胸部X光常見異常之專家回顧 Expert Review of Common Chest X-Ray Abnormalities

本節旨在建立準確判讀的關鍵基礎。在識別病理變化之前，必須先確認影像的技術品質是否足夠，並採用嚴謹、系統性的方法來避免感知錯誤。 This section aims to establish the critical foundation for accurate interpretation. Before identifying pathological changes, it is essential to confirm the technical quality of the image and adopt a rigorous, systematic approach to avoid perceptual errors.

1.1 評估技術品質：診斷的先決條件 1.1 Assessing Technical Quality: A Prerequisite for Diagnosis

對基本技術參數的詳細檢視至關重要。一份品質不佳的影像可能會產生模擬疾病的假影或掩蓋真實的病理變化。 A detailed review of basic technical parameters is crucial. A poor-quality image may create artifacts that mimic disease or obscure genuine pathological changes.

• 投射角度（PA vs. AP）：後前位（PA）是標準視圖，能提供更準確的心臟與縱膈腔尺寸。前後位（AP）通常在床邊拍攝，會因放大效應造成心臟假性擴大。 Projection Angle (PA vs. AP): A posteroanterior (PA) view is the standard and provides more accurate heart and mediastinal dimensions. An anteroposterior (AP) view, typically taken at the bedside, can cause a false enlargement of the heart due to magnification.
• 吸氣程度：一張吸氣充足的影像應能看到橫膈膜位於第8至第10後肋骨之間的高度。吸氣不足會使肺紋理擁擠，可能遮蔽病灶。 Inspiration Level: A properly inspired image should show the diaphragm at the level of the 8th to 10th posterior ribs. Poor inspiration can crowd lung markings and potentially obscure lesions.
• 旋轉：病患的身體旋轉會嚴重扭曲縱膈腔的解剖結構。應檢查兩側鎖骨頭相對於胸椎棘突是否對稱。 Rotation: Patient rotation can severely distort the anatomy of the mediastinum. Check for symmetry between the medial ends of the clavicles and the spinous processes of the thoracic vertebrae.
• 曝光（穿透度）：一張穿透度適中的影像，應能隱約看見心臟後方的胸椎椎體。 Exposure (Penetration): An image with adequate penetration should allow the vertebral bodies behind the heart to be faintly visible.

1.2 系統性判讀方法：ABCDEF記憶法 1.2 Systematic Interpretation Method: The ABCDEF Mnemonic

ABCDEF記憶法不僅僅是一張檢查清單，更是一種認知工具，旨在強制執行結構化的審視流程，從而減少常見的感知錯誤。這種系統性方法確保所有關鍵結構都得到評估。 The ABCDEF mnemonic is more than just a checklist; it’s a cognitive tool designed to enforce a structured review process, thereby reducing common perceptual errors. This systematic method ensures all key structures are evaluated.

• A – Airways（呼吸道）：氣管、氣管分岔、主支氣管。 A – Airways: Trachea, carina, main bronchi.
• B – Breathing（呼吸）：肺部與肋膜。 B – Breathing: Lungs and pleura.
• C – Circulation（循環系統）：心臟輪廓、縱膈腔輪廓、大血管。 C – Circulation: Cardiac silhouette, mediastinal contours, great vessels.
• D – Diaphragm（橫膈膜）：橫膈膜位置、肋膈角、橫膈膜下結構。 D – Diaphragm: Diaphragm position, costophrenic angles, subdiaphragmatic structures.
• E – Everything Else/External（其他/外部）：胸廓骨骼（肋骨、脊椎、鎖骨）與軟組織。 E – Everything Else/External: Thoracic bones (ribs, spine, clavicles) and soft tissues.
• F – Foreign Material（異物）：醫療裝置（管線）、手術夾、外來物體。 F – Foreign Material: Medical devices (tubes), surgical clips, foreign bodies.

2.1 呼吸道異常 2.1 Airway Abnormalities

氣管偏移：氣管可能被張力性氣胸或大量肋膜積液「推」向對側，或被肺葉塌陷等造成體積減少的病灶「拉」向患側。 Tracheal Deviation: The trachea may be “pushed” to the opposite side by a tension pneumothorax or a large pleural effusion, or “pulled” toward the affected side by a lesion causing volume loss, such as lobar collapse.

氣管分岔增寬：正常的氣管分岔角度小於105度。若角度大於此值，則暗示有氣管分岔下方的病變，最常見的是淋巴結腫大或腫瘤。 Widening of the Carina: A normal carina angle is less than 105 degrees. An angle greater than this suggests a lesion below the carina, most commonly lymphadenopathy or a tumor.

