A simple method for evaluating stereotactic accuracy of Magnetic Resonance Imaging and Computed Tomography Imaging in Frame Based Radiosurgery.

PURPOSE: To design a simple and reproducible method with minimum uncertainty for evaluating the stereotactic accuracy of Computed Tomography imaging and Magnetic Reso-nance Imaging and to compare the results. METHODS: 3D phantom has been designed with 1 mm diameter targets in eight sectors for stereotactic MR imaging and CT imaging. The phantom was connected to Leksell stereotactic frame and the images obtained are exported to treatment planning system. Leksell stereotactic coordinates (X, Y, Z) of the holes are determined in each slice and mean maximum errors were calculated along with 3D vector distances from center of stereotactic coordinate system (100,100,100) to five known Targets. The target volumes are calculated independently for each image data sets. RESULTS: The mean of maximum absolute error estimated for MR images from the Siemens Magnetom vision MR unit were 0.46 mm (X-Axis), 1.66 mm (Y-Axis) and 2.11 mm (Z-Axis). Mean of absolute maximum error estimated using CT images from the Philips Brilliance 16 CT scanner were 0.29mm (X-axis), 0.51mm (Y-Axis) and 0.90mm (Z-Axis). 3D vector calculations were 0.38 mm for CT and 0.72 mm for MRI. No significant variation is noticed in volume calculations from both image data sets. CONCLUSION: This study showed that accuracy and quality of stereotactic CT- imaging and MR-imaging are limited by localization devices and their designs in frame based Radiosurgery. This method is simple, direct and economical with good resolution and high reproducibility. KEYWORDS: Stereotactic accuracy, Computed Tomography, Magnetic Resonance Imaging, frame based Radiosurgery.

Trends in oesophagus and Stomach cancer incidence in Bangalore, India.

BACKGROUND: During recent decades, an increase in the incidence of certain oesophago-gastric cancer has been reported in some countries and in India. This study sought to analyze oesophageal and gastric cancer incidence trends in Bangalore by sex and morphology for the period 1982-2007. PATIENTS AND METHODS: Oesophageal and gastric cancer cases were drawn from Bangalore population-based cancer registry locating in Kidwai memorial Institute of Oncology started in 1982 under national cancer Registry Programme funded by Indian Council of Medical Research. Time trends in sex- and age-standardized cancer incidence rates were analyzed by site and histology over the study period, using relative change. RESULTS: Age-standardised oesophageal cancer incidence rates increased in males, in females failed to register a significant trend over the study period. Overall, gastric cancer decreased from 9.81 and 5.48 rates per 100 000 person-years in 1982-86 to 9.45 and 5.25 in 2002-07, among men and women, respectively. Where as oesophageal adenocarcinomas increased sharply in both sex, among men, oesophageal squamous cell cancer rates increased steadily from the mid-1982s onwards a bit decline was observed from 1997, the same trend observed in females. The gastric cancer decreased over the study period. There was a marked decrease in the incidence of oesophago-gastric cancer presenting with unknown and unspecified morphology reported. KEYWORDS: adenocarcinoma, Oesophageal and stomach, incidence, age specific rate, age adjusted rate, population-based registry, trends.

Dosimetric comparison between bone marrow sparing intensity-modulated radiation therapy and conventional techniques in the treatment of cervical cancer: a retrospective study.

PURPOSE: To investigate enlargement of prostate volume by edema during brachytherapy seed implantation and develop a nomogram model to calculate air-kerma strength (AKS) required for implantation of the enlarged transient prostatic volume. MATERIALS AND METHODS: The prostate volume was measured prior and after seed implantation using trans-rectal ultrasound imaging in the operating room to obtain volume enlargement. A nomogram model was developed that calculates AKS required for implantation of the enlarged transient prostate volume with optimal dose coverage. RESULTS: The measured prostate enlargement in this study was up to 60% of the initial volume. The effective prostatic volume enlargement was calculated for three isotopes: 125I, 103Pd and 131Cs. The effective volume enlargement for 125I implants was relatively small (< 10%) because of its long half-life. For 103Pd and 131Cs with short half-lives, additional AKS up to 20% and 30%, respectively, might be required to provide appropriate dose coverage of possible enlarged prostatic volumes. CONCLUSIONS: Prostate volume enlargement should be considered to obtain optimal dose coverage particularly for short half-life isotopes such as 131Cs and 103Pd. The nomogram model developed in this work provides the AKS required for implants with a wide range of prostatic volume enlargements (5-100%) for three isotopes. KEYWORDS: prostate brachytherapy, nomogram, airkerma strength, edema, volume enlargement.

