Relevance of quantification in brain PET studies with 18F-FDG

The inclusion of ¹⁸F-FDG PET as a biomarker in the diagnostic criteria of neurodegenerative diseases and its indication in the presurgical assessment for drug-resistant epilepsies allow to improve specificity of these diagnosis. The traditional interpretation of neurological PET studies has been performed qualitatively, although in the last decade, several quantitative evaluation methods have emerged. This technical development has become relevant in clinical practice, improving specificity, reproducibility and reducing the interrater reliability derived from visual analysis. In this article we update/review the main imaging processing techniques currently used. This may allow the Nuclear Medicine physician to know their advantages and disadvantages when including these procedures in daily clinical practice.

Amyloid PET in neurodegenerative diseases with dementia

Alzheimer's disease (AD) is a neurodegenerative condition characterized by progressive cognitive decline and memory loss, and is the most common form of dementia. Amyloid plaques with neurofibrillary tangles are a neuropathological hallmark of AD that produces synaptic dysfunction and culminates later in neuronal loss. Amyloid PET is a useful, available and non-invasive technique that provides in vivo information about the cortical amyloid burden. In the latest revised criteria for the diagnosis of AD biomarkers were defined and integrated: pathological and diagnostic biomarkers (increased retention on fibrillar amyloid PET or decreased Aβ_1-42 and increased T-Tau or P-Tau in CSF) and neurodegeneration or topographical biomarkers (temporoparietal hypometabolism on ¹⁸F-FDG PET and temporal atrophy on MRI). Recently specific recommendations have been created as a consensus statement on the appropriate use of the imaging biomarkers, including amyloid PET: early-onset cognitive impairment/dementia, atypical forms of AD, mild cognitive impairment with early age of onset, and to differentiate between AD and other neurodegenerative diseases that occur with dementia. Amyloid PET is also contributing to the development of new therapies for AD, as well as in research studies for the study of other neurodegenerative diseases that occur with dementia where the deposition of Aβ amyloid is involved in its pathogenesis. In this paper, we review some general concepts and study the use of amyloid PET in depth and its relationship with neurodegenerative diseases and other diagnostic techniques.

Monitoring system for isolated limb perfusion based on a portable gamma camera

Background: The treatment of malignant melanoma or sarcomas on a limb using extremity perfusion with tumour necrosis factor (TNF-α) and melphalan can result in a high degree of systemic toxicity if there is any leakage from the isolated blood territory of the limb into the systemic vascular territory. Leakage is currently controlled by using radiotracers and heavy external probes in a procedure that requires continuous manual calculations. The aim of this work was to develop a light, easily transportable system to monitor limb perfusion leakage by controlling systemic blood pool radioactivity with a portable gamma camera adapted for intraoperative use as an external probe, and to initiate its application in the treatment of MM patients. Methods: A special collimator was built for maximal sensitivity. Software for acquisition and data processing in real time was developed. After testing the adequacy of the system, it was used to monitor limb perfusion leakage in 16 patients with malignant melanoma to be treated with perfusion of TNF-α and melphalan. Results: The field of view of the detector system was 13.8 cm, which is appropriate for the monitoring, since the area to be controlled was the precordial zone. The sensitivity of the system was 257 cps/MBq. When the percentage of leakage reaches 10% the associated absolute error is ± 1%. After a mean follow-up period of 12 months, no patients have shown any significant or lasting side-effects. Partial or complete remission of lesions was seen in 9 out of 16 patients (56%) after HILP with TNF-α and melphalan. Conclusion: The detector system together with specially developed software provides a suitable automatic continuous monitoring system of any leakage that may occur during limb perfusion. This technique has been successfully implemented in patients for whom perfusion with TNF-α and melphalan has been indicated.

[In-transit sentinel lymph nodes in malignant melanoma. What is their importance?]

The sentinel lymph node (SLN) is the first node in a lymph node basin to receive direct drainage from the primary tumour. However, in some cases, lymphoscintigraphy images demonstrate the presence of lymph nodes located in the area between the primary tumour and the first regional lymph node basin. These nodes are called in-transit nodes and have to be considered SLNs as well.

AIM

It was to determine the incidence and location of in-transit SLNs in patients with malignant melanoma and to evaluate whether it is necessary to harvest them. METHOD. Nine hundred patients with malignant melanoma were included. Lymphoscintigraphy was performed on the day before surgery following intradermal injection of 74-111 MBq of 99mTc-Nanocolloid in four doses around the primary lesion or the biopsy scar.

RESULTS

The presence of in-transit SLNs was revealed in 80 patients. During surgery, in-transit SLNs were identified and excised in all but 3 patients (96.2 %). Metastatic cell deposits were identified in these in-transit SLNs in 15 patients (19.4 %), with 4 patients with no tumour involvement of the regional lymph node basin.

