Diagnostic value of CT, PET and combined PET/CT performed with low-dose unenhanced CT and full-dose enhanced CT in the initial staging of lymphoma.

AIM: The aim of this paper was to compare the accuracy of contrast-enhanced computed tomography (CT), positron emission tomography (PET), unenhanced low-dose PET/CT (LD-PET/CT) and full-dose enhanced PET/CT (FD-PET/CT) for the initial staging of lymphoma. METHODS: One hundred and one lymphoma patients were examined by [18F]FDG-PET/CT including unenhanced low-dose CT and enhanced full-dose CT. Each modality of PET/CT was evaluated by a nuclear medicine physician and a radiologist unaware of the other modality, while the CT and PET images were interpreted separately by another independent radiologist and nuclear medicine physician respectively. The nodal and extranodal lesions detected by each technique were compared with a reference standard. RESULTS: For nodal assessment, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative LR (LR-) of LD-PET/CT were 97%, 96%, 98%, 95%, 26 and 0.02 respectively, and those of FD-PET/CT were 97%, 97%, 98%, 95%, 36 and 0.02. These results were significantly better than those of PET (sensitivity 82%, specificity 81%, PPV 88%, NPV 72%, LR+ 4.3, LR- 0.21). Likewise, both PET/CT displayed a higher sensitivity, NPV and LR- than CT (91%, 84%, 0.1 respectively). For organ evaluation, both modalities of PET/CT also had significantly better sensitivity and NPV than that of PET (LD-PET/CT: sensitivity 92%, NPV 90%; FD-PET/CT sensitivity 94%, NPV 92%; PET: sensitivity 70%, NPV 69%). The sensitivity, specificity, PPV and NPV for bone marrow involvement were 29%, 84%, 45% and 72% respectively for PET, and 29%, 90%, 56%, and 74% for both, LD-PET/CT, and FD-PET/CT. No significant differences were found between LD-PET/CT and FD-PET/CT, but FD-PET/CT detected important incidental findings in 5.9% of patients. CONCLUSION: PET/CT is an accurate technique for the initial staging of lymphomas without significant differences between LD-PET/CT and FD-PET/CT. FD-PET/CT detects relevant incidental findings that are missed on LD-PET/CT.

[PET/CT: protocol aspects and legal controversies]. / PET/TC: aspectos de protocolo y controversias legales.

The combination of positron emission tomography (PET) and computed tomography (CT) in a single scanner (PET/CT) allows anatomic and metabolic images to be fused and correlated with a high degree of accuracy; this represents a very important landmark in the history of medicine and especially in the area of diagnostic imaging. Nevertheless, the implementation, startup, and operation of a PET/CT scanner presents particularly interesting challenges, because it involves the integration of two well-established and consolidated techniques (CT and PET, which provide complementary information) that have traditionally been carried out in the context of two different specialties (radiology and nuclear medicine). The rapid diffusion of this new integrated technology raises a series of questions related to the optimal protocols for image acquisition, the supervision of the examinations, image interpretation, and reporting, as well as questions related to the legal competence and responsibility of the specialists involved in a PET/CT study. The objective of this article is to approach these aspects from a constructive perspective and to stimulate the dialog between the specialties of radiology and nuclear medicine, with the aim of maximizing the diagnostic potential of PET/CT and thus of providing better care for patients.

PET/TC: aspectos de protocolo y controversias legales / PET/CT: protocol aspects and legal controversies

