Pancreatic involvement in Erdheim-Chester disease: Rare presentation of a rare disease

Erdheim-Chester disease (ECD) as a rare non-Langerhans histiocytosis has various clinical manifestations. It is characterized histologically by infiltration of every organ, more commonly bone, retroperitoneum, cardiovascular and CNS systems with foamy, lipid -laden macrophage. Pancreatic involvement as a manifestation of this uncommon disease has very rarely been reported. Here we report a 73-year-old woman with ECD and pancreas involvement in CT, MRI and PET scans. We also aim to increase radiologist knowledge about considering ECD as a differential diagnosis for pancreas mass in the appropriate clinical situation.

Incidental Skeletal Findings on Sodium-fluoride Positron Emission Tomography: A Collection of Benign Tumors

Sodium-fluoride (NaF) positron emission tomography (PET) is a sensitive method to detect altered bone mineralization. Its increasing use in routine clinical practice for metastatic bone disease has also resulted in the detection or characterization of incidental benign bone lesions. A spectrum of NaF PET scan cases with benign bone tumors are presented in this article, including whole body PET bone scan and selected PET/computed tomography (CT), CT, or magnetic resonance imaging (MRI) of the region of interest. The reader will be able to improve their knowledge related to the clinical presentation of these entities, some are rare and recognize based on NaF PET and CT/MRI patterns by reviewing these cases.

Phase II trial of perioperative chemotherapy + avelumab in locally advanced gastroesophageal adenocarcinoma: Preliminary results

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Background: Perioperative chemotherapy improves cure rate in locally advanced gastroesophageal adenocarcinoma (GEA), and immune checkpoint inhibitors are active at the metastatic stage. This trial tests the hypothesis that the addition of avelumab to perioperative chemotherapy will increase the major pathologic response (MPR) rate in comparison with historical controls. Methods: Phase II study of avelumab + chemotherapy (docetaxel, cisplatin and 5-FU or mDCF) given every 2 weeks for 4 cycles before and after surgery. Main inclusion criteria: GEA, cT3 and/or cN+, M0, WHO PS 0-1. Main exclusion criteria: use of immunosuppressants, serious autoimmune disease, daily intake >10 mg prednisone. Staging studies: CT, PET-CT, endoscopic ultrasound, diagnostic laparoscopy. Surgical resection: D2 lymphadenectomy, en-bloc esophagectomy for type I/II gastroesophageal junction (GEJ) tumors. Aim of the study: MPR as defined as tumor regression grades 0-1 (modified Ryan scheme); as per hypothesis, this experimental regimen will result in a 20% rate of MPR, compared with 7% with chemotherapy alone. Simon 2-stage design: if less than 2 MPR are seen in the first 16 patients, the study will be closed. The study hypothesis cannot be rejected if at least 6 MPR are seen in the first 50 patients. All adverse effects are prospectively recorded per CTCAE guidelines in patients who have received at least one treatment cycle. Survival rates are calculated with Kaplan-Meier method. Preliminary results are presented since the study has met its primary endpoint. Results: Feb 2018-Feb 2020: 28 patients enrolled (25 M/3 F, age 45-78). Location: GEJ (23), stomach (5). Staging: cT3 (25), cT4 (1), cN+ (20). Biomarkers expression: mismatch repair (MMR) protein loss (3/28); PD-L1(clone 73-10) expression in 1% (TPS) or more of tumor cells seen in 12/28 samples, and >10% in 6 patients. Grade 3 toxicity: stomatitis (2/28); nausea (2/28); vomiting (1/28); diarrhea (1/28); hypothyroidism (1/28); arthralgia (3/28); neutropenia (1/28). Grade 4 toxicity: pneumonia (1/28); neutropenia (2/28). Postoperative 30-day mortality: 0%. One patient was excluded from efficacy analyses for M1 staging; 27 patients underwent surgery, 26 with R0 (96%). Six cases (22%) show MPR: 3 grade 0 (11%) and 3 grade 1 (11%) tumor regressions. No correlation was seen between MMR proteins or PD-L1 expression and tumor regression. With a median follow-up of 1.5 years (range 0.4-2.5), the disease-free survival rate is projected to be 0.92 (95% CI 0.83-1.00) at 12 months and 0.77 (95% CI 0.58-1.00) at 24 months. Conclusions: The combination of mDCF chemotherapy with Avelumab demonstrates a promising safety and activity profile. Ongoing laboratory investigations are underway to correlate our findings with tumor molecular features before exposure to treatment. Clinical trial information: NCT03288350.

PET/Computed Tomography in the Diagnosis and Staging of Gastric Cancers

Although there has been a reduction of the incidence and mortality of gastric cancer, it remains among the commonest causes of cancer-related death. Accurate staging and evaluation of treatment response are vital for management. PET is used to complement anatomic imaging in cancer management. PET/computed tomography (CT) has demonstrated its potential value for preoperative staging, evaluation of response to therapy, and detection of recurrence. Not all types of gastric cancers have a high affinity for fluorodeoxyglucose. PET/CT in the evaluation and staging of gastric cancer is not established, but studies indicate that there may be an evolving role for this imaging modality.