CONCLUSIONS

Lymphoscintigraphy is mandatory in the location of in-transit SLNs. Moreover, although the incidence of these nodes is relatively low in malignant melanoma, the presence of metastatic cells in these in-transit SLNs reaches a significant percentage. Therefore, excision of in-transit SLNs is necessary in all cases.

[Potential use of bone marrow scintigraphy in suspected prosthetic hip infection evaluated with 99mTc-HMPAO-leukocytes]

AIM

To evaluate the usefulness of (99m)Tc-Sulphur colloid when combined with leukocyte scintigraphy in suspected prosthetic hip infection, comparing the results with information from (99m)Tc-HMPAO-leukocyte scintigraphy alone.

MATERIALS AND METHODS

Seventy patients (42 women, 28 men; mean age 68 +/- 13 years) with painful hip prostheses and suspicion of infection were evaluated prospectively. All patients had bone scintigraphy, (99m)Tc-HMPAO-labelled white blood cell scintigraphy and (99m)Tc-Sulphur colloid bone marrow scintigraphy. ESR and CRP levels were measured in all patients. The final diagnosis was made with microbiological findings or by clinical follow up of at least 12 months.

RESULTS

Infections were diagnosed in 12 of the 70 patients (3 coagulase-negative Staphylococcus, 2 Staphylococcus aureus, 2 Staphylococcus epidermidis, 2 enterococcus and 3 polymicrobial agents). ESR and CRP values were higher in patients with infection than in patients without infection (51.8 +/- 29.4 vs. 25.4 +/- 16.4 and 2.8 +/- 2.2 vs. 1.1 +/- 1.3, respectively; p < 0.05). Bone scintigraphy did not show a characteristic pattern to differentiate infection from aseptic loosening. The pool phase of the bone scintigraphy was positive in only 3/12 patients with infection (25 %). Sensitivity and specificity of the leukocyte scintigraphy was 83 % and 57 %, respectively. When the results of the bone marrow scintigraphy were added, these values increased to 92 % and 98 %, respectively.

CONCLUSION

Performing bone marrow scintigraphy significantly improves results when compared with leukocyte scintigraphy alone in the diagnosis of infected hip prostheses. Bone scintigraphy did not help to differentiate aseptic loosening from infection in this series.

[Localization of sentinel node in squamous cell carcinoma of the penis. Initial experience]

OBJECTIVE

To assess the validity of radioguided sentinel node biopsy in squamous cell penile carcinoma.

MATERIAL AND METHODS

Fifteen patients were studied. The first 5 patients were included in a group for validation of the technique, in which a standard inguinal lymphadenectomy was performed after the procedures described below. The remaining 10 patients were included in the technique application group. The day before surgery, lymphoscintigraphy was performed on all patients. During the operation, radioguided biopsy to locate the sentinel node was done. Methylene blue dye was injected shortly before surgery in 10 patients. All patients were followed for an average of 32 months.

RESULTS

In the validation group, lymphoscintigraphy revealed inguinal drainage in 5/5 patients. Unilateral metastases were detected in 3/5 patients. No metastatic nodes were detected among the nodes removed during inguinal lymphadenectomy. In the application group, lymphoscintigraphy showed inguinal drainage in 9/10 patients. Nineteen nodes were removed, none of which showed tumour involvement. During the follow-up period, no disease progression or recurrence were observed in either patient group.

CONCLUSIONS

Radioguided localization and biopsy of the sentinel nodes can avoid unnecessary lymphadenectomies in patients with squamous cell penile carcinoma and high or intermediate risk of lymph node involvement. This technique shows high reliability and negative predictive value in penile carcinoma.

Utilidad de la gammagrafía con plaquetas marcadas con 111In-oxina en el manejo del síndrome febril en pacientes en diálisis portadores de injerto renal no funcionante

AIM

To evaluate the usefulness of 111In-oxine-labelled platelet scan in the therapeutic management of prolonged febrile syndrome in dialysis patients with a non-functional renal allograft.

MATERIAL AND METHODS

One hundred and fifty-eight patients (94 men, 64 women; mean age 44 +/- 9 years) were studied. Duration of fever was 42 days (range 7-112). A total of 68 % of the patients (107/158) were on low doses of corticosteroids (<10 mg/day). Platelet scans were performed 48 hours after reinjection of 111In-ixone-labelled platelets. A platelet uptake index (PUI) was calculated by dividing the cpm/pixel in the allograft by the cpm/pixel in a mirror background. A PUI > or = 1.5 was considered as threshold for immunological fever. The final diagnosis of immunological fever was established when it disappeared after transplantectomy, embolization or high doses of corticosteroid therapy. Fever of non-immunological origin was established when it disappeared after antibiotic therapy.

