Acute Brain Stroke Evolution Detected by 18F-FDG PET/CT and MRI Justifies the Discordance of Lesions in a Patient With Lymphoproliferative Syndrome

Abnormal Cerebral FDG Accumulation in Acute Intracerebral and Subarachnoid Hemorrhages Due to Different Mechanisms

ABSTRACT

Changes in cerebral glucose metabolism after acute intracranial hemorrhage have been rarely described. We present a patient with abnormal cerebral FDG accumulation in acute intracerebral and subarachnoid hemorrhages due to different mechanisms on FDG PET/CT. The patient received conservative management and died 2 months later. This case demonstrated the different mechanisms of cerebral FDG accumulation in different types of intracranial hemorrhage, which may be helpful for future research to optimize patient care.

Focal FDG Uptake in the Cerebral Parenchyma Beneath the Subdural Hematoma

ABSTRACT

Changes in cerebral glucose metabolism after subdural hematoma have been rarely reported. We present a case with acute subdural hematoma detected unexpectedly on FDG PET/CT. Focal intense FDG uptake in the cerebral parenchyma beneath the subdural hematoma was seen on PET. The density of the cerebral parenchyma was normal on CT. The patient received conservative management. He recovered without any complication. This case indicates that familiarity with the changes in cerebral glucose metabolism on PET after subdural hematoma may be helpful for optimal patient care.

Increased Accumulation of 18F-FDG Incidentally Observed in Hyperacute Cerebral Infarction

ABSTRACT

A 75-year-old man with lung cancer undertook an 18F-FDG PET/CT for staging. He presented neurological symptoms immediately after the 30-minute scan. An emergent MRI study revealed hyperacute cerebral infarction with occlusion of a left MCA branch. At PET/CT, an increased 18F-FDG uptake was observed in the corresponding areas of infarction. In literature, acceleration of compensatory anaerobic glycolysis has been proposed as 1 of the causes of increased uptake in the penumbra of acute cerebral infarction, and a similar process was hypothesized in this case. In addition, a decreased 18F-FDG uptake in the ipsilateral thalamus was noted on the PET/CT images.

FDG-PET/CT Variants and Pitfalls in Haematological Malignancies

Hematologic malignancies represent a vast group of hematopoietic and lymphoid cancers that typically involve the blood, the bone marrow, and the lymphatic organs. Due to extensive research and well defined and standardized response criteria, the role of [¹⁸F]FDG-PET/CT is well defined in these malignancies. Never the less, the reliability of visual and quantitative interpretation of PET/CT may be impaired by several factors including inconsistent scanning protocols and image reconstruction methods. Furthermore, the uptake of [¹⁸F]FDG not only reflects tissue glucose consumption by malignant lesions, but also in other situations such as in inflammatory lesions, local and systemic infections, benign tumors, reactive thymic hyperplasia, histiocytic infiltration, among others; or following granulocyte colony stimulating factors therapy, radiation therapy, chemotherapy or surgical interventions, all of which are a potential source of false-positive or negative interpretations. Therefore it is of paramount importance for the Nuclear Medicine Physician to be familiar with, not only the normal distribution of [¹⁸F]FDG in the body, but also with the most frequent findings that may hamper a correct interpretation of the scan, which could ultimately alter the patients management. In this review, we describe these myriad of situations so the interpreting physician can be familiar with them, providing tools for their correct identification and interpretation when possible.