Geometrical differences in target volumes based on 18F‐fluorodeoxyglucose positron emission tomography/computed tomography and four‐dimensional computed tomography maximum intensity projection images of primary thoracic esophageal cancer

The objective of the study was to compare geometrical differences of target volumes based on four‐dimensional computed tomography (4DCT) maximum intensity projection (MIP) and ¹⁸F‐fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F‐FDG PET/CT) images of primary thoracic esophageal cancer for radiation treatment. Twenty‐one patients with thoracic esophageal cancer sequentially underwent contrast‐enhanced three‐dimensional computed tomography (3DCT), 4DCT, and ¹⁸F‐FDG PET/CT thoracic simulation scans during normal free breathing. The internal gross target volume defined as IGTV_MIP was obtained by contouring on MIP images. The gross target volumes based on PET/CT images (GTV_PET) were determined with nine different standardized uptake value (SUV) thresholds and manual contouring: SUV ≥ 2.0, 2.5, 3.0, 3.5 (SUV_n); ≥20%, 25%, 30%, 35%, 40% of the maximum (percentages of SUV_max, SUV_n%). The differences in volume ratio (VR), conformity index (CI), and degree of inclusion (DI) between IGTV_MIP and GTV_PET were investigated. The mean centroid distance between GTV_PET and IGTV_MIP ranged from 4.98 mm to 6.53 mm. The VR ranged from 0.37 to 1.34, being significantly (P < 0.05) closest to 1 at SUV_2.5 (0.94), SUV_20% (1.07), or manual contouring (1.10). The mean CI ranged from 0.34 to 0.58, being significantly closest to 1 (P < 0.05) at SUV_2.0 (0.55), SUV_2.5 (0.56), SUV_20% (0.56), SUV_25% (0.53), or manual contouring (0.58). The mean DI of GTV_PET in IGTV_MIP ranged from 0.61 to 0.91, and the mean DI of IGTV_MIP in GTV_PET ranged from 0.34 to 0.86. The SUV threshold setting of SUV_2.5, SUV_20% or manual contouring yields the best tumor VR and CI with internal‐gross target volume contoured on MIP of 4DCT dataset, but 3DPET/CT and 4DCT MIP could not replace each other for motion encompassing target volume delineation for radiation treatment.     

Advantages of positron emission tomography‐computed tomography imaging in esophageal squamous cell carcinoma

To explore the value of positron emission tomography‐computed tomography (PET‐CT) scan in esophageal squamous cell carcinoma (ESCC), we retrospectively summarize the results of PET‐CT scan from 118 patients, with ESCC who underwent PET‐CT scan in the different courses during treatment. Then, the results of PET‐CT scan plus other conventional methods were analyzed to identify the value of PET‐CT scan in diagnosis, staging, response evaluation, monitoring recurrence, and metastasis following treatment. It is suggested that PET‐CT scan possess high value in diagnosis and gives more favorable indication in N and M staging. PET‐CT scan should be translated into routine surveillance for postoperation follow up and is one of more helpful evaluators of response to chemoradiotherapy or chemotherapy.     

Diagnostic value of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography in patients with fever of unknown origin

Background

While fever of unknown origin (FUO) remains a challenging problem in clinical practice, fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) has been considered helpful in diagnosing its cause. The present study is set to evaluate the diagnostic value of PET/CT for patients with FUO.

Methods

We analyzed the records of 48 patients with FUO (34 men and 14 women; mean age of 57-year-old with a range between 24- and 82-year-old). The patients were examined by ¹⁸F-FDG PET/CT and the results were compared to a final diagnosis that was established by additional procedures.

Results

A final diagnosis was established for 36 patients (75%). Among them, 15 patients had infectious diseases, 12 patients had malignancies, and 9 patients had non-infectious inflammatory diseases. Thirty-two abnormal PET/CT results correctly revealed the source of fever (true-positives). Abnormal PET/CT results were considered false-positives for 8 patients without diagnoses. Normal PET/CT results in 4 patients with no diagnoses were classified as true-negatives. Four patients with normal PET/CT results with diagnosed cause for FUO were considered false-negatives. Therefore, PET/CT had a positive predictive value of 80%, a negative predictive value of 50%, a sensitivity of 89%, and a specificity of 33% in patients with FUO.

Conclusions

Our study demonstrated that FDG-PET/CT is a valuable imaging tool for the identification of the etiology in patients with FUO. The results suggest that this procedure may be considered as a second-line test, especially when conventional structural imaging was normal or unable to distinguish lesions from benign and malignant.     