18F-FDG PET/CT superior to serum CEA in detection of colorectal cancer and its recurrence

The aim of this study was to examine whether positron emission tomography (PET)/computed tomography (CT) can detect more cases of colorectal cancer (CRC) than serum carcinoembryonic antigen (CEA), both at initial staging and during surveillance for recurrence. A retrospective review of 639 CRC patients imaged with PET/CT was performed. PET/CT was superior to serum CEA in detecting CRC, identifying 2.5 times as many CRC at initial staging compared to serum CEA and 1.5 times as many CRC recurrences. The current guideline recommendations of utilizing PET/CT only in the context of a rising serum CEA will miss more than one third of all CRC recurrences.

Extraovarian primary peritoneal carcinoma: staging with 18F-FDG PET/CT

A 69-year-old woman who presented with left lower quadrant abdominal pain and elevated serum cancer antigen 125 (CA-125) levels was referred for an MRI and an (18)F-FDG PET/CT to evaluate a suspicious abdominal mass seen on ultrasound. PET/CT showed extensive, intensely FDG-avid, omental and pelvic peritoneal thickening with no suspicious ovarian or colon masses. Based on the PET/CT results, the patient had extensive debulking surgery and histopathological evaluation revealed an extraovarian primary peritoneal carcinoma (EOPPC). (18)F-FDG PET/CT may be useful in differentiating EOPPC from other types of peritoneal carcinomatosis, and in determining the extent of the disease to better guide surgical management and improve long term outcomes.

Spectrum of gastric malignancy on 18F-FDG PET/CT: a pictorial essay

A wide variety of malignant gastric diseases can be detected, staged, and followed on (18)F-FDG PET/CT. Although the PET/CT findings are often nonspecific and some can be seen in certain benign gastric diseases, the aim of this atlas was to demonstrate that the wide histological spectrum of gastric tumors that can be evaluated, staged, and followed with PET/CT is much broader than current medical literature would suggest. PET/CT readers and oncologists should be aware of the utility of PET/CT in these tumors and the imaging characteristics and patterns of (18)F-FDG uptake that can be demonstrated in these cases.

Spectrum of malignant renal and urinary bladder tumors on 18F-FDG PET/CT: a pictorial essay

A wide variety of malignant renal and urinary bladder diseases can be detected on (18)F-FDG PET/CT. Although the PET/CT findings are often nonspecific, the aim of this atlas was to demonstrate that the spectrum of renal and urinary bladder malignancy that can be evaluated with PET/CT is much broader than current medical literature would suggest. PET/CT readers and oncologists should be aware of the variety of urological tumor types that can be detected on PET/CT and some of the patterns of (18)F-FDG uptake that can be observed in these cases.

Giant Cell Tumor Pulmonary Metastases Mimic Primary Malignant Pulmonary Nodules on (18)F-FDG PET/CT

A 59-year-old man with a 30-year history of multiple recurrences of a giant cell tumor (GCT) of the left knee was referred for an (18)F-FDG PET/CT to evaluate a solitary pulmonary nodule. The nodule was mildly FDG-avid, raising suspicion of malignancy. It was excised and histologically proven to be a GCT pulmonary metastasis. A follow-up PET/CT done 2 years later revealed a new, larger lung mass that was more intensely FDG-avid, but of the same histology. This rare report highlights a pitfall in the evaluation of solitary pulmonary lesions by (18)F-FDG PET/CT in patients with GCT of the bone.

Myeloid Sarcoma and Acute Myelomonocytic Leukemia in an Adolescent with Tetrasomy 8: Staging with (18)F-FDG PET/CT

Tetrasomy 8 is a relatively rare chromosomal abnormality that has been reported in only 33 cases in hematologic disorders. It is known for its association with aggressive acute myeloid leukemia (AML) and myeloid sarcoma and is considered a very poor prognostic factor. Myeloid sarcoma is a rare hematologic malignancy characterized by tumor masses consisting of immature myeloid cells, presenting at an extramedullary site. We present a case of a 17-year-old boy referred for an (18)F-FDG PET/CT for the evaluation of pleural masses and spinal bone lesions seen on CT, after presenting with a 4 month history of chest pain. The PET/CT revealed extensive FDG-avid extramedullary disease in the soft tissues of the chest, abdomen, and pelvis, which were biopsy-proven to be myeloid sarcoma, as well as extensive intramedullary disease biopsy proven to be AML. This is the first report of the use of (18)F-FDG PET/CT to stage a subset of aggressive AML and myeloid sarcoma in a patient with an associated chromosomal abnormality (tetrasomy 8).

Gastric recurrence of a primary colon plasmacytoma: staging and evaluating response to therapy with 18F-FDG PET/CT

A 53-year-old male with a remote history of colon adenocarcinoma presented with weakness, severe anaemia and an actively bleeding ulcerated lesion in the stomach. An 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT showed FDG-avid masses in the stomach and mesentery, which were biopsied to reveal an unsuspected diagnosis of plasmacytoma. The original colon tumour pathology was identical and this prompted its re-evaluation to a primary colon plasmacytoma. The patient was treated with chemotherapy and a follow-up PET/CT scan showed complete resolution of the gastric and mesenteric masses. 18F-FDG PET/CT is useful in the restaging and follow-up of this very rare extramedullary plasmacytoma.

