18F-FDG PET/CT imaging in the diagnosis of drug-induced lung disease and pulmonary infection in lymphoma

OBJECTIVE

Lymphoma is a hematological disease with high prevalence. Multi-cycle chemotherapy (CHT) or local radiotherapy is applied usually; however, adverse events have been reported, such as drug-induced lung disease (DILD). Positron emission tomography/computed tomography (PET/CT) is often used to evaluate the lesion, treatment effect, and prognosis of lymphoma. We investigated DILD and pulmonary infection (PI) after multi-cycle CHT in lymphoma patients, to identify DILD and PI, provide guidance for later treatment for them.

METHODS

In all, 677 patients diagnosed with lymphoma and who underwent CHT were included. These patients underwent 18fluorodeoxyglucose (18F-FDG) PET/CT before and after CHT at Shandong Cancer Hospital (affiliated with Shandong University) between April 2015 and November 2019. Fifty patients developed DILD, 41 patients had lung infections; lesion characteristics were analyzed based on clinical characteristics, laboratory examinations, and PET/CT imaging.

RESULTS

Among the 677 lymphoma patients, there were 50 cases of DILD, with an incidence rate of 7.4%. PET/CT showed an elevated 18fluorodeoxyglucose uptake lung background, septal thickening and reticulation, multiple ground glass-like shadows, and grid-shaped blur shadows, which were more common in the lung periphery and under the pleura. The maximum standardized uptake value in the lung was 2.45 ± 0.52. Pulmonary infections occurred in 41 patients, and the maximum standardized uptake value was 4.05 ± 1.42. Age, sex, CHT cycle, Ann-Arbor stage, and lymphocyte levels were not significantly different between DILD and PI patients. Leukocyte and neutrophils showed significant differences; the PI patients had increased laboratory indexes of leukocyte and neutrophils. The mean number of CHT cycles was 4 cycles for DILD and PI.

CONCLUSIONS

PET/CT imaging has high sensitivity and detection rates for primary and metastatic lymphoma lesions. DILD mostly occurs in the middle and late stages of CHT. Laboratory tests and PET/CT can evaluate the lesions and treatment effects, and provide guidance for subsequent treatment plans for patients.

FDG-positron emission tomography/computed tomography and standardized uptake value in the primary diagnosis and staging of hilar cholangiocarcinoma

BACKGROUND

The diagnosis and staging of hilar cholangiocarcinoma (HCCA) remain challenging despite recent advances in imaging. Little is known about the use of positron emission tomography/computed tomography (PET/CT) in HCCA.

OBJECTIVES

This study aimed to evaluate the additional value of FDG-PET/CT and standardized uptake value (SUV) in patients with highly suspected HCCA.

METHODS

Between February 2006 and August 2009, PET/CT was performed in 30 patients with highly suspected HCCA, all of whom were deemed resectable by conventional staging methods, including laparoscopy. The results of PET-CT and SUV were compared with intraoperative and histopathological findings.

RESULTS

The primary tumour was (18) F-FDG-positive in 88% of patients. Sensitivity and specificity for the detection of regional lymph node metastases and distant metastases were 67% and 68%, and 33% and 96%, respectively. The median SUV in the primary tumour was significantly (P < 0.05) higher in patients with (mean: 8.9) than without (mean: 6.1) distant metastases. The SUV in patients with benign disease (n= 4) showed a trend towards lower values than in patients with cholangiocarcinoma, although this was not significant.

CONCLUSIONS

After conventional staging including diagnostic laparoscopy, the additional value of PET/CT is limited. This somewhat disappointing finding may reflect the fact that extensive staging studies were carried out prior to PET/CT. The SUV potentially predicts patients with distant metastases and may differentiate between HCCA and benign lesions that mimic malignancies.

Statistical sinogram restoration in dual-energy CT for PET attenuation correction

Dual-energy (DE) X-ray computed tomography (CT) has been found useful in various applications. In medical imaging, one promising application is using low-dose DECT for attenuation correction in positron emission tomography (PET). Existing approaches to sinogram material decomposition ignore noise characteristics and are based on logarithmic transforms, producing noisy component sinogram estimates for low-dose DECT. In this paper, we propose two novel sinogram restoration methods based on statistical models: penalized weighted least square (PWLS) and penalized likelihood (PL), yielding less noisy component sinogram estimates for low-dose DECT than classical methods. The proposed methods consequently provide more precise attenuation correction of the PET emission images than do previous methods for sinogram material decomposition with DECT. We report simulations that compare the proposed techniques and existing approaches.