Impact of cutout off axis on electron beam dosimetric parameters.

Dosimetric changes caused by the positional uncertainty of centering a small electron cutout to the machine central axis (CAX) of the linear accelerator (linac) were investigated. Six circular cutouts with 4 cm diameter were made with their centres shifted off by 0, 2, 4, 6, 8 and 10 mm from the machine CAX. The 6 x 6 cm(2) electron applicator was used for the measurement. The percentage depth doses (PDDs) were measured at the Machine CAX and also with respect to cutout centre for 6, 9, 12, 16 and 20 MeV electron beams. The in-line and cross-line profiles were measured at the depth of maximum dose (R100). The relative output factor (ROF) was measured at the reference depth. All the measurements were made at nominal source to surface distance (100 cm SSD) as well as at extended SSDs (100, 102, 106 and 110 cm). When the cutout centre was shifted away from the machine CAX for low energy beams the depth of 100% dose (R(100)), the depth of 90% dose (R(90)) and the depth of 80% dose (R(80)) had no significant change. For higher energies (>9 MeV) there was a reduction in these dosimetric parameters. The isodose coverage of the in-line and cross-line profile was reduced when the cutout centre was shifted away from the machine CAX. At extended SSDs the dosimetric changes are only because of geometric divergence of the beam and not by the positional uncertainty of the cutout. It is important for the radiation oncologist, dosimetrist, therapist and physicist to note such dosimetric changes while using the electron beam to the patients.

Comparison of homogeneity indices for quantitative evaluation of dose homogeneity for IMRT treatments of head and neck cancers.

The purpose of this study was to evaluate different homogeneity indices for IMRT of head and neck cancers and to suggest the best representative homogeneity index for quantitative measure of dose homogeneity. In this study 3 different homogeneity indices were evaluated for 22 head and neck cancer patients receiving dynamic IMRT treatments on Clinac-DHX linear accelerator with 6 MV photon beam. IMRT planning was carried out with Helios software on Eclipse treatment planning system. H index, HI index and S index proposed by Yoon (2007) were calculated for these patients. The H-index, HI index and S index values varied between 1.024 to 1.112, 4.03 to 16.9 and 0.94 to 3.43 respectively. H index values for patient 5 and 10 are identical (H index-1.06) though different in DVH distributions but the S index values for these patients are different (1.36 and 2.01). Similarly the HI index for the patient 11 and 16 are identical in spite of different DVH distributions but S index values are different for patient 11 and 16. Since the S index represents the whole DVH curve unlike the conventional indices which depends on dose at a point, it is the better method to quantify the dose homogeneity. These results indicate that H and HI indices do not provide the accurate dose homogeneity information, but the S indices uniquely provide quantitative information about the dose homogeneity.

Peripheral dose from a dual energy linear accelerator equipped with tertiary multileaf collimators and enhanced dynamic wedge.

Peripheral dose (PD) or the dose outside the geometrical boundaries of the radiation field is of clinical importance when anatomical structures with low dose tolerances might be involved(1). It is the aim of this study is to estimate the PD on linear accelerators on different wedge systems without multileaf collimator (MLC). Measurements were performed on a dual energy linear accelerator equipped with tertiary MLC and enhanced dynamic wedge (EDW). Measurements were made using an ionization chamber embedded in a Radiation Field Analyser (RFA-300) with the secondary collimator and MLC setting of 5x5, 10x10, 15x15, and 20x20 cm2, and with the MLC fully retracted. The effects of SSD on PD were measured at three SSDs of 90, 100, and 110 cm for the irradiation fields of 5x5, 10x10, 15x15, and 20x20 cm2 and the effects of the three different wedges (Upper wedge, Lower Wedge and Enhanced Dynamic Wedge) on PD were measured for 45° wedges with field size of 15x15 cm2. Data were taken from 3 cm to 24 cm away from the field edge. Results show that due to tertiary MLC, PD can be reduced by means of a factor of two to three at certain distance from the edge of the field compared with TG-36 data. In between the wedges, the PD was less for the EDW when compared with the upper and lower physical wedges. We conclude that the reduction in PD is significant in reducing or eliminating the need for external peripheral shielding to reduce the dose on affected critical organs.

