Bone involvement in patients with lymphoma: the role of FDG-PET/CT

Purpose To evaluate the diagnostic impact and clinical significance of FDG-avid bone lesions detected by FDG-PET/CT in patients with lymphoma. Methods The study population comprised 50 consecutive patients (mean age 41.7±15.5 years; 27 female, 23 male; 41 staging, 9 restaging) with Hodgkin’s disease (n=22) or aggressive non-Hodgkin’s lymphoma (n=28) in whom FDG-avid bone lesions were detected by FDG-PET/CT. All patients had either direct biopsy of the FDG-avid bone lesion (n=18), standard bone marrow biopsy at the iliac crest (BMB; n=43) or both procedures (n=11). In 15 patients, additional MRI of the bone lesions was performed. All patients underwent FDG-PET/CT after the end of treatment. All CT images of FDG-PET/CT scans were analysed independently regarding morphological osseous changes and compared with FDG-PET results. Results In the 50 patients, 193 FDG-avid lesions were found by PET/CT. The mean standardised uptake value was 6.26 (±3.22). All direct bone biopsies (n=18) of the FDG-avid lesions proved the presence of lymphomatous infiltration. BMB (n=43) was positive in 12 patients (27.9%). In CT, 32 of 193 (16.6%) lesions were detected without the PET information. No additional morphological bone infiltration was detected on CT compared with FDG-PET. All morphological bone alterations on CT scans persisted after the end of therapy. Additional PET/CT information regarding uni- or multifocal bone involvement resulted in lymphoma upstaging in 21 (42%) patients compared with the combined information provided by CT and BMB. Conclusion In patients with FDG-avid bone lesions, FDG-PET is superior to CT alone or in combination with unilateral BMB in detecting bone marrow involvement, leading to upstaging in a relevant proportion of patients.     

<Superscript>18</Superscript>F-FDG PET/CT in paediatric lymphoma: comparison with conventional imaging

Purpose  

In children with Hodgkin’s disease and non-Hodgkin’s lymphoma, the ability of ¹⁸F-fluoro-2-deoxy-D-glucose PET/CT and conventional imaging (CI) to detect malignant lesions and predict poor lesion response to therapy was assessed and compared.     

Value of PET/CT versus PET and CT performed as separate investigations in patients with Hodgkin’s disease and non-Hodgkin’s lymphoma

Purpose The aim of this study was to assess the clinical benefit of combined [¹⁸F]FDG PET/CT in patients with malignant lymphoma as compared to separately performed PET and CT. Methods Overall, 100 patients with Hodgkin’s disease (HD) or non-Hodgkin’s lymphoma (NHL) were included in this study. Co-registered PET/CT with [¹⁸F]FDG and contrast medium was performed in 50 consecutive patients with NHL (n=38) or HD (n=12) for initial staging (IS) (n=12) or re-treatment staging (RS) (n=38). Another 50 patients with NHL (n=32) or HD (n=18) underwent separate PET and CT investigations within a time frame of 10 days for IS (n=22) or RS (n=28). Lymphoma involvement was separately evaluated for seven different regions in each patient. Each patient had clinical follow-up evaluation for >6 months. PET and CT data were analysed separately as well as side-by-side or in fused mode. Results In the PET/CT group, region-based evaluation for lymphoma involvement suggested a sensitivity/specificity of 85%/91% for CT, 98%/99% for PET and 98%/99% for PET/CT. In the PET and CT group, region-based evaluation showed a sensitivity/specificity of 87%/80% for CT, 98%/99% for PET and 98%/100% for PET and CT read side by side. Conclusion PET was superior to CT alone and was improved further by side-by-side reading of both examinations. However, no significant difference was observed between PET/CT and separate PET and CT imaging in patients with lymphoma. Christian la Fougère and Walter Hundt contributed equally to this work.     

