SOMATOM Definition Flash 

History

A 75-year-old male patient was referred to the radiology department for detailed imaging, after a mass was seen on his chest radiography. He is an ex-smoker with 53 pack years who quit two years ago. He has been taking anti-hypertensive medication for the past 20 years. The lung auscultation sounded normal and superficial lymph nodes were not palpable. Focal neurological deficits were not found. A Dual Energy xenon ventilation CT scan using single breath technique and a lung perfusion scintigraphy by SPECT examination were ordered for detailed examination of the lung mass and lung function. Brain MRI was ordered to detect occult brain metastases.

Diagnosis

The lung perfusion scintigraphy and SPECT showed a defect corresponding to the mass. Perfusion of the other areas of the lung was homogeneous and normal. The ratio of the sum of the pixel counts of the left upper lobe to that of the whole lung was 0.86. On unenhanced CT, the lung mass measured 6 cm at its greatest diameter. Enlarged lymph nodes, pleural nodules and pulmonary nodes other than the mass were notnoted. Dual Energy xenon CT showed a ventilation defect corresponding to the mass and the ratio of the sum of the pixel values of the xenon images covering the left upper lobe to that of the whole lung was 0.83, which was in accordance with the scintigraphy results. The patient was diagnosed with T2b M0 N0 (UICC 7^th edition) primary lung cancer (poorly differentiated squameous cell carcinoma) and was scheduled for left upper lobectomy. MRI revealed an occlusion of the right intracranial internal carotid artery. Brain perfusion SPECT revealed hypoperfusion of the right frontal and parietal lobe.

Comments

Xenon ventilation mapping using Dual Energy CT single breath technique¹ depicted the ventilation defect at the mass and also showed normal ventilation in other portions of the lungs. Risk of peri-operative cerebral infarction was estimated as high due to the presence of the right carotid artery occlusion. The patient underwent a left upper lobectomy. Metastases were absent in the intra-operative pathological examination. Post-operative pathological analysis of the sampled nodes revealed metastases in one out of fourteen dissected lymph nodes. The patient was staged as pT2b N1 M0. He recovered uneventfully.

Fig. 1-2 : Coronal (Fig. 1) and sagittal MPR (Fig. 2) showed the mass in the left upper lobe.

Fig. 3-4: Xenon ventilation mapping by Dual Energy CT depicted the ventilation defect at the mass and also showed normal ventilation in other portions of the lungs

Fig. 5-6: Xenon ventilation mapping by Dual Energy(Fig. 5) in comparison to SPECT(Fig. 6) - both showed a defect corresponding to the mass.