IMRT implementation and patient specific dose verification with film and ion chamber array detectors.

Implementation of Intensity Modulation Radiotherapy (IMRT) and patient dose verification was carried out with film and I'mariXX using linear accelerator with 120-leaf Millennium dynamic multileaf collimator (dMLC). The basic mechanical and electrical commissioning and quality assurance tests of linear accelerator were carried out. The leaf position accuracy and leaf position repeatability checks were performed for static MLC positions. Picket fence test and garden fence test were performed to check the stability of the dMLC and the reproducibility of the gap between leaves. The radiation checks were performed to verify the position accuracy of MLCs in the collimator system. The dMLC dosimetric checks like output stability, average leaf transmission and dosimetric leaf separation were also investigated. The variation of output with gravitation at different gantry angles was found to be within 0.9 %. The measured average leaf transmission for 6 MV was 1.6 % and 1.8% for 18 MV beam. The dosimetric leaf separation was found to be 2.2 mm and 2.3 mm for 6 MV and 18 MV beams. In order to check the consistency of the stability and the precision of the dMLC, it is necessary to carryout regular weekly and monthly checks. The dynalog files analysis for Garden fence, leaf gap width and step wedge test patterns carried out weekly were in good agreement. Pretreatment verification was performed for 50 patients with ion chamber and I'mariXX device. The variations of calculated absolute dose for all treatment fields with the ion chamber measurement were within the acceptable criterion. Treatment Planning System (TPS) calculated dose distribution pattern was comparable with the I'mariXX measured dose distribution pattern. Out of 50 patients for which the comparison was made, 36 patients were agreed with the gamma pixel match of >95% and 14 patients were with the gamma pixel match of 90-95% with the criteria of 3% delta dose (DD) and 3 mm distance-to-agreement (DTA). Commissioning and quality assurance of dMLC for IMRT application requires considerable time and effort. Many dosimetric characteristics need to be assessed carefully failing which the delivered dose will be significantly different from the planned dose. In addition to the issues discussed above we feel that individual MU check is necessary before the treatment is delivered.

Forward scatter dose effect at metallic interfaces irradiated by X and gamma ray therapy beams.

AIM: In this study forward scattering effects near different metallic interfaces are measured for Co-60 gamma and 6 and 18 MV photon beams. The studied effects are the transport of secondary electrons across the metallic interface and the scattering of photons by the metallic inhomogeneity. MATERIALS AND METHODS: All measurements were carried out with a PTW thin-window, parallel plate ionisation chamber (B 23344-036) and an RDM-1F electrometer with digital readout. Thin sheets of aluminium, mild steel, copper, cadmium and lead were used as inhomogeneities. The inhomogeneities were placed between the polystyrene phantom and the front window of the chamber which was maintained at 100 cm SSD. RESULTS: It was noticed that for a high energy photon beam (18 MV) the forward scatter dose factor (FSDF) increases rapidly as the thickness of the metallic inhomogeneity increases. For low energy photons, there is a sharp initial decrease of the FSDF until a minimum value is reached followed by a slow increase with increasing thickness of the inhomogeneity. It was also noted that the FSDF variation at off-axis distances has slightly more slope compared with the ionization ratio (IR) curves for both 6 MV and 18 MV photons. However, the variation in slope is prominent for 18 MV compared with 6 MV photon beam. CONCLUSION: The sharp dose decrease observed downstream of a metallic inhomogeneity at relatively low photon energies (Co-60, 6 MV) is attributed to the internal scattering of secondary electrons within the metal. The dose enhancement observed for high energy photon beams is attributed to the domination of the pair production process, increasing with atomic number. Since FSDF is dependent on the photon beam spectra, it can be used as a measure of beam quality across the beam.

Factors influencing the evaluation of an article in cancer literature.

Casual Interpretation of results in a given article has several pitfalls. In order to assess the strengths and limitations of a given article several factors need to be considered. This review article is intended to list, classify and describe briefly the factors that should be considered in the evaluation of an article. The three primary criteria which help in proper assessment of an article are (1) Accurate and adequate description of material and methods; (2) Data on the total sample size and elimination criteria; (3) Statistical methodology employed.