Mucosa-associated lymphoid tissue lymphoma studied with FDG-PET: a comparison with CT and endoscopic findings

OBJECTIVE: We investigated the accumulation of 2-deoxy-2-[(18)F] fluoro-D: -glucose positron emission tomography (FDG-PET) in patients with mucosa-associated lymphoid tissue (MALT) lymphoma patients as compared with computerized tomography (CT) and endoscopic imaging. METHODS: FDG-PET was performed on 13 untreated patients with MALT lymphoma. CT scanning of the affected areas was performed in all the patients to compare with the FDG-PET images. In five patients with gastric MALT lymphoma, comparison was also made with the endoscopic findings. RESULTS: Of the 13 untreated MALT lymphoma patients, all 8 non-gastric MALT lymphoma patients exhibited abnormal accumulation of FDG. However, in the five gastric MALT lymphoma patients, no abnormal FDG accumulation was observed. Although lesions could be confirmed on CT images from the patients other than those with gastric MALT lymphoma, the mucosal lesions of gastric MALT lymphoma could be observed only by endoscopy. CONCLUSIONS: FDG-PET can be used to detect MALT lymphoma when it forms mass lesions, whereas it is difficult to detect non-massive MALT lymphoma of gastrointestinal origin.     

Usefulness of 18F-FDG PET/CT for the Evaluation of Bone Marrow Involvement in Patients with High-Grade Non-Hodgkin’s Lymphoma

Purpose

To assess the usefulness of ¹⁸F-fluorodeoxyglucose PET/CT in the detection of bone marrow (BM) involvement of high-grade non-Hodgkin’s lymphoma (NHL).

Methods

One hundred twenty patients with newly diagnosed diffuse large B-cell lymphoma or peripheral T-cell lymphoma between January 2007 and June 2011, who received BM trephine biopsy and ¹⁸F-FDG PET/CT before chemotherapy, were included in this retrospective study. We reviewed their ¹⁸F-FDG PET/CT images and bone marrow biopsy (BMB) results. After reviewing the images, we reviewed the medical records and radiological findings of interesting patients.

Results

There were 23 ¹⁸F-FDG PET/CT scans in which the marrow was considered to be abnormal (either positive or equivocal), and 97 ¹⁸F-FDG PET/CT scans were regarded as having negative FDG uptake. Of 120 patients, 100 (83.3 %) had a concordant result of BM interpretation between ¹⁸F-FDG PET/CT and BMB, and the remaining 20 patients had discordant results. Among 23 patients with either positive or equivocal ¹⁸F-FDG PET/CT scans, 1 of 12 patients with ‘positive’ ¹⁸F-FDG PET/CT had a lymphomatous involvement on BMB. In contrast, 10 of 11 patients with ‘equivocal’ BM hypermetabolism were reported as having positive involvement by BMB. Patients with abnormal ¹⁸F-FDG PET/CT had significantly higher mSUV_highest than those with normal FDG-PET/CT.

Conclusions

¹⁸F-FDG PET/CT and BMB are complementary techniques in assessing the presence of BM involvement in patients with high-grade NHL. The increasing availability of ¹⁸F-FDG PET/CT will raise the need for additional biopsy for FDG-avid lesions, especially in patients with negative standard BMBs. ¹⁸F-FDG PET/CT can be useful as a decision-making tool for determining whether to perform a standard BMB or targeted biopsy to the FDG-avid lesion as an initial staging procedure. A direct bone biopsy for FDGpositive bone lesions should be included in staging guidelines in future. In ¹⁸F-FDG PET/CT-negative cases, BMB is still a powerful procedure, but BMB alone is insufficient for full evaluation of BM.     

FDG-PET/CT imaging in the management of HIV-associated multicentric Castleman’s disease

Purpose  To evaluate the role of FDG-PET/CT scanning in the management of HIV-associated multicentric Castleman’s disease (MCD) a rare lymphoproliferative disorder associated with infection by human herpesvirus 8 (HHV8). Materials and methods  Nine patients with histologically confirmed MCD underwent fused FDG-PET/CT scans at initial MCD diagnosis (n = 3), at MCD relapse (n = 4), or during remission (n = 2). All seven patients with active MCD had markedly elevated plasma HHV8 viral loads, but the patients in remission had no HHV8 viraemia. The three patients with newly diagnosed MCD were not on antiretroviral therapy at the time of imaging, but the other six were all on fully suppressive antiretroviral regimens. Results  In the seven patients with active MCD (newly diagnosed or relapse) 33/91 lymph node groups (36%) included radiologically enlarged nodes on the CT scan, whilst 57/91 lymph node groups (63%) showed enhanced FDG uptake on the PET scan. In scans from patients in remission, there were no enlarged lymph nodes on the CT scan but 3 lymph nodes (11%) demonstrated enhanced FDG uptake. The median SUV recorded for the seven patients with active MCD was 4.8 (range 2.6–9.3) which was significantly higher than the median value of 2.5 recorded for the patients in remission (Mann-Whitney U test, p = 0.011). Conclusion  Despite the small number of patients, in HIV-positive individuals with active MCD, FDG-PET scans more frequently detected abnormal uptake than CT scans detected enlarged lymph nodes. FDG-PET scanning has a useful role in the management of HIV-associated MCD in selecting appropriate sites for biopsy, and in staging and monitoring these lymphoproliferations.     