La combinación de una tomografía por emisión de positrones (PET) y de una tomografía computarizada (TC) en un único equipo (PET/TC) permite fusionar y correlacionar con un elevado grado de precisión imágenes anatómicas y metabólicas, y ha supuesto un hito reciente muy importante en la historia de la Medicina, y especialmente en el área del diagnóstico por la imagen. No obstante, la implementación, puesta en marcha y desarrollo de un equipo de PET/TC presenta desafíos particularmente interesantes, ya que supone la integración de dos técnicas diagnósticas reconocidas y consolidadas (la TC y la PET, que proporcionan información complementaria), pero que se han desarrollado tradicionalmente al amparo de dos especialidades diferentes (Radiología y Medicina Nuclear). La rápida difusión de esta nueva tecnología integrada plantea una serie de cuestiones relacionadas con los protocolos óptimos de adquisición de las imágenes, supervisión de los estudios, interpretación de las mismas, elaboración de informes y, especialmente, con la competencia y responsabilidad de los especialistas responsables de un estudio de PET/TC. El objetivo de este artículo es abordar estos aspectos desde una perspectiva constructiva, y estimular el diálogo entre las especialidades de Radiología y Medicina Nuclear, en un intento de maximizar el potencial diagnóstico de la PET/TC y así ofrecer una mejor atención a los pacientes (AU)

The combination of positron emission tomography (PET) and computed tomography (CT) in a single scanner (PET/CT) allows anatomic and metabolic images to be fused and correlated with a high degree of accuracy; this represents a very important landmark in the history of medicine and especially in the area of diagnostic imaging. Nevertheless, the implementation, startup, and operation of a PET/CT scanner presents particularly interesting challenges, because it involves the integration of two well-established and consolidated techniques (CT and PET, which provide complementary information) that have traditionally been carried out in the context of two different specialties (radiology and nuclear medicine). The rapid diffusion of this new integrated technology raises a series of questions related to the optimal protocols for image acquisition, the supervision of the examinations, image interpretation, and reporting, as well as questions related to the legal competence and responsibility of the specialists involved in a PET/CT study. The objective of this article is to approach these aspects from a constructive perspective and to stimulate the dialog between the specialties of radiology and nuclear medicine, with the aim of maximizing the diagnostic potential of PET/CT and thus of providing better care for patients (AU)

[Extraosseous accumulation of 99mTc-HMDP in knees with synovial effusion]. / Acúmulo extraóseo de 99mTc-HMDP en rodillas con derrame sinovial.

In the presence of extraosseous activity seen in the late phase of the bone scintigraphy (BS) localized in the distal femur of patients prior to radiation synovectomy, we decided to review the frequency of this finding in 20 patients (24 joints) and its relationship with scintigraphic and clinical parameters. Mild soft tissue accumulation was seen in the late phase of the BS in 14 out of 24 joints, without association between this finding and knee uptake in vascular blood pool and late phases of the BS. However, a significant association with synovial effusion was found, and patients with higher degree of effusion presented extraosseous activity more frequently. In conclusion, we think that soft tissue accumulation in the late phase of the BS is a sign of synovial effusion.

Acúmulo extraóseo de 99mTc-HMDP en rodillas con derrame sinovial / Extraosseous accumulation of 99mtc-hmpd in knees with synovial effusion

Ante la observación de actividad extraósea alrededor del tercio distal del fémur durante la fase tardía en algunos pacientes a los que se realizó una gammagrafía ósea (GO) y posterior radiosinoviortesis, revisamos en 20 pacientes (24 articulaciones) la frecuencia con la que apareció este hallazgo y su relación con parámetros gammagráficos o clínicos. Hemos encontrado una leve captación extraósea en la imagen tardía de la GO en 14 de 24 articulaciones, sin que haya existido asociación entre ésta y la intensidad de captación de la rodilla en las fases de pool vascular y tardía de la GO, pero sí con la presencia de derrame articular siendo más frecuente en aquellos con derrame más severo. En conclusión, pensamos que la presencia de captación (AU)

In the presence of extraosseous activity seen in the late phase of the bone scintigraphy (BS) localized in the distal femur of patients prior to radiation synovectomy, we decided to review the frequency of this finding in 20 patients (24 joints) and its relationship with scintigraphic and clinical parameters. Mild soft tissue accumulation was seen in the late phase of the BS in 14 out of 24 joints, without association between this finding and knee uptake in vascular blood pool and late phases of the BS. However, a significant association with synovial effusion was found, and patients with higher degree of effusion presented extraosseous activity more frequently. In conclusion, we think that soft tissue accumulation in the late phase of the BS is a sign of synovial effusion (AU)