Comparison of the diagnostic value of 3-deoxy-3-18F-fluorothymidine and 18F-fluorodeoxyglucose positron emission tomography/computed tomography in the assessment of regional lymph node in thoracic esophageal squamous cell carcinoma: a pilot study

We used pathological examination as golden standard to determine whether 3-deoxy-3-(18)F-fluorothymidine positron emission tomography/computed tomography (FLT PET/CT) can detect regional lymph node metastasis in untreated thoracic esophageal squamous cell carcinoma and additionally performed (18)F-fluorodeoxyglucose (FDG) PET/CT for direct comparison with that of FLT. Twenty-two patients with thoracic esophageal squamous cell carcinoma underwent dual-tracer PET/CT examinations before surgery. The results of reviewing CT images and side-by-side FDG PET and FLT PET images for the diagnosis of locoregional lymph node metastasis were compared prospectively in relation to pathologic findings. All patients underwent esophagectomy and lymphadenectomy. Pathologic examination confirmed nodes positive for metastasis in 16 patients and 47 of 424 excised nodes. The uptake of FDG (median SUVmax, 5.4; range, 2.4-10.6) in locoregional lymph nodes metastases was significantly higher than that of FLT (median SUVmax, 2.8; range, 1.3-4.6). There were 14 false-positive nodes in FDG PET/CT and only 3 in FLT PET/CT; 8 false-negative nodes in FDG PET/CT, while there were 12 false negative nodes in FLT PET/CT. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of FLT PET/CT were 74.47%, 99.20%, 96.46%, 92.11%, and 96.89%, respectively, whereas those of FDG PET/CT were 82.98%, 96.29%, 94.81%, 82.98%, and 96.29%, respectively. P-values were 0.450, 0.014, 0.313, 0.050, and 0.555, respectively. FLT uptake in regional lymph nodes of esophageal carcinoma is significantly lower compared with FDG uptake. FLT PET/CT has fewer false-positive findings and higher specificity compared with FDG PET/CT.     

Comparative study between endoscopic ultrasonography and positron emission tomography‐computed tomography in staging patients with esophageal squamous cell carcinoma

Treatment strategy of esophageal cancer mainly depends on accurate staging. At present, no single ideal staging modality is superior to another in preoperative tumor‐node‐metastasis (TNM) staging of patients with esophageal cancer. We aimed to investigate the efficacy of endoscopic ultrasonography (EUS) and positron emission tomography‐computed tomography (PET‐CT) for staging of esophageal cancer. We retrospectively studied 118 consecutive patients with esophageal squamous cell carcinoma who underwent esophagectomy with or without neoadjuvant chemoradiotherapy (CRT) over a near 3‐year period between January 2005 and November 2008 at a tertiary hospital in Taiwan. Patients were separated into two groups: without neoadjuvant CRT (group 1, n= 28) and with CRT (group 2, n= 90). Medical records of demographic data and reports of EUS and PET‐CT of patients before surgery were reviewed. A database of clinical staging by EUS and PET‐CT was compared with one of pathological staging. The accuracies of T staging by EUS in groups 1 and 2 were 85.2% and 34.9%. The accuracies of N staging by EUS in groups 1 and 2 were 55.6% and 39.8%. The accuracies of T and N staging by means of PET‐CT scan were 100% and 54.5% in group 1, and were 69.4% and 86.1% in group 2, respectively. In group 2, 38 of 90 patients (42.2%) achieved pathologic complete remission. Among them, two of 34 (5.9%) and 12 of 17 (70.6%) patients were identified as tumor‐free by post‐CRT EUS and PET‐CT, respectively. EUS is useful for initial staging of esophageal cancer. PET‐CT is a more reliable modality for monitoring treatment response and restaging. Furthermore, the accuracy of PET‐CT with regard to N staging is higher in patients who have undergone CRT than those who have not.     

Comparison of patient‐specific internal gross tumor volume for radiation treatment of primary esophageal cancer based separately on three‐dimensional and four‐dimensional computed tomography images

To compare the target volume, position and matching index of the patient‐specific internal gross tumor volume (IGTV) based on three‐dimensional (3D) and four‐dimensional (4D) computed tomography (CT) images for primary esophageal cancer. Twenty‐nine patients with primary thoracic esophageal cancer underwent 3DCT and 4DCT scans during free breathing. IGTVs were constructed using three approaches: combining the gross target volumes from the 10 respiratory phases of the 4DCT dataset to produce IGTV₁₀; IGTV₂ was acquired by combining the two extreme phases; and IGTV_3D was created from the 3DCT‐based gross target volume by enlarging the 95th percentile of motion in each direction measured by the 4DCT. 0.16 cm lateral (LR), 0.14 cm anteroposterior (AP) and 0.29 cm superoinferior (SI) in the upper; 0.18 cm LR, 0.10 cm AP and 0.63 cm SI in the middle; and 0.40 cm LR, 0.58 cm AP and 0.82 cm in the lower thoracic esophagus could account for 95% of respiratory‐induced tumor motion. The centroid position shift between IGTV₁₀ and IGTV₂ was all below 0.10 cm, and less than 0.20 cm between IGTV₁₀ and IGTV_3D. IGTV₁₀ was bigger than IGTV₂; the mean value of matching index for IGTV₂ to IGTV₁₀ was 0.87 ± 0.05, 0.85 ± 0.06 and 0.83 ± 0.05 for upper, middle and distal thoracic esophageal tumors, respectively, and just 0.57 ± 0.11, 0.56 ± 0.13 and 0.40 ± 0.03 between IGTV_3D and IGTV₁₀. 4DCT‐based IGTV₁₀ is a reasonable patient‐specific IGTV for primary thoracic esophageal cancer, and IGTV₂ is considered as an acceptable alternative to IGTV₁₀. However, it seems unreasonable to use IGTV_3D substitute IGTV₁₀.     