Brown fat in breast cancer patients: analysis of serial 18F-FDG PET/CT scans

Purpose It has recently been suggested that FDG accumulation in the brown adipose tissue varies as a function of age, sex and outdoor temperature. The aim of this study was to assess changes in FDG uptake in brown fat in patients based on serial PET/CT scans and to compare our results with previous findings. Methods Early response to neoadjuvant chemotherapy in 33 female breast cancer patients was assessed by FDG PET. Five PET/CT scans were performed for each patient. PET/CT images were analysed retrospectively. PET scans were considered positive when diffuse, symmetrical, abnormal “USA” (uptake in supraclavicular area) fat was detected. Results A total of 163 PET images were analysed. Seventy-four PET scans (45%) revealed abnormal FDG uptake in the supraclavicular area. These foci were present on uncorrected and attenuation-corrected images. FDG uptake was identical on all five scans in only five patients. No significant relationship was found between abnormal FDG uptake and outdoor temperature, age or time interval between chemotherapy and PET. Abnormal FDG uptake in the neck seemed to predominantly occur in patients with a low body mass index (p<0.05). Most significant changes in the PET/CT scan results were observed during chemotherapy with docetaxel (p<0.05). When observed, bilateral uptake in the neck was more intense than background uptake (p<0.00001). Conclusion This study shows that FDG uptake in the neck varies as a function of time, that it is unrelated to age or outdoor temperature, and that bilateral uptake is generally intense.     

Demonstrations of AIDS-associated malignancies and infections at FDG PET-CT

HIV infection results in profound alterations of immunologic function that render the patient severely immunocompromised, and susceptible to malignancies and opportunistic infections. Three AIDS-defining malignancies include Kaposi’s sarcoma (KS), non-Hodgkin’s lymphoma (NHL) and invasive cervical cancer. In AIDS patients, KS is often aggressive and multifocal, with visceral involvement and widespread cutaneous and nodal spread; NHL is always high grade and often widely disseminated at the time of diagnosis with frequent involvement of extranodal sites; cervical cancer is invasive and has greater likelihood of progression and metastasis. Although there are very sparse systemic data available in the literature, limited studies has shown that FDG PET-CT is a valuable imaging technique in the diagnosis, staging, restaging and monitoring therapeutic response in these malignancies. In addition, a unique application of FDG PET/CT is the differentiation of cerebral lesions between lymphoma and toxoplasmosis in AIDS patients, which cannot be reliably achieved with either CT or MRI. HIV-associated opportunistic infections may involve different pathogens and multiple tissues, organs or systems. Some preliminary observations have revealed a promising role of FDG PET-CT in the diagnosis and identification of these infections such as tuberculosis, fever of unknown origin, pneumocystis pneumonia and candidiasis. However, it should be stressed that FDG PET-CT alone has no role in identifying the pathology of abnormalities. FDG PET-CT, at best, can localize the sites of abnormalities and impact on patient’s management in clinical decision making.     

The impact of FDG positron emission tomography imaging on the management of lymphomas

The role of 2-(F-18)-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) imaging in the management of patients with lymphoma has been evaluated. 29 patients (12 Hodgkin's disease, 17 non-Hodgkin's lymphoma (NHL)) who underwent FDG-PET imaging during their lymphoma treatment programme were reviewed retrospectively. Correlation between FDG-PET and CT was evaluated, together with the impact upon clinical management of the findings on FDG-PET imaging. FDG-PET added extra information to the findings on clinical examination and CT in 12 patients (41%). This was seen both in patients with negative and positive CT scan. Two false positive FDG-PET scans were seen, reflecting FDG uptake in extranodal sites. Information from FDG-PET imaging resulted in a change in clinical management in 10 patients (34%); in two, initial management was altered, and in eight consolidation therapy after completion of initial chemotherapy was influenced. These changes in clinical management occurred in six patients with high grade NHL, two with low grade NHL and two with Hodgkin's disease. No specific subgroup was identified in whom FDG-PET was particularly discriminant.     