Perioperative chemotherapy for upper gastrointestinal cancer: Correlation between response to treatment and outcome

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Background: Perioperative chemotherapy improves outcomes of surgery for upper GI cancer. Some patients have rapid recurrence. We hypothesized that any type of response to chemotherapy would predict better disease-free survival (DFS).

Methods: From May 2007 to Sep 2009, 43 patients with operable adenocarcinoma of the esophagus, stomach or gastroesophageal junction went on a multicenter phase II trial. 3 cycles of docetaxel/cisplatin/5FU were given pre and post surgery. We compared DFS between responders and nonresponders after 3 cycles. Clinical response was defined as improvement of ≥ 2 points on a dysphagia score (0: normal swallowing, to 4: total obstruction), metabolic response as ≥ 35% reduction of maximum SUV by PET scan. Lack of nodal involvement or significant histologic regression (less than 50% viable tumor) was considered pathologic response. Log-rank test was used for univariate analysis, Cox regression model for multivariate analysis. All p values are double sided, median follow-up from surgery is 808 days.

Results: Clinical response data for 29/40 patients: 26 responses (90%). Median DFS was 405 days for clinical responders vs. 210 days for nonresponders (p= 0.018). Metabolic response data for 28/40 patients : 22 responses (70%). Median DFS was 276 days in metabolic nonresponders, and has not been reached in responders (p = 0.009). 14 patients had no nodal involvement at resection (N0) and had longer DFS (median not reached) than the 26 with N+, who had median DFS of 562 days (p = 0.045). A nonsignificant trend (p = 0.192) was seen in favor of the 20 with significant tumor regression (DFS 565 days) compared to the 20se without it (median DFS not reached). All results were supported by multivariate analysis.

Conclusions: These preliminary results indicate that clinical, metabolic and pathologic responses may be individually predictive of longer DFS in patients receiving perioperative chemotherapy for upper GI adenocarcinoma. This requires confirmation in larger datasets. The optimal management of nonresponders is unclear at present. Acknowledgements: Biostatistics Unit (McGill University Health Centre) and Cedars Cancer Institute (Henry R Shibata Fellowship to Dr Alcindor).

Perioperative docetaxel, cisplatin, and 5-fluorouracil (DCF) for locally advanced esophageal and gastric adenocarcinoma: a multicenter phase II trial

BACKGROUND

Although perioperative chemotherapy for esophagogastric adenocarcinoma (ADC) improves survival, the overall poor prognosis suggests that further refinement of treatment is required. Docetaxel, cisplatin, and 5-fluorouracil (5-FU) (DCF) is effective for metastatic ADC of the upper gastrointestinal (GI) tract; we thus sought to investigate the efficacy of this regimen in patients with resectable disease.

PATIENTS AND METHODS

Patients with resectable ADC of the upper GI tract received DCF [docetaxel (Taxotere) 75 mg/m(2) I.V. day 1, cisplatin 75 mg/m(2) I.V. day 1, 5-FU 750 mg/m(2) continuous infusion for 120 h, every 3 weeks] for three cycles before and after resection. Primary end point was complete resection; secondary end points were response, toxicity, surgical morbidity, and overall survival.

RESULTS

Forty-three patients with ADC of the esophagus (11), gastroesophageal junction (25), or stomach (7) started treatment and 86% completed all preoperative cycles with grade 3-4 toxicity arising in 47%. Metabolic response to chemotherapy (reduction in maximal standard uptake value >35%) was achieved in 25/33 (76%) patients. Surgery was carried out in 41/43 and complete resection was achieved in all 41 patients with pathologic complete response in 4/41. Postoperative chemotherapy was started in 29 patients and completed in 24. Three-year overall survival was 60%.

CONCLUSION

Perioperative DCF is a tolerable and highly effective regimen for the treatment of esophagogastric ADC.

Initial McGill experience with fluorodeoxyglucose pet/ct staging of soft-tissue sarcoma

BACKGROUND

Soft-tissue sarcoma spreads predominantly to the lung. The frequency with which positron-emission tomography (pet) detects metastases not already obvious by chest computed tomography (ct) or clinical examination is currently unclear.

METHODS

We retrospectively identified cases of soft-tissue sarcoma. Ewing sarcoma, rhabdomyosarcoma, and gastrointestinal stromal tumour were excluded, as were cases in which patients underwent imaging for follow-up, response assessment, or recurrence. Patients all had undergone diagnostic chest ct as part of their staging. Directed studies were requested to follow up on abnormal findings in the clinical history or physical examination. All charts and pre-treatment imaging were reviewed retrospectively.

