Unintentional intra-arterial injection of a bone-imaging agent

"Bilateral Hot Forearm Sign": Ingeminating the Pattern of Physiological Uptake of 18F-Fludeoxyglucose

Exertion and exercise increase glucose metabolism within the skeletal muscles causing increased fludeoxyglucose (FDG) uptake on 18F-FDG positron emission tomography/computed tomography (PET/CT). Here, we present findings of 18F-FDG PET/CT in a patient with acute viral hepatitis A-induced liver failure with multiple foci of pyoderma and incessant itching resulting in increased FDG uptake in the muscles of the bilateral forearm, producing the "bilateral hot forearm sign."

Unintentional Intra-arterial Injection of 177Lu-PSMA-1 in a Patient With a Peritoneal Carcinosis Secondary to a Metastatic Prostate Cancer

ABSTRACT

We report the case of an 81-year-old man presenting with peritoneal carcinosis secondary to a metastatic castrate-resistant prostate cancer addressed for 177Lu-PSMA-1 therapy. During the second cycle, a diffuse uptake in his left forearm was observed on the 1-hour postinjection scintigraphy, typical for an accidental intra-arterial injection. Less than 24 hours postinjection, a full removal of the intra-arterial injection was observed in the man, without any pain or symptoms. Moreover, the man demonstrated an 85% PSA reduction and a CT OR following the RECIST 1.1 criteria after 3 cycles.

Inadvertent Arterial Injection of 123I-MIBG Does Not Necessarily Cause Any Symptoms

An 123I-MIBG scan was obtained to evaluate a right adrenal mass in a 10-year-old boy, which showed no elevated activity in the lesion. However, diffuse increased activity was noted in the right forearm with typical manifestation of an "arterial injection." Different from a prior case report, no symptoms or signs related to arterial injection were observed in our patient.

Interesting Signs in Nuclear Medicine

Classic radiological and nuclear medicine signs have been reported extensively because of a myriad of pathophysiological processes. When encountered, they aid in diagnosis of conditions and add confidence for the reader, at times even hinting at a specific diagnosis. The naming of signs is commonly associated with objects from everyday life to establish familiarity with visual findings. Association of signs and disease comes with regular practice and improves understanding of the image and its underlying cause. In this article, we have collated nuclear medicine signs reported in the literature since 1970.

Focal hot spot induced by a central subclavian line on bone scan

The diagnostic accuracy of nuclear medicine reporting can be improved by awareness of these instrument-related artifacts. Both awareness and experience are also important when it comes to detecting and identifying normal (and abnormal) variants. We present a case of hot spot on the upper right chest in the region of right subclavicular region resulting from injection of radiotracer from central subclavian line. A 52-year-old woman with a history of left breast cancer and recent bone pain was referred to our nuclear medicine department for skeletal survey. Anterior views of chest show a focus of increased radiotracer uptake corresponding to anterior arch of one of the right second rib. The nuclear physician reported it as a focal rib bony lesion and recommended radiological evaluation. As technician later explained, physicians realized that injection site was a central subclavian line on the right side and hot spot on that region is due to injection site. The appearance of both skeletal and soft-tissue uptake depends heavily on imaging technique (such as the route of radiotracer administration) and the interpreting physicians should be aware of the impact of technical factors on image quality.

Inadvertent intra-arterial injection of (123)I-MIBG in a patient with metastatic pheochromocytoma

We present an interesting image of the inadvertent arterial injection of I-MIBG (metaiodobenzylguanidine) in a 36-year-old man with hereditary, metastatic pheochromocytoma, who underwent a diagnostic whole-body scan for the evaluation of extent of disease before possible I-MIBG therapy. During the tracer injection in the left antecubital area, the patient experienced tingling and skin redness in the left forearm and hand.

Abnormally increased uptake of 18F-FDG in the forearm and hand following intra-arterial injection -- hot forearm and hot hand signs

The aim of this study is to describe the appearance of intra-arterial administration of 18F-fluorodeoxyglucose (18F-FDG). The effect of this finding on the standard uptake values (SUVs) is also briefly discussed. Three cases of 18F-FDG positron emission tomography (PET) scans, detected over 2 years (2004-2006), with different presentations producing hot forearm and hot hand signs are described. It was shown that intra-arterial injections of 18F-FDG producing "the hot forearm sign" and the hot hand sign" are similar to the glove pattern of uptake noted following intra-arterial administration of technetium-99m methylene diphosphonate. Following intra-arterial injection, uptake of 18F-FDG is accentuated by hypoxia and exercise. A comparison is also made with the pattern of soft-tissue uptake seen following true intravenous injections with similar pre-injection vein enhancement techniques to the intra-arterial injections. Evaluation of the maximum intensity projection (MIP) and transaxial PET/CT fusion images of the arm, forearm and hand helps to confirm the diagnosis. Hands are often not included in PET/CT imaging and therefore cases might be missed. In conclusion, intra-arterial injection of 18F-FDG produces a "hot forearm sign" and "hot hand sign". Hands are often not included in PET/CT imaging, and therefore the presence of hot forearm sign should suggest further investigation. It should be mentioned in the radiology report, as it may alter the sensitivity and specificity of the SUV value.