Comparison of imaging with FDG PET/CT with other imaging modalities in myeloma

Objective To determine the usefulness of FDG PET/CT scanning in the management and staging of myeloma and to assess its strengths and limitations.Design FDG PET/CT scans and all other available imaging studies were reviewed retrospectively from 16 consecutive patients by two experienced musculoskeletal radiologists and two nuclear medicine physicians working in consensus.Patients The 16 patients had undergone a total of 19 FDG PET/CT scans. Radiographs were available in all cases, including 13 skeletal surveys; 25 CT scans (16 chest, three abdominal, four pelvic, one spine, one neck) and 22 MR imaging studies (17 spine, three pelvic, two extremity) also were reviewed. Patients’ records were examined for relevant clinical information. All focal areas of abnormal FDG uptake were correlated with the other imaging studies to determine clinical significance. FDG PET/CT scans also were reviewed to see if small lesions shown on the other imaging studies could be identified in retrospect.Results The 12 men and four women had an average age of 58 years (range 30–69 years). All 16 patients had an established diagnosis of multiple myeloma, with average duration of disease, from time of initial diagnosis to review, of 30 months (range 6 months to 11+ years). The FDG PET/CT scans revealed a total of 104 sites (90 in bone, 14 soft tissue) that were suspicious for neoplastic activity based on a standardized uptake value (SUV) greater than 2.5. Fifty-seven of these sites (55%) were new or previously undetected. The other imaging studies (X-ray, CT, MR) and clinical information confirmed the other 47 areas but also revealed 133 other small skeletal lesions. Six of these 133 additional lesions showed mild FDG uptake on re-review of the PET/CT scans. The FDG PET/CT findings led to management changes in 9/16 patients. MR imaging revealed five cases of diffuse bone involvement (four spine, one scapula) that were not evident by FDG PET/CT.Conclusion FDG PET/CT scans are useful for the management and staging of myeloma. However, if PET/CT were the sole imaging study done, it would miss many additional small lytic skeletal lesions and could miss diffuse spine involvement.     

Comparison of 18F-FDG-PET and standard procedures for the pretreatment staging of children and adolescents with Hodgkin’s disease

Purpose The aim of this study was to perform a prospective, blinded comparison of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) and conventional staging methods (CSMs) for initial staging of children and adolescents with Hodgkin’s disease (HD). Methods Over a period of 4 years, 55 children and adolescents with HD (mean age 15.5 years, range 3.9–18.9 years) were prospectively recruited into the study. They underwent 61 FDG-PET studies using a dedicated whole-body PET scanner as a part of their initial staging work-up. PET findings were correlated with the results of CSMs, including computed tomography (CT), ultrasound, bone scanning and bone marrow examination. Discordant findings were resolved by magnetic resonance imaging or clinical follow-up (range 2–47 months). Results PET correctly changed the staging in 15% of patients (seven upstagings, two downstagings). Only two out of 61 patients (3%) were not accurately staged by PET; in these children, PET missed small lymphoma nodules detected on lung CT. The sensitivity of PET and CSMs for pretreatment staging was 96.5% and 87.5%, respectively; specificity was 100% and 60%, and accuracy, 96.7% and 85.2%, respectively. Upon combination of FDG-PET and lung CT, the diagnostic accuracy reached 100% in our series. Conclusion Our study showed that whole-body FDG-PET is an efficient and useful method for the initial staging of children with HD. FDG-PET in combination with lung CT should be recommended as a screening method prior to other conventional imaging modalities to plan a rational staging protocol. Large multicentre prospective studies are necessary to verify this conclusion.     

