Can a penalized-likelihood estimation algorithm be used to reduce the injected dose or the acquisition time in 68Ga-DOTATATE PET/CT studies?

BACKGROUND: Image quality and quantitative accuracy of positron emission tomography (PET) depend on several factors such as uptake time, scanner characteristics and image reconstruction methods. Ordered subset expectation maximization (OSEM) is considered the gold standard for image reconstruction. Penalized-likelihood estimation (PL) algorithms have been recently developed for PET reconstruction to improve quantitation accuracy while maintaining or even improving image quality. In PL algorithms, a regularization parameter ß controls the penalization of relative differences between neighboring pixels and determines image characteristics. In the present study, we aim to compare the performance of Q.Clear (PL algorithm, GE Healthcare) and OSEM (3 iterations, 8 subsets, 6-mm post-processing filter) for 68Ga-DOTATATE (68Ga-DOTA) PET studies, both visually and quantitatively. Thirty consecutive whole-body 68Ga-DOTA studies were included. The data were acquired in list mode and were reconstructed using 3D OSEM and Q.Clear with various values of ß and various acquisition times per bed position (bp), thus generating images with reduced injected dose (1.5 min/bp: ß = 300-1100; 1.0 min/bp: ß = 600-1400 and 0.5 min/bp: ß = 800-2200). An additional analysis adding ß values up to 1500, 1700 and 3000 for 1.5, 1.0 and 0.5 min/bp, respectively, was performed for a random sample of 8 studies. Evaluation was performed using a phantom and clinical data. Two experienced nuclear medicine physicians blinded to the variables assessed the image quality visually. RESULTS: Clinical images reconstructed with Q.Clear, set at 1.5, 1.0 and 0.5 min/bp using ß = 1100, 1300 and 3000, respectively, resulted in images with noise equivalence to 3D OSEM (1.5 min/bp) with a mean increase in SUVmax of 14%, 13% and 4%, an increase in SNR of 30%, 24% and 10%, and an increase in SBR of 13%, 13% and 2%. Visual assessment yielded similar results for ß values of 1100-1400 and 1300-1600 for 1.5 and 1.0 min/bp, respectively, although for 0.5 min/bp there was no significant improvement compared to OSEM. CONCLUSION: 68Ga-DOTA reconstructions with Q.Clear, 1.5 and 1.0 min/bp, resulted in increased tumor SUVmax and in improved SNR and SBR at a similar level of noise compared to 3D OSEM. Q.Clear with ß = 1300-1600 enables one-third reduction of acquisition time or injected dose, with similar image quality compared to 3D OSEM.

Anatomic Asymmetry in Sentinel Lymph Node Detection in Endometrial Cancer.

STUDY OBJECTIVE: To determine whether the concomitant use of indocyanine green (ICG) with technetium-99m-filtered sulfur colloid (Tc99m-FSC) improves bilateral sentinel lymph node (SLN) detection rate in endometrial cancer and whether anatomic concordance of pelvic lymph nodes exists and can be used to predict SLN location in cases of unilateral mapping failure. DESIGN: Retrospective cohort study. SETTING: Tertiary academic medical center in Holon, Israel. PATIENTS: Patients diagnosed with endometrial cancer, who underwent SLN mapping with Tc99m-FSC, ICG, or both, at our center between 2014 and 2019. INTERVENTIONS: A total of 111 patients were included in the study. SLN mapping using Tc99m-FSC was performed in 101 (91.9%) patients, and ICG injection was given to 64 (57.6%) patients of whom 55 (49.5%) received both. We compared SLN detection rates (unilateral and bilateral) and anatomic symmetry for each method alone and for a combination of the 2. MEASUREMENTS AND MAIN RESULTS: The overall detection rate for unilateral SLNs was 96.4%; 96.9% with ICG, 93.1% with gamma-probe, and 98.2% by combining both methods. The total bilateral detection rate was 72.1%, with ICG performing better as a single tracer than Tc99m-FSC (75% vs 63.4%, respectively). In 55 women in whom both tracers were used, the bilateral detection rate was significantly higher compared with Tc99m-FSC alone. Symmetric pelvic anatomic concordance of SLN was found in only 35 of 80 patients with bilateral SLN detection (43.8%). CONCLUSION: The combination of preoperative radioisotope injection and intraoperative ICG administration may yield the best bilateral SLN detection rate. In cases of unilateral mapping failure, one cannot rely on the anatomic location of the ipsilateral SLN detected to harvest the complementary node because the symmetric concordance is poor.