RESULTS

From 2004 to 2008, 75 patients met the criteria for the present review. Their median age was 51 years. In 21% of cases, the primary tumour had been removed (by excisional biopsy or unplanned excision) before staging. Of the previously unresected primary tumours, 97% were avid for fluorodeoxyglucose. Of all tumours, 81% were intermediate or high grade (Fédération Nationale des Centres de Lutte Contre le Cancer grades 2-3). The primary tumour was stage T2b in 69% of cases. The most common primary site was a lower extremity (55%). The most common pathologic diagnoses were leiomyosarcoma (21%), liposarcoma (19%), and synovial sarcoma (17%). At the end of staging, 17% of patients were considered to have metastatic disease. Imaging by pet was negative for distant disease in 64 of the 75 cases. In 7 of the 64 cases, metastatic disease was evident on chest ct (negative predictive value: 88%). Imaging by pet was positive in 8 cases, with 5 of those already known to have metastases, 2 having pathologically proven false positives, and 1 being a new finding of a pulmonary metastasis (positive predictive value: 75%). The pet imaging was indeterminate in 3 patients (none of whom subsequently developed metastatic disease). Two incidental benign parotid tumours were found. Overall, only 1 patient was upstaged as a result of pet imaging (1.3%). In addition, pet did not alter the management of patients already know to have M1 disease (no new organ sites identified).

CONCLUSIONS

Although pet may be helpful in specific circumstances, routine use of fluorodeoxyglucose pet imaging for detection of metastatic disease as part of the initial staging of soft-tissue sarcoma added little to imaging by chest ct and was unlikely to alter management in our series.

Review of Physiologic and Pathophysiologic Sources of Fluorodeoxyglucose Uptake in the Chest Wall on PET

The chest wall can be defined as the osseous and soft tissue structures that form the outer framework of the thorax and move during breathing. Topics discussed in this article include physiologic uptake of fluorodeoxyglucose, benign diseases of the chest wall, and malignant tumors of the chest wall.

Intravenous administration of diazepam significantly reduces brown fat activity on 18F-FDG PET/CT

BACKGROUND

Brown adipose tissue (BAT) activity on (18)F-fluorodeoxyglucose (FDG) PET/CT can introduce an undesirable element of complexity when attempting to discern physiologic activity from more ominous entities. Recent studies have demonstrated several methods to reduce BAT FDG uptake. Benzodiazepines, however, have yet to been proven effective against BAT.

METHODS

Twenty-five patients with increased BAT FDG uptake were selected retrospectively from our PET/CT database between November 2004 and January 2011. These patients had been asked to return on a different day for repeat scanning with 5mg of intravenous diazepam, administered ten minutes prior to FDG. Two patients underwent this procedure on a second occasion (for a follow-up scan at a later date), thus resulting in a total of twenty-seven scans from twenty five patients. FDG uptake in BAT was recorded using the maximum standardized uptake value (SUVmax).

RESULTS

The mean basal BAT SUVmax was 10.1 ± 4.6 compared to a mean SUVmax of 2.8 ± 3.3 post IV diazepam (p < 0.0001). Approximately 89% (24 of 27) of scans had no significant residual BAT activity. The three remaining scans had a reduction in SUVmax ranging from 23-64% following diazepam administration. No adverse effects were noted.

CONCLUSION

We observed a significant reduction in brown fat activity in para-spinal, cervical, mediastinal, para-adrenal, and supra- and infra-clavicular regions on PET/CT following premedication with intravenous diazepam. We feel that IV benzodiazepines should be considered a pharmacologic option for reducing BAT FDG uptake, which in turn, will aid in distinguishing physiologic metabolic activity from pathology.

FDG PET/CT imaging in primary osseous and soft tissue sarcomas: a retrospective review of 212 cases

PURPOSE

The aims of this study are to evaluate the sensitivity of FDG PET/CT for detection of soft tissue and osseous sarcomas on the basis of FDG avidity.

METHODS

We retrospectively evaluated 212 consecutive patients with known soft tissue or osseous sarcoma who had undergone a FDG PET/CT study for the initial staging or assessment of recurrence of disease. The maximum standardized uptake value (SUVmax) of each primary and/or most intense metastatic lesion was measured and compared with the histological data provided in the final pathological reports. An SUVmax of 2.5 or greater was considered positive for our analysis.

RESULTS

Sufficient histopathological data were available for 160 soft tissue sarcomas and 52 osseous sarcomas. FDG PET/CT detected 93.9% of all sarcomas with a sensitivity of 93.7% for soft tissue sarcomas and 94.6% for osseous sarcomas. The sensitivities of the most common sarcoma histologies were 100% for leiomyosarcomas, 94.7% for osteosarcomas, 100% for Ewing's sarcomas, 88.9% for liposarcomas, 80.0% for synovial sarcomas, 100% for gastrointestinal stromal tumors, 87.5% for malignant peripheral nerve sheath tumors, 100% for fibroblastic and myoblastic sarcomas, and 100% for malignant fibrohistiocytic tumors. The receiver-operating characteristic curve revealed an area under the curve of 94% for the discrimination of low-grade and high-grade sarcomas imaged for initial staging by FDG PET/CT.

CONCLUSION

The combined metabolic and morphological information of FDG PET/CT imaging allows high sensitivity for the detection of various sarcomas and accurate discrimination between newly diagnosed low-grade and high-grade sarcomas.

