Light Emitting Diodes based Photoacoustic Imaging and Potential Clinical Applications.

Using low cost and small size light emitting diodes (LED) as the alternative illumination source for photoacoustic (PA) imaging has many advantages, and can largely benefit the clinical translation of the emerging PA imaging technology. Here, we present our development of LED-based PA imaging integrated with B-mode ultrasound. To overcome the challenge of achieving sufficient signal-to-noise ratio by the LED light that is orders of magnitude weaker than lasers, extensive signal averaging over hundreds of pulses is performed. Facilitated by the fast response of the LED and the high-speed driving as well as the high pulse repetition rate up to 16 kHz, B-mode PA images superimposed on gray-scale ultrasound of a biological sample can be achieved in real-time with frame rate up to 500 Hz. The LED-based PA imaging could be a promising tool for several clinical applications, such as assessment of peripheral microvascular function and dynamic changes, diagnosis of inflammatory arthritis, and detection of head and neck cancer.

Advanced Collapsed cone Engine dose calculations in tissue media for COMS eye plaques loaded with I-125 seeds.

PURPOSE: To investigate the dose calculation accuracy of the Advanced Collapsed cone Engine (ACE) algorithm for ocular brachytherapy using a COMS plaque loaded with I-125 seeds for two heterogeneous patient tissue scenarios. METHODS: The Oncura model 6711 I-125 seed and 16 mm COMS plaque were added to a research version (v4.6) of the Oncentra® Brachy (OcB) treatment planning system (TPS) for dose calculations using ACE. Treatment plans were created for two heterogeneous cases: (a) a voxelized eye phantom comprising realistic eye materials and densities and (b) a patient CT dataset with variable densities throughout the dataset. ACE dose calculations were performed using a high accuracy mode, high-resolution calculation grid matching the imported CT datasets (0.5 × 0.5 × 0.5 mm3 ), and a user-defined CT calibration curve. The accuracy of ACE was evaluated by replicating the plan geometries and comparing to Monte Carlo (MC) calculated doses obtained using MCNP6. The effects of the heterogeneous patient tissues on the dose distributions were also evaluated by performing the ACE and MCNP6 calculations for the same scenarios but setting all tissues and air to water. RESULTS: Average local percent dose differences between ACE and MC within contoured structures and at points of interest for both scenarios ranged from 1.2% to 20.9%, and along the plaque central axis (CAX) from 0.7% to 7.8%. The largest differences occurred in the plaque penumbra (up to 17%), and at contoured structure interfaces (up to 20%). Other regions in the eye agreed more closely, within the uncertainties of ACE dose calculations (~5%). Compared to that, dose differences between water-based and fully heterogeneous tissue simulations were up to 27%. CONCLUSIONS: Overall, ACE dosimetry agreed well with MC in the tumor volume and along the plaque CAX for the two heterogeneous tissue scenarios, indicating that ACE could potentially be used for clinical ocular brachytherapy dosimetry. In general, ACE data matched the fully heterogeneous MC data more closely than water-based data, even in regions where the ACE accuracy was relatively low. However, depending on the plaque position, doses to critical structures near the plaque penumbra or at tissue interfaces were less accurate, indicating that improvements may be necessary. More extensive knowledge of eye tissue compositions is still required.

[Quality standards for ultrasonographic assessment of peripheral vascular malformations and vascular tumors. Report of the french society for vascular medicine. 2018 Update]. / Standards de qualité pour la pratique de l'examen écho-Doppler dans l'étude des malformations et tumeurs vasculaires. Rapport de la Société française de médecine vasculaire (SFMV) : actualisation 2018.

The quality standards of the French Society of Vascular Medicine for the ultrasonographic assessment of vascular malformations are based on the two following requirements: (1) technical know-how: mastering the use of ultrasound devices and the method of examination; (2) medical know-how: ability to adapt the methods and scope of the examination to its clinical indication and purpose, and to rationally analyze and interpret its results. AIMS OF THE QUALITY STANDARDS: To describe an optimal method of examination in relation to the clinical question and hypothesis. To homogenize practice, methods, glossary, and reporting. To provide good practice reference points, and promote a quality process. ITEMS OF THE QUALITY STANDARDS: The 3 levels of examination; their clinical indications and goals. The reference standard examination (level 2), its variants according to clinical needs. The minimal content of the examination report; the letter to the referring physician (synthesis, conclusion and proposal for further investigation and/or therapeutic management). Commented glossary (anatomy, hemodynamics, semiology). Technical bases. Setting and use of ultrasound devices. Here, we discuss ultrasonography methods of using of ultrasonography for the assessment of peripheral vascular malformations and tumors (limbs, face, trunk).

Accurate estimation of dose distributions inside an eye irradiated with 106Ru plaques.