A case of pulmonary choriocarcinoma metastasis with unusual FDG-PET and CT findings: correlation with pathology

A 26-year-old female who had had a hydatidiform mole at 20?years of age showed high levels of serum human chorionic gonadotropin. Because pelvic ultrasound did not show any gestational sac in her uterus, she was suspected to have had an extrauterine pregnancy and a spontaneous abortion. About 6?months later, a pulmonary nodule in the patient??s right upper lung field was found on a routine chest X-ray film. Contrast- enhanced CT scans revealed a solitary lobulated nodule 2.0?×?1.3?×?3.0?cm in diameter in the S2 segment of the right lung. CT suggested a vessel malformation. Positron emission tomography using 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG-PET) was performed and showed weak FDG accumulation (SUVmax?=?2.0) in the nodule, which did not positively indicate malignancy. Because a follow-up CT showed a rapid increase in the size of the nodule, partial resection of S2 segment in the right upper lobe was performed. The histopathological diagnosis was a metastasis from choriocarcinoma. The tumor consisted largely of necrosis and hemorrhage, and it was considered to be a major cause of the unusual FDG-PET and CT findings.     

Drug-induced pneumonitis detected earlier by 18F-FDG-PET than by high-resolution CT: a case report with non-Hodgkin’s lymphoma

Drug-induced pneumonitis is a serious and an unpredictable side effect of chemotherapy in patients with malignant lymphoma. We present the case of a 51-year-old man who developed drug-induced pneumonitis during chemotherapy for non-Hodgkin’s lymphoma in which pneumonitis was detected earlier by ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) than by high-resolution computed tomography (HRCT). After five courses of chemotherapy, ¹⁸F-FDG-PET was performed for assessing residual lesions, and diffuse lung uptake was incidentally observed. No symptoms were present, and HRCT performed immediately following PET revealed no abnormalities. Mild dyspnea appeared 3 days after PET, and additional HRCT revealed patchy ground-glass opacities disseminated with the appearance of interlobular septum thickening. Drug-induced pneumonitis was finally diagnosed, and treatment was initiated. ¹⁸F-FDG-PET can be an imaging modality for detecting drug-induced pneumonitis at an extremely early stage in which HRCT is incapable of revealing any abnormal changes.     

Role of whole body FDG-PET imaging in predicting relapse of malignant lymphoma in patients with residual masses after treatment

Purpose: The present study investigated the utility of whole body positron emission tomography (PET) with 2-[¹⁸F]-fluoro-2-deoxy-D-glucose (FDG) in predicting relapse of malignant lymphoma in patients with residual masses persisting after treatment.Methods: Thirty-six patients with Hodgkin's disease (n=14) or non-Hodgkin's lymphoma (n=22) were prospectively enrolled and subjected to 1–4 FDG-PET imaging sessions after completion of therapy. A residual mass had been previously demonstrated in all patients by computed tomography (CT). Sensitivity, specificity, positive and negative predictive value of the method are reported. Tumour-to-normal soft-tissue contrast ratios (TCR) were measured by region of interest (ROI) as a quantitative approach to the evaluation of PET images in patients with positive FDG uptake.Results: Twenty-five of 27 patients with negative FDG-PET after treatment remained in complete remission (CR), and only two patients relapsed. In contrast, of the nine patients with positive scans, four patients retained their CR status, while five showed evidence of relapse. Overall, the sensitivity of FDG-PET was 71%, specificity 86%, negative predictive value 93% and positive predictive value 56%. The probability of relapse-free survival was significantly (P=0.0057) predicted by a negative FDG-PET. High FDG uptake in the residual tumours was not associated with a high relapse rate (P=0.117).Conclusion: These studies demonstrate that lack of FDG uptake in residual masses after completion of treatment is associated with a high probability of long-term disease-free survival. Furthermore, when comparing results of FDG-PET imaging with those obtained by CT, our data emphasize that the demonstration of a mass on CT does not necessarily imply the persistence of residual disease.     

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.     

