of
allowing therapeutic intervention.
Static Airway CT is mainly performed to assess xed airway narrowing or stenosis. It is acquired in infants and young children while they breathe freely, and in
older children, they hold their breath at the end of inspiration with the fast scan
speed of multidetector CT.Dynamic Airway CT is performed in a paired inspiratory
and expiratory phase to evaluate a large airway disorder, most commonly tracheobronchomalacia. The resultant effective dose from this paired study is typically in
the range of 3.5–7.5mSv [14].
12 Radiologic Evaluation ofLower Respiratory System
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a
b
c
Fig. 12.17 A 15-year-old female patient with stridor. In the axial and coronal plane contrast CT
examination, there is a lobulated contoured air-lled diverticular formation associated with the left
main bronchus (a, b). In 3D images obtained from thin-section CT images, the relationship
between the diverticula and the left main bronchus can be more clearly identied (c)
Minimum intensity projection (MinIP) can be used to show the central airway
and air trapping in the lungs. Sometimes, expiratory CT is required to conrm air
trapping. For this, patient cooperation or anesthesia is mandatory. In uncooperative
infants and young children, lateral decubitus CT may be used as an alternative [15].
The HRCT technique is taken with a section thickness of 1mm and a gap of
10mm. It is mostly preferred in bronchiectasis, bronchiolitis obliterans, and interstitial lung diseases. The HRCT technique should not be used for metastasis screening because there are areas of the lung that are not examined. The classic HRCT
technique still may be used in pediatric patients because of the overall decreased
radiation exposure compared with volumetric data acquisition.
The HRCT technique is taken with a section thickness of 1mm and a gap of
10mm. It is mostly preferred in bronchiectasis, bronchiolitis obliterans, and interstitial lung diseases. The HRCT technique should not be used for metastasis screening because there are areas of the lung that are not examined. The classic HRCT
technique may still be used in pediatric patients because of the overall decreased
radiation exposure compared to volumetric data acquisition.
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Fig. 12.18 3D
reconstructive images
obtained from MDCT,
double aortic arch (a), and
compression of the
trachea (b)
S. Taşar and R. Savaş
Childhood interstitial lung disease (chILD) encompasses a heterogeneous group
of rare diffuse lung diseases that can develop due to acute or chronic causes.
Disease processes may affect not only the interstitium but also the alveoli, airways,
lymphatic channels, blood vessels, and pleural spaces. Plain radiography is the rst
preferred method in these diseases, but it may be normal in some cases. Some of
the diffuse lung diseases have a characteristic pattern that allows a specic diagnosis to be made, while others manifest with a nonspecic appearance requiring further investigation. HRCT is indicated in patients with suspected diffuse lung
disease to demonstrate the pattern and distribution of these opacities radiologically
(Fig.12.19).
12.2.5 Magnetic Resonance Imaging (MRI)
There are some limitations in chest MRI due to the low signal-to-noise ratio of the
lung, lengthy examination time, and cardiac-respiratory motion artifacts. In most
pediatric patients, it requires sedation. There are some technical methods to improve
MRI, like parallel imaging and multichannel body-array coils to reduce examination time. Moreover, electrocardiogram triggering, respiratory triggering, and navigator gating may be used to suppress motion artifacts. The lack of ionizing radiation
and the superior soft tissue imaging are advantages of MRI (Fig.12.20). MRI is also
useful in the evaluation of spinal canal extension, especially in neurogenic tumors
located in the posterior mediastinum (Fig.12.21). Additionally, the cellularity of
thoracic masses may be evaluated with diffusion-weighted imaging. Central airways and cardiovascular structures can be assessed with black-blood MRI without
using a contrast agent [16]. Also, the allergy risk of contrast material used in MRI is
lower than the risk of allergy to the contrast agent in CT.In addition, tracheobronchomalacia can be diagnosed with real-time dynamic airway MRI.
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a
b
Fig. 12.19 A 14-year-old boy with diffuse reticulonodular and ground glass opacities observed in
both lungs. In the coronal section CT examination, there are diffuse interlobular septal thickenings,
more prominent in the lower lobes
CT or MRI can be used in the evaluation of lymphoma, leukemia-related inltration, thymus-located cysts and tumors (Fig.12.22).
Although diagnostic accuracy is still largely unknown, three-dimensional volumetric MRI images can contribute to diagnosis in most modern scanners.
12.2.6 Angiography
Computed tomography, magnetic resonance angiography, and digital subtraction
angiography (DSA) are the radiological modalities used to demonstrate the pulmonary vascular tree. In recent years, noninvasive imaging methods have been increasingly utilized. With the widespread use of MRI and CT, the indications for
conventional angiography for diagnostic purposes have signicantly decreased.
Angiography in pediatric patients is mostly used for therapeutic purposes, such as
vascular tumor embolization, arteriovenous stula embolization before surgery, or
vascular stenosis requiring angioplasty (Fig.12.23).
12.2.7 Positron Emission Tomography (PET)
In pediatric patients, PET is useful for evaluating intrathoracic tumors, including
Hodgkin and non-Hodgkin lymphoma, rhabdomyosarcoma, osteosarcoma, Ewing
sarcoma, and neuroblastoma. PET offers an advantage over anatomic imaging by
detecting metabolically active viable tissue. Therefore, PET is employed in oncologic imaging for both initial diagnosis and monitoring metabolic responses to
treatment.
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S. Taşar and R. Savaş
a
b
c
Fig. 12.20 There is a mass lesion that lls the left hemithorax and causes a rightward shift in the
mediastinal structures. The diaphragmatic border cannot be selected. The relationship of the mass
with the bone was shown in the PA chest X-ray (a) and coronal CT (b) examination. There is lytic
expansile destruction in the left rib (white arrow). In coronal MRI, dense uid in the vicinity of the
mass in the left hemithorax (arrowhead) and collapse in the lung are selected (black arrow) (c).
Pathology was Ewing sarcoma
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a
b
c
Fig. 12.21 The patient diagnosed with neuroblastoma has a paravebral mass in the posterior
mediastinum (a) in the axial CT image. Spinal canal extension and cord compression are observed
in axial and sagittal MRI (b, c)
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S. Taşar and R. Savaş
a
b
c
Fig. 12.22 Chest X-ray, CT, and MRI revealed a giant mass lesion surrounding the vascular structures in the anterior mediastinum. On MRI, an involvement compatible with pleural metastasis is
also observed on the right
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a b
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c
Fig. 12.23 Six-month-old girl. In the newborn period, opacity was detected in the right hemithorax and she received pneumonia treatment (a). However, because the clinical and radiological
ndings persisted despite the treatment, a contrast-enhanced thorax CT examination was performed (b). In CT and angiography examinations, sequestered lung tissue and its systemic vascularization were identied (c, d). Angiography was performed to occlude the aberrant vessel
d
12.3 Conclusion
Using imaging methods such as Ultrasound (US), Computed Tomography (CT),
and Magnetic Resonance Imaging (MRI) following a chest X-ray with a welldened algorithm is crucial for the benet of both the patient and the physician.
Effective communication between clinicians and radiologists is essential to select
the most appropriate imaging modality for the specic disease or symptom. This
should consider factors such as minimizing ionizing radiation exposure, accessibility, and cost-effectiveness. The choice of imaging modality should always be made
with the patient’s best interests and health in mind.