BACKGROUND: Irradiation of intraocular tumors requires dedicated techniques, such as brachytherapy with (106)Ru plaques. The currently available treatment planning system relies on the assumption that the eye is a homogeneous water sphere and on simplified radiation transport physics. However, accurate dose distributions and their assessment demand better models for both the eye and the physics. METHODS: The Monte Carlo code PENELOPE, conveniently adapted to simulate the beta decay of (106)Ru over (106)Rh into (106)Pd, was used to simulate radiation transport based on a computerized tomography scan of a patient's eye. A detailed geometrical description of two plaques (models CCA and CCB) from the manufacturer BEBIG was embedded in the computerized tomography scan. RESULTS: The simulations were firstly validated by comparison with experimental results in a water phantom. Dose maps were computed for three plaque locations on the eyeball. From these maps, isodose curves and cumulative dose-volume histograms in the eye and for the structures at risk were assessed. For example, it was observed that a 4-mm anterior displacement with respect to a posterior placement of a CCA plaque for treating a posterior tumor would reduce from 40 to 0% the volume of the optic disc receiving more than 80 Gy. Such a small difference in anatomical position leads to a change in the dose that is crucial for side effects, especially with respect to visual acuity. The radiation oncologist has to bring these large changes in absorbed dose in the structures at risk to the attention of the surgeon, especially when the plaque has to be positioned close to relevant tissues. CONCLUSION: The detailed geometry of an eye plaque in computerized and segmented tomography of a realistic patient phantom was simulated accurately. Dose-volume histograms for relevant anatomical structures of the eye and the orbit were obtained with unprecedented accuracy. This represents an important step toward an optimized brachytherapy treatment of ocular tumors.

TOPAS: an innovative proton Monte Carlo platform for research and clinical applications.

PURPOSE: While Monte Carlo particle transport has proven useful in many areas (treatment head design, dose calculation, shielding design, and imaging studies) and has been particularly important for proton therapy (due to the conformal dose distributions and a finite beam range in the patient), the available general purpose Monte Carlo codes in proton therapy have been overly complex for most clinical medical physicists. The learning process has large costs not only in time but also in reliability. To address this issue, we developed an innovative proton Monte Carlo platform and tested the tool in a variety of proton therapy applications. METHODS: Our approach was to take one of the already-established general purpose Monte Carlo codes and wrap and extend it to create a specialized user-friendly tool for proton therapy. The resulting tool, TOol for PArticle Simulation (TOPAS), should make Monte Carlo simulation more readily available for research and clinical physicists. TOPAS can model a passive scattering or scanning beam treatment head, model a patient geometry based on computed tomography (CT) images, score dose, fluence, etc., save and restart a phase space, provides advanced graphics, and is fully four-dimensional (4D) to handle variations in beam delivery and patient geometry during treatment. A custom-designed TOPAS parameter control system was placed at the heart of the code to meet requirements for ease of use, reliability, and repeatability without sacrificing flexibility. RESULTS: We built and tested the TOPAS code. We have shown that the TOPAS parameter system provides easy yet flexible control over all key simulation areas such as geometry setup, particle source setup, scoring setup, etc. Through design consistency, we have insured that user experience gained in configuring one component, scorer or filter applies equally well to configuring any other component, scorer or filter. We have incorporated key lessons from safety management, proactively removing possible sources of user error such as line-ordering mistakes. We have modeled proton therapy treatment examples including the UCSF eye treatment head, the MGH stereotactic alignment in radiosurgery treatment head and the MGH gantry treatment heads in passive scattering and scanning modes, and we have demonstrated dose calculation based on patient-specific CT data. Initial validation results show agreement with measured data and demonstrate the capabilities of TOPAS in simulating beam delivery in 3D and 4D. CONCLUSIONS: We have demonstrated TOPAS accuracy and usability in a variety of proton therapy setups. As we are preparing to make this tool freely available for researchers in medical physics, we anticipate widespread use of this tool in the growing proton therapy community.

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.

Accuracy of proton beam range verification using post-treatment positron emission tomography/computed tomography as function of treatment site.

