Monitoring proton radiation therapy with in-room PET imaging.

We used a mobile positron emission tomography (PET) scanner positioned within the proton therapy treatment room to study the feasibility of proton range verification with an in-room, stand-alone PET system, and compared with off-line equivalent studies. Two subjects with adenoid cystic carcinoma were enrolled into a pilot study in which in-room PET scans were acquired in list-mode after a routine fractionated treatment session. The list-mode PET data were reconstructed with different time schemes to generate in-room short, in-room long and off-line equivalent (by skipping coincidences from the first 15 min during the list-mode reconstruction) PET images for comparison in activity distribution patterns. A phantom study was followed to evaluate the accuracy of range verification for different reconstruction time schemes quantitatively. The in-room PET has a higher sensitivity compared to the off-line modality so that the PET acquisition time can be greatly reduced from 30 to <5 min. Features in deep-site, soft-tissue regions were better retained with in-room short PET acquisitions because of the collection of (15)O component and lower biological washout. For soft tissue-equivalent material, the distal fall-off edge of an in-room short acquisition is deeper compared to an off-line equivalent scan, indicating a better coverage of the high-dose end of the beam. In-room PET is a promising low cost, high sensitivity modality for the in vivo verification of proton therapy. Better accuracy in Monte Carlo predictions, especially for biological decay modeling, is necessary.

Bone invasion by adenoid cystic carcinoma of the lacrimal gland: preoperative imaging assessment and surgical considerations.

PURPOSE: To identify the incidence of radiologically and histologically documented bony invasion of the lacrimal gland fossa by adenoid cystic carcinoma. PATIENTS AND METHODS: The authors reviewed the records of all 18 patients with lacrimal gland adenoid cystic carcinoma surgically treated at their institution from 1997 to 2009 for imaging findings (blinded review) and histologic findings on evaluation of the lacrimal gland fossa. Preoperative CT and/or MRI findings were available for 17 patients. RESULTS: The 8 men and 10 women ranged in age from 9 to 69 years. American Joint Committee on Cancer tumor stages after preoperative imaging were as follows: T1N0M0, 2 patients; T2N0M0, 5 patients; T3aN0M0, 2 patients; T3bN0M0, 5 patients; T3bN0M1, 2 patients; T4bN0M0, one patient; and TxN0M0, one patient. Preoperative imaging suggested bony involvement of the lacrimal gland fossa in 13 patients (76.5%); this was histologically confirmed in 11 of the 13. Preoperative imaging suggested no bone involvement in 4 patients, 3 of whom had bone involvement by histology. Overall, 14 of 17 histologically evaluable cases (82.3%) had invasion of the lacrimal gland fossa. Histologic findings of bone/periosteal involvement led to upstaging of 3 tumors. Metastases developed in 8 of 18 patients and trended with basaloid histology (p = 0.066). CONCLUSIONS: Adenoid cystic carcinoma of the lacrimal gland is associated with bone invasion in essentially all but the smallest of tumors (T1). This high rate of bone involvement may warrant addressing the bony walls during surgery for adenoid cystic carcinoma of the lacrimal gland.

Assessment of parotid gland dose changes during head and neck cancer radiotherapy using daily megavoltage computed tomography and deformable image registration.

PURPOSE: To analyze changes in parotid gland dose resulting from anatomic changes throughout a course of radiotherapy in a cohort of head-and-neck cancer patients. METHODS AND MATERIALS: The study population consisted of 10 head-and-neck cancer patients treated definitively with intensity-modulated radiotherapy on a helical tomotherapy unit. A total of 330 daily megavoltage computed tomography images were retrospectively processed through a deformable image registration algorithm to be registered to the planning kilovoltage computed tomography images. The process resulted in deformed parotid contours and voxel mappings for both daily and accumulated dose-volume histogram calculations. The daily and cumulative dose deviations from the original treatment plan were analyzed. Correlations between dosimetric variations and anatomic changes were investigated. RESULTS: The daily parotid mean dose of the 10 patients differed from the plan dose by an average of 15%. At the end of the treatment, 3 of the 10 patients were estimated to have received a greater than 10% higher mean parotid dose than in the original plan (range, 13-42%), whereas the remaining 7 patients received doses that differed by less than 10% (range, -6-8%). The dose difference was correlated with a migration of the parotids toward the high-dose region. CONCLUSIONS: The use of deformable image registration techniques and daily megavoltage computed tomography imaging makes it possible to calculate daily and accumulated dose-volume histograms. Significant dose variations were observed as result of interfractional anatomic changes. These techniques enable the implementation of dose-adaptive radiotherapy.

MRI in the pre-operative assessment of tracheal cylindroma. Case report.

Compared with malignant neoplasms of the chest, benign tumours are quite rare; cylindroma (or salivary gland adenoma) is exceptional. The apparent histological benignancy belies its high potential for invasiveness. This can, in some cases, lead to extensive, non-conservative surgery. By a different approach in the imaging of the chest, Magnetic Resonance Imaging in this condition may provide an accurate pre-operative assessment. We present a case in which MRI provided the information necessary for the surgical approach, and describe its accuracy and the results obtained.