Bone scintigraphy in pulmonary alveolar microlithiasis: a comparative study of radioactivity and density distribution

Extraosseous distribution of 99mTc-diphosphonates during bone scintigraphy: review of the literature with case series presentation

PURPOSE

Technetium-99m (99mTc)-diphosphonates represent the most common radiopharmaceutical used for bone scintigraphy. Even if the uptake in bone tissue has been widely explored, atypical uptake could be seen in soft tissue malignancies during bone scintigraphy. Increased vascularization and endothelium permeability represent front-row players in the biodistribution of the tracer, albeit other causes have been identified such as trauma, necrosis, the presence of calcification in metastasis, the pH of the tissue and consequently the type of ion concentration.

CONCLUSION

The aim of this paper is to summarize the state of art of atypical soft tissue uptake seen in cancer tissues. The research was conducted on PubMed. The analysis of the literature suggests that calcium metabolism and ionic saturation have a pivotal role in the biodistribution of bone tracers. This phenomenon ranks in a complex scenario that includes carcinogenesis and cancer environment aspects. We also report two cases in our Institution in which atypical uptake in cancer tissues was observed.

Intense and diffuse lung uptake of 99mTc-MDP in a patient with pneumonia associated with secondary hemophagocytic lymphohistiocytosis

99mTc-methylene diphosphonate (MDP) bone scan was performed in a 49-year-old female patient who had non-Hodgkin lymphoma. 99mTc-MDP uptake was significant in both lungs. Bilateral bacterial pneumonia associated with secondary hemophagocytic lymphohistiocytosis was diagnosed after extensive examination.

Diffuse Pulmonary Uptake of Tc-99m Methylene Diphosphonate in a Patient with Non-tuberculosis Mycobacterial Infection

Extra-osseous uptake of bone-seeking radiopharmaceuticals has been reported at various sites and it is known to be induced by various causes. Diffuse pulmonary infection, such as tuberculosis, can be a cause of lung uptake of bone-scan agent. Here we report on a patient with non-tuberculosis mycobacterial infection (NTM) who demonstrated diffuse pulmonary uptake on Tc-99m MDP bone scan. After medical treatment for NTM, the patient's lung lesions improved. Extraskeletal lung Tc-99m MDP uptake on bone scan may suggest lung parenchymal damage associated with disease activity.

FDG-PET/CT finding of high uptake in pulmonary alveolar microlithiasis

Pulmonary alveolar microlithiasis (PAM) is a rare lung disease characterized by progressive intra-alveolar calcification. We present a case of PAM with abnormal accumulation of 18F-fluorodeoxyglucose (FDG) in both lungs. A 55-year-old man was referred to our hospital for progressive dyspnea. He had been diagnosed with PAM 25 years earlier by transbronchial lung biopsy. High-resolution computed tomography revealed multiple dense calcifications with little aerated lung. Combined positron emission tomography and computed tomography using 18F-FDG (FDG-PET/CT) showed the abnormal accumulation of FDG in both lungs with a maximal standardized uptake value of 7.3. High FDG uptake was observed mainly in the lung regions showing sparing calcification. The patient died of respiratory failure a month later and an autopsy revealed no significant inflammatory changes in either lung. We suspect that the markedly enhanced pulmonary FDG uptake may have some relation to the pathophysiology of PAM.

Diffuse, intense lung uptake on a bone scan: a case report

PURPOSE

Clinical and scintigraphic findings are described in a patient with unexpected diffuse lung uptake on bone scan after a heroin overdose.

METHODS

The patient's Tc-99m MDP bone scan is reviewed along with the pertinent clinical history and laboratory findings.

RESULTS

Marked diffuse and symmetric lung uptake is present on bone scintigraphy in a patient with a history of acute renal failure and a markedly elevated calcium-phosphate product but normal renal function and laboratory values at the time of the examination.

CONCLUSIONS

The incidental observation of metastatic calcification by bone scintigraphy is important, because it may aid in the diagnosis of a previously unsuggested elevated calcium-phosphate product, renal failure, or both. Furthermore, the intensity of tracer localization on bone tracer-specific imaging may help evaluate the activity of the metastatic calcification process.

Bilateral sequential lung transplantation for pulmonary alveolar microlithiasis

Pulmonary alveolar microlithiasis (PAM) is characterized by deposition of calcium phosphate within the alveolar airspaces. There is currently no effective medical therapy and affected individuals may progress to end-stage lung disease requiring transplantation. Two patients with PAM underwent bilateral sequential lung transplantation. This study reviews the clinical manifestations of PAM and discusses the particular difficulties that may be encountered in the use of lung transplantation as treatment for this uncommon disease. Also addressed is the question of recurrence in the allograft.

Diffuse pulmonary uptake of 99mTc bone-imaging agents: case report and survey

Over the past 5 years, we have encountered 6 cases of diffuse pulmonary uptake of 99m-Tc bone-scanning agents (incidence, 0.04%). To assess the significance of this phenomenon, we reviewed all of the cases reported since 1974 (Including our series, a total of 32 cases). Three groups can be discerned, the first consisting of 24 patients without radiological calcifications in the lungs and with hypercalcemia of different origins (mostly hyperparathyroidism). Of the eight autopsies performed in this group, seven revealed extensive calcifications in alveolar walls and lung vessels; the other autopsy showed no calcification at all and only bronchopneumonic lesions. The second group consists of 6 patients in chronic dialysis. The last group consists of 2 patients having diffuse pulmonary alveolar microlithiasis with extensive radiologic calcifications. The mechanism of lung uptake of 99m-Tc bone-imaging agents is probably the same as that of bone uptake (chemisorption on hydroxyapatite crystals), although other uptake mechanisms have also been discussed. Bone scintigraphy can be useful in the detection of early pulmonary calcifications, which have been associated with impaired pulmonary function and, due to their size, are generally not detected by X-ray.