PET/CT in Disease Detection and Follow-up of Subcutaneous Involvement in Marginal Zone Lymphoma.

BACKGROUND: The value of positron emission tomography/computed tomography (PET/CT) in the staging and assessment of treatment response in marginal zone lymphoma (MZL) lymphomas remains controversial. We investigated radiologic characteristics of subcutaneous MZL as imaged on PET/CT scans. PATIENTS AND METHODS: From the records of a single medical center, for the years 2008 and 2017, we identified subcutaneous lesions in PET/CT scans of patients with histopathologically confirmed MZL in sites other than subcutaneous tissue. RESULTS: Of 571 scans of 178 patients, subcutaneous lesions were found in 20 (11%). Lesions were located in soft tissue structures, mainly along the lateral aspects of the buttocks, thighs and lower and upper back areas, the flank, and the shoulders. Median lengths of the long and short axes of the lesions were 2.0 (range, 1.1-6.0) cm and 0.8 (range, 0.3-2.0) cm, respectively. Median standardized maximum uptake value was 2.3 (range, 0.9-7.6). In 12 patients (60%), MZL was diagnosed at an early stage; 15 (75%) had lymph node involvement and 10 (50%) extranodal involvement. One had spleen and 2 had cutaneous involvement; none had gastric findings. CONCLUSION: The findings of this study support the usefulness of PET/CT in the detection of subcutaneous MZL as well as in staging and treatment decisions.

Gallium-68 prostate-specific membrane antigen PET-CT and the clinical management of prostate cancer.

OBJECTIVES: The purpose of this study was to evaluate the use of Gallium-68 prostatic-specific membrane antigen (PSMA) PET-computerized tomography (CT) in patients with prostate cancer undergoing imaging for initial staging, biochemical failure or the evaluation of metastatic disease. METHODS: This is a single institution retrospective study of 95 patients with prostate cancer who were referred for PSMA PET-CT scans. The National Comprehensive Cancer Network guidelines were used to generate treatment recommendations. Univariate and multivariate statistical analyses were performed to identify parameters associated with positive findings on a PET-CT PSMA scan. RESULTS: Mean age, Gleason score, and median prostate serum antigen (PSA) were: 72 years, 7.6 and 4 ng/ml, respectively. PSMA PET-CT was positive in 75.5% of the patients. A maximum standardized uptake value was 10.7 ± 8.8. PSMA avidity increased with rising PSA level: PSA ≤ 1 ng/ml: 5/15 patients (33%); PSA 1-5 ng/ml: 18/27 patients (67%), and PSA ≥ 5 ng/ml: 33/34 patients (97%). Following imaging in nine high-risk patients referred for staging, changes in treatment occurred in 6 (67%). Treatment recommendations changed in 27/35 (65%) patients referred due to biochemical failure; these included recurrences suitable for salvage therapy (n = 14), metastatic disease not suitable for salvage therapy (n = 10), and no lesion (n = 17). No changes in treatment occurred in any of the 35 patients referred to evaluate metastatic disease. DISCUSSION: PSMA PET-CT imaging may have a substantial impact on clinical management in prostate cancer patients at the time of initial staging or with biochemical failure; yet this modality does not appear useful in the management of patients with known metastatic disease.

68Ga-PSMA PET/CT in prostate cancer patients - patterns of disease, benign findings and pitfalls.