RESULTS

In 102/158 patients the fever was considered of immunological origin. In 56/158 patients the fever was considered of non immunological origin. Sensitivity and the specificity of the platelet scan was 80 % and 100 %, respectively. All those patients considered as having fever of immunological origin who had PUI <1.5 had been using corticosteroids during platelet scan.

CONCLUSION

111In-labelled platelet scintigraphy is a useful technique in the therapeutic management of prolonged febrile syndrome in dialysis patients with non-functional renal allograft. The use of corticosteroids can reduce the sensitivity of 111In- labelled platelet scan.

High prevalence of oncogenic human papillomavirus in the genital tract of women with human immunodeficiency virus

OBJECTIVE

The goal of this study was to determine the prevalence of human papillomavirus (HPV) and squamous intraepithelial lesions (SILs) in women infected with human immunodeficiency virus (HIV) in Mexico.

METHODS

Cases included women who were positive for human immunodeficiency virus (HIV) and accepted to participate. There were two control groups in this study: group A, heterosexual partners of HIV+ men; group B, commercial sex workers. Gynecologic examination was performed in all participants. Also, a cervical smear with colposcopy and a sample for detection of HPV DNA by polymerase chain reaction (PCR) were obtained in all subjects, as were CD4+ counts. Relative risks (RR) and 95% confidence interval were calculated.

RESULTS

Eighty-five HIV+ women agreed to participate in this study; the route of HIV infection was heterosexual in 78.8%; transfusion in 8.2%; paid donors in 3.5%; and 9.4% unknown. A total of 9 controls were included: 4 from group A and 5 from group B. HPV DNA was detected by PCR in 57 (69%) cases and in 26 (29%) controls from both groups (P < 0.0001). The RR of HPV infection was 5.5 (2.7-11.5). Also, a significant difference in the prevalence of high-risk HPV types was observed between cases and controls, RR = 12.8 (4.07-42.9). These associations were independent of CD4+ counts and antiretroviral therapy. No association was observed between HIV infection and the risk for high-grade SIL.

CONCLUSIONS

We observed a high prevalence of oncogenic HPV types in HIV-positive women. These women should be screened regularly for early diagnosis of premalignant lesions and prevention of cervical cancer.

[Infections by anaerobes in children: frequency of isolation and antimicrobial resistance]

We studied the frequency of isolation and antimicrobial susceptibility of strict anaerobic bacteria isolated in a paediatric hospital. A total of 1,753 samples from purulent material and hemocultures were processed. One hundred and thirty strains were isolated from 95 children: 44 from 48 cases of peritonitis (91.7%), 2 from 8 brain abscesses (25%), 23 from 124 soft tissue abscesses (18.5%), 4 from 64 empyemas or lung abscesses (6.3%) and 22 from 1,509 hemocultures (1.5%). Mixed infection (anaerobic and aerobic bacteria) was detected in 38.5% of the cases; however, in peritonitis 81.3% of the cases showed mixed infection. The more frequently isolated bacteria were: Bacteroides (44.6%), Clostridium (19.2%), Fusobacterium (7.7%) and gram positive cocci (7.7%). Propionibacterium acnes was isolated in 15 specimens; however, most of them were considered as contamination. Bacteroides was isolated more frequently from patients with peritonitis (51.6%). The susceptibility to five antibiotics was tested in 124 strains using the method of serial dilutions in agar plates. The genus Bacteroides showed a high resistance to penicillin (73.1%), moderate to clindamycin (11.5%) and low to cefoxitin, chloramphenicol and metronidazole (6.8%, 2% and 5.8%). The rest of the anaerobic strains tested (other gram negatives and grampositives) were highly sensitive to all the antimicrobials tested, except for clindamycin (26.7% and 36.9% resistance, respectively). Cefoxitin, chloramphenicol and metronidazole had the lower CMI50 and CMI90 for the genus Bacteroides; and for the rest of the bacteria, penicillin had the highest activity (CMI90 less than 0.025). Since the frequency of isolation of anaerobic bacteria in children with severe infections, presumably originated from the digestive tract, paranasal sinus and middle ear is high, anaerobic cultures must be practiced in these patients. Empiric antimicrobial treatment should also be started. This treatment should be with penicillin when the probability of isolation of Bacteroides is low (infections in the face, neck, thorax and soft tissues) and with metronidazole in intraabdominal infections. Because of the severity and probable etiology of brain abscesses, treatment with penicillin and chloramphenicol or metronidazole is recommended in these cases.