Malignant extrarenal rhabdoid tumor of the spine: staging and evaluation of response to therapy with F-18 FDG PET/CT

Malignant extrarenal rhabdoid tumor (ERRT) is a very rare type of soft-tissue sarcoma with a reported incidence of 0.3% of all soft-tissue sarcomas. Only 7 cases of spinal malignant ERRT have been reported in the literature, and to our knowledge, F-18 FDG PET/CT imaging for staging and evaluation of response to therapy for these tumors has not been previously described. This is a case of an 8-month-old boy with malignant ERRT of the spine, who was staged with F-18 FDG PET/CT, and had his tumor burden assessed with PET/CT after chemotherapy, which altered the subsequent chemotherapy regimen.

Incidental thyroid "PETomas": clinical significance and novel description of the self-resolving variant of focal FDG-PET thyroid uptake

BACKGROUND

Recent series of incidental thyroid activity on fluorodeoxyglucose positron emission tomography (FDG-PET) in patients evaluated for nonthyroidal malignancy, which we refer to as a "PEToma," have suggested that such lesions are associated with a significant incidence of primary thyroid cancer.

METHODS

We retrospectively reviewed 6457 FDG-PET scans performed on 4726 patients from May 2004 to March 2007. We reviewed the cases of patients whose PET or computed tomography (CT) radiology reports described PET uptake within the thyroid to identify incidence and malignant potential of PETomas and evaluate their clinical and histopathologic features.

RESULTS

We found that 160 patients (3.4%) had incidental, abnormal FDG uptake in the thyroid gland, 103 of whom had focal uptake (the PEToma group). Of these patients, 50 (48%) underwent further investigations, including ultrasonography in 48, fine-needle aspiration cytology in 38 and computed tomography in 3. Ten patients underwent surgery, and papillary thyroid cancer was identified in 9. The remaining 53 patients with PETomas underwent no further investigation. Interestingly, 5 patients who had focal uptake within the thyroid showed either spontaneous resolution on repeat FDG-PET (self-resolving) or no focal lesion on subsequent ultrasonography (false-positive).

CONCLUSION

The incidence of papillary thyroid cancer in the present series is similar to that in the literature. Although some patients will show self-resolving or false-positive focal thyroid uptake on FDG-PET, we believe that, if the patient's clinical status permits, the evaluation of patients with incidental thyroid PEToma should include ultrasonographic confirmation and fine-needle aspiration cytology.

Utility of total body FDG PET/CT imaging in the initial staging of soft-tissue sarcoma

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Background: Soft-tissue sarcoma spreads predominantly to the lung. It is currently unclear how often PET scan will detect metastases not already obvious by chest imaging or clinical examination. Methods: Soft-tissue sarcoma cases were identified retrospectively. Ewing's sarcoma, rhabdomyosarcoma and GIST tumors were excluded as were patients imaged for follow-up, response assessment or recurrence. Patients all had had a diagnostic chest CT scan as part of their staging. Directed studies were requested to follow-up on abnormal findings in the clinical history or physical examination. All charts and pre-treatment imaging were reviewed retrospectively. Results: From 2004 to 2008, 75 patients met the criteria for this review. These 75 patients had total body FDG-PET/CT imaging on routine initial staging of their sarcoma. The median age was 51. In 21% of cases, the primary tumor had been removed by excisional biopsy or unplanned excision prior to staging. 97% of the previously unresected primary tumors were FDG avid (SUV ≥ 2). 81% of tumors were high-grade (FNCLCC Grade 2–3). The primary tumor was stage T2b in 68% of cases. The most common primary site was the lower extremity (55%). The most common pathological diagnoses were: leiomyosarcoma (21%), liposarcoma (19%) and synovial sarcoma (17%). At the end of staging, 17% of patients were considered to have metastatic disease. PET scans were negative for distant disease in 64/75 cases. Seven of these 64 cases had metastatic disease on chest CT (negative predictive value 89%). 8 PET scans were positive - of these, 4 patients were already known to have metastases, 2 were pathologically proven false positives and 1 was a new finding of a pulmonary metastasis (sensitivity 46%). Three patients had indeterminate PET scans (subsequently none developed metastatic disease). Two incidental benign parotid tumors were found. In total, only 1 patient was upstaged by the PET imaging (1.3%). In addition, PET did not alter management of patients already know to have M1 disease (no new organ sites identified). Conclusions: Although PET scans may be of use in specific circumstances, routine use of FDG PET imaging for detection of metastatic disease as part of the initial staging of soft-tissue sarcoma adds little to chest CT scanning and is unlikely to alter management.

No significant financial relationships to disclose.

PET/CT for radiotherapy treatment planning in patients with soft tissue sarcomas

PURPOSE

To study the possibility of incorporating positron emission tomography/computed tomography (PET/CT) information into radiotherapy treatment planning in patients with high-grade soft tissue sarcomas (STS).

METHODS AND MATERIALS

We studied 17 patients treated with preoperative radiotherapy at our institution from 2005 to 2007. All patients had a high-grade STS and had had a staging PET/CT scan. For each patient, an MRI-based gross tumor volume (GTV), considered to be the contemporary standard for radiotherapy treatment planning, was outlined on a T1-gadolinium enhanced axial MRI (GTV(MRI)), and a second set of GTVs were outlined using different threshold values on PET images (GTV(PET)). PET-based target volumes were compared with the MRI-based GTV. Threshold values for target contouring were determined as a multiple (from 2 to 10 times) of the background soft tissue uptake values (B) sampled over healthy tissue.

