99m Technetium-HMPAO-labeled platelet scan in practice: Preparation, quality control, and biodistribution studies

Abstract There is no biodistribution or imaging data on 99mtechnetium (Tc)-hexamethyl propylamine oxime (HMPAO)-labeled platelets in the literature. The current study aimed to present updated information about the clinical procedures for preparation and use of labeled platelets. Following two-step centrifugation at 1500 and 2500 rpm, the platelets were extracted from whole blood into platelet-rich plasma (PRP) above the buffy coat and then from PRP into a platelet pellet at the bottom of the tube. The 99mTc-HMPAO-labeled platelets were inspected for purity, viability, release of 99mTc from platelets, and sterility. Also, microscopic examination and thin layer chromatography (TLC) were performed. Biodistribution was assessed following necropsy in BALB/c mice and through imaging of New Zealand rabbits. The separation ratio was estimated at 98%, and radiochemical purity was measured to be 80%. The labeling efficiency was above 30% in more than half of the assays (range: 17-43%). The release of 99mTc from platelets was 9% per hour at 37ºC. After 24 hours, stability was estimated at 54% in the human serum. The target organs of mice included the spleen and liver. In rabbits, the imaging results indicated liver as the target organ. Thyroid uptake was negligible up to 90 minutes. Based on the findings, extraction of platelets and labeling them with 99mTc-HMPAO is a feasible and safe approach in routine practice.

Usefulness of hybrid SPECT/CT for the 99mTc-HMPAO-labeled leukocyte scintigraphy in a case of cranial osteomyelitis

Cranial osteomyelitis is a potentially fatal lesion. White blood cell scanning (WBC) with 99mTc-hexamethylpropylene amine oxime (HMPAO) has proven highly sensitive and specific in the diagnosis and follow-up of patients with suspected osteomyelitis. In this report we show the usefulness of SPECT and transmission CT performed simultaneously using a hybrid imaging device for the functional anatomic mapping of soft tissue and cranial bone infections. 99mTc-HMPAO-labeled leukocytes scintigraphy was performed on an elderly diabetic man with an intracranial mass lesion and with suspected temporal bone infection. Planar scans were acquired 30 min, 4 h, and 24 h after injection. SPECT/CT was obtained 6 h after tracer injection, using a dual-head camera coupled with a low-power X-ray tube. The scintigraphic results were matched with the results of surgery and of clinical follow-up. The planar images alone were true-positives for abscess in this patient. SPECT/CT improves the accuracy of99mTc-HMPAO scintigraphy especially in discriminating between soft-tissue and bone involvement. In fact, SPECT/CT also showed temporal bone osteomyelitis. This result indicates that SPECT/CT performed using a hybrid device can improve imaging with 99mTc-HMPAO-labeled leukocytes in patients with suspected osteomyelitis by providing accurate anatomic localization and precise definition of the extent of infection.

Experimental evaluation of brain spect using d,1 -HMPAO99mTc in dogs. Anatomo-physiological implications / Avaliação experimental de "spect" cerebral mediante utilização do d,1 - HMPAO 99mTc em cães. Considerações anátomo-fisiológicas

Technetium-99m-d,1-hexamethylpropyleamine oxime (99mTc-HMPAO) is an important radiopharmaceutical used for both brain SPECT imaging and "in vitro" labelling of white blood cells. An increasing utilization of this radiopharmaceutical for studies of several neurologic and psychiatric diseases in humans, lead us to the preparation of the kits of HMPAO to be labeled with technetium-99m. This paper presents animal experimental studies with d,l-HMPAO99mTc prepared from liofilized kits developed in our laboratories and also comparison to those commercially available. The brain scans have been done initially in rabbits, however better results were obtained with dogs. Six mongrel dogs clinically qualited as normals, were used in order to get scintigraphic brain pictures and washout curves of region of interest (ROIs). The value of experimental studies in animals and the considerable reduction in price of the so obtained radiopharmaceutical, have shown the viability of such procedure in the clinical practice as well in the veterinary clinic of small animals. By the other side, the perfusion of d,l-HMPAO99mTc showed that such a product concentrates at the same time in the cerebral area and nasal fossa, showing evidence of similar structures as the hemato encephalic barrier, also in the nasal area.