BACKGROUND: 68Ga-PSMA PET/CT has an important role in assessment of prostate cancer patients with biochemical recurrence and is evolving in staging high- and intermediate risk disease. The aim of present study was to describe the metastatic patterns and frequency of involved sites of prostate cancer and to assess the incidence of benign Ga68-PSMA avid PET/CT findings in a large patient population. METHODS: 68Ga-PSMA PET/CT studies performed in two tertiary medical centers over a period of 24 months were retrospectively reviewed. The incidence and location of pathological 68Ga-PSMA avid foci, suspicious to represent malignancy, as well as those of unexpected benign foci of increased 68Ga-PSMA activity were documented and analyzed. RESULTS: There were 445 68Ga-PSMA studies in 438 men (mean age 72.4, range 51-92 years) with prostate cancer referred for biochemical failure (n = 270, 61%), staging high-risk disease (n = 112, 25%), response assessment (n = 30, 7%), follow-up (n = 22, 5%) and suspected bone metastases (n = 11, 2%). 68Ga-PSMA avid disease sites were observed in 319 studies (72%), in 181 studies (67%) for biochemical recurrence, 94 studies for staging (84%) (p < 0.05), in 22 studies for response assessment (73%), 10 follow up studies (45%) and in five patients with suspected bone metastases (45%). 68Ga-PSMA avid lesions were most commonly detected in the prostate (n = 193, 43%), loco-regional spread (n = 51, 11%), abdomino-pelvic nodes (n = 129, 29%) and distant metastases (n = 158, 36%), including bone metastases (n = 11, 25%), distant lymphadenopathy (n = 29, 7%) and other organs (n = 18, 4%). Distant 68Ga-PSMA-avid metastases were commonly seen in patients with biochemical recurrence (14/21 lesions), but were not seen in patient referred for staging (p < 0.013). There were 96 non-malignant 68Ga-PSMA avid foci in 81 studies, most common in reactive lymph nodes (n = 36, 38%), nonmalignant bone lesions (n = 21, 22%), thyroid nodules (n = 9, 9%), ganglions (n = 9, 9%) and lung findings (n = 8, 8%). CONCLUSION: The distribution of 68Ga-PSMA avid metastatic lesions is similar to data previously reported mainly from autopsy with comparable detection rates, indicating 68Ga-PSMA PET/CT is an accurate detection tool in patients with metastatic prostate cancer. If confirmed by further prospective studies 68Ga-PSMA PET/CT should be included in the guidelines to evaluate disease extent in these patients.

Feasibility study of a novel general purpose CZT-based digital SPECT camera: initial clinical results.

BACKGROUND: The performance of a prototype novel digital single-photon emission computed tomography (SPECT) camera with multiple pixelated CZT detectors and high sensitivity collimators (Digital SPECT; Valiance X12 prototype, Molecular Dynamics) was evaluated in various clinical settings. Images obtained in the prototype system were compared to images from an analog camera fitted with high-resolution collimators. Clinical feasibility, image quality, and diagnostic performance of the prototype were evaluated in 36 SPECT studies in 35 patients including bone (n = 21), brain (n = 5), lung perfusion (n = 3), and parathyroid (n = 3) and one study each of sentinel node and labeled white blood cells. Images were graded on a scale of 1-4 for sharpness, contrast, overall quality, and diagnostic confidence. RESULTS: Digital CZT SPECT provided a statistically significant improvement in sharpness and contrast in clinical cases (mean score of 3.79 ± 0.61 vs. 3.26 ± 0.50 and 3.92 ± 0.29 vs. 3.34 ± 0.47 respectively, p < 0.001 for both). Overall image quality was slightly higher for the digital SPECT but not statistically significant (3.74 vs. 3.66). CONCLUSION: CZT SPECT provided significantly improved image sharpness and contrast compared to the analog system in the clinical settings evaluated. Further studies will evaluate the diagnostic performance of the system in large patient cohorts in additional clinical settings.

Low rate of spleen involvement in sporadic Burkitt lymphoma at staging on PET-CT.

BACKGROUND: Burkitt lymphoma is a highly aggressive B cell non-Hodgkin lymphoma. Cross-sectional imaging techniques that are used to detect liver and spleen involvement by lymphoma have high rates of false negative and false positive findings, and as such may reduce the accuracy of staging. PURPOSE: This retrospective study evaluated the use of FDG PET-CT in determining splenic involvement at staging, in a relatively large cohort of adult patients with the sporadic form of Burkitt lymphoma (SBL). PATIENTS AND METHODS: All adult patients who underwent FDG PET-CT for staging of SBL at one medical center during 2005-2014 were enrolled for this retrospective study. RESULTS: Data were analyzed of 20 patients, with median age 49 years; 17 were male. PET-CT revealed highly intense FDG uptake, mean SUV max 11.4 ± 7.49 (range 4.3-38) in various tissues. None of the 20 patients had either focal or diffuse increased uptake of FDG in the spleen parenchyma. In 2 patients, there were highly FDG-avid soft tissue masses adjacent to the spleen, both in the context of direct peritoneal disease extension. CONCLUSION: The spleen is rarely involved in SBL at the time of staging, according to PET-CT, except in cases with direct extension from adjacent peritoneal mass. The low rate of spleen involvement according to PET-CT may serve as a specific characteristic of SBL. Larger-scale clinical studies incorporating PET-CT scans in SBL are needed to confirm our observation.

FDG PET-CT evaluation in neurolymphomatosis: imaging characteristics and clinical outcomes.

Neurolymphomatosis (NL) often represents unidentified non-Hodgkin lymphoma relapses. Considering its severity, early detection and treatment are crucial. We outline one hospital's 18F-FDG-PET-CT imaging findings of NL, along with the patients' clinical characteristics. Clinical records and imaging findings of 19 NL patients, PET-CT diagnosed, were retrospectively reviewed. Patient data, FDG-PET-CT findings and the presence of coexisting diseases, especially CNS involvement, were documented. Available MRI and clinical data verified the findings. All cases had increased linear FDG uptake along anatomic nerve sites. CTs showed varying degrees of corresponding soft-tissue-thickening. Clinical correlations also contributed to the diagnosis. In 4/19 patients, lymphoma presented with NL, in 15/19 it appeared with disease recurrence/progression. In 9/19, clinical symptoms suggested neural involvement while 10/19 had nonspecific symptoms. Eleven died of lymphoma within 0.9 years of diagnosis despite directed-therapy. Eight, however, survived up to 7.82 years post-diagnosis. Whole-body FDG-PET-CT can assist in early NL diagnosis, possibly enhancing survival.

Fat necrosis after abdominal surgery: A pitfall in interpretation of FDG-PET/CT.

OBJECTIVE: We describe FDG-PET/CT findings of postoperative fat necrosis in patients following abdominal surgery, and evaluate their changes in size and FDG uptake over time. METHODS: FDG-PET/CT scans from January 2007-January 2016 containing the term 'fat necrosis' were reviewed. Lesions meeting radiological criteria of fat necrosis in patients with prior abdominal surgery were included. RESULTS: Forty-four patients, 30 males, mean age 68.4 ± 11.0 years. Surgeries: laparotomy (n=37; 84.1 %), laparoscopy (n=3; 6.8 %), unknown (n=4; 9.1 %). CTs of all lesions included hyperdense well-defined rims surrounding a heterogeneous fatty core. Sites: peritoneum (n=34; 77 %), omental fat (n=19; 43 %), subcutaneous fat (n=8; 18 %), retroperitoneum (n=2; 5 %). Mean lesion long axis: 33.6±24.9 mm (range: 13.0-140.0). Mean SUVmax: 2.6±1.1 (range: 0.6-5.1). On serial CTs (n=34), lesions decreased in size (p=0.022). Serial FDG-PET/CT (n=24) showed no significant change in FDG-avidity (p=0.110). Mean SUVmax did not correlate with time from surgery (p=0.558) or lesion size (p=0.259). CONCLUSION: Postsurgical fat necrosis demonstrated characteristic CT features and may demonstrate increased FDG uptake. However, follow-up of subsequent imaging scans showed no increases in size or FDG-avidity. Awareness of this entity is important to avoid misinterpretation of findings as recurrent cancer. KEY POINTS: • Postsurgical fat necrosis may mimic cancer in FDG-PET/CT. • Follow-up of fat necrosis showed no increase in FDG intensity. • CT follow-up showed a decrease in lesion size. • FDG uptake did not correlate with time lapsed from surgery.

Clinical Problem Solving: A Tobacco Merchant Who Can't Spit.

BACKGROUND: A 47 year old man presented with a combination of dry mouth and lightheadedness while standing. His medical background was unremarkable except for cigarette smoking and hyperlipidemia. Sjögren's syndrome was ruled out, and he was referred for evaluation of orthostatic hypotension, which by then included syncopal episodes and injuries. Additional symptoms included dry eyes, constipation, reduced sweating, and erectile dysfunction. After excluding medications and structural cardiac abnormalities as causes of orthostatic hypotension, a clinical autonomic evaluation was performed. The pattern of beat-to-beat blood pressure associated with performance of the Valsalva maneuver, and a low plasma norepinephrine level that did not increase in response to standing, established that the orthostatic hypotension was neurogenic. Treatment with an alpha-adrenoceptor agonist and fludrocortisone yielded partial improvement. After systemic diseases involving autonomic failure were excluded, cardiac sympathetic neuroimaging was performed by 123I-metaliodobenzylguanidine (MIBG) scanning. The normal uptake seen in the heart indicated intact post ganglionic sympathetic innervation. There were no signs of central neurodegeneration or peripheral neuropathy. Because of symptoms and signs of both parasympathetic and sympathetic failure without denervation, an autonomic ganglionopathy was considered. A high titer of antibody to the neuronal nicotinic receptor, which mediates ganglionic neurotransmission, was obtained. The diagnosis of autoimmune autonomic ganglionopathy (AAG) was made, and the management strategy shifted to first lowering the antibody burden by plasma exchanges and then instituting chronic anti-autoimmune treatment with rituximab and a low dose of cortiosteroid. The patient showed remarkable improvement.

The PET-CT Radiological Appearance of Facial Cosmetic Injections: A Pitfall in the Evaluation of the Oncological Patient.

BACKGROUND: Facial rejuvenation using different dermal and sub-dermal injectable compounds is a popular cosmetic procedure which may pose a diagnostic dilemma to the radiologist. OBJECTIVES: To describe the appearance of cosmetic facial fillers on PET-CT. METHODS: All PET-CT exams performed between January 2015 and May 2017 in which findings suggestive of prior facial filler procedures was evident and where anamnestic confirmation with the patient was possible were reviewed. RESULTS: We describe five females who had undergone facial filler procedures leading to calcifications around the mouth and nasolabial triangle. CONCLUSIONS: Familiarity with the appearance of such cosmetic procedures on PET-CT is of paramount importance in order to avoid misinterpretation of the findings leading to unnecessary apprehension and work-up.

Use of 18F-FDG PET-CT imaging to determine internal mammary lymph node location for radiation therapy treatment planning in breast cancer patients.

PURPOSE: Adjuvant internal mammary lymph node (IMN) radiation is often delivered with 2-dimensional techniques that use anatomic landmarks and predetermined depths for field placement and dose specification. In contrast, 3-dimensional planning uses the internal mammary vessels (IMVs) to localize the IMNs for planning. Our purpose was to determine if localization of the involved IMN (i-IMN) by 18F-labeled fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) offers opportunities to improve treatment. METHODS AND MATERIALS: Breast cancer patients (n = 80) who had i-IMNs (n = 112) on PET-CT for initial staging (n = 40) or recurrence (n = 40) were studied. Size, intercostal space (IC), and distance from skin, sternum, and IMVs were recorded. Effects on 2- and 3-dimensional planning were evaluated. RESULTS: Most i-IMNs (94.6%) were in the first to third ICs. Few were in the fourth (4.5%) or fifth (0.9%) IC. Mean i-IMN depth was 3.4 cm (range, 1.1-7.3 cm). Prescriptive depths of 4, 5, and 6 cm would result in undertreatment of 25%, 10.7%, and 5.3% of IMNs, respectively. Most IMNs (86.6%) were lateral or adjacent to the sternal edge. Only 13.4% of IMNs were posterior to the sternum. Use of the ipsilateral or contralateral sternal edge for field placement increases the risk of geographic miss or excess normal tissue exposure. Most i-IMNs were adjacent to (83%) or ≤0.5 cm (14%) from the IMV edge. Three (3%) were >0.5 cm beyond the IMV edge. The clinical target volume (CTV) defined by the first to third ICs encompassed 78% of i-IMNs. IMN-CTV coverage of i-IMNs increased with inclusion of the fourth IC (82%), 0.5 cm medial and lateral margin expansion (93%), or both (96.5%). CONCLUSION: Two-dimensional treatment techniques risk geographic miss of IMNs and exposure of excess normal tissue to radiation. An IMN-CTV defined by the IMVs from the first to third ICs with 0.5-cm medial and lateral margin expansion encompasses almost all i-IMNs identified on PET-CT imaging. Inclusion of the fourth IC offers modest coverage improvement, and its inclusion should be weighed against potential increase in cardiac exposure. SUMMARY: The use of 2-dimensional treatment techniques for adjuvant internal mammary lymph node (IMN) radiation may cause geographic miss of tumor and expose normal tissue to radiation injury. Conformal 3-dimensional planning improves coverage and reduces risk of normal tissue damage by using the internal mammary vessel to define an IMN clinical target volume (CTV). Contouring the IMN-CTV from the first to third intercostal spaces with a 0.5-cm expansion medially and laterally encompasses most IMN. Positron emission tomography-computed tomography may have a role in radiation planning by identifying involved-IMN for dose escalation.

Focal fluorine-18 fluorodeoxyglucose-avid parotid findings in patients with lung cancer: prevalence and characteristics.

OBJECTIVE: Correct interpretation of incidental tumors is important to plan an appropriate treatment. We assessed the incidence and imaging characteristics of fluorine-18 fluorodeoxyglucose (F-FDG)-avid focal parotid findings (FPFs) in patients with lung cancer. PATIENTS AND METHODS: FPFs in PET-computed tomography reports of cancer patients were searched. Those with known parotid malignancies, lymphoma, and diffuse F-FDG uptake in the entire parotid gland were not included in the analysis. RESULTS: FPFs were detected in 38/3120 cancer patients (1.23%), observed as a soft tissue mass with a mean diameter 1.6±0.5 cm (range 0.8-2.7 cm) and a mean maximum standardized uptake value of 7.7±3.7 (range 2.5-17.8). FPFs were observed in 23/604 (3.8%) patients with lung cancer, compared with 6/1366 (0.4%) with breast cancer and 5/842 (0.6%) with gastrointestinal malignancies. We assessed FPFs appearances in 23 patients with lung cancer (18 men, mean age 72.8±9.2); 20 (87%) were current or past smokers. There was no correlation between the stage or histopathological type of the lung cancer and the prevalence of parotid lesions. In four patients with histopathology, no malignancy was detected. For an additional 11 patients with available imaging and clinical follow-up (mean follow-up 15.5±13.5 months, range 3-42 months), FPFs were consistent with benign lesions. CONCLUSION: FPFs were more prevalent among patients with lung cancer than in patients with other malignancies. As F-FDG avidity was moderate to high, FPFs may mimic distant metastases. It is important to consider FPFs in the interpretation of a focal parotid lesion as misinterpretation may result in denial of appropriate therapy.

Incidental detection of elastofibroma dorsi on PET-CT: initial findings and changes in tumor size and standardized uptake value on serial scans.

OBJECTIVE: We describe changes in elastofibroma dorsi (EFD) as observed in serial fluorine-18 fluorodeoxyglucose (F-FDG) PET-computed tomography (CT) imaging studies. MATERIALS AND METHODS: F-FDG PET-CT studies carried out between January 2006 and January 2015 at a single institution were reviewed by an experienced radiologist and nuclear medicine specialist. When available, previous or subsequent imaging studies were reviewed to evaluate changes in EFD. RESULTS: Of 28 500 PET-CT studies carried out, EFD was identified in 68 from 20 patients (mean age 67.1±10.2 years; 14 women). Five patients had unilateral lesions and 15 patients had bilateral lesions. Eighteen patients had oncologic diseases. The mean size of EFD at first presentation was 13.95±5.90 mm and the mean homogeneous low-grade F-FDG uptake was maximum standardized uptake value (SUVmax) 2.24±0.95. One or more additional CT scans were performed in 17 patients; the mean interval between the first and last scans was 57.4±39.2 months. EFD was unchanged in size in 7/17 (41%) and showed slow growth in 10/17, reaching a mean size of 19 mm. The mean monthly growth rate was 0.1±0.10 mm. PET imaging in 11 patients showed a mean first SUVmax of 2.08±1.17 and a mean last SUVmax of 2.74±1.05 after a mean of 47.5±31.5 months (P=0.63). CONCLUSION: Serial PET-CT studies may show a stable or slowly enlarging mass on a CT scan without changes in F-FDG uptake on PET imaging. Familiarity with CT appearances and F-FDG uptake of EFD are important for correct interpretation of F-FDG PET-CT studies.

Metabolic assessment of Merkel cell carcinoma: the role of 18F-FDG PET/CT.

OBJECTIVES: Merkel cell carcinoma (MCC) is a rare aggressive skin tumor associated with a high mortality rate. The present study evaluated the role of fluorine-18 fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) in subsequent management of patients with MCC. METHODS: A total of 101 consecutive F-FDG PET/CT studies of 46 patients with MCC (28 men, 68±15.4 years) were retrospectively evaluated and the role in clinical care was documented. RESULTS: There were 40 positive studies (40%) in 28 patients (61%); of these, 33 studies (33%) in 27 patients (59%) showed metastatic disease. Fifty-two PET/CT studies (51%) in 23/46 (50%) patients were negative. Fifty-three studies (52%) were performed for staging or restaging in 41 patients, 29 scans (29%) were performed for routine follow-up in 10 patients, nine studies were carried out for suspected recurrent disease in eight patients, and 10 studies were carried out for assessment of response to therapy in seven patients. On the basis of PET/CT results, there was a change in disease stage in 12 studies in 12 patients (26%) and further change in the management of seven patients (15%). Overall, 2/29 routine follow-up studies were positive with further impact on management in one patient. CONCLUSION: F-FDG PET-CT altered the stage of one of four patients and changed the management of one of seven MCC patients. In the majority of patients, a negative F-FDG PET-CT study excluded active MCC with a high degree of confidence. PET-CT contributed toward patient management when performed for staging and restaging, monitoring response to treatment, and suspected recurrent disease, but not in the routine follow-up of asymptomatic patients with MCC.

The impact of R-VACOP-B and interim FDG-PET/CT on outcome in primary mediastinal large B cell lymphoma.

The choice of a rituximab-based regimen and the prognostic significance of interim 2-[fluorine-18]fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) in primary mediastinal large B cell lymphoma (PMBCL) are debatable. We evaluated the clinical features and outcomes of 95 consecutive patients with PMBCL who were treated between 1985 and 2009. Forty-three patients received rituximab-based chemotherapy, R-VACOP-B (N = 30) or R-CHOP21 (N = 13), whereas 52 patients were treated with VACOP-B (N = 47) or CHOP21 (N = 5). Radiotherapy was not given. Patients who received rituximab had a 5-year progression-free survival (PFS) of 79 % and overall survival (OS) of 97 % compared with 58 % (p = 0.06) and 88 % (p = 0.2), respectively, without rituximab. Five-year PFS in patients treated with R-VACOP-B, R-CHOP21, VACOP-B, and CHOP21 were 83, 69, 62, and 20 %, respectively (p = 0.039). However, direct comparison showed that the difference between PFS rates in patients receiving R-VACOP-B compared to R-CHOP21 was not statistically significant (p = 0.3). None of the standard clinical risk factors predicted for PFS and OS in patients receiving rituximab (R)-chemotherapy. Mid-interim FDG-PET/CT scans were performed in 30/43 patients who received R-chemotherapy. The negative predictive values of mid-PET activity were high (100 % for R-VACOP-B and 86 % for R-CHOP21) while the positive predictive values (PPV) were relatively low (30 and 75 %, respectively). Despite the low PPV, the 5-year PFS for mid-PET-negative patients (N = 16) was significantly higher (94 %) than that for mid-PET-positive (N = 14) patients (57 %, p = 0.015). This retrospective analysis demonstrates that the superiority of VACOP-B over CHOP21 for treatment of PMBCL disappeared once rituximab was added. The potential benefit of using interim PET activity as a guide for continuing therapy in patients with PMBCL remains unclear due to the relatively low PPV.

Is there a role for therapy response assessment with 2-[fluorine-18] fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography in mantle cell lymphoma?

2-[Fluorine-18] fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) scanning is used for response assessment in mantle cell lymphoma (MCL). However, its ability to predict outcome is debatable. We retrospectively evaluated the prognostic impact of interim and post therapy FDG-PET/CT scan on outcome of 58 consecutive MCL patients. Scans performed at diagnosis, mid-therapy, post-chemotherapy and post-transplant were reviewed and outcome analyzed. Median age was 59; MCL International Prognostic Index (MIPI) was low in 45%, intermediate in 41% and high in 14%. Thirty-four patients (58%) received R-CHOP (rituximab, cyclophosphamide, hydroxydaunorubicin, oncovin, prednisone) or R-CHOP-like chemotherapy, 24 (42%) underwent upfront autologous stem-cell transplant (ASCT). Three-year overall (OS) and progression-free-survival (PFS) were 81% and 45%, respectively. No differences in OS or PFS between PET-positive and PET-negative groups both for interim and post-therapy scans were observed. We conclude that in patients treated with R-CHOP, using the International-Harmonization-Project criteria for FDG-PET/CT interpretation, there is no role for interim or post-therapy PET.

18F- FDG-PET/CT for the diagnosis of tumor thrombosis.

BACKGROUND: Venous thromboembolism is a well-recognized and relatively frequent complication of malignancy, whereas tumor thrombosis is a rare complication of solid cancers. The correct diagnosis of tumor thrombosis and its differentiation from VTE can alter patient management and prevent unnecessary long-term anticoagulation treatment. OBJECTIVES: To evaluate the contribution of 18F-fluorodeoxyglucose positron emission tomography/computed tomography to the diagnosis of tumor thrombosis and its differentiation from VTE. METHODS: PET/CT scans from 11 patients with suspected tumor thrombosis were retrospectively evaluated. Suspicion arose from positive PET/CT in eight cases, or from findings on contrast-enhanced CT in three patients. Criteria for positivity of PET/CT included increased focal or linear uptake of 18F-FDG in the involved vessel. Findings were categorized as PET/CT positive, or PET/CT negative and compared to contrast-enhanced or ultrasound Doppler, pathology where available, and clinical follow-up. RESULTS: Eight occult tumor thromboses were identified by PET/CT-positive scans. Underlying pathologies included pancreatic, colorectal, renal cell, and head-neck squamous cell carcinoma, as well as lymphoma (4 patients). Three thrombotic lesions on contrast-enhanced CT were PET/ CT negative, due to VTE (2 patients) and leiomyomatosis. Accuracy of PET/CT to differentiate between tumor thrombosis and benign VTE was 100% in this small study. CONCLUSIONS: Contrast-enhanced CT defines the extent of thrombotic lesions, while the functional information from PET/CT characterizes the lesions. It appears that PET/CT may be helpful in the diagnosis of occult tumor thrombosis and its differentiation from VTE.

Diffuse lymphangiomatosis--a fatal case with atypical skeletal features.

Diffuse lymphangiomatosis is a rare idiopathic condition that occurs mostly in children, is characterized by a non-neoplastic proliferation of lymphatic vessels, leading to organ dysfunction, chylous effusions, and death. A closely related condition-the Gorham-Stout syndrome-is also characterized by lymphangiomatosis and chylous effusions, but also with massive osteolytic changes ("vanishing bone disease"). A 33-year-old woman presented with a 5-year history of worsening chylous effusions and organomegaly. An extensive evaluation has ruled out most diagnoses. A complete radiographic skeletal study did not disclose any osteolytic changes. However, a Tc99 bone scan has demonstrated an absence of osteoblastic activity in some bones. An autopsy confirmed the diagnosis of diffuse lymphangiomatosis, but with histologically normal bone. If this unusual imaging pattern will be reproduced in future cases, a much needed diagnostic aid may help decrease the frequent diagnostic delays in diffuse lymphangiomatosis.

PET/CT in the evaluation of lymphoma in patients with HIV-1 with suppressed viral loads.

OBJECTIVE: Positron emission tomography (PET) with F-18 fluorodeoxyglucose detects active lymphoid tissue during HIV-1 infection, with distinct patterns of lymphoid activation correlating to various stages of disease activity. Patients with HIV-1 are at risk for lymphoma, making the differential diagnosis between benign and malignant lymphadenopathy imperative. This study retrospectively evaluated the role of PET/computed tomography (CT) in differentiating active lymphoma from persistent generalized lymphadenopathy in patients with HIV-1. MATERIALS AND METHODS: Seven patients with HIV-1 underwent PET/CT. Six, with known non-Hodgkin lymphoma underwent a total of 16 PET/CT scans; 5/16 scans were performed for initial staging, and 10/16 for evaluating treatment response and follow-up. One patient was referred for evaluation of lymphadenopathy suspected of being lymphoma. PET/CT findings were compared with concurrent clinical, immunologic, and virological data. RESULTS: PET/CT accurately depicted the extent of lymphoma in 12/16 patients' scans (75%), yet in 4/16 (25%) scans increased fluorodeoxyglucose uptake was noted in lymph nodes of normal CT appearance (PET+/CT-). Viral loads ranged from 0 to 84,000 copies/mL, CD4 T-cell count ranged from 130 to 474 cells/muL in the group. The highest values of both laboratory parameters were concurrent with the discrepant PET+/CT- scans, seen in 4 scans, in 2 patients. The PET+/CT- findings in both these patients were observed in neck, axillae, mediastinum, spleen, and inguinal regions, and sample biopsies of the PET (+) nodes consequently proved benign findings in both patients. All PET+/CT+ findings correctly indicated lymphoma status, as proven by clinical follow-up. CONCLUSION: PET/CT accurately detected lymphoma in patients with HIV-1 and had been used confidently as a management tool in this patient group. In the context of discrepant PET/CT findings, increased viral loads and CD4 levels may imply benign HIV-related lymphadenopathy.