RESULTS

PET-based GTVs contoured using a threshold value of 2 or 2.5 most closely resembled the GTV(MRI) volumes. Higher threshold values lead to PET volumes much smaller than the GTV(MRI). The standard deviations between the average volumes of GTV(PET) and GTV(MRI) ratios for all thresholds were large, ranging from 36% for 2 xB up to 93% for 10 xB. Maximum uptake-to-background ratio correlated poorly with the maximum standardized uptake values.

CONCLUSIONS

It is unlikely that PET/CT will make a significant contribution in GTV definition for radiotherapy treatment planning in patients with STS using threshold methods on PET images. Future studies will focus on molecular imaging and tumor physiology.

Correlation of the ERPF with the extraction fraction values of technetium-99m mercaptoacetyltriglycine

OBJECTIVE

The objective of this study was to determine if a correlation exists between the effective renal plasma flow (ERPF) and the extraction fraction (EF) using 99mTc MAG3 in children. This EF has been previously described with 9mTc DTPA. However, the renal imaging agent of choice has become 9mTc MAG3.

MATERIAL AND METHOD

The study was approved by The Children's Hospital of Philadelphia's institutional review board. Informed consent was also obtained A retrospective study of 29 children (16 males, 13 females) of ages 1 month to 19.5 years who underwent 99mTc MAG3 renal scintigraphy from September 2001 to December 2001 was analysed. EF values were calculated with and without attenuation correction in each kidney by determining the counts in a region of interest, correcting for background and comparing the counts with the injected dose. The EF was compared to the ERPF calculated using the Schlegel's method. The correlation between the EF and the ERPF corrected and non-corrected for soft tissue attenuation, were determined and were identified by using linear regression analysis.

RESULTS

There was significant correlation between the ERPF and the EF with (r = 0.62, p < 0.05 on the left, r = 0.51, p = 0.005 on the right) than without attenuation correction (r = 0.54, p = 0.003 on the left, r = 0.42, p = 0.022 on the right).

CONCLUSION

These results indicate a correlation of the ERPF calculated using the Schlegel's method with EF obtained from a 99mTc MAG3 renal scintigraphy. The EF may be the good alternative parameter for calculation of renal function, potentially more practical in pediatric patient and the ERPF for 99mTc MAG3 using the established software program based on Schlegel's formula.

Demonstration of excessive metabolic activity of thoracic and abdominal muscles on FDG-PET in patients with chronic obstructive pulmonary disease

PURPOSE

The purpose of this study was to determine if an FDG-PET study was able to visualize muscle uptake of the chest and abdomen in patients with chronic obstructive pulmonary disease (COPD).

METHODS

This study included 25 patients with COPD and 25 patients without COPD who had undergone a FDG-PET study. The nonattenuation-corrected images were used to determine the degree of FDG uptake in the intercostals, subscapular, abdominal rectus, and abdominal oblique muscles. The intensity of uptake in the muscles was rated on a 4-point grading scale with 1 being less, 2 the same, 3 slightly more, and 4 markedly more intense than the sternum.

RESULTS

Thirteen patients with COPD demonstrated FDG activity in the intercostal muscles that was equal to or greater than the sternum and the tracer was demonstrated predominantly in the inferolateral chest wall (n = 8), the entire lateral chest wall (n = 2), the posteroinferior chest wall (n = 2), and the entire chest wall (n = 1). In all 13 patients with COPD who demonstrated FDG activity in the abdominal oblique muscles, the site of muscle activity was predominantly in the anteroinferior abdominal wall (n = 8), the lateral wall (n = 4), and the anterior wall (n = 1). In patients without known COPD, the frequency and intensity of uptake in the muscles were less than those with the disease.

CONCLUSION

This study demonstrates the ability of FDG-PET imaging to assess muscle function in respiratory disorders and may prove to be of some value in further characterizing this disorder.

Rapid normalization of osseous FDG uptake following traumatic or surgical fractures

It is known that following a traumatic fracture or surgical intervention, bone scintigraphy reveals positive results for an extended period of time, posing a challenge when evaluating patients for possible malignancy or superimposed osteomyelitis. Previous reports indicate that acute fractures can also result in increased fluorine-18 fluorodeoxyglucose (FDG) accumulation and therefore cause difficulties when patients are evaluated for other indications by FDG-PET. The purpose of this study was to assess the pattern and time course of abnormal FDG uptake following traumatic or surgical fracture. A total of 1,517 consecutive patients who underwent whole-body FDG-PET imaging were retrospectively studied. A history of fractures or orthopedic intervention was obtained from an interview prior to scanning. The FDG-PET results were compared with the results of other imaging studies, including bone scans, radiographs, CT, and MRI, as well as surgical pathology reports. Thirty-seven patients with a known date of traumatic or surgical fracture were identified. Among these, 14 had fractures or surgery within 3 months prior to FDG-PET, while 23 had fractures or surgical intervention greater than 3 months prior to FDG-PET. FDG-PET showed no abnormally increased uptake at the known fracture or surgical sites in 30 of these patients. Notably, in the 23 patients with fractures more than 3 months old, all but one showed no abnormally increased uptake. Furthermore, the positive FDG uptake in this exception was a result of complicating osteomyelitis. In the 14 patients with a history of fracture less than 3 months old, only six had abnormally increased FDG uptake. Following traumatic or surgical fractures, FDG uptake is expected to be normal within 3 months unless the process is complicated by infection or malignancy.