Bone marrow involvement in diffuse large B-cell lymphoma: correlation between FDG-PET uptake and type of cellular infiltrate

Purpose  To assess, in patients with diffuse large B-cell lymphoma (DLBCL), whether the low sensitivity of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) for bone marrow assessment may be explained by histological characteristics of the cellular infiltrate. Methods  From a prospective cohort of 110 patients with newly diagnosed aggressive lymphoma, 21 patients with DLBCL had bone marrow involvement. Pretherapeutic FDG-PET images were interpreted visually and semiquantitatively, then correlated with the type of cellular infiltrate and known prognostic factors. Results  Of these 21 patients, 7 (33%) had lymphoid infiltrates with a prominent component of large transformed lymphoid cells (concordant bone marrow involvement, CBMI) and 14 (67%) had lymphoid infiltrates composed of small cells (discordant bone marrow involvement, DBMI). Only 10 patients (48%) had abnormal bone marrow FDG uptake, 6 of the 7 with CBMI and 4 of the 14 with DBMI. Therefore, FDG-PET positivity in the bone marrow was significantly associated with CBMI, while FDG-PET negativity was associated with DBMI (Fisher’s exact test, p=0.024). There were no significant differences in gender, age and overall survival between patients with CBMI and DBMI, while the international prognostic index was significantly higher in patients with CBMI. Conclusion  Our study suggests that in patients with DLBCL with bone marrow involvement bone marrow FDG uptake depends on two types of infiltrate, comprising small (DBMI) or large (CBMI) cells. This may explain the apparent low sensitivity of FDG-PET previously reported for detecting bone marrow involvement.     

Intravascular large B-cell lymphoma with diffuse FDG uptake in the lung by 18FDG-PET/CT without chest CT findings

We report a rare case of intravascular large B-cell lymphoma (IVLBCL) with diffuse fluorodeoxyglucose (FDG) uptake in the lung by (18)FDG-positron emission tomography/computed tomography (PET/CT). CT showed nodular shadow, whereas diffuse FDG uptake in PET/CT suggested IVLBCL in the lung. A random skin biopsy provided histological evidence of IVLBCL. The patient responded well to combination chemotherapy. Only two cases of IVLBCL in which diffuse pulmonary FDG uptake was demonstrated have been reported previously. FDG-PET/CT plus random skin biopsy may be useful for the early diagnosis of IVLBCL with pulmonary involvement even without convincing radiological findings in the lung.     

18F-FDG PET in malignant lymphoma: significance of positive findings

Purpose The aim of this study was to evaluate the significance of increased uptake of ¹⁸F-fluorodeoxyglucose (FDG) in patients with malignant lymphoma (ML) studied by positron emission tomography (PET).Methods A total of 1,120 consecutive scans carried out in 848 patients were reviewed; all patients had a diagnosis of ML [574 non-Hodgkins lymphoma (NHL) and 274 Hodgkins disease (HD)] and were studied at completion of therapy, for suspected recurrence or during follow-up. PET was carried out after intravenous injection of 370 MBq of ¹⁸F-FDG; images were recorded after 60–90 min. Patients were selected whose reports indicated areas of increased FDG uptake. PET findings were considered positive for lymphomatous localisation when uptake occurred at sites of previous disease, in asymmetrical lymph nodes or in nodes unlikely to be affected by inflammation (mediastinal, except for hilar, and abdominal). PET findings were adjudged negative for neoplastic localisations in the following instances: physiological uptake (urinary, muscular, thymic or gastrointestinal in patients without MALT), symmetrical nodal uptake, uptake in lesions unrelated to lymphoma that had already been identified by other imaging methods at the time of PET scan, uptake at sites atypical for lymphoma, very low uptake and non-focal uptake. PET findings were compared with the results of other diagnostic procedures (including CT and ultrasound), biopsy findings and follow-up data.Results Overall, 354 scans (in 256 patients) showed increased FDG uptake (244 scans in NHL and 110 in HD): in 286 cases, FDG uptake was considered pathological and indicative of ML, in 41 cases the findings were described as uncertain or equivocal and in 37 cases, FDG uptake was considered unrelated to ML (in ten scans, concurrent findings of abnormal FDG uptake attributed to ML and uptake assigned to other causes were obtained) . Of the 286 patients with positive PET findings, 274 (95.8%) were found to have residual or recurrent ML (i.e. true positives). Four of the 41 patients with inconclusive findings turned out to have ML, while in 13 patients, pathological processes other than ML could be identified as the cause of FDG uptake. ML was excluded in all patients with findings reported as non-pathological (100% true-negative rate). Therefore, the false-positive rate in our series was about 5%. The main cause of increased FDG uptake mimicking ML was inflammation.Conclusion Our data confirm that ¹⁸F-FDG-PET has very high but not absolute specificity for ML. As already suggested, increased FDG uptake may also be observed in patients without active disease; in most cases, however, non-pathological FDG accumulation is properly identified. Less frequently, inconclusive scans are encountered; these cases are usually caused by inflammation, which subsequently resolves.     