O d,1 - Hexametilpropileno oxima marcado com o tecnécio-99m(99mTc-HMPAO) é um importante radiofármaco usado tanto para imagens tomográficas cerebrais quanto na marcação in vitro" de leucócitos. A crescente utilização deste radiofármaco no estudo de doenças neurológicas no homem levou-nos à obtenção de "kits" de HMPAO para ser marcado pelo tecnécio-99m. Neste trabalho apresentamos o estudo experimental efetuado com "kits" liofilizados de d,1 HMPAO99mTc desenvolvidos em nossos laboratórios, comparando inclusive com aqueles encontrados no comércio. As imagens cerebrais inicialmente foram feitas em coelhos, entretanto os melhores resultados foram obtidos em cães. Assim, selecionaram-se seis cães sem raça definida, considerados clinicamente normais para obtenção das imagens cintilográficas do cérebro e o washout das regiões de interesse (ROls). Os estudos experimentais em animais e a considerável redução do custo do radiofármaco mostrou-nos a possibilidade da utilização destes exames na clínica veterinária, especialmente de pequenos animais. Por outro lado, a perfusão do d,l HMPAO99mTc mostra que a concentração do radiofármaco se faz ao mesmo tempo na região do cérebro e nas fossas nasais, demonstrando a existência de estruturas iguais às da barreira hemo-encefálica nesta última região.

Experimental evaluation of brain spect using d,1 -HMPAO99mTc in dogs. Anatomo-physiological implications / Avaliação experimental de "spect" cerebral mediante utilização do d,1 - HMPAO 99mTc em cães. Considerações anátomo-fisiológicas

Technetium-99m-d,1-hexamethylpropyleamine oxime (99mTc-HMPAO) is an important radiopharmaceutical used for both brain SPECT imaging and "in vitro" labelling of white blood cells. An increasing utilization of this radiopharmaceutical for studies of several neurologic and psychiatric diseases in humans, lead us to the preparation of the kits of HMPAO to be labeled with technetium-99m. This paper presents animal experimental studies with d,l-HMPAO99mTc prepared from liofilized kits developed in our laboratories and also comparison to those commercially available. The brain scans have been done initially in rabbits, however better results were obtained with dogs. Six mongrel dogs clinically qualited as normals, were used in order to get scintigraphic brain pictures and washout curves of region of interest (ROIs). The value of experimental studies in animals and the considerable reduction in price of the so obtained radiopharmaceutical, have shown the viability of such procedure in the clinical practice as well in the veterinary clinic of small animals. By the other side, the perfusion of d,l-HMPAO99mTc showed that such a product concentrates at the same time in the cerebral area and nasal fossa, showing evidence of similar structures as the hemato encephalic barrier, also in the nasal area.

O d,1 - Hexametilpropileno oxima marcado com o tecnécio-99m(99mTc-HMPAO) é um importante radiofármaco usado tanto para imagens tomográficas cerebrais quanto na marcação in vitro" de leucócitos. A crescente utilização deste radiofármaco no estudo de doenças neurológicas no homem levou-nos à obtenção de "kits" de HMPAO para ser marcado pelo tecnécio-99m. Neste trabalho apresentamos o estudo experimental efetuado com "kits" liofilizados de d,1 HMPAO99mTc desenvolvidos em nossos laboratórios, comparando inclusive com aqueles encontrados no comércio. As imagens cerebrais inicialmente foram feitas em coelhos, entretanto os melhores resultados foram obtidos em cães. Assim, selecionaram-se seis cães sem raça definida, considerados clinicamente normais para obtenção das imagens cintilográficas do cérebro e o washout das regiões de interesse (ROls). Os estudos experimentais em animais e a considerável redução do custo do radiofármaco mostrou-nos a possibilidade da utilização destes exames na clínica veterinária, especialmente de pequenos animais. Por outro lado, a perfusão do d,l HMPAO99mTc mostra que a concentração do radiofármaco se faz ao mesmo tempo na região do cérebro e nas fossas nasais, demonstrando a existência de estruturas iguais às da barreira hemo-encefálica nesta última região.