Use of a corrected standardized uptake value based on the lesion size on CT permits accurate characterization of lung nodules on FDG-PET

The purpose of this study was to determine the actual standardized uptake value (SUV) by using the lesion size from computer tomography (CT) scan to correct for resolution and partial volume effects in positron emission tomography (PET) imaging. This retrospective study included 47 patients with lung lesions seen on CT scan whose diagnoses were confirmed by biopsy or by follow up CT scan when the PET result was considered negative for malignancy. Each lesion's FDG uptake was quantified by the SUV using two methods: by measuring the maximum voxel SUV (maxSUV) and by using the lesion's size on CT to calculate the actual SUV (corSUV). Among small lesions (2.0 cm or smaller on CT scan), ten were benign and 17 were malignant. The average maxSUV was 1.43+/-0.77 and 3.02+/-1.74 for benign and malignant lesions respectively. When using an SUV of 2.0 as the cutoff to differentiate benignity and malignancy, the sensitivity, specificity, and accuracy were 65%, 70%, and 67% respectively. When an SUV of 2.5 was used for cutoff, the sensitivity, specificity, and accuracy were 47%, 80%, and 59% respectively. The average corSUV was 1.65+/-1.09 and 5.28+/-2.71 for benign and malignant lesions respectively. Whether an SUV of either 2.0 or 2.5 was used for cutoff, the sensitivity, specificity, and accuracy remained 94%, 70%, and 85% respectively. The only malignant lesion that was falsely considered benign with both methods was a bronchioalveolar carcinoma which did not reveal any elevated uptake of fluorine-18 fluorodeoxyglucose (FDG). Of the large lesions (more than 2.0 cm and less than 6.0 cm), one was benign and 19 were malignant and the corSUV technique did not significantly change the accuracy. It is concluded that measuring the SUV by using the CT size to correct for resolution and partial volume effects offers potential value in differentiating malignant from benign lesions in this population. This approach appears to improve the accuracy of FDG-PET for optimal characterization of small lung nodules.

Positron emission tomography imaging in nonmalignant thoracic disorders

The role of the fluorodeoxyglucose (FDG) technique positron emission tomography (PET) is well established in the management of patients with lung cancer. Increasingly, it is becoming evident that FDG-PET can be effectively employed to diagnose a variety of benign pulmonary disorders. Knowledge of such applications further expands the domain of this powerful modality and further improves the ability to differentiate benign from malignant diseases of the chest. We describe pertinent technical factors that substantially contribute to optimal imaging of the thoracic structures. Particularly, the complementary role of attenuation correction (AC) to that of non-AC images is emphasized. We further outline the need for and the state of the art for co-registration of PET and anatomic images for diagnostic and therapeutic purposes. We then review patterns of physiologic uptake of FDG in thoracic structures, including the lung, the heart, the aorta and large arteries, esophagus, thymus, trachea, thoracic muscles, bone marrow, and joints and alterations following radiation therapy to the thorax. A great deal of information is provided with regard to differentiating benign from malignant nodules and in particular, we emphasize the role of dual time point imaging and partial volume correction for accurate assessment of such lesions. Following a brief review of the diagnostic issues related to the assessment of mediastinal adenopathies, the role of FDG-PET imaging in environment-induced lung diseases, including pneumoconiosis, smoking, and asthma are described. A large body of information is provided about the role of this technology in the management of patients with suspected infection and inflammation of the lungs such as acquired immunodeficiency syndrome, fever of unknown origin, sarcoidosis, chronic granulomatous disease and monitoring the disease process and response to therapy. Finally, the value of FDG-PET in differentiating benign from malignant diseases of the pleura including asbestosis-related disorders is described at the conclusion of this comprehensive review.

Incidental detection of colon cancer by FDG positron emission tomography in patients examined for pulmonary nodules

PURPOSE

Fluorodeoxyglucose (FDG) positron emission tomographic (PET) imaging has been used extensively to diagnose cancer with high rates of sensitivity and specificity. One of its applications is to distinguish benign from malignant pulmonary nodules. It is common to observe colonic uptake on whole-body FDG-PET images. Because patients with lung cancer also tend to be in the age group with the highest incidence of colon cancer, the authors tried to assess the efficacy of FDG-PET for detecting occult colon cancer in patients referred for the evaluation of lung nodules.

METHODS

The records of 500 consecutive patients referred for the evaluation of pulmonary nodules were reviewed retrospectively. Among the patients, 197 had no previous clinical or radiographic evidence of abnormalities in the gastrointestinal tract, and none had been found to have any cancer before undergoing an FDG-PET study. All colon lesions were verified either by histologic analysis or by clinical course.