Role of electron beam treatment in postoperative management of carcinoma of the breast.

The aim of post operative radiotherapy to chest wall and drainage areas in advanced breast cancer is to sterilize the possible microscopic disease. Fifty cases of post surgical breast cancers were evaluated in a prospective study of chest wall radiation therapy by electrons. Fifty women of histologically proved post operative invasive breast cancers underwent simple mastectomy with axillary dissection followed by post-operative radiotherapy (Electron) to chest wall +/- drainage area. The chest wall and IMC was treated by a direct electron beam (9/12 MeV and 12 MeV) at fixed angle. 6 MV X-ray beam was used to treat axillary apex and supraclavicular area. In some cases, supplement RT was given by 6 MV X-rays through small posterior axillary portal. The energy of electron beam was 9 MeV or 12 MeV depending on the thickness of treated area. The supraclavicular and axillary lymphatic regions were treated, by direct custom shaped anterior portal. The dose delivered was 50 Gy over 5 weeks at 2 Gy per fraction. Adjuvant chemotherapy was given to patients who were pre-menopausal with histologically proved axillary node involvement as Cyclophosphamide, Methotrexate and 5-Fluorouracil (CMF) after radiotherapy. Post menopausal patients received adjuvant tamoxifen 10 mg.bid. The overall time varied from 26 to 87 days with a median of 41.5 days (SD 11.7). The followup period varied from 4-32 months with a mean of 22 months (SD 6.4). All the fifty patients developed dense pigmentation towards the end of radiation therapy, along with patchy dry desquamation. Moist desquamation occurred in 6 patients. The median OTT in the patients who developed moist desquamation was 34.5 days. The moist reaction healed over 10-15 days after completion of radiotherapy. Lung Fibrosis (Apical lobe) occurred in four patients. The fibrosis was evident at a median of 12 months of follow up. Lymphoedema of the ipsilateral arm occurred in six patients. None of 50 patients developed late sequalae like Cardiac effects, Rib fracture, Brachial Plexopathy, Shoulder joint impairement and Soft tissue effects. Local control in this study was 96% (48 patients). The two year actuarial overall survival was 80%. In early stages survival was significantly better compared to late stages. The actuarial two year DFS was 72%. In early stages DFS was significantly better compared to late stages.

Prognostic factors for spinal cord myelitis--an analysis of compiled literature data.

The effectiveness of radiotherapy in the treatment of malignant tumors in the head and neck, thorasic and upper abdominal regions is frequently limited by the tolerance of the spinal cord. Therefore knowledge of the factors that influence the tolerance of the spinal cord to radiation is of the upmost important. Safe limits for irradiation of the spinal cord determined in a number of clinical studies is on the conservative side from the point of view of tumor control probability. The bioeffect of a physical dose takes into account the treatment variables and the radiobiological characteristics of the relevant tissue; hence deciding spinal cord tolerance on the basis of bioeffect models would be better approach. The aim of the present study was to analyze the relationship of the prognostic factors with percentage incidence of spinal cord myelitis and to arrive at a spinal cord tolerance bioeffect dose TDF and ERD for optimum incidence of radiation myelitis.

Extrapolated response dose as a potential tool in radiotherapy and chemo-radiotherapy of head and neck cancers.

An analysis of head and neck cancer patients treated by radiotherapy (RT) alone (114 patients) and by chemo-radiotherapy (RT + CT) (115 patients) was carried out; the doses varied from 40-77 Gy and 35-71 Gy in RT and RT + CT groups respectively. The chemotherapy (CT) (induction/concurrent) drugs used were 5-FU, cisplatin, methotrexate either single or in combination. Extrapolated response dose values were evaluated with alpha/beta values of 10, 2.5 and 6 Gy for acute, late complications and tumour response, respectively. Dose enhancement factor (DEF) and Therapeutic gain factor (TGF) values were evaluated on the basis of ERD for patients receiving 5-FU RTCT (72 patients). ERD vs late complication rate and response rate curves were drawn for RT, RT + CT (< 7 cycles), RT + CT (> 6 cycles) and RT + CT (cumulative). DEF values for response rate were 0.95, 0.95 and 0.82 for the three RT + CT groups respectively. Similarly DEF values for late complication rate were evaluated as 0.87, 0.93 and 0.88. TGF values for RT + CT were 1.09, 1.02 and 0.93. TGF values indicated lack of significant influence of CT on clinical outcome. The correlation of ERD with late complication, response and status at last follow up (NED) was statistically significant for both groups (P < 0.01). ERD did not correlated with acute complication in RT group (P > 0.01). From the present analysis, in RT + CT treatments of head and neck cancers, an ERD value of 69 Gy is suggested as the limit for an acceptable 5% late complication rate.