Role of attenuation correction for fluorine-18 fluorodeoxyglucose positron emission tomography in the primary staging of malignant lymphoma

Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has been shown to improve the diagnostic accuracy in the staging of malignant lymphomas, based on the metabolic signal of the lesions. This study was undertaken to determine the effect of attenuation correction in the detection of nodal and extranodal lesions in the primary staging of malignant lymphomas. Fifty-one untreated patients with either non-Hodgkin lymphoma (NHL, n=29) or Hodgkin’s disease (n=22) were retrospectively evaluated. Static FDG-PET imaging of the trunk was performed following administration of 250–350 MBq FDG. Attenuation correction was performed in all patients. Images were reconstructed iteratively with or without transmission scans. Image evaluation was performed independently by two observers, who each examined one set of images (i.e. attenuation-corrected or uncorrected). The final decision as to whether results were discordant was reached by consensus of both observers. Out of 593 evaluated lymph node regions, 187 regions of increased FDG uptake were identified by both techniques. Differences between the readers concerned mainly the anatomical assignment of lesions (n=33) or the status (benign/malignant) of individual lesions (n=24). However, direct comparison of the two sets of images demonstrated very similar lesion contrast on attenuation-corrected and non-attenuation-corrected images. Real differences could be determined only in five regions (neck, 1; mediastinum, 1; upper abdomen, 3). Thirty-seven extranodal lesions (including lung, liver, spleen, bone marrow and soft tissue) were detected by both techniques without significant differences. It is concluded that in this study, attenuation correction did not improve the diagnostic accuracy of FDG-PET in the detection of lymph node or organ involvement during the primary staging of malignant lyphomas. Of more importance seemed to be the experience of the reader regarding the classification of a lesion’s status the anatomical assignment, knowledge of physiological uptake and artefacts, and systematic and skilful examination of all regions scanned. Received 1 July and in revised form 19 September 1998     

Hodgkin disease: diagnostic value of FDG PET/CT after first-line therapy--is biopsy of FDG-avid lesions still needed?

PURPOSE: To retrospectively determine the sensitivity and specificity of co-registered fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in patients with Hodgkin lymphoma after first-line therapy, with use of clinical follow-up or biopsy results as the reference standard. MATERIALS AND METHODS: Informed consent was obtained for imaging and included consent to use patient data for research purposes. Institutional review board approval was obtained. Between May 2001 and July 2005, the data for all patients (n=66) at the authors' institution with proved Hodgkin lymphoma after first-line therapy were retrospectively reviewed. PET/CT scans were evaluated for the presence of abnormal FDG uptake and residual masses after the end of treatment and at further follow-up. All patients with pathologic FDG lesions underwent surgical biopsy for histopathologic confirmation. All patients with negative PET/CT scans at follow-up were evaluated for disease-free survival. RESULTS: An FDG-avid lesion was detected at PET/CT in 27 of the 66 patients (mean age +/- standard deviation, 33.0 years +/- 12.2). Recurrence of Hodgkin lymphoma was confirmed with biopsy in 23 of the 27 patients. The mean maximum standardized uptake value (SUV) of the histopathologically proved lesions was 7.32 (+/-2.01). Four patients had false-positive findings at PET/CT: Biopsy revealed only inflammatory changes, and the mean maximum SUV was 7.30 (+/-2.53). Thirty-nine patients (mean age, 36.7 years +/- 10.8) did not have FDG-avid lesions and remained free of disease after a mean clinical follow-up of 26.2 months (+/-12.5) (specificity, 91% [39 of 43 patients]; sensitivity, 100% [23 of 23 patients]). The presence of bulky disease (>5 cm) after the end of treatment was a significant predictor of recurrent disease (P<.05). CONCLUSION: The authors conclude that FDG PET/CT can help exclude persistent and/or recurrent Hodgkin lymphoma after first-line therapy. Because of the false-positive results and the toxicity of salvage chemotherapy, including high-dose chemotherapy with autologous stem cell support, biopsy of the FDG-avid lesion is still needed.