RESULTS

Among the 197 patients analyzed, 59 had diffuse colonic uptake in various segments of the colon. Seventeen of the patients had focal colonic uptake, five of which were proved to be colon cancer.

CONCLUSIONS

The routine use of FDG PET to characterize lung lesions significantly increases the probability of detecting unexpected extrathoracic disease. In these patients, the incidental finding of colon cancer had an important effect on their treatment and may prove to be very cost-effective.

Persistent non-specific FDG uptake on PET imaging following hip arthroplasty

Hip arthroplasty is a common surgical procedure, but the diagnosis of infection associated with hip arthroplasty remains challenging. Fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) has been shown to be a promising imaging modality in settings where infection is suspected. However, inflammatory reaction to surgery can result in increased FDG uptake at various anatomic locations, which may erroneously be interpreted as sites of infection. The purpose of this study was to assess the patterns and time course of FDG accumulation following total hip replacement over an extended period of time. Firstly, in a prospective study nine patients with total hip replacement were investigated to determine the patterns of FDG uptake over time. Three FDG-PET scans were performed in each patient at about 3, 6 and 12 months post arthroplasty. Secondly, in a retrospective analysis, the medical and surgical history and FDG-PET imaging results of 710 patients who had undergone whole-body scans for the evaluation of possible malignant disorders were reviewed. The history of arthroplasty and FDG-PET findings in the hip region were reviewed for this study. Patients with symptomatic arthroplasties or related complaints during FDG-PET scanning were excluded from the analysis. During the entire study period, all nine patients enrolled in the prospective study were demonstrated to have increased FDG uptake around the femoral head or neck portion of the prosthesis that extended to the soft tissues surrounding the femur. Among the patients reviewed in the retrospective study, 18 patients with a history of 21 hip arthroplasties who were asymptomatic at the time of FDG-PET scan met the criteria for inclusion. The time interval between the hip arthroplasty and the FDG-PET study ranged from 3 months to 288 months (mean+/-SD: 80.4+/-86.2 months). In 81% (17 of 21) of these prostheses, increased FDG uptake could be noted around the femoral head or neck portion of the prosthesis. The average time interval between arthroplasty and FDG-PET scan in these patients was 71.3 months. In only four prostheses (19%, 4 of 21) was no abnormally increased FDG uptake seen around the prostheses or adjacent sites. The average time interval in these patients was 114.8 months. It is concluded that following hip arthroplasty, non-specifically increased FDG uptake around the head or neck of the prosthesis persists for many years, even in patients without any complications. Therefore, to minimize the number of false-positive results for infection with PET studies obtained to evaluate a painful hip prosthesis, caution should be exercised when interpreting FDG uptake around the head or neck portion of the prosthesis.

Dual time point 18F-FDG PET for the evaluation of pulmonary nodules

18F-FDG PET has reached widespread application in the assessment of pulmonary nodules. This study compares the diagnostic accuracy of standard 18F-FDG PET scanning with those of dual time point 18F-FDG PET scanning.

METHODS

Thirty-six patients (21 women, 15 men; mean age, 67 y; range, 36-88 y) with 38 known or suspected malignant pulmonary nodules underwent PET of the thorax at 2 time points: scan 1 at 70 min (range, 56-110 min) and scan 2 at 123 min (range, 100-163 min) after the intravenous injection of 2.5 MBq 18F-FDG per kilogram of body weight. All scanning was performed on a dedicated C-PET scanner. The mean interval between the scans was 56 min (range, 49-64 min). Regions of interest were overlaid onto each fully corrected image in the areas of the radiographically known lung densities. The standardized uptake values (SUVs) were calculated for both time points.

RESULTS

Surgical pathology and follow-up revealed 19 patients with 20 malignant tumors, whereas 16 patients had benign lesions. The tumor SUVs (mean +/- SD) were 3.66 +/- 1.95 (scan 1) and 4.43 +/- 2.43 (scan 2) (20.5% +/- 8.1% increase; P < 0.01). Four of 20 malignant tumors had SUVs of <2.5 on scan 1 (range, 1.12-1.69). Benign lesions had SUVs of 1.14 +/- 0.64 (scan 1) and 1.11 +/- 0.70 (scan 2) (P = not significant). Standard PET scanning (single time point) with a threshold SUV of 2.5 (at time point 1) reached a sensitivity of 80% and a specificity of 94%; dual time point scanning with a threshold value of 10% increase between scan 1 and scan 2 reached a sensitivity of 100% with a specificity of 89%.

CONCLUSION

Dual time point 18F-FDG PET results in a very high sensitivity and specificity for detection of malignant lung tumors.

Assessment of viable splenic tissue in massive splenic infarction with a Tc-99m heat-damaged RBC scan

A 59-year-old man with essential thrombocytosis was examined for abdominal pain. Splenic infarction was diagnosed on a computed tomographic scan. The Tc-99m heat-denatured RBC scan showed viable splenic tissue that was not evident on the computed tomographic scan or Tc-99m sulfur colloid scintigraphy.