Physical characteristics of photon and electron beams from a dual energy linear accelerator.

Clinically pertinent data of the photon beams of nominal energy 6 MV and 18 MV from a dual photon energy linear accelerator are measured using a radiation field analyser with semiconductor diodes and ionisation chambers. Percentage depth dose values are compared with available data from other linacs and BJR-17. Measurements made in the buildup region using a parallel plate chamber show a marked increase in the surface dose and dmax shifts by 3 mm and 14 mm for 6 MV and 18 MV photons, respectively as the field size is increased from 4 x 4 cm2 to the maximum. Variations of wedge angles with energy and field size are also determined up to wedge widths of 15 cm for all the four available wedge angles. Isodose plots of both the energies are plotted using semiconductor diodes in a RFA-3 system. Output factors, wedge transmission factors, and shielding tray factors were also measured in clear polystyrene phantom for both the photon energies at the depths of maximum ionisation. Beam characteristics of the electron beams of energies 6, 9, 12, 16, and 20 MeV produced by the Clinac-1800 have also been studied. The characteristics include percentage depth dose, isodose distribution, depth of maximum dose, surface dose, photon contamination, uniformity index, and penumbra. Most of the measurements were carried out using semiconductor detectors, whereas small volume ionization chambers and a plane-parallel chamber were kept as standards for comparison. Isodose distributions were drawn from the film densitometry method. Range-energy parameters are obtained from the observed depth dose data. These parameters vary from machine to machine and must be ascertained for individual units. The parameters differ to a considerable extent from their theoretically predicted values but generally follow the trend, experimentally observed by others, for similar types of units.

Dosimetric accuracy of a dual photon energy linac at low monitor setting for various pulse repetition frequencies.

Accuracy of dose delivery at low monitor unit setting is studied for a dual photon energy linear accelerator. Dose delivered per MU is found to be constant for both the photon beams for MU settings above 30. For lower MUs there is definite deviation from the calibrated value and the error is found to be increasing as fewer MUs are set for dose delivery. This dose/MU ratio at low MU setting is found to be dose-rate dependent, showing an increasing trend with pulse repetition frequency (PRF). Also, the dosimetric ratio is observed to be mode dependent; its value for an 18 MV beam is almost double that observed in the case of a 6 MV beam at very low MU setting. The magnitude of this error should be determined for each energy so that appropriate corrections can be applied if very low MUs are to be used.

Influence of intraluminal brachytherapy dose on complications in the treatment of esophageal cancer.

PURPOSE: Demonstration of the influence of intraluminal brachytherapy dose on complications in the treatment of esophageal carcinoma. METHODS AND MATERIALS: Between January 1990 and June 1991, 75 patients with esophageal cancer were treated with external radiotherapy followed by intraluminal brachytherapy. Patients had a Karnofsky score of over 70, with no supra-clavicular nodal or distant disease. An external radiotherapy dose between 40 and 55 Gy (mean 52 Gy), 5 times a week, 2 to 2.06 Gy/fraction, followed by a single session of Intraluminal brachytherapy using a locally developed, manual, afterloading applicator with Cs-137 sources with dose ranges of 8-10 Gy (Group 1: 42 patients), 10-12 Gy (Group 2: 11 patients), and 12-15 Gy (Group 3: 22 patients) at a mean dose rate of 2.09 Gy/hr was delivered. RESULTS: The actuarial figures at 1 year were 39% for overall survival, 29% for disease-free survival, and 38% for local control. Fourteen patients (18.6%) developed complications of either an esophageal stricture or fistula. These were dependent on intra-luminal brachytherapy dose, whereas external radiotherapy and intra-luminal brachytherapy doses did not contribute significantly to local control. For Groups 1, 2, and 3, actuarial local control were 28%, 45%, and 63% (p < 0.1) and of complications were 6%, 20%, and 70% (p < 0.001), respectively. Also, on applying the Time/Dose/Fractionation formula on brachytherapy doses, it was found that the complication rate was 6% for TDF of < 31, 25% for TDF of 32-37, and 70% for TDF of > 38 (p < 0.001). CONCLUSION: External radiotherapy doses in the range of 50 to 55 Gy followed by a dose of 10-12 Gy of intraluminal brachytherapy was found optimal with respect to complications and local control in the radiotherapeutic management of esophageal cancer.