PURPOSE: For 23 patients, an off-line positron emission tomography scan and a computed tomography scan after proton radiotherapy was performed at the Massachusetts General Hospital to assess in vivo treatment verification. A well-balanced population of patients was investigated to assess the effect of the tumor location on the accuracy of the technique. METHODS AND MATERIALS: Range verification was achieved by comparing the measured positron emission tomography activity distributions with the corresponding Monte Carlo-simulated distributions. Observed differences in the distal end of the activity distributions were analyzed as potential indicators for the range differences between the actual delivered and planned dose. RESULTS: The average spatial agreement between the measured and simulated activity distribution was within ±3 mm, and the corresponding average absolute agreement was within ±45% (derived from gamma index analysis). The mean absolute range deviation at 93 randomly chosen positions in 17 treatment fields delivered to 11 patients was 3.6 mm. Characteristic differences in the agreement of the measured and simulated activity distribution for the different tumor/target sites were found. This resulted from the different effect of factors such as biologic washout effects, motion, or limitations in the Monte Carlo-simulated activity patterns. CONCLUSION: We found that intracranial and cervical spine patients can greatly benefit from off-line positron emission tomography and computed tomography range verification. However, for the successful application of the method to patients with abdominopelvic tumors, major technological and methodologic improvements are needed. Among the intracranial and cervical spine target sites, patients with arteriovenous malformations or metal implants represent groups that could especially benefit from the approach.

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.

[Doppler ultrasound assessment of intraocular and orbital tumors]. / Ultrasonografia Doppler în patologia tumorala oculo-orbitala.

PURPOSE: To assess the role of spectral and color Doppler ultrasonography in the positive and differential diagnosis of ocular and orbital tumoral masses. MATERIAL AND METHODS: Retrospective clinical study of 153 patients with 163 ocular or / and orbital masses who were examined by spectral and color Doppler ultrasonography in the Clinic of Radiology, Cluj County Emergency Hospital, between 1997 and 2004. In all patients, the arterial impedance indices were measured by pulsed Doppler examination. The color Doppler characterization of the mass consisted in the description of intratumoral vascularity: presence, vessel number and appearance and peculiar aspects. The final diagnosis was established by histopathology in 123 tumors. In 40 tumors, the diagnosis was established by correlating the clinical findings with the results of other imaging modalities. RESULTS: The study identifies and describes peculiar ultrasonographic aspects of the vascularity in various intraocular and orbital tumors. It describes and illustrates the Doppler ultrasonographic appearance of choroidal melanoma, retinoblastoma, eyeball metastases, hemangioma, lymphangioma, optic nerve sheath glioma, inflammatory pseudotumors and tumors invading the orbit. CONCLUSIONS: The association of vascular information to the two-dimensional ultrasonographic image allows for an improved characterization of ocular and orbital tumoral masses.

Three-dimensional posterior segment ultrasonography: clinical experience.

PURPOSE: To introduce a commercially available three-dimensional ultrasonography unit into everyday clinical practice and to evaluate the qualitative and quantitative information of the acquired images and to clarify the indications for 3-D echography. MATERIALS AND METHODS: 3-D scanning was performed on 59 referred patients with indications for conventional B/A-scan. On 7 patients with an intraocular mass with well-delineated borders 10 repeated volume measurements were carried out. RESULTS: The duration of the ultrasound examination was extended with 8-10 min. 3-D echography offered images of unique perspectives, not previously available with conventional B-scan. The digital technology allowed easy (re)evaluation and follow-up. The coefficient of variation of the repeated volume measurements was less than 5% for all the patients. The standard deviations ranged from 2.22 to 4.75 mm3. CONCLUSIONS: At its current level of technological development 3-D posterior segment ultrasonogaphy left the status of an entirely research laboratory tool and entered the clinical practice. Nevertheless 3-D imaging is neither a rival nor a substitute of conventional B-scan since it is static and needs time intervals for reconstruction. However 3-D ultrasonography is a useful clinical supplement to conventional B/A echography in departments to which a substantial number of complicated cases (esp. intraocular tumours) is referred. It enables volume measurements with good intraobserver reproducibility and is excellent for teaching and training purposes of ophthalmology residents.

CT-scan and intraocular tumours: detection and assessment of size and extrascleral growth of uveal melanomas.

Twenty-two patients, who were suspected of an intraocular tumour, were examined with the high resolution thin slice CT-scan (1.5 or 3 mm slices). The final diagnosis in 14 cases was an uveal melanoma, and in 3 cases in which an uveal melanoma was suspected a chorioretinal haemorrhage, an exudative macular degeneration type Junius Kuhnt and an intrascleral foreign body were respectively found. In 2 cases intraocular metastases were demonstrated, and in 2 other cases malignant lymphomata. One patient had a haemangioma. In 10 of the 14 patients with uveal melanomata enucleation was performed and 4 were treated by ruthenium application. The CT-scan was compared with ultrasonographic, operative and histological findings. From the study it appears that the CT-scan is useful for screening uveal melanomas. It is however difficult to distinguish the uveal melanoma from a secondary retinal detachment; differentiation from an exudative macular degeneration was not possible. The size of the tumour was only represented correctly on the CT-scan in half the cases. CT examination fails to demonstrate or exclude epi- and extrascleral growth. The multiple metastases and the haemangioma could only be seen with difficulty on the CT-scan; the latter was however clearly visible after the injection of contrast. The foreign body could be clearly seen without contrast.