2.2 肺部密度增加的模式 2.2 Patterns of Increased Lung Density

肺部密度增加（白化）是胸部X光最常見的異常之一。是否存在「體積減少」的徵象是區分肺實質化與肺塌陷最核心的特徵。 Increased lung density (opacification) is one of the most common abnormalities on a chest X-ray. The presence of signs of “volume loss” is the key feature distinguishing between lung consolidation and atelectasis.

• 肺實質化（Lung Consolidation）：肺泡內的空氣被液體、膿液、血液或細胞取代。體積正常或增加，常可見「空氣支氣管攝影徵象」。 Lung Consolidation: Alveolar air is replaced by fluid, pus, blood, or cells. Volume is normal or increased, and an “air bronchogram sign” is often visible.
• 肺塌陷（Atelectasis）：與肺實質化最大的區別在於有體積減少的證據，例如氣管移位、橫膈膜抬高、肋間變窄。 Atelectasis: The main difference from consolidation is the presence of evidence of volume loss, such as tracheal deviation, elevated diaphragm, and narrowed intercostal spaces.
• 肺水腫（Pulmonary Edema）：通常由左心衰竭引起，早期可見克利氏B線，晚期呈現典型的「蝙蝠翼」分佈。 Pulmonary Edema: Usually caused by left heart failure. Early signs include Kerley B lines, while a typical “batwing” distribution is seen in later stages.
• 局部不透明影：結節與腫塊：結節直徑≤30 mm，腫塊直徑>30 mm。不規則或毛刺狀邊緣暗示惡性可能。 Focal Opacities: Nodules and Masses: A nodule has a diameter of ≤30 mm, and a mass has a diameter of >30 mm. Irregular or spiculated margins suggest malignancy.

表一：肺部密度增加模式之鑑別診斷 Table 1: Differential Diagnosis of Increased Lung Density Patterns

2.3 肺部密度降低的模式 2.3 Patterns of Decreased Lung Density

氣胸（Pneumothorax）：診斷的決定性徵象是可見一條纖細的「臟層肋膜線」，線條外側無肺紋理。 Pneumothorax: The definitive diagnostic sign is a thin “visceral pleural line,” with no lung markings lateral to it.

2.4 肋膜異常 2.4 Pleural Abnormalities

肋膜積液（Pleural Effusion）：在直立位X光上，最早的徵象是肋膈角變鈍，隨後形成上緣凹陷的彎月狀陰影。 Pleural Effusion: On an upright X-ray, the earliest sign is blunting of the costophrenic angle, followed by a meniscus-shaped opacity with a concave upper border.

3.1 評估心臟輪廓：心臟肥大 3.1 Assessing the Cardiac Silhouette: Cardiomegaly

心胸比（Cardiothoracic Ratio, CTR）：在標準PA視圖上，CTR大於0.50（或50%）被視為異常，暗示心臟肥大。此為粗略指標，常需心臟超音波進一步確認。 Cardiothoracic Ratio (CTR): On a standard PA view, a CTR greater than 0.50 (or 50%) is considered abnormal, suggesting cardiomegaly. This is a crude indicator that often requires further confirmation with echocardiography.

3.2 縱膈腔增寬 3.2 Mediastinal Widening

在AP片上，縱膈腔寬度大於8公分值得關注。平滑、瀰漫性的增寬傾向於急性過程（如主動脈剝離）；分葉狀或局部性隆起則指向慢性過程（如淋巴瘤、腫塊）。 On an AP film, a mediastinal width greater than 8 cm is a cause for concern. Smooth, diffuse widening suggests an acute process (e.g., aortic dissection), while lobulated or focal bulging points to a chronic process (e.g., lymphoma, mass).

表二：縱膈腔增寬之鑑別診斷 Table 2: Differential Diagnosis of Mediastinal Widening

D – 橫膈膜 (Diaphragm) D – Diaphragm

氣腹（Pneumoperitoneum）：在直立位胸部X光片上，橫膈膜下方出現新月形的黑色空氣，是外科急症的信號，最常見的原因是胃或十二指腸潰瘍穿孔。 Pneumoperitoneum: On an upright chest X-ray, a crescent-shaped lucency of air beneath the diaphragm is a sign of a surgical emergency, most commonly caused by a perforated gastric or duodenal ulcer.

E & F – 其他與異物 E & F – Everything Else & Foreign Material

骨骼與軟組織：應仔細檢查肋骨、脊椎等是否有骨折或病變。皮下氣腫（軟組織出現空氣）通常暗示存在氣胸。 Bones and Soft Tissues: Ribs, spine, and other bones should be carefully checked for fractures or lesions. Subcutaneous emphysema (air in soft tissues) often suggests the presence of a pneumothorax.

醫療裝置：檢查氣管內管、中央靜脈導管等裝置的位置是否正確，是判讀X光片的重要環節。 Medical Devices: Checking for the correct position of devices like endotracheal tubes and central venous catheters is a critical part of X-ray interpretation.