Intraluminal brachytherapy in carcinoma of the oesophagus: comparison of afterloading techniques.

For improved local control or palliation of oesophageal cancers, Intra-luminal brachytherapy (ILB) has emerged as an increasingly popular treatment modality of therapy in recent years. In combination with external radiotherapy, afterloaded ILB can increase local control rates and may prolong survival of these patients. In this paper two techniques of ILB viz., manual and low dose-rate remote after loading methods, using Caesium-137 tubes and pellets respectively, are described in detail. On comparison of these two techniques it was found that both of them were similar with respect to their physical characteristics (dose rate, dose fall-off, maximum spinal cord dose, total reference air kerma, etc.). Clinically, the manual afterloaded ILB technique was found to be easier to use when compared with the low-dose rate remote afterloader. In addition, the number of patients with uterine cancers being high in a developing country, it was found that it was inappropriate to use the low dose remote afterloaders, designed for use in gynaecological cancers, for ILB of oesophageal cancers. Therefore, in the absence of high dose rate afterloaders, which can be utilized for intracavitary treatments of both uterine and oesophageal malignancies effectively, the manual after-loading ILB system as described in this paper could be a practical alternative. Cancer Oesophagus, Intraluminal radiotherapy technique.

The dose time relationship in the radiotherapy of carcinoma of the cervix--application of CRE formalism.

A retrospective analysis of 291 patients with cancer of the uterine cervix treated with a combination of external and intracavitary radiotherapy was carried out. Patients were either treated with 45 Gy in 20 fractions by five fractions per week or with 42 Gy in 14 fractions by three fractions per week or with 42 Gy in 14 fractions by three fraction per week schedule by external radiotherapy. For brachytherapy the total dose was 24 to 32 Gy at a dose rate of 1.4 to 2.2 Gy per hour. Complication were correlated with total CRE values for point A (CRE TA) and for rectum CRE TR. Correlations of CRE TA with overall complication rate (p value < 0.05) and rectal complication rate (p value < 0.01) were excellent. Lack of correlation was observed between CRETR and overall complication rate (p value > 0.1) as well as rectal complication rate (p value > 0.1). In order to limit Grade II and III rectal and bladder complications to acceptable level, in combined external and intracavitary treatments, CRETA value of less than 2500 reu is suggested.

Determination of virtual SSDs for electron beams from a dual energy linear accelerator.

Electron beams from an accelerator appear to originate from a point away from the vacuum window designated as virtual source. Virtual source to isocenter distances are determined experimentally by measurements in a polystyrene phantom with inverse square law method. Corrections required for percentage depth dose are also determined. Results of our study are compared with that of other investigators.

Application of radiation effect models in combined external and intracavitary radiotherapy of carcinoma of the uterine cervix.

A retrospective analysis of 291 patients with cancer of the uterine cervix treated with a combination of external and intracavitary radiotherapy was carried out. Patients were treated with an external radiotherapy dose of 45 Gy in 20 fractions, 5 fractions per week, or 42 Gy in 14 fractions, 3 fractions per week. For brachytherapy the total dose was 24 to 32 Gy at a dose rate of 1.4 to 2.2 Gy per hour. Treatment results in terms of survival, local disease-free survival and complication rates were compared with cumulative radiation effect (CRE) and extrapolated response dose (ERD) values for point A (CRETA and ERDTA respectively) and for rectum (CRETr and ERDTr respectively). CRETA and ERDTA values did not significantly correlate with local disease-free and survival rates. Correlations of CRETA and ERDTA with overall complication rate and with rectal complication rate (p-value less than 0.025) were good. No significant correlation was observed between CRETr or ERDTr and overall complication rate and rectal complication rate. In order to limit grades II and III rectal complications to acceptable level, in combined external and intracavitary treatment, CRETA and ERDTA values of less than 2,500 and 93 respectively are suggested.