Impact of whole‐body 18F‐fluorodeoxyglucose positron emission tomography on therapeutic management of non‐small cell lung cancer

Background and objective: Accurate staging at the time of diagnosis is very important in deciding on the appropriate treatment for cancer patients. FDG PET indicates metabolic changes in cancer cells, enabling the early detection of lesions. This has the advantage of allowing more accurate staging than is possible with conventional staging tools, and has led to the incorporation of FDG PET in the initial work‐up protocols for lung cancer patients. In this study, we evaluated the clinical impact of FDG PET as an initial staging tool, on the therapeutic management of patients with non‐small cell lung cancer (NSCLC). Methods: Patients diagnosed with NSCLC by histopathology were retrospectively identified and both chest CT and FDG PET were performed for initial staging. Information was collected regarding the results of conventional versus FDG PET staging, and any resulting modifications of treatment were evaluated. Results: Among the 537 patients who were evaluated FDG PET resulted in upstaging of the tumour in 91 (17%) and downstaging of the tumour in 68 (13%). Consequently, therapeutic management was modified in 118 patients (22%). Furthermore, use of FDG PET resulted in the detection of a second primary cancer in six patients. Conclusions: This study confirms that FDG PET has a considerable impact on the initial staging and therapeutic management of patients with NSCLC.     

Repetitive 18F‐fluorodeoxyglucose positron emission tomography in giant cell arteritis: A prospective study of 35 patients

Objective

To study fluorodeoxyglucose (FDG) uptake in the different vascular beds and in the large joints of patients with giant cell arteritis (GCA) at diagnosis, during steroid treatment, and at relapse.

Methods

All consecutive patients admitted to our department with a diagnosis of GCA underwent FDG–positron emission tomography (PET) scan before treatment with methylprednisolone was started. PET scans were repeated at 3 and 6 months, if the initial PET scans showed vascular FDG uptake. PET scans were scored at 7 different vascular areas and a total vascular score (TVS) was calculated, ranging from 0 to 21.

Results

A total of 35 patients entered the study. At diagnosis, vascular FDG uptake was noted in 29 patients (83%), especially in the subclavian arteries (74%), but also in the aorta (>50%) and up to the femoral arteries (37%). TVS decreased from a mean ± SD score of 7.9 ± 5.5 at baseline to 2.4 ± 3.5 on repeat PET scan at 3 months (P < 0.0005), but did not further decrease at 6 months. The patients who relapsed had similar earlier decreases of TVS compared with those who did not relapse. FDG uptake in the shoulders at diagnosis correlated significantly with the presence of polymyalgia rheumatica (P = 0.005).

Conclusion

FDG uptake in the large vessels is a sensitive marker for GCA, which can involve the larger thoracic, abdominal, and peripheral arteries. Polymyalgia rheumatica symptoms in patients with GCA correlate with (peri)synovitis of the shoulders. Relapses of GCA cannot be predicted by results of former PET scintigraphies.

     

Two cases with solitary pulmonary nodule due to non‐tuberculous mycobacterial infection showing intense 18F‐fluorodeoxyglucose uptake on positron emission tomography scan

We report an 81‐year‐old man and a 65‐year‐old woman with a solitary pulmonary nodule (SPN) due to infection with non‐tuberculous mycobacteria (NTM). In each case, the nodule showed a high ¹⁸F‐fluorodeoxyglucose (FDG) uptake with the maximum standardized uptake values (SUV) of 13.2 and 4.8 on positron emission tomography (PET) imaging, respectively. Both cases required partial lung resection for confirmation of the histological diagnosis. A review of six reported patients with SPN due to NTM infections showed that the SUV of FDG was more than 4.0 in the nodules of all cases. Positive results on FDG‐PET should be interpreted cautiously when evaluating SPN, especially in patients having predisposing factors for NTM infections. Geriatr Gerontol